HomeMy Public PortalAbout2006 Final Rules and Regulations (COMPLETE DOCUMENT)THE
METROPOLITAN ST, LOUIS
SEWER DISTRICT
Iv'
SI'
RULES AND REGULATIONS
AND
ENGINEERING DESIGN
REQUIREMENTS
FOR
SANITARY SEWER
AND STORMWATER
DRAINAGE FACILITIES
FEBRUARY 2006
Revised 2/15/2015 2
RULES AND REGULATIONS AND ENGINEERING DESIGN REQUIREMENTS
FOR SANITARY SEWER AND STORMWATER
DRAINAGE FACILITIES
FEBRUARY 2006
TABLE OF CONTENTS
1. GENERAL .............................................................................................................................................................. 10
1.010 Projects Requiring Review By the District............................................................................................... 10
1.020 Regulations Governing the Use of Public and Private Sewerage Facilities ........................................... 10
1.020.01 Unlawful Discharges and Sewage Disposal ...................................................................................... 10
1.020.02 Public Sewer Available ....................................................................................................................... 10
1.020.03 Public Sewer Not Available ................................................................................................................ 10
1.020.04 Prohibited Discharges and Waste Disposal Into Sanitary Sewers .................................................. 11
1.020.05 Wastes Having Excessive Biochemical Oxygen Demand (B.O.D.), ................................................. 11
1.020.06 Measurements, Tests or Analyses ...................................................................................................... 12
1.020.07 Furnishing Records ............................................................................................................................. 12
1.030 Submission, Review and Approval of Plans and Specifications ............................................................... 12
1.040 Procedures..................................................................................................................................................... 13
1.040.01 Preliminary Conferences .................................................................................................................... 13
1.040.02 Required Submittals by the Engineer ............................................................................................... 13
1.040.03 Subdivisions ......................................................................................................................................... 14
1.040.04 Projects Normally Requiring a Sewer Connection - Permit Only .................................................. 14
1.040.05 Return of Plans Without Review ....................................................................................................... 15
1.040.06 Return of Plans for Revision .............................................................................................................. 15
1.040.07 Failure to Revise or Correct Plans Promptly ................................................................................... 15
1.040.08 Fees for Review ................................................................................................................................... 15
1.050 Plan Requirements ....................................................................................................................................... 15
1.050.01 Drawing Sizes ...................................................................................................................................... 15
1.050.02 Plans Submitted Shall Include: .......................................................................................................... 15
1.060 Storm Drainage Design Data, Maps and Computation ............................................................................. 16
1.060.01 General Criteria:................................................................................................................................. 16
1.060.02 Basic Design Data To Include: ........................................................................................................... 17
1.070 Sanitary Sewer Design Data, Maps and Computations ............................................................................ 17
1.070.01 General Criteria:................................................................................................................................. 17
1.070.02 Basic Design Data To Consider: ........................................................................................................ 17
2. DEFINITIONS ....................................................................................................................................................... 18
3. DESIGN REQUIREMENTS FOR SANITARY SEWERS ................................................................................ 23
3.010 General .......................................................................................................................................................... 23
3.020 General Requirements of Sanitary Sewer Construction ........................................................................... 23
3.020.01 Size and Shape ..................................................................................................................................... 23
3.020.02 Materials ............................................................................................................................................. 23
Revised 2/15/2015 3
3.020.03 Bedding ................................................................................................................................................ 23
3.020.04 Pipe or Conduit Under Streets and Pavements ................................................................................ 24
3.020.05 Joints ................................................................................................................................................... 24
3.020.06 Monolithic Structures ......................................................................................................................... 24
3.020.07 Alignment ........................................................................................................................................... 24
3.020.08 Location .............................................................................................................................................. 24
3.020.09 Flowline ................................................................................................................................................ 25
3.020.10 Manholes ............................................................................................................................................. 25
3.020.11 Sewage Treatment Facilities .............................................................................................................. 26
3.030 Design Requirements .................................................................................................................................... 27
3.030.01 General................................................................................................................................................. 27
3.030.02 Gradients ............................................................................................................................................ 27
3.030.03 Depth and Minimum Cover .............................................................................................................. 27
3.030.04 Flow Design ........................................................................................................................................ 28
3.030.05 Population Factors ............................................................................................................................. 28
3.030.06 Sanitary Flow Table .......................................................................................................................... 28
3.030.07 Hydraulic Grade Line........................................................................................................................ 29
1. Hydraulic Grade Line Limits ................................................................................................................. 29
2. Computation Methods ............................................................................................................................. 29
a. Friction Loss ......................................................................................................................................... 29
b. Curve Loss ............................................................................................................................................ 30
c. Turn Loss .............................................................................................................................................. 30
d. Junction Chamber Loss ......................................................................................................................... 31
e. Losses at Junctions of Several Flows in Manholes ............................................................................... 32
f. Transition Loss ..................................................................................................................................... 33
(1) Closed Conduits ............................................................................................................................... 33
3.030.08 Infiltration .......................................................................................................................................... 34
3.030.09 Special Situations and Design Requirements ................................................................................... 34
l. Connections to Manholes ........................................................................................................................ 34
2. Adjusting Manholes to Grade................................................................................................................. 35
3. Swimming Pools ....................................................................................................................................... 35
4. Storm Sewers Crossing Over Sanitary Sewers ..................................................................................... 35
5. Location in Conjunction with Water Service ........................................................................................ 35
6. Sanitary Sampling Appurtenance .......................................................................................................... 35
7. Abandonment of Sanitary Sewer Services ............................................................................................. 36
8. Private Force Main Connections ............................................................................................................ 36
9. Oil/Gas Separators, Sand Filters, and Grease Traps............................................................................ 36
10. Coldwater Creek Gravity Elevation .................................................................................................. 37
11. Common Laterals ................................................................................................................................ 37
12. Private Lateral .................................................................................................................................... 37
13. Separate Laterals and Sewers ............................................................................................................ 37
14. Protection from Surcharging ............................................................................................................. 38
15. Residential Basement Garage Flooding ............................................................................................ 38
16. Lateral for Commercial Use ............................................................................................................... 38
3.040 Sanitary Detention Requirements ............................................................................................................... 38
3.040.01 Surcharged Sanitary Sewers ............................................................................................................. 38
4. DESIGN REQUIREMENTS FOR STORM DRAINAGE FACILITIES .......................................................... 42
4.010 General ............................................................................................................................................................. 42
4.020 General Requirements of Storm Sewer Construction .................................................................................. 42
4.020.01 Size and Shape .................................................................................................................................... 42
4.020.02 Materials ............................................................................................................................................. 42
Revised 2/15/2015 4
4.020.03 Bedding ............................................................................................................................................... 42
4.020.04 Concrete Pipe or Conduit Strengths ................................................................................................. 42
4.020.05 Monolithic Structures ......................................................................................................................... 43
4.020.06 Alignment ............................................................................................................................................ 43
4.020.07 Location .............................................................................................................................................. 43
4.020.08 Sinkhole Areas .................................................................................................................................... 44
1. Sinkhole Report ....................................................................................................................................... 44
2. Procedure for Utilization of Sinkholes ................................................................................................... 45
4.020.09 Flowline ............................................................................................................................................... 45
4.020.10 Manholes ............................................................................................................................................. 46
4.020.11 Overflow/Design System .................................................................................................................... 47
4.030 Stormwater Design Criteria ........................................................................................................................ 47
4.030.01 Flow Quantities .................................................................................................................................. 47
1. Rainfall Frequency .................................................................................................................................. 48
2. Impervious Percentages and Land Use .................................................................................................. 48
3. Reduction in P.I. with Time and Area ................................................................................................... 49
4.030.02 Hydraulic Grade Line for Closed Conduits .................................................................................... 50
1. Computation Methods ............................................................................................................................. 50
a. Friction Loss ......................................................................................................................................... 50
b. Curve Loss ............................................................................................................................................ 51
c. Entrance Loss at Terminal Inlets ........................................................................................................... 51
d. Turn Loss .............................................................................................................................................. 51
e. Junction Chamber Loss ......................................................................................................................... 52
f. Losses at Junctions of Several Flows in Manholes and/or inlets 53
g. Transition Loss ..................................................................................................................................... 54
(1) Closed Conduits ............................................................................................................................... 54
(2) Open Channel Transitions ................................................................................................................ 55
4.030.03 Hydraulic Grade Line Limits ............................................................................................................ 55
4.030.04 Inlets .................................................................................................................................................... 56
4.030.05 Open Channels ................................................................................................................................... 57
1. Size and Shape ......................................................................................................................................... 57
2. Materials................................................................................................................................................... 57
3. Bedding ..................................................................................................................................................... 58
4. Structural Considerations ....................................................................................................................... 58
5. Alignment ................................................................................................................................................. 58
6. Locations .................................................................................................................................................. 58
7. Flowline .................................................................................................................................................... 58
8. Other Open Channel Considerations and Requirements ..................................................................... 58
9. Design Limitations ................................................................................................................................... 59
10. Hydraulic Grade Line......................................................................................................................... 59
a. Computation Methods ........................................................................................................................... 59
(1) Control Sections ............................................................................................................................... 60
(2) Friction Loss .................................................................................................................................... 60
(3) Flow in Curved Channels ................................................................................................................. 60
(a) Curve Losses ............................................................................................................................... 60
(b) Superelevations ........................................................................................................................... 60
(4) Transitions ........................................................................................................................................ 61
(a) Proportioning ............................................................................................................................... 61
(b) Losses .......................................................................................................................................... 61
(c) Freeboard .................................................................................................................................... 62
(d) Hydraulic Jump ........................................................................................................................... 62
(e) Sudden Enlargement and Contraction ......................................................................................... 62
(5) Constrictions .................................................................................................................................... 63
(6) Obstructions ..................................................................................................................................... 63
b. Hydraulic Grade Line Limits ................................................................................................................ 63
Revised 2/15/2015 5
11. Hydraulic Jump .................................................................................................................................. 63
12. Open Channel Junctions .................................................................................................................... 63
a. General .................................................................................................................................................. 63
b. Confluence Design Criteria ................................................................................................................... 63
13. Erosion Protection .............................................................................................................................. 64
14. Sanitary Sewer Crossings ................................................................................................................... 64
4.030.06 Culverts ............................................................................................................................................... 64
1. Hydraulic Design ..................................................................................................................................... 64
2. Entrances and Headwalls - Outlets and Endwalls ................................................................................ 64
4.040 Bridges ........................................................................................................................................................... 64
4.040.01 Waterway Capacity and Backwater Effects .................................................................................... 64
4.040.02 Clearance ............................................................................................................................................ 65
4.040.03 Waterway Alignment ......................................................................................................................... 65
4.040.04 Erosion Protection ............................................................................................................................. 65
4.050 Outlet Erosion Protection ............................................................................................................................ 65
4.060 Limitations on Areas Draining Across Sidewalks or Driveways ............................................................. 65
4.070 Impervious Areas - In City of St. Louis ...................................................................................................... 65
4.080 General Performance Criteria for Stormwater Management ................................................................. 65
4.080.01 When Required .................................................................................................................................. 65
4.080.02 Unified Stormwater Sizing Criteria ................................................................................................. 67
1. General ..................................................................................................................................................... 67
2. Water Quality Volume (WQv) ................................................................................................................ 67
3. Channel Protection Storage Volume Requirements (Cpv) ................................................................... 68
4. Flood Protection Volume Requirement (Qp2 & Qp100) ........................................................................... 70
4.080.03 Limits of Maximum Ponding in Stormwater Ponds ....................................................................... 71
4.080.04 General Stormwater Basin Design Requirements .......................................................................... 72
4.080.05 Acceptable Urban BMP Options ...................................................................................................... 74
1. BMP Group 1. Stormwater Ponds ......................................................................................................... 75
2. BMP Group 2. Stormwater Wetlands.................................................................................................... 75
3. BMP Group 3. Infiltration Practices ..................................................................................................... 76
4. BMP Group 4. Filtering Practices .......................................................................................................... 76
5. BMP Group 5. Open Channel Practices ................................................................................................ 76
4.080.06 Stormwater Credits ........................................................................................................................... 76
4.080.07 Easement Required ............................................................................................................................ 77
4.080.08 Maintenance Agreement ................................................................................................................... 77
4.090 Dam Permit Requirements .......................................................................................................................... 77
4.100 Detention Report .......................................................................................................................................... 77
EXHIBIT 4-A .............................................................................................................................................................. 78
Check List for Review of Stormwater Detention ................................................................................................ 78
5. FLOOD PLAIN REQUIREMENTS .................................................................................................................... 91
5.010 Flood Plain Study/100 – Year Hydraulic Study ......................................................................................... 91
5.010.01 When Required .................................................................................................................................. 91
5.010.02 Criteria For Preparation ................................................................................................................... 91
5.010.03 Filling in Flood Plain Areas .............................................................................................................. 93
5.010.04 Detention Basins in Flood Plains ...................................................................................................... 93
5.010.05 Bridges in Flood Plains ...................................................................................................................... 93
Revised 2/15/2015 6
5.010.06 Parking Lots in Flood Plains ............................................................................................................. 93
5.010.07 Site Plan Requirements ..................................................................................................................... 94
6. RECOUPMENT RULES AND REGULATIONS ............................................................................................... 95
6.010 General .......................................................................................................................................................... 95
6.020 Contract Between District and Owner(s) ................................................................................................... 95
6.030 Recoupment Provisions ................................................................................................................................ 95
6.040 Recoupment Procedures and Project Costs ............................................................................................... 95
6.050 Objections to Certified Completed Construction Costs ............................................................................ 95
6.060 Recoupment Fees .......................................................................................................................................... 95
6.070 Areas Served by More Than One Sewer Facility Under Recoupment .................................................... 96
6.080 Connection to Recoupment Sewer Facility................................................................................................. 96
6.090 Reports of Owner of Sewer Facility ............................................................................................................ 96
6.090.01 Annual .................................................................................................................................................. 96
6.090.02 Interim ................................................................................................................................................. 96
6.100 Extent of and Time Limits of Recoupment ................................................................................................. 96
7. EASEMENTS ......................................................................................................................................................... 97
7.010 General .......................................................................................................................................................... 97
7.020 Use of Existing Easements ........................................................................................................................... 97
7.030 Location of Easements ................................................................................................................................. 97
7.040 Width of Easements ...................................................................................................................................... 97
7.050 Wording of Easements ................................................................................................................................. 97
7.060 Easement Plat Preparation Information Guidelines ................................................................................. 97
7.060.01 Label Established Lines Affecting Tract and/or Mentioned in its Legal Description: ................ 97
7.060.02 Identify Parcel or Tract: ................................................................................................................... 98
7.060.03 Provide Accurate Title Box Information: ........................................................................................ 98
7.060.04 Easement Plat Drafting Guidelines ................................................................................................... 98
7.070 Vacation of Easements ................................................................................................................................. 99
7.080 Easement Encroachment............................................................................................................................ 100
7.090 Indemnity Agreement ................................................................................................................................. 101
8. APPROVAL AND DEDICATION OF PROJECTS WITH PUBLIC SEWERS ........................................... 102
8.010 General ........................................................................................................................................................ 102
Revised 2/15/2015 7
8.020 Requirements for Plan Approval and Issuance of Permits ..................................................................... 102
8.020.01 Agreement to Dedicate .................................................................................................................... 102
8.020.02 Construction Escrow Deposit and Cash Deposit Agreement ....................................................... 102
8.020.03 Conditional Plan Approval ............................................................................................................. 102 8.020.04 Flexibility for BMP Permitting & Inspection 102
8.030 Requirements for Construction Approval ................................................................................................ 103
8.030.01 Construction Inspection .................................................................................................................. 103
8.030.02 Field Changes and Plan Revisions ................................................................................................... 103
8.030.03 As-Built Drawings ............................................................................................................................ 103
1. Storm, Sanitary and Combined Sewers ............................................................................................... 104
2. Detention Basin ...................................................................................................................................... 104
3. Pump Station Construction................................................................................................................... 104
4. Subdivision Plats .................................................................................................................................... 105
5. Geotechnical Engineer's Certification ................................................................................................. 105
6. State Plane Coordinates ........................................................................................................................ 105
a. Horizontal Data ................................................................................................................................... 105
b. Vertical Data ....................................................................................................................................... 105
c. Deliverables ........................................................................................................................................ 105
8.030.04 Stormwater Quality mangem Facilities and Construction Deposit Agreement .......................... 106 8.030.05 Notification of Construction Approval 106
8.040 Requirments for District Approval of Stormwater Management Facility Construction ..................... 106
8.040.01 Contruction Inspections ................................................................................................................... 106
8.040.02 Field Changes and Plan Revisions ................................................................................................... 106
8.040.03 As-Built Drawings ............................................................................................................................. 107
8.050 Dedication and Release of Construction Deposit ..................................................................................... 107 8.050.01 Residential and Commercial Subdivisions, Apartments and Condominiums 107
a. Initial Dedication Inspection 107
b. Final Dedication Inspection 107
8.050.02 Sewer Extensions and Single Lot Developments 108
8.050.03 Dedication Inspection Fees 108
8.060 Pump Stations ............................................................................................................................................. 108
8.070 Abandonment of Work 109
8.080 Release of Stormwater Quality Management Facilities Construction Deposit 109
9. FEES AND DEPOSITS REQUIRED BEFORE PLAN APPROVALAND ISSUANCE OF
CONSTRUCTION PERMITS ................................................................................................................................. 111
9.010 Fees Required Before Plan Approval ....................................................................................................... 111
9.010.01 Submittal Fee .................................................................................................................................... 111
9.010.02 Review Fee ........................................................................................................................................ 111
9.010.03 Connection and System Development Fees .................................................................................... 111
9.010.04 Recording Fees ................................................................................................................................. 111
9.020 Deposits Required Before Issuance of Construction Permits ................................................................. 111
9.020.01 As-Built Deposit ............................................................................................................................... 112
9.020.02 Construction Deposit ....................................................................................................................... 112
9.020.03 Pump Station Escrow Deposit ......................................................................................................... 112
9.020.04 Conditional Plan Approval Deposit................................................................................................ 112 9.020.05 BMP Deposit 112
Revised 2/15/2015 8
10. CONSTRUCTION PERMITS .......................................................................................................................... 113
10.010 General ........................................................................................................................................................ 113
10.010.01 Permits Required ............................................................................................................................. 113
10.010.02 Defaults ............................................................................................................................................. 113
10.020 Permittee ..................................................................................................................................................... 113
10.030 Performance Bond ...................................................................................................................................... 113
10.040 Construction and Connection Permit and Fees ....................................................................................... 114
10.040.01 Connection Permit and Fee .............................................................................................................. 114
10.040.02 Construction Permit and Fee ........................................................................................................... 114
10.040.03 Machine Tap Permit and Fee ........................................................................................................... 114
10.050 Inspection Fee Deposit ............................................................................................................................... 115
10.060 Expiration and Extension of Permits and Approved Plans .................................................................... 115
10.060.01 Approved Plans ................................................................................................................................ 115
10.060.02 Construction and Connection Permits ........................................................................................... 115
10.070 Cancellation of Permits and Refunds of Fees and Deposits .................................................................... 115
10.070.01 Prior to the Start of Work ............................................................................................................... 115
10.070.02 After the Start of Work ................................................................................................................... 116
10.070.03 Connection Permits .......................................................................................................................... 116
10.080 Final Determination of Construction Inspection Fees ............................................................................. 116
10.090 Minimum Insurance Requirements for Off Site Construction ............................................................... 116
10.090.01 Comprehensive Automobile Liability: ........................................................................................... 117
10.090.02 Commercial General Liability (occurrence from): ....................................................................... 117
10.090.03 Cancellation & Replacement Policy ............................................................................................... 117
11. INSPECTION .................................................................................................................................................... 120
11.010 General ........................................................................................................................................................ 120
11.020 Privately Constructed Sewers and Treatment Facilities ......................................................................... 120
11.030 Maintenance and Operation Inspection ................................................................................................... 120
11.040 Fees .............................................................................................................................................................. 120
11.050 Inspection ................................................................................................................................................... 120
12. REGULATION AND CORRECTION OF IMPROPER PRIVATE SEWER FACILITIES ..................... 121
12.010 General ........................................................................................................................................................ 121
12.020 Notification to Owner................................................................................................................................. 121
12.030 Expiration of Period Without Work Being Done .................................................................................... 121
12.040 District to Proceed with Work................................................................................................................... 121
Revised 2/15/2015 9
12.050 Cost of Work - A Lien ................................................................................................................................ 121
12.060 Appeal from Decision to Proceed with Work ........................................................................................... 121
13. SEWAGE PUMPING STATIONS ................................................................................................................... 122
13.010 General ........................................................................................................................................................ 122
13.020 Pump Station Plan Review Procedure ...................................................................................................... 122
13.020.01 Design Report .................................................................................................................................... 122
13.020.02 Design Drawings .............................................................................................................................. 122
13.020.03 Required Submittal .......................................................................................................................... 123
13.030 Low Pressure Sewer Systems (LPSS) ....................................................................................................... 123
13.030.01 General............................................................................................................................................... 123
13.030.02 LPSS Plan Review Procedure ......................................................................................................... 123
1. Low Pressure Sewer System Design Report: ....................................................................................... 123
2. Design Drawings: ................................................................................................................................... 123
13.030.03 Required Submittal ........................................................................................................................... 123
14. APPENDIX – VOLUMETRIC METHOD
15. RESERVED (FOR FUTURE INDEX)
Revised 2/15/2015 10
THE METROPOLITAN ST. LOUIS SEWER DISTRICT
1. GENERAL
The readers of this document should be aware that parts of this document may change from time to time. Those changes,
including dates of revised pages and date of most recent change will be available on the District’s website by link at
www.stlmsd.com . Design engineers must verify that they are using the most recent version.
1.010 Projects Requiring Review By the District
All public or private sewerage and drainage works proposed to be constructed, altered or reconstructed by any person or
corporation, public or private, within the District boundaries, require review by the District. This includes any altering of
any storm drainage channel, site drainage or flood plain within those boundaries.
1.020 Regulations Governing the Use of Public and Private Sewerage Facilities
The following sections are summarized from the District Sewer Use Ordinance. The current Sewer Use Ordinance in
effect shall be considered the governing document and should be consulted for elaboration. Requests for variances or
clarification of these regulations should be addressed to the attention of the Director with information supporting the
request. A request for variance will be reviewed by the Director or his designee(s) and either granted or rejected in whole
or part.
1.020.01 Unlawful Discharges and Sewage Disposal
1. Discharges and deposits of any sewage, industrial wastes, garbage, polluted water or
any other substance that constitutes a nuisance or hazard to the public health or
welfare into any natural outlet, drainage channel, or watercourse, are prohibited.
2. No cesspool, septic tank or other facility intended or used for the disposal of sewage
shall be installed except as hereinafter provided.
1.020.02 Public Sewer Available
A public sanitary or combined sewer shall be considered to be available if it is within two
hundred (200) feet of any part of the property to be connected to the sewer. Under such
conditions a direct connection must be made to the public sewer. Where an extension of the
sewer system is required to make this connection, such extension shall be made public to
insure other areas within the District of adequate sanitary disposal and conformance with
3.030.09.12. Combined sewers and storm sewers shall also comply with 3.030.09.12 with
some exceptions for certain storm pipes.
1.020.03 Public Sewer Not Available
Where a public sanitary or combined sewer is not available to service an existing or proposed
residential property which is 3.0 acres or larger and if the District approves in writing, the
sewer lateral from the building shall be connected to an approved private or semi-public sewer
or sewage disposal or sewage treatment facility complying with the rules and regulations of the
District and any other appropriate authority. When a public sewer becomes available and a
direct connection to it is made, any septic tank, cesspool, or other private or semi-public
sewage disposal or treatment facilities shall be abandoned as approved by the District.
New residential lots that are less than 3.0 acres will be required to connect to the public sewer
regardless of the proximity of the property to the public sewer.
All new non-residential development and redevelopment or modification to an existing non-
residential development will be required to connect to the public sewer, regardless of the
proximity of the development to the public sewer. An exception will be made, however, for an
Revised 2/15/2015 11
expansion of an existing building involving minimal extra water usage and where it’s original
private treatment system is certified to still have adequate capacity after the proposed addition.
1.020.04 Prohibited Discharges and Waste Disposal Into Sanitary Sewers
1. Surface water, stormwater, groundwater, roof runoff, subsurface drainage,
uncontaminated cooling water, unpolluted industrial process waters, shall not be
discharged to a sanitary sewer.
2. No person shall deposit or throw into any sewer, or into any private drain connecting
with a public sewer any waste, product or material of manufacture, rags or garbage
which has not been properly shredded, or any substance which may constrict, cause a
nuisance, dam or otherwise obstruct any sewer.
3. No gasoline service station, garage, car wash facility, refining plant, chemical plant,
packing house, slaughter house, lard rendering establishment, dairy, steam plant, or
any other establishment from which any substance would be discharged into the
sewers which could tend to obstruct or damage the sewers, or cause a nuisance, or
endanger the public health or safety, or endanger persons who might be in such
sewers, shall be connected with any public sewer, or to any private sewer which
discharges directly or indirectly into any public sewer. EXCEPTION would be
through one or more District approved interceptors or traps. Any approved trap shall
be maintained and operated in a manner satisfactory to the District, and the substance
removed from such traps shall not be deposited in a way or place not previously
approved by the District.
Where grease, oil and grit interceptors, and other preliminary treatment facilities are
provided, they shall be maintained continuously in satisfactory and efficient
operation by the owner at his expense. Such facilities shall be subject to inspection
by the District at all times. A Sampling appurtenance (“T” or manhole) may be
required that would be easily accessible by the District.
If the substance discharged by any establishment is deemed harmful to the sewer,
detrimental to the public health or safety, and dangerous to persons who may enter
such sewers, the discharge from such establishment shall be entirely excluded from
the sewer.
1.020.05 Wastes Having Excessive Biochemical Oxygen Demand (B.O.D.),
Suspended Solids or Toxic Elements
If excessive B.O.D., suspended solids or toxic elements could occur and constitute a nuisance
or adversely affect the operation of any existing force main, gravity system, sewage lift or
pump station or proposed sewage treatment plant or overload any sewage treatment plant
owned or operated by the District, the owner shall provide, at his expense, such preliminary
treatment as may be necessary to:
1. Control objectionable characteristics or constituents in such a manner as to not
obstruct or interfere with the maintenance or operation of any public sewerage
facility.
2. Control the quantities and rates of discharge of such waters or wastes. Plans,
specifications, and other pertinent information relating to proposed preliminary
treatment facilities shall be submitted for the approval of the District, and
construction of such facilities shall not commence until such approval is granted in
writing.
Revised 2/15/2015 12
1.020.06 Measurements, Tests or Analyses
The District shall be provided means to monitor the discharge into the public sewers of any
waters or wastes discharging into sewer or any treatment facility maintained and operated by
the District that contain any quantity of substances having the characteristics described in
Section 1.020.04, or have an average daily flow greater than two percent (2%) of the average
daily sewage capacity of the treatment facility. All discharges shall be subject to the analytical
inspection and approval of the District.
Measurements, tests, and analyses of the characteristics of the water and wastes referred to in
Sections 1.020.04 and 1.020.05 shall be determined in accordance with the current edition of
"Standard Methods for Examination of Water and Wastewater" published jointly by the
American Public Health Association, the American Water Works Association and the Water
Environment Federation. Other approved testing methods as specified by the Environmental
Protection Agency in 40 CFR PART 136 may also be used. Additional methods of making
measurements, tests or analyses of the characteristics of water or wastes may be provided by
the Director with the approval of the Board of Trustees of the District, when, in the opinion of
the Director, they are necessary.
All measurements, tests or analyses shall be upon suitable samples taken at the sampling
appurtenance ("T" or manhole) All non-residential facilities shall have a six (6) inch
(minimum) diameter, straight "T" vent or 42-inch (minimum) standard manhole for taking
samples. This "T" vent or manhole shall be located on the lateral line outside the building.
The "T" or manhole placement shall be before the lateral connects to the public sewer and
downstream from any grease traps, interceptors, or any other private wastewater treatment
system.
1.020.07 Furnishing Records
It shall be the duty of every person, public utility or institution holding a permit to operate a
sewerage system or sewage treatment plant to furnish records as may be required by the
District to ascertain compliance with the rules and regulations and ordinances of the District.
1.030 Submission, Review and Approval of Plans and Specifications
Designs, plans and specifications of all sewerage and drainage works proposed to be constructed, altered or reconstructed
by any person or corporation, private or public, within District boundaries, shall be submitted to the District for review,
revision, approval or rejection. In addition, for projects with facilities requiring industrial pretreatment, an Industrial
Wastewater Survey Form must be completed and a set of plans submitted to the Division of Environmental Compliance of
the District. Such designs, plans and specifications (excluding house connections, curb cuts, etc.) shall be prepared and
sealed by a Professional Engineer, registered in the State of Missouri, and shall meet the minimum standards of the District
and Missouri Department of Natural Resources before approval is granted. The District is designated as the Missouri
Department of Natural Resources reviewing agency.
Plans for projects that will be reviewed by the District, but will not require permits to be issued by the District and do not
involve site grading and storm sewer construction, may be allowed to be sealed by an Architect registered in the State of
Missouri. This will be up to the discretion of the District. A Surveyor’s seal is required for As-Built plans, but will not be
accepted for Proposed Construction plans.
The final set of plans submitted to the District for approval must be signed, sealed and dated by the Professional Engineer
in accordance with the Missouri Revised Statutes, Chapter 327, of the Missouri Board for Architects, Professional
Engineers, Professional Land Surveyors and Landscape Architects, except as above. Plans must be resubmitted if sealing
date is more than a year old or if site or project conditions have changed. Missouri Rule 4 CSR 30-3.030 and MSD’s
requirements will be deemed met if the following procedures are used. Place the original signature, wet seal and date on
Revised 2/15/2015 13
each sheet of one set of final plans submitted for approval. Other sets may be reproductions, with wet seal, signature, and
date only on the cover sheet along with a list of sheets which comprise the set.
1.040 Procedures
1.040.01 Preliminary Conferences
Prior to formal submission of project plans, the owner's Engineer can request a preliminary
conference to obtain informal guidance in project plan preparation. Preliminary conferences
are encouraged in unique or unusual situations. Most projects, however, should not require a
preliminary conference or conceptual approval, nor can more than a few be currently provided
as a courtesy.
Use of non-structural best management practices (BMPs) and site designs that conserve
natural resources to meet water quality requirements are also encouraged. They are best
considered by the Consultant and the Developer, prior to land disturbance at site; from the
perspective of “Master” planning; and with an eye towards sustainability for the long term.
This is in the ultimate Owner’s best interest.
1.040.02 Required Submittals by the Engineer
Refer to the District's information sheet, the District Form (E.2), for information to be
submitted. Plan Review may be delayed if all required information is not provided.
To facilitate the review of plans before approval for construction, the Engineer shall submit
with the plans all necessary data, maps and computations in support of the designs and plans.
The following listed requested information is a minimum and may be supplemented by any
additional information, which the Engineer considers to be helpful in the review process.
1. The following information shall be provided, as applicable:
a. Engineer's name, mailing address, telephone number, fax number and
contact name.
b. Owner and/or developer's name, mailing address, telephone number, fax
number and contact name.
c. Accurate location of property relative to an intersection.
d. "Wunnenberg's" page and grid number for the project, the District Base
Map Number, the St. Louis County Locator Number for the property, and
the property address.
e. Total acreage of property, and impervious acres if other than residential.
f. Land use of the improvement area, i.e.; commercial, residential, etc.
g. For connection fee calculations: total number of dwelling units or lots, and
domestic use water tap size (especially for non-residences, and not
including fire and irrigation component).
h. The District reference number shall be used in all subsequent
correspondence concerning the project, and shall be utilized as soon as
possible after issued. The St. Louis County Permit Application Center
(PAC) number shall also be used as soon as possible.
Revised 2/15/2015 14
i. If the submittal is a revision or addendum to a previous project, the
previous project shall be properly identified, and the particulars of the
revision or addendum shall be described.
j. For any project, a very brief description giving scope and significant
characteristics.
2. Number of Copies of Plans and Supporting Data to be Submitted.
Plans shall be complete and a minimum of three (3) sets of plans and two (2) sets of
the storm and sanitary hydraulic calculations will be required. Complete includes
number and extent of multi-stories and basements or sub basements and lowest floor
elevations.
Flood Plain: Submit one (1) additional set of plans and a total of
one (1) sets of The Flood Plain Report.
Detention: Submit one (1) additional set of plans and a total of two (2) set of the
detention calculations.
Water Quality: Submit one (1) additional set of plans for BMPs and a total of two
(2) sets of water quality calculations.
Pump Station: Submit three (3) additional sets of plans and a total of four (4)
copies of the pump station design report and specifications.
1.040.03 Subdivisions
For projects within a proposed subdivision, a subdivision plat shall be provided substantially
ready for filing, adequately dimensioned and located from well established points and lines to
permit accurate platting on record maps. The Engineer shall provide a statement concerning
the established zoning requirements of the governing municipality, including the City of St.
Louis or St. Louis County, as appropriate, together with any other pertinent information.
1.040.04 Projects Normally Requiring a Sewer Connection - Permit Only
Plans for connections to existing storm and/or sanitary sewers for commercial, industrial,
public or private non-residential projects, for parking areas and for multiple-dwelling projects
with paved areas shall show thereon:
1. Location, size and elevations of the existing sanitary, storm or combined sewer to
which connections for the project are to be made.
2. The location, size and elevation of the required sanitary sewer connection at the point
of origin.
3. The location, size and elevations of proposed storm drainage facilities.
4. Existing and proposed grade elevations with limits and direction of stormwater
flows tributary to drainage facilities within the property.
5. Private sewers requiring permits from municipalities, the City of St. Louis, or
St. Louis County may require project approval by such municipality or the County
prior to submittal of permit application to the District.
Revised 2/15/2015 15
1.040.05 Return of Plans Without Review
Plans lacking the required information or those that are difficult to read or interpret due to
poor drafting, poor arrangement or poor writing, will be returned without review for
correction, additional information, or redrafting as may be required.
1.040.06 Return of Plans for Revision
On completion of the review, one set of plans or a letter with comments with requested
revisions and notations will be returned to the Engineer for revision of the original tracings.
The assigned District reference number and Base Map number shall be shown in or near the
Title Block upon resubmittal of the plans. Additional sets of plans for further review or final
approval will then be requested.
1.040.07 Failure to Revise or Correct Plans Promptly
Plans returned to the Owner's Engineer for revision, correction or additional information shall
be modified and returned to the District within one year for final approval or the project will
be considered abandoned. Further review will be continued only upon resubmittal as a new
project, complete with all necessary data, submittal fee, review fee, etc.
1.040.08 Fees for Review
See Chapter 9 for fees required for plan submittal and approval.
1.050 Plan Requirements
1.050.01 Drawing Sizes
Plan sizes shall be uniform for each set. Where practical, plan and profile sheets 24" x 36" are
preferred. No drawings shall exceed 36" x 42". When the sheet size is considerably smaller
than 24" x 36", a size which is a multiple of 8½" x 11", or 11” x 17” is preferred for filing
convenience. White line prints on blue background will not be approved. Good drafting
practice, either manual or automated, at a suitable scale to facilitate the plan review and field
construction shall be followed. The scale for a residential subdivision shall be a minimum of
fifty (50) feet to the inch. The District reserves the right to require a larger scale to improve
clarity. Not-to-scale (NTS) details are very strongly discouraged, and may be rejected.
1.050.02 Plans Submitted Shall Include:
1. Location of the project with respect to arterial roads, local streets, or subdivisions.
2. Key map of the entire project to scale, showing easements, sewer lines and facilities,
both existing and to be constructed.
3. Recorder of Deeds book and page from City of St. Louis or St. Louis County for
existing recorded easements when not part of a recorded subdivision plat.
4. Plans and profiles of each sewer line, channel or retaining wall showing location,
size, flowline elevations, design flows for all segments, construction gradients,
hydraulic grade lines, materials, proposed and original ground lines, boring
information and rock elevations along the proposed sewer line, location, depths and
sizes of adjacent or crossing sewer lines and utilities and special construction
requirements such as a concrete cradle or encasement, type of backfill, strength class
of pipe, etc. Sanitary or combined sewer profiles shall include the following
information for each lateral connection: station, side (LT or RT), Lot Number,
Basement Lowest Finished Floor Elevations and Property Address.
Revised 2/15/2015 16
5. All elevations shall be based upon U.S.G.S. datum with location of the benchmark
indicated on the plans.
Acceptable benchmarks include those established by the District, St. Louis County
Department of Highways and Traffic, Missouri State Highway and Transportation
Department, or City of St. Louis Street Department. To convert from the City of St.
Louis datum to U.S.G.S. datum, add 413. 69 feet to City of St. Louis datum (relates
to Sandy Hook, New Jersey MSL.).
6. Profiles and typical cross-sections of existing and proposed swales, ditches or
channels.
7. Details of special structures, channel improvements, culverts, transitions, headwalls,
aprons and junction chambers, all adequately detailed and dimensioned, including
placement of steel in reinforced concrete structures. Unless otherwise indicated,
standard the District structures are assumed to be utilized.
Use of not-to-scale (NTS) details will generally not be allowed. Past use and
experience has shown resulting conflicts, misperceptions and unrealized poor to even
unbuildable designs and otherwise unnecessary unexpected “field changes”. Details
“practically drawn to scale” however, may use NTS, if key elevations and
dimensions are shown.
8. A drainage area map showing original and proposed topography with drainage areas
identified.
9. A subdivision plat, dimensioned and substantially complete and ready for filing.
10. The location of all utilities anticipated to be encountered during construction shall be
shown. Plans must be submitted to all utility companies for verification of conflicts.
Storm and sanitary sewers shall be located to comply with State laws and regulations
governing such placement.
11. Plans must contain sufficient and verifiable, record information regarding size and
location of existing water taps and their use to the project (to be used-in-place or
destroyed) and the size of any proposed domestic water services and including
service line(s), meter(s) and tap(s) to mains.
12. Details of all structural and non-structural best management practices (BMPs) for
meeting water quality requirements.
13. Easement and other required exhibits and associated text, including specialized ones
(e.g. pump station easements).
1.060 Storm Drainage Design Data, Maps and Computation
(Also see Part 4 "Design Requirements For Storm Drainage Facilities")
1.060.01 General Criteria:
The project drainage area map or maps shall accurately show the watershed boundary lines
and areas tributary to each inlet, sewer and channel section. The established elevations,
gradients and contours of the finished graded surfaces and streets shall be shown in support of
the inlet drainage area lines and indicated directions of flow. The information shown shall be
the same as given on a development plat usually required by financing agencies, which shows
the project, the dwellings, streets, walks, finish grades at corners of the buildings, finish
Revised 2/15/2015 17
contours, street elevations and gradients, inlet, sewer and utility locations. Sufficient
information showing locations, elevations, cross-sections of downstream watercourses,
channels, sewers, culverts, structures and adjoining land shall be provided to determine the
effects of the stormwater discharge and the possible needs for special easement requirements
and/or downstream drainage modifications or protection.
1.060.02 Basic Design Data To Include:
1. Rainfall frequency.
2. Tributary area in acres with percentage of imperviousness.
3. Runoff factor(s) used.
1.070 Sanitary Sewer Design Data, Maps and Computations
(Also see Part 3 "Design Requirements For Sanitary Sewers")
1.070.01 General Criteria:
Sufficient information shall be provided as to location, elevations, sizes, slopes, capacities,
downstream pump stations and treatment facilities of the proposed project.
1.070.02 Basic Design Data To Consider:
1. Delineation of land use type(s).
2. Persons per dwelling unit.
3. Average and peak flow rate per person and per non-residential connection.
4. Commercial/Industrial User Wastewater Survey Letter (if applicable) if required.
5. Population equivalent for industrial/commercial areas, schools, parks, hotels/motel
institutions, and/or public buildings.
6. Point of connection to existing or proposed sewer and capacity of outfall system,
including effects on next pump station downstream if one exist.
7. Allowances for future extension of proposed sewer to serve upstream areas of the
watershed shall include both capacity and physical access. Lowest floor elevations
of homes near the project or along an outfall line may be required.
8. Treatment facility to receive flows.
9. Some sources of useful equivalents are in parts of the 10 State Standards, MDNR,
the District Design and planning factors, et cetera.
Revised 2/15/2015 18
2. DEFINITIONS
2.010 Definitions [See Amendment 2]
In addition to words and terms that may be defined elsewhere in this manual, the following words and terms shall have the
meanings defined below:
AASHTO: American Association of State Highway and Transportation Officials.
Allowable Release Rate: The pre-development or existing condition peak flow corresponding to a
selected rainfall frequency event.
Backfill: The material used to fill an excavation.
Base Flood: The flood having a one (1) per cent chance of being equaled or exceeded in
any given year. (The base flood, adopted by the Federal Emergency
Management Agency (FEMA), is the 100-year flood.)
Bedding: The material on which the pipe or conduit is supported and protected.
BMP: “Best Management Practices”. Structural and non-structural stormwater
management methods designed to improve stormwater quality by meeting
pollutant removal goals; to reduce minimize increases in stormwater runoff
volume and discharge rate from a site; and, for certain features appropriate
designs, to provide a degree of channel protection. [See Amendment 2]
B.O.D.: "Biochemical Oxygen Demand"; the quantity of oxygen utilized in the
biochemical oxidation of organic matter in 5 days as determined by
Standard Methods and expressed in milligrams per liter.
Board: The Board of Trustees of the District.
Building Structure: Walled or roofed building that is principally above ground, as well as a
manufactured home, and a gas or liquid storage tank that is principally
above ground.
Channels: A natural or artificial water course.
Channel Protection Storage Volume: The storage needed for extended detention of the one-year 24-hour storm
event to reduce erosion and sediment in natural water courses.
Combined Flow: A combination of stormwater and wastewater.
Combined Sewer: A sewer receiving both surface runoff and wastewater.
Common Lateral: A lateral serving more than one property or unit owner, including the
potential for same.
Condominiums: Multiple residential or commercial units in a building where each unit is
separately owned.
Culvert: A closed conduit for the free passage of surface drainage water under a
highway, railroad, or other embankment.
Curve, Long: A curve having a centerline length of curve equal to or greater than one
hundred fifty (150) feet.
Revised 2/15/2015 19
Curve, Short: A curve having a centerline length of curve of less than one hundred fifty
(150) feet.
Dedication: The process by which the owner gives approved sanitary, combined and/or
storm sewers and facilities to the District for public use and maintenance.
Detention: (See Sanitary Detention)
(See Stormwater Detention)
Developed Runoff Rate: The peak flow corresponding to a selected rainfall event as a result of
developed site conditions.
Differential Runoff Rate: The difference between the pre-developed runoff rate and the developed
runoff rate normally using PI factors.
Differential Volume of The amount of differential stormwater volume
Stormwater: between the pre-developed and developed runoff rates which the detention
basin must detain (hold).
Director: The Executive Director of the District or his properly authorized agents.
District: The Metropolitan St. Louis Sewer District.
Drainage Facility: Any system of artificially constructed drains, including open channels and
sewers used to convey stormwater, surface or groundwater, either
continuously or intermittently to natural watercourses.
Drop: A structural configuration where flow falls into a structure from an
incoming pipe.
Engineer: A registered Professional Engineer currently certified by law in the State of
Missouri.
FEMA: Federal Emergency Management Agency.
Flood Insurance Floodway Maps: Current maps from the Federal Emergency Management Agency Flood
Insurance Study.
Flood Insurance Study: The Official Report provided by the Federal Emergency Management
Agency containing flood profiles; flood boundaries; floodway maps and the
water surface elevation of the base flood.
Flood Plain: A geographic area susceptible to periodic inundation from the overflow of
natural waterways during the base (100-year) flood.
Flood Plain Study: An Engineering analysis to determine the hydraulic effect, if any, of the
proposed development to the existing Flood Plain.
Floodway: The channel of a river or other watercourse and the adjacent land areas that
must be reserved in order to discharge the base flood without cumulatively
increasing the water surface elevation more than one foot and so delineated
in the Flood Insurance Study.
Force Main: A pressurized sewer carrying wastewater.
Revised 2/15/2015 20
Foulwater Drops: A structure permitting sanitary flow to pass from an incoming pipe at a
higher elevation to an outgoing pipe at a lower elevation.
Freeboard: The difference in elevation (expressed in feet) between the hydraulic grade
line elevation and (1) the inlet sill elevation; or (2) the top of structure
elevation; or (3) the top of channel bank elevation; or (4) the top of wall
elevation.
House Lateral: Private sewer from building drain to the public sewer. This shall include the
connection to the sewer.
Hydraulic Grade Line: A line coinciding with the level of flowing water at any given point along
an open channel; or the level to which water would rise in a vertical tube
connected to any point along a pipe or closed conduit flowing under
pressure.
HS-10: The live truck wheel loads as designated by the AASHTO Specifications.
HS-20: The live truck wheel loads as designated by the AASHTO Specifications.
Industrial Waste Survey: the District Form to be submitted to the Environmental Compliance
Department of the District for review and recommendations.
Inlet Time: The overland flow time for runoff to reach the inlet.
Intrados: The inside top of the sewer pipe.
Lateral Sewer: A sewer that discharges into a branch or other sewer and has no other
common sewer tributary to it.
Low Sill: The lowest elevation of any opening in a building.
Main Sewer: The principal sewer to which branch sewers and submains are tributary;
also called trunk sewers.
MDNR: The Missouri Department of Natural Resources.
MSD: The Metropolitan St. Louis Sewer District.
“n” Value: A dimensionless coefficient used in the Mannings Equation to account for
frictional losses in steady uniform flow.
Ordinance: An Ordinance duly adopted by the Board of Trustees of the District.
Outfall: The point location or structure where wastewater or drainage discharges.
PAC: Permit Application Center (of St. Louis County).
Person: Any individual, firm, proprietorship, partnership, company, municipality,
association, society, corporation, group, or other entity.
Plan of the District: The document also known as the “Charter” of the Metropolitan St. Louis
Sewer District, as approved by the voters on February 9, 1954.
Pre-Developed Runoff Rate: The amount of flow from an existing site prior to new development or
improvements as computed by the Rational Formula.
Revised 2/15/2015 21
Prismatic Channel: A channel characterized by uniform cross sections and constant bottom
slope.
Private Sewer: A sewer not accepted for public maintenance as determined by the District.
PSDR: Pump Station Design Requirements
Public Sewer: A sewer, which has been accepted for public maintenance by the District.
Reach: A distance, in pipe or channel, between two identified points.
Resolution: Any Resolution duly adopted by the Board of Trustees of the District.
Sampling Appurtenance: A manhole or a riser section “T” installed on the buildings private lateral
for purposes of monitoring wastewater discharged.
Sanitary Detention: An “On-Site” private facility to collect and store the sanitary wastewater of
a development for such time as may be required until it can be pumped or
otherwise discharged into the downstream sanitary sewer system.
Sanitary Sewer: A sewer which carries wastewater.
Semi-Public: A governmental, institutional, educational or municipal building, structure
or facility.
Separate Sewer: A sewer intended to receive only wastewater or stormwater runoff.
Sewer: A pipe or closed conduit carrying wastewater, stormwater or a combination
thereof.
Sinkhole: A topographic depression with no natural surface drainage outlet.
Springline: The line or plane in which an arch rises from its impost. In circular
conduits, the horizontal plane through the midpoint of the section.
Standard Details of Sewer Construction: Plans of structures or devices or construction details commonly used on
District work and referred to on the plans or in the specifications.
Steady Flow: The quantity of water passing a cross section is constant, i.e.; has patterns
and magnitudes which do not vary with time.
Stormwater Detention: A stormwater runoff facility or feature designed to detain (hold) stormwater
temporarily during and immediately after a runoff event. [See Amendment
2]
Stormwater Quality Management Facility: A stormwater runoff facility or feature designed to improve quality of
and/or reduce volume of stormwater runoff (generally referred to as a
BMP). These facilities, to be approved, must properly use appropriate
techniques and features as approved by MSD over time and for intended
water quality and/or volume reduction strategies and compliance goals.
[See Amendment 2]
Stormwater Sewer: A sewer which carries surface runoff and subsurface waters.
Swale: A broad, shallow water course.
Revised 2/15/2015 22
Time of Concentration: Consists of inlet time plus the travel time in the sewer or channel from the
most remote point in the watershed to the point under consideration.
Travel Time: The time it takes for the runoff to flow through the drainage system from
one point of reference to the next point of reference.
Trunk Sewer: The principal sewer to which branch sewers and subtrunks are tributary;
also called main sewers.
Uniform Flow: The flow in a channel, conduit or pipe, having a uniform cross section and
velocity at every location within a given reach.
U.S.G.S.: United States Geological Survey.
Utilities: Public service facilities for supplying gas, electricity, water, power, steam,
cable T.V., telephone and fiber optic communication, railway
transportation, and the like. Sewers are not considered utilities.
Wastewater: The spent water of a community.
Watercourse: A stream of water or a natural channel through which water may flow.
Water Quality Volume: The storage needed to capture and treat runoff from 90% of the recorded
daily rainfall events to reduce stormwater nonpoint source pollution.
Wunnenberg’s: A commercial street guide, published by St. Louis Area Maps, Inc., for the
St. Louis Metropolitan Area.
Zero Increase Rate: A routed release rate for a 24-hour storm, which represents no allowed
increase in peak discharge.
Revised 2/15/2015 23
3. DESIGN REQUIREMENTS FOR SANITARY SEWERS
3.010 General
This section gives the minimum technical design requirements of the District for sanitary sewerage and sewage treatment
facilities. Adherence to these will expedite review and approval of plans. In general, the formulae presented herein for
hydraulic design represent acceptable procedures not necessarily to the exclusion of other sound and technically
supportive formulae. Any departure from these design requirements should be brought to the attention of the District and
discussed before submission of plans for approval, and should be justified. All construction details pertaining to sanitary
sewer improvements shall be prepared in accordance with the District Standard Construction Specifications unless
otherwise noted.
3.020 General Requirements of Sanitary Sewer Construction
All sanitary sewers shall meet the following general requirements:
3.020.01 Size and Shape
The minimum diameters of pipe for combined sewers shall be twelve (12) inches, and for
sanitary sewers, eight (8) inches. Sewers shall not decrease in size in the direction of the flow.
Circular pipe sewers shall be used for all sizes of sanitary sewers.
3.020.02 Materials
All materials shall conform to the District Standard Construction Specifications, including
periodically updated “Approved Materials”. Trench backfill material for sewers beneath street
pavement may be as required by the local jurisdiction for the street pavement and its
maintenance. That shall not alter standard pipe bedding, cradling or immediate pipe covering
procedures or materials, however, unless otherwise specifically approved by MSD.
3.020.03 Bedding
The project Plans and Project Specifications shall indicate the specific type or types of
bedding, cradling, or encasement required in the various parts of the sanitary sewer
construction if different than the current the District Standard Construction Specifications.
Special provisions shall be made for pipes laid under or over fills or embankments in shallow
or partial trenches either by specifying extra strength pipe for the additional loads due to
differential settlement, or by special construction methods, including ninety (90%) modified
proctor compaction of fill, to prevent or to minimize such additional loads.
Compacted granular backfill shall be required in all trench excavation within public (or
private) streets rights-of-way or areas where street rights-of-way are anticipated to be
dedicated for public use. Under areas to be paved, the compacted granular backfill shall be
placed to the subgrade of the pavement. Under unpaved areas, the compacted granular
backfill shall be placed to within two (2) feet of the finished surface, and generally not more
than two (2) feet beyond street pavement or curb lines. Local street jurisdiction shall govern,
where more stringent.
Pipes having a cover of less than three (3) feet shall be encased in concrete, or a stronger pipe
be used, unless otherwise directed by the District.
If the storm and sanitary sewers are parallel and in the same trench, the upper pipe shall be
placed on a shelf and the lower pipe shall be bedded in compacted granular fill to the flow line
of the upper pipe.
Revised 2/15/2015 24
3.020.04 Pipe or Conduit Under Streets and Pavements
Any pipe or conduit material beneath a highway, road, street, or pavement, or with reasonable
probability of being so located, shall have ample strength for all vertical loads, including the
live load required by the highway authority having jurisdiction, but in no case shall provide for
less than an AASHTO HS-20 loading. For other locations, the minimum live load shall be the
HS-10 loading. Special considerations may be required for adverse conditions. Compacted
granular backfill shall be utilized to the base of the pavement.
3.020.05 Joints
The joint type required for the type of pipe used and the application shall conform to the latest
standards set forth in the Standard Construction Specifications of the District or as approved
by the District.
3.020.06 Monolithic Structures
Monolithic reinforced concrete structures shall be designed structurally as continuous rigid
units. Wall thickness shall be 8” minimum with one row of reinforcement, horizontal and
vertical. Wall thickness 10” and greater shall require 2 rows of reinforcement, horizontal and
vertical. (Where approved, District precast structures are allowed, less steel & thickness may
be accepted).
3.020.07 Alignment
Sanitary sewer alignments are normally limited by the available easements, which in turn
should reflect proper alignment requirements.
Sanitary sewers shall be aligned:
1. To be in a straight line between structures for all pipe sewers thirty inches (30) in
diameter and smaller.
2. To be parallel with or perpendicular to the centerlines of straight streets unless
otherwise unavoidable. Deviations may be made only with approval of the District.
3. To avoid meandering, off-setting and unnecessary angular changes.
4. To make angular changes in alignment for sewers thirty (30) inches in diameter or
smaller in a manhole located at an angle point and for sewers thirty-three (33) inches
in diameter or larger, by a uniform curve between two tangents. Curves shall have a
minimum radius of ten times the pipe diameter.
5. To avoid angular changes in direction greater than necessary and any exceeding
ninety (90) degrees.
3.020.08 Location
Sanitary sewer locations are determined primarily by the requirements of service and purpose.
It is also necessary to consider accessibility for construction and maintenance, site availability
and competing uses, and effects of easements on private property.
Sanitary Sewers shall be located:
1. To serve all property conveniently and to best advantage.
Revised 2/15/2015 25
2. In public streets, roads, alleys, rights-of-way, or in sewer easements dedicated to
the District.
3. In easements on private property only when unavoidable.
4. On private property along property lines or immediately adjacent to public
streets, avoiding crossing through the property.
5. At a sufficient distance from existing and/or proposed buildings
(including footings) and underground utilities or other sewers to avoid
encroachment and reduce construction hazards.
6. To avoid interference between house connections to foul water or sanitary
sewers and stormwater sewers.
7. In unpaved or unimproved areas whenever possible.
8. To avoid, whenever possible, any locations known to be or probably to be
beneath curbs, paving or other improvements particularly when laid
parallel to centerlines.
9. To avoid sinkholes and creeks.
10. No sanitary lateral clean outs or sampling tees shall be placed within the area of the
stormwater overflow path.
3.020.09 Flowline
The flowline of sanitary sewers shall meet the following requirements:
1. The flowline shall be straight or without gradient change between the inner walls of
connected structures.
2. Gradient changes in successive reaches normally shall be consistent and
regular, with small or insignificant differences in successive reaches. Gradient
designations less than the nearest 0.001 foot per foot, except under special
circumstances and for larger sewers, shall be avoided.
3. For sanitary or combined sewers the hydraulic grade line shall not rise above the
intrados of the pipe.
4. When the grade of a sewer is twenty percent (20%) or greater, a concrete cradle or
collars is required. For grades exceeding fifty percent (50%) a special design and
Project Specifications are required.
3.020.10 Manholes
Manholes provide access to sewers for purposes of inspection, maintenance and repair. They
also serve as junction structures for connecting lines. Requirements of sewer maintenance
determine the main characteristics of manholes.
1. Manholes shall be located at changes in direction, changes of pipe size, flowline
gradient, and at junction points with connecting sewers.
Revised 2/15/2015 26
For sewers thirty-three (33) inches in diameter and larger, manholes shall be located
on special structures at junction points with other sewers and at changes of size or
gradient.
2. Spacing of manholes shall not exceed four hundred (400) feet for pipe sewers thirty-
six (36) inches in diameter and smaller, five hundred (500) feet for pipe sewers forty-
two (42) inches in diameter and larger, except under special approved conditions.
Spacing shall be approximately equal, whenever possible.
In addition, street access manholes should be located at a spacing of not more than
1200 feet apart to facilitate sewer maintenance requirements. “Street access
manholes” are those manholes in or adjacent to a paved street accessible to MSD.
3. Manholes on sanitary and combined sewers ten (10) inches through thirty-six (36)
inches shall be a minimum of forty-eight (48) inches in diameter and/or have a square
bottom section with sides of forty-eight (48) inches, depending on the sewer
diameter. Manholes on sewers eight (8) inches in diameter shall have a minimum
bottom section of forty-two (42) inches. Manholes on sewers greater than thirty-six
(36) inches in diameter shall be built in accordance with the Standard Specifications.
4. At stream and channel crossings, manholes shall be located on both sides of the
crossing at changes in pipe material. The manholes shall be a minimum of ten (10)
feet from the top of the bank on both sides of the crossing.
5. All manholes on sanitary sewers that are built within the 100-year flood limits, the
stormwater overflow path, or in other areas determined to be subject to flooding shall
be provided with lock type watertight manhole covers.
6. Manholes for sanitary or combined sewers shall be precast concrete or poured in
place type and waterproofed on the exterior, as approved by the District.
3.020.11 Sewage Treatment Facilities
1. New treatment plants will not be allowed.
2. Treatment using a septic system for continued use of an existing individual residence
may be considered only where the District determines that no public sanitary sewer is
available. Replacement of a burned down or otherwise destroyed individual
residence may also be so considered, but only if an affidavit is provided from an “A”
rated insurance company to show non-arson and claims approval for residence
replacement. Approval from the local Plumbing Authority will be required.
Availability of sanitary sewers is assumed if any point on the property to be served is
within a distance of two hundred (200) feet of a public sanitary sewer. In any case,
the District will make the final determination based on specific site conditions.
3. Septic systems will not be allowed for a property or a lot size less than three (3)
acres.
4. For new or replacement construction or development, including residential, refer to
1.020.03
Revised 2/15/2015 27
3.030 Design Requirements
3.030.01 General
All sanitary sewers shall be designed and constructed as to conform to these design
requirements. Hydraulic calculations must be submitted as part of the plan review for all
public sewer construction. Calculations must be submitted for the existing and ultimate
upstream development condition.
3.030.02 Gradients
The following minimum slopes of sanitary pipe sewers are those giving at least three (3) feet
per second velocities flowing full, based on Manning's formula using an "n" value of 0.013
unless otherwise directed by the District. Slopes greater than these minimums shall be used
wherever possible.
For sewers with a design grade less than one percent (1%), field verification of the pipe grade
will be required for each installed reach of sewer, prior to any surface restoration or
installation of any surface improvements.
The District may require the submittal of revised hydraulic calculations for any sewer reach
having an as-built grade flatter than the design grade by more than 0.1%. Based on a review
of this hydraulic information, the District may require the removal and replacement of any
portion of the sewer required to ensure sufficient hydraulic capacity and cleansing velocity of
the system.
Pipe Size Minimum Slope in Ft.
per 100 Ft. (% Grade)
6 (house lateral)* 2.0
8 1.0
10 0.6
12 0.6
15 0.4
18 0.3
21 0.3
24 0.2
27 0.2
30 0.2
36 0.1
Pipes larger than thirty (36) inches in diameter shall maintain a cleansing velocity of three (3)
feet per second.
3.030.03 Depth and Minimum Cover
Sewer depths shall be determined primarily by the requirements of pipe or conduit size, utility
obstructions, required connections, future extensions, and adequate cover. The minimum depth
requirements shall be as follows:
1. For sewers which may be extended in the future, the minimum depth shall be nine (9)
feet below the finish grade to flowline, except where upstream topography indicates
that this depth is not necessary as determined by the District.
Revised 2/15/2015 28
2. The minimum depth of sewers shall be not less than three (3) feet plus the sewer
diameter. The flowline of the sewer must have a vertical distance from the low point
of a basement or low floor of not less than 2.5 feet plus the sewer diameter. *The
minimum depth shall be increased as required to insure a minimum of two percent
(2%) slope and 2.5 feet of cover for a six (6) inch house lateral.
3. At stream and channel crossings, a minimum depth of two (2) feet shall be allowed
where greater depths cannot be achieved. Where this minimum cover can not be
achieved, Schedule 50 ductile iron pipe with Field Lok Mechanical restrained joints
or approved equal must be used from manhole to manhole unless otherwise directed
by the District. Stream and channel crossings must be protected with rock blanket or
other approved stream stabilization/channel protection methods. Concrete
encasement is not an option. Aerial crossings are not allowed unless attached to a
bridge.
4. Sewer depths at manholes shall be sufficient to ensure the use of standard manholes.
Special manholes will only be allowed upon approval by the District.
3.030.04 Flow Design
All lateral and sub-main or collecting sewers shall be designed on the basis of an average per
capita use of not less than one hundred (100) gallons per day, and on that basis shall be
designed with capacities of four hundred (400) gallons per capita per day at peak flow unless
otherwise directed by the District. Sanitary flow from day schools with gymnasiums, showers
and cafeterias shall be computed on the basis of thirty (30) gallons per capita per day
discharged in eight (8) hours. On this basis the daily peak flow rate shall be 90 x 4 gallons per
capita per day for the lateral sewers. Sanitary flow from tourist camps and trailer courts shall
be computed on the basis of 2.5 persons per each unit for each twenty four (24) hour period at
fifty (50) gallons per capita per day times a peak factor of four (4). Sanitary flow from
apartments, boarding schools and condominiums and other smaller facilities shall be computed
at the same rate as residential property. Sanitary flow from all other types of institutions,
commercial property, industrial plants, etc., shall be separate and individual studies based on a
conservative ultimate anticipated flow multiplied by the peak factors applicable to each case.
In the case of industrial flow, when the rate and volume can be predetermined with a
reasonable degree of accuracy, no dilutions or diminishing factor shall be applied against this
flow in the outfall, sub-trunk or trunk sewers.
3.030.05 Population Factors
Family population factors for the various areas in the District are to be determined from the
latest United States Census Tracts. An acceptable figure is 3.7 persons per household unit.
3.030.06 Sanitary Flow Table
Population Unit Cu. Ft./Sec.
One Person @ 400 G/D 0.00062
One Household Unit @ 3.7 Persons 0.00229
@ 400 G/C/D
Where G/C/D = Gallons per Capita per Day
Basic Formula:
Flow in Cu. Ft./Sec. = Population x Flow(in G/C/D) / 646,317
Revised 2/15/2015 29
3.030.07 Hydraulic Grade Line
1. Hydraulic Grade Line Limits
The hydraulic grade line for sanitary and combined sewers shall not rise above the
pipe intrados.
The beginning point for the hydraulic grade line computations shall be the higher
(i.e. more conservative) elevation as determined below:
For connection to existing pipe systems
a. Top of pipe intrados at least two reaches downstream of the connection
point to the existing system; or
b. The hydraulic grade line computed for the existing system, especially where
the downstream system has suspected or known lack of capacity issues.
Field verified structure and flowline elevations, pipe sizes and
characteristics shall be used.
2. Computation Methods
Sanitary or combined sewers shall be designed to flow not more than 80% full at
ultimate peak design flow conditions. The hydraulic grade line shall be computed to
show its elevation at manholes, transition structures, and junction points of flow in
pipes, and shall provide for the losses and the differences in elevations as required
below.
a. Friction Loss
The major energy loss in a sanitary or combined sewer will be the energy
loss due to friction. It is determined by the equation:
hf = L x Sh
Where:
hf = difference in water surface elevation, or in length L
L = length in feet of pipe
Sh = hydraulic slope required for a pipe of
given diameter and for a given roughness
"n", expressed as feet of slope per foot of
length
From Manning's formula:
Sh = [(V)(n) /(1.486 R0.667)]2
Where:
R = hydraulic radius of pipe or conduit in feet
V = velocity of flow in feet per second
Revised 2/15/2015 30
n = Manning's value for coefficient of roughness; where
n = .013 for concrete, vitrified clay and plastic pipe;
n = .012 for concrete pipe greater than forty eight (48)
inches in diameter
b. Curve Loss
Curve loss in pipe flow is the additional head required to maintain the
required flow because of curved alignment, and is in addition to the friction
loss of an equal length of straight alignment. If concrete pipe, it may be
evaluated from Figure 4-2 which includes an example.
c. Turn Loss
Head losses in manholes due to change in direction of flow (turns) will be
determined in accordance with the following:
Multiplier of
Change in Direction Velocity Head of
of Flow (A) Water Being Turned (K)
90 Deg. 0.7
60 Deg. 0.55
45 Deg. 0.47
30 Deg. 0.35
15 Deg. 0.18
0 Deg. 0.0
Other Angles By Interpolation
Formula: HL = K(VL)2/2g
Where:
HL = Feet of head lost in manhole due to change in direction of pipe flow
A
MainManhole
DIAGRAM
Revised 2/15/2015 31
VL = Velocity of flow in pipe in Ft/Sec
g = Acceleration of gravity, 32.2 Ft/Sec/Sec
K = Multiplier of Velocity Head of water
being turned
d. Junction Chamber Loss
A sewer junction occurs for large pipes or conduits too large to be brought
together in a forty two (42) inch diameter manhole where one or more
branch sewers enter a main sewer. Allowances should be made for head
loss due to curvature of the paths and due to impact at the converging
streams.
Losses in a junction chamber for combining large flows shall be minimized
by setting flowline elevations so that pipe centerlines (spring lines) will be
approximately in the same planes.
At junction points for combining large flows, a manhole with a slotted or
lock-down cover shall be required depending on the type of sewer.
A computation method for determining junction chamber losses is
presented below:
Hj = ∆y + Vh1 - Vh2
Where:
Hj = junction chamber loss
∆y = change in hydraulic grade line through
the junction in feet
Vh1 = upstream velocity head
Vh2 = downstream velocity head
Where:
y = [(Q2V2)-((Q1V1) + (Q3V3CosӨ3) + (QnVnCosӨn))]
0.5(A1+A2)g
Where:
Q2 = Discharge in cfs at the exiting conduit
V2 = Velocity in fps at the exiting conduit
A2 = Cross section area of flow in sq. ft. for the exiting conduit.
Q1 = Discharge in cfs for the incoming pipe (main flow)
V1 = Velocity of fps for the incoming pipe (main flow)
A1 = Cross sectional area of flow in sq. ft. for the incoming pipe
(main flow)
Q3,Qn = Discharge(s) in cfs for the branch pipe(s)
V3,Vn = Velocity(ies) in fps for the branch pipe(s)
Ө3, Өn = The angle between the axes of the exiting pipe and the
branch pipe(s)
g = Acceleration of gravity, 32.2 ft/sec/sec.
Revised 2/15/2015 32
Where:
Ө= The angle between the axes of the outfall and the incoming pipe(s)
e. Losses at Junctions of Several Flows in Manholes
The computation of losses in a manhole with several flows entering the
structure should utilize the principle of the conservation of energy. This
involves both the elevation of water surface and momentum (mass times the
velocity head). Thus, at a manhole with two or more incoming pipes, the
sum of the energy content for inflows is equal to the sum of the energy
content of the outflows plus the additional energy required by the
turbulence of the flows passing through the structure.
DIAGRAM:
The upstream hydraulic grade line may be calculated as follows:
Hu = [VD2/2g]-[((QU/QD)(1-K)(VU2/2g))+((QL1/QD)(1-K)(VL12/2g))+
((QLN/QD)(1-K)(VLN2 /2g))] + HD
Where:
HU = Upstream hydraulic grade line in feet
QU = Upstream main line discharge in cubic feet per
second
QD = Downstream main line discharge in cubic feet per
second
QL1-QN =Pipe discharges in cubic feet per second
VU = Upstream main line velocity in feet per second
VD = Downstream main line velocity in feet per second
VL1-VLN =Pipe velocities in feet per second
HD = Downstream hydraulic grade line in feet
K = Multiplier of Velocity of Water being turned
g = Acceleration of gravity, 32.2 ft/sec/sec
The above equation does not apply when two (2) almost equal and opposing
flows, each perpendicular to the downstream pipe, meet and no other flows
exist in the structure. In this case the head loss is considered as the total
velocity head of the downstream discharge.
Revised 2/15/2015 33
f. Transition Loss
The relative importance of the transition loss is dependent on the velocity
head of the flow. If the velocity and velocity head of the flow are quite low,
the transition losses cannot be very great. However, even small losses may
be significant in flat terrain. The sewer design shall provide for the
consideration of the necessary transitions and resulting energy losses. The
possibility of objectionable deposits is to be considered in the design of
transitions.
For design purposes it shall be assumed that the energy loss and changes in
depth, velocity and invert elevation, if any, occur at the center of the
transition. These changes shall be distributed throughout the length of the
transition in actual detailing. The designer shall carry the energy head,
piezometric head, and invert as elevations, and work from the energy grade
line.
(1) Closed Conduits
Transitions in small sewers may be confined within a manhole.
Special structures may be required for larger sewers. The energy
loss in a transition shall be expressed as a coefficient multiplied by
the change in velocity head ()V2/2g) in which )V is the change in
velocity before and after the transition. The coefficient may vary
from zero to one, depending on the design of the transition.
If the areas before and after a transition are known, it is often
convenient to express the transition loss in terms of the area ratios
and either the velocity upstream or downstream.
For an expansion:
HL = K(V1-V2)2/2g ≈ {K(V1)2/2g}[1-(A1/A2)]2
in which HL is the energy loss; K is a coefficient equal to 1.0 for a
sudden expansion and approximately 0.2 for a well-designed
transition, and the subscripts 1 and 2 denote the upstream and
downstream sections, respectively, i.e., A1 = Area Before
Transition and A2 = Area After Transition.
For a contraction:
HL = K[(V2)2/2g][(1/Cc)-1]2 ≈ K[(V2)2/2g][1-(A2/A1)]2
in which K is a coefficient equal to 0.5 for a well-designed
transition, Cc is a coefficient of contraction, and the other terms
and subscripts are similar to the previous equation. Losses in
closed conduits of constant area are expressed in terms of (V2/2g).
The above equations may be applied to approximate the energy
loss through a manhole for a circular pipe flowing full. If the
invert is fully developed, that is, semi-circular on the bottom and
vertical on the sides from one-half depth up to the top of the pipe,
for the expansion A1/A2 = 0.88, and for the contraction A2/A1 =
0.88. The expansion is sudden; therefore, K = 1. The contraction
Revised 2/15/2015 34
may be rounded if the downstream pipe has a bell or socket. In
this case, K may be assumed to be 0.2.
The expansion energy loss is 0.014 [(V1)2/2g] and the contraction
energy loss is 0.010 [(V2)2/2g]. Thus it may be seen that if the
invert is fully developed, the manhole loss is small.
3.030.08 Infiltration [See Amendment 4]
An additional amount of flow due to infiltration shall be evaluated. All sanitary sewers shall
be limited to a maximum of one two hundred (100) (200) gallons per inch of diameter per
day per mile of line, as required by MDNR Specifications, when tested by appropriate water of
low pressure air testing. In addition, there shall be no visible leaks.
3.030.09 Special Situations and Design Requirements [See Amendments 4 and 6]
l. Connections to Manholes
a. Foulwater drops are required only for sewers containing sanitary flow and then
only when it is necessary that sanitary flow enter a manhole at a height more
than two (2) feet above its flowline. If an inside drop is to be used, a forty-eight
(48) inch diameter manhole is required. However, new inside drops are
generally, no longer allowed. Sewer lines shall not enter the manhole in the
transition conical section, or through a joint. The slope on incoming pipes
should be limited to a maximum one percent (1%) for inside drops; slopes
greater than this require an outside drop structure. Incoming pipe, upstream of
an outside drop, should be limited to a maximum slope of 5%. Manhole inverts
should be shaped to assure proper flow through drop structures. The largest size
to be used for an outside drop is twelve (12) inches.
b. If it is necessary to enter a manhole with a force main this should be done within
twelve (12) inches of the flowline of the manhole, and the manhole invert should
be shaped to insure proper flow through the structure. Consideration shall be
given to the detention time of the sewage in the force main, and the potential
detrimental effects of the release of hydrogen sulfide from the force main on the
concrete structure of the manhole. Where it is determined that the release of
hydrogen sulfide may be a problem, the concrete manhole shall be protected by
a liner or epoxy coating. All existing manholes will have steps removed prior to
the installation of any form of protective sealant, such as epoxy coatings or
plastic liners. All new manholes will not have steps installed if the structure is to
be sealed from H2S exposure. Connection of a public force main to a manhole
will require that protections for at least one manhole and possibly as many as
five (5) downstream. Connection of a private forced lateral may require some
similar protection.
c. The number of sewers coming into one manhole should be kept to a minimum.
A special detail may be required to assure the proper constructability and
maintenance of the structure, especially for larger pipes, angled approaches or
multiple incoming pipes.
d. Pipes entering and exiting manholes at the flowline should project toward the
center of the structure and the manhole invert should be shaped to assure proper
flow through the structure.
e. Private house lateral connections should be made to the main sewer, at existing
wyes of record. In the absence of a wye, connect to the public sewer pipe using
Revised 2/15/2015 35
another approved method, and not to the manholes unless an 8 inch private
lateral connecting to an 8 inch public sewer.
f. All connections to sanitary manholes are subject to the District review and
approval and will be made at the District's discretion.
g. Connections to existing structures may require rehabilitation or reconstruction of
the structure being utilized. This work will be considered part of the project
being proposed.
2. Adjusting Manholes to Grade
When a project requires a manhole to be adjusted to grade, a maximum of twelve
(12) inches of rise is allowed if not previously adjusted. When adjustments to raise
or lower a manhole are required, the method of adjustment must be stated on the
project plans and approved by the District.
3. Swimming Pools
Swimming pool backwash connections to the sanitary sewer must not exceed fifty
gallons per minute (50 gpm). Commercial swimming pools will require a Missouri
State Operating Permit.
4. Storm Sewers Crossing Over Sanitary Sewers
When a storm pipe crosses over a sanitary sewer and the vertical clearance is less
than two (2) feet, the sanitary sewer must be encased in concrete through the crossing
and for ten (10) lineal feet each side of the crossing unless otherwise directed by the
District.
5. Location in Conjunction with Water Service
Sanitary sewers and manholes shall be at least ten (10) feet horizontally from any
existing or proposed water main. On crossings, a minimum vertical clearance of
eighteen (18) inches shall be provided between the outside of the water main and
outside of the sanitary sewer. MoDNR provisions for waiver will be considered on a
case by case basis.
6. Sanitary Sampling Appurtenance
A sanitary sampling appurtenance (“T” or manhole) is required for non-residential,
commercial, and industrial projects. A sampling appurtenance shall be located on
each private building lateral, in a location readily accessible to the District personnel,
downstream from any traps, interceptors or other pretreatment facilities, and before
connection to the public sewer. Each sampling appurtenance shall be fitted with a
cover that can readily be removed for sampling access. If a locking cover is desired
for security purposes, the District’s Office of Environmental Compliance shall be
provided with any keys or special tools required to remove the cover. (See sections
1.020.04 and 1.020.06, also.)
a. For all industrial projects the sampling appurtenance shall be a standard
manhole in accordance with Chapter 3, Sections 3.020.10 or a similar structure
which affords an equivalent degree of access for the installation of flow
monitoring and sampling equipment. An industrial project is any development,
which will be occupied by an “industrial user” as defined by the District’s Sewer
Use Ordinance.
Revised 2/15/2015 36
b. For commercial projects, the sampling appurtenance shall be a minimum of a
“T” of the same diameter as the private lateral except that no sampling “T” shall
be less than six (6) inches in diameter. The District may, at its discretion, require
a standard manhole or equivalent structure, as described above in lieu of a
sampling “T” for a commercial project.
7. Abandonment of Sanitary Sewer Services
Sanitary sewer laterals, from buildings to be demolished, shall be plugged with
concrete unless the lateral is to be used for the replacement building. The lateral
shall be plugged with concrete at the foundation wall or at the last trap leaving the
building. The District need not be notified unless the lateral is being cut off or
plugged at the main sewer. A detail must be provided.
8. Private Force Main Connections
Private force lateral main connections to the public gravity sewers will only be
considered where site topography does not allow for gravity lateral service to the
sanitary sewer or the gravity extension of the sanitary sewer is not feasible. See
Chapter 13.1 for requirements for connecting into a public force main or a private
force main extending outside its property line. Make the force connection into a
public gravity sewer by one of the following two methods:
• Directly into a manhole one foot above its flowline. See Section
3.030.09.1b.
• Connect the private small diameter force main into a private 6” clean-out
assembly. From the clean-out, install a 6” gravity lateral with a two percent
slope into the public sewer through a wye connection.
For all properties, the operation and maintenance of private grinder pumps and their
pressure laterals shall be the responsibility of the property owner.
9. Oil/Gas Separators, Sand Filters, and Grease Traps [See Amendment 6]
If required by the District, grease, oil and sand interceptors or traps shall be provided
when such devices are necessary for the proper handling of liquid wastes containing
grease or oil in excessive amounts or any flammable wastes, sand, or other harmful
materials which can be trapped. Such interceptors or traps shall not be required for
private dwelling units. Prior to the installation of any interceptor or trap, drawings
and specifications shall be submitted to the District for approval. All interceptors
and traps shall be located so as to be readily accessible for cleaning and visual
inspection on influent and effluent sides. An exterior location shall be the norm.
Design of interceptors and traps shall be per local plumbing codes. Discharge of
wastewater into the MSD sewer system shall not exceed sewer use ordinance limits
and prohibitions.
Grease and oil interceptors or traps shall be constructed of impervious materials
capable of withstanding sudden and extreme changes in temperature. All such
devices shall be of substantial construction, water-tight, and equipped with easily
removable covers which, when bolted in place, shall be gas tight and watertight,
unless otherwise approved by the District.
All grease, oil and sand interceptors or traps shall be maintained in effective
operation at all times by and at the expense of the user.
Revised 2/15/2015 37
10. Coldwater Creek Gravity Elevation
In the Coldwater Creek watershed, the elevation of the lowest gravity outlet from any
building shall not be lower than U.S.G.S. Elevation 470.5.
11. Common Laterals
A common lateral will only be allowed for a building of same use, vertically stacked
condominiums, i.e. one owned unit above a unit owned by another, all residential or
commercial. For side by side, non-vertically stacked condominium units, each unit
shall have its own lateral and each lateral shall be connected directly to a public
sewer. In all other cases, each building shall be provided with a separate lateral
sewer for each use from the building to the public or private main within the
boundaries of the property line extensions. Connection of a building’s lateral to a
private sewer will only be allowed where the District determines future subdividing
without the District approval is highly unlikely, or structurally impossible per a
building code official. Free-standing commercial leaseholds which could become
outlots and any leaseholds which could be come separately owned (unstacked) will
each be connected directly and separately to a public sewer. The lateral shall be
installed in accordance with the local building code, and in a manner consistent with
these Rules and Regulations.
12. Private Lateral
Where a private sanitary sewer crosses a property line it must be immediately and
directly connected to a public sewer in the District easement or public right-of-way.
Where the receiving public sewer is immediately across the street or alley, the private
lateral may extend directly across the street or alley to it. Existing private sewers
traversing multiple properties or parts of properties shall be made public upon failure
of the existing private sewer or any further development of such properties and in the
manner described first above. New private sewers shall not serve multiple properties
beyond the property in which the private sewer originates, except where otherwise
allowed in these Rules as a common lateral. A new private sewer serving two or
more properties is not allowed. Legally recorded consolidation of multiple properties
into one property is another acceptable method of eliminating the situation.
Conversely, subdividing or other creation of multiple properties will necessitate
conforming public sewers, as part of Plat and Plan approvals, to assure the
availability of proper sewer maintenance and service for future owners.
Private sewers are not to utilize public easements or public right-of-ways for long
distances or to cross same as long diagonals. Crossings are to be kept to a minimum,
be direct and should not course in front of an adjacent owners property. Reasonable,
traditional, semi-radial patterns in cul-de-sac situations and the like may be allowed,
unless prohibited by another jurisdiction.
13. Separate Laterals and Sewers
New sewers and laterals constructed as part of all development or redevelopment
within areas served by existing combined sewers shall be separated storm and
sanitary systems. Combined sewers currently serving redevelopment areas shall be
removed or fully grout filled and abandoned, unless suitable for recycling as public
separate sewer. Construction of new combined sewers is not allowed unless approved
by the District for special cases only.
Revised 2/15/2015 38
If existing public combined sewers can be recycled as separate storm sewers with
needed capacity, then that is more desirable. However, lining or other refurbishing or
stabilization/repair may be required, especially for the very old sewers.
14. Protection from Surcharging
Due to sewer overcharge and water backup potential, building structures shall be
protected with appropriate backflow prevention measures (i.e. approved
backwater valves or strapped plumbing) as outlined in local plumbing codes.
It is noted that the District may prohibit gravity sewer service to basements in some
combined sewer areas and some known problem areas served by separate sanitary
sewers. In these situations a backwater valve will not suffice for surcharge protection
and instead strapped plumbing shall be required as directed by the District. See most
recent Figures 3-1 and 3-2.
Due to sewer overcharge and water backup potential, gravity sewer service to
basements is prohibited in some combined sewer areas and as directed by the District
in known problem areas served by separate sanitary sewers. This requirement is for
all new construction and all rehabilitation construction. Strapped plumbing and
grinder pumps serving individual basements shall be used as necessary (See Figure 4-
5). Limited variance to this rule will only be granted per the District review of project
plans. All variance requests shall be submitted as a District “P-job” for formal review
and must include elevations and demonstration of existing sewer system capacity or
other allowable relief.
15. Residential Basement Garage Flooding
Basement garages will only be allowed as directed by the District. Driveways to
basement garages shall be designed whenever possible to allow for positive drainage
away from the garage and to an acceptable location such as the street gutter. When
sump driveways are necessary and allowed by the District, gravity drains shall be
provided to intercept stormwater and discharge to an acceptable surface location or
storm or combined sewer. Pumped discharge will not be allowed. Finished floor
elevations of sump (basement) garages shall be a minimum of 1 foot below the
lowest basement finished floor elevation and sanitary sewer floor drain elevation.
The District reserves the right to deny construction of sump (basement) garages.
16. Lateral for Commercial Use
For mixed use buildings (example: commercial on lower floors, with residential on
upper floors) separate sanitary laterals shall be provided for each “use-section” of the
building (example: commercial sanitary lateral and a residential lateral). These “use-
section” sanitary laterals may be connected together on private property outside the
building limits and downstream of any external grease traps or sampling
appurtenance.
3.040 Sanitary Detention Requirements
3.040.01 Surcharged Sanitary Sewers
When it has been determined that the outfall sewer or the downstream system serving a
proposed development is overcharged, the District may require the developer to provide
Revised 2/15/2015 39
special facilities that the District deems necessary, for example, a sanitary holding tank
(detention) for eighteen (18) hours of storage, with discharge during the off-peak hours or
upgrading the downstream system to provide additional capacity.
In the design of such facilities, consideration should be given for the protection of structures
and equipment against corrosive and/or explosive gasses that may result from the detention of
sewage.
Figure 3-1
Figure 3-2
Revised 2/15/2015 42
4. DESIGN REQUIREMENTS FOR STORM DRAINAGE FACILITIES
4.010 General
Stormwater sewers or channels provide the facility for removing and transporting surface runoff produced from rainfall.
Design requirements differ from those for either sanitary or combined sewers.
This section gives the minimum technical design requirements of the District storm drainage facilities. In general, the
formulae presented herein for hydraulic design represent "acceptable" procedures not necessarily to the exclusion of other
sound and technically supportive formulae. Any departure from these design requirements should be discussed before
submission of plans for approval and should be justified. All construction details pertaining to storm sewer improvements
shall be prepared in accordance with the District Standard Construction Specifications unless otherwise noted.
4.020 General Requirements of Storm Sewer Construction
All storm sewers shall meet the following general requirements:
4.020.01 Size and Shape
The minimum diameters of pipe for stormwater or combined sewers shall be twelve (12) inches.
Sewers shall not decrease in size in the direction of the flow unless approved by the District.
Circular pipe sewers are preferred for stormwater sewers, although rectangular or elliptical
conduits may be used with special permission.
4.020.02 Materials
All materials shall conform to the District Standard Construction Specifications. Reinforced
concrete pipe joints shall be Type "A" or better, as required.
4.020.03 Bedding
The Project Plans and Specifications shall indicate the specific type or types of bedding,
cradling, or encasement required in the various parts of the storm sewer construction if different
than current the District Standard Construction Specifications.
Special provisions shall be made for pipes laid within fills or embankments and/or in shallow or
partial trenches, either by specifying extra strength pipe for the additional loads due to
differential settlement, or by special construction methods, including ninety percent (90%)
modified proctor compaction of fill to prevent or to minimize such additional loads.
Compacted granular backfill shall be required in all trench excavation within public (or private)
streets rights-of-way or areas where street rights-of-way are anticipated to be dedicated for public
use. Under areas to be paved, the compacted granular backfill shall be placed to the subgrade of
the pavement. Under unpaved areas, the compacted granular backfill shall be placed to within
two (2) feet of the finished surface, and generally not more than two (2) feet beyond street
pavement or curb lines. Local street jurisdiction shall govern where more stringent.
Pipes having a cover of less than three (3) feet shall be encased in concrete, unless otherwise
directed by the District.
The Storm and sanitary sewers are parallel and in the same trench, the upper pipe shall be placed
on a shelf and the lower pipe shall be bedded in compacted granular fill to the flow line of the
upper pipe.
4.020.04 Concrete Pipe or Conduit Strengths
Reinforced Concrete pipe shall be Class II, minimum. Any concrete pipe, conduit or culvert beneath a
street right-of-way, or with reasonable probability of being so located, shall be a minimum of Class III, but
Revised 2/15/2015 43
also shall account for all vertical loads, including the live load required by the highway authority having
jurisdiction. In no case shall the design provide for less than HS-20 loading of the AASHTO. For other
locations, the minimum design live load shall be the HS-10 loading.
4.020.05 Monolithic Structures
Monolithic reinforced concrete structures shall be designed structurally as continuous rigid units.
Generally these are poured in place units. Wall thickness shall be 8” minimum with one row of
reinforcement, horizontal and vertical. Wall thickness 10” and greater shall require 2 rows of
reinforcement, horizontal and vertical. (Where approved District precast structures are allowed, less steel
& thickness may be accepted).
4.020.06 Alignment
Sewer alignments are normally limited by the available easements, which in turn should reflect proper
alignment requirements. Since changes in alignment affect certain hydraulic losses, care in selecting
possible alignments can minimize such losses and use available head to the best advantage.
Sewers shall be aligned:
1. To be in a straight line between structures, such as manholes, inlets, inlet manholes and
junction chambers, for all pipe sewers thirty (30) inches in diameter and smaller.
2. To be parallel with or perpendicular to the centerlines of straight streets unless
otherwise unavoidable. Deviations may be made only with approval of the District.
3. To avoid meandering, off-setting and unnecessary angular changes.
4. To make angular changes in alignment for sewers thirty (30) inches in diameter or
smaller in a manhole located at the angle point, and for sewers thirty- six (36) inches in
diameter or larger, by a uniform curve between two tangents. Curves shall have a
minimum radius of ten times the pipe diameter.
5. To avoid angular changes in direction greater than necessary and any exceeding ninety
(90) degrees.
4.020.07 Location
Storm sewer locations are determined primarily by the requirements of service and purpose. It is
also necessary to consider accessibility for construction and maintenance, site availability and
competing uses, and effects of easements on private property.
Storm sewers shall be located:
1. To serve all property conveniently and to best advantage.
2. In public streets, roads, alleys, rights-of-way, or in sewer easements dedicated to the
District.
3. On private property along property lines or immediately adjacent to public streets,
avoiding diagonal crossings through the central areas of the property.
4. At a sufficient distance from existing and proposed buildings including footings, and
underground utilities or other sewers to avoid encroachments and reduce construction
hazards.
5. To avoid interference between other stormwater sewers and house connections to
foulwater or sanitary sewers.
Revised 2/15/2015 44
6. In unpaved or unimproved areas whenever possible.
7. To avoid, whenever possible, any locations known to be or probably to be beneath
curbs, paving or other improvements particularly when laid parallel to centerlines.
8. To avoid sinkhole areas if possible. However, if sinkhole areas cannot be avoided, see
sub-section 4.020.08 for requirements.
9. Crossing perpendicular to street, unless otherwise unavoidable.
4.020.08 Sinkhole Areas
1. Sinkhole Report
Where improvements are proposed in any area identified as sinkhole areas, a sinkhole
report will be required. This report is to be prepared by a Professional Engineer,
registered in the State of Missouri, with demonstrated expertise in geotechnical
engineering, and shall bear his or her seal.
The sinkhole report shall verify the adaptability of grading and improvements with the
soil and geologic conditions available in the sinkhole areas. Sinkhole(s) shall be
inspected to determine its functional capabilities with regard to handling drainage.
The report shall contain provisions for the sinkholes to be utilized as follows:
a. All sinkhole crevices shall be located on the plan. Functioning sinkholes
may be utilized as a point of drainage discharge by a standard drainage
structure with a properly sized outfall pipe provided to an adequate natural
discharge point, such as a ditch, creek, river, etc.
b. Non-functioning sinkholes and sinkholes under a proposed building may be
capped.
c. If development affects sinkholes, they may be left in their natural state;
however they will still require a properly sized outfall pipe to an adequate
natural discharge point.
d. An overland flow path shall be required for all sinkholes assuming the outfall
pipe and sinkhole become blocked.
Where the topography will not allow for an overland flow path:
1. The storm sewer shall be designed for the 100-year,
20-minute storm, and
2. If this storm pipe is smaller than thirty six (36) inches in diameter, a
designated ponding area shall be identified, assuming the pipe is
blocked, and
3. The ponding area shall be based on the 100-year, 24-hour storm, and
4. The low sill of all structures adjacent to the ponding area shall be a
minimum of two (2) feet above the 100-year highwater elevation.
5. Special siltation measures shall be installed during the excavation of
sinkholes and during the grading operations to prevent siltation of
the sinkhole crevice.
Revised 2/15/2015 45
2. Procedure for Utilization of Sinkholes
a. Excavation. Prior to filling operations in the vicinity of a sinkhole,
the earth in the bottom of the depression will be excavated to expose
the fissure(s) in the bedrock. The length of fissure exposed will
vary, but must include all unfilled voids or fissure widths greater
than one-half (1/2) inch maximum dimensions which are not filled
with plastic clay.
b. Closing Fissures. The fissure or void will be exposed until bedrock
in its natural attitude is encountered. The rock will be cleaned of
loose material and the fissures will be hand-packed with quarry-run
rock of sufficient size to prevent entry of this rock into the fissures,
and all the voids between this hand-packed quarry-run rock filled
with smaller rock so as to prevent the overlying material's entry into
the fissures. For a large opening, a structural (concrete) dome will be
constructed with vents to permit the flow of groundwater.
c. Placing Filter Material. Material of various gradations, as approved,
will be placed on top of the hand-packed rock with careful attention
paid to the minimum thicknesses. The filter material must permit
either upward or downward flow without loss of the overlying
material.
The fill placed over the granular filter may include granular material
consisting of clean (no screenings) crushed limestone with ten (10)
inch maximum size and one (1) inch minimum size or an earth fill
compacted to a minimum density of ninety percent (90%) modified
Proctor as determined by ASTM D-1557.
d. Supervision. Periodic supervision of the cleaning of the rock
fissures must be furnished by the Engineer who prepared the Soil
Report. Closing of the rock fissures will not begin until the cleaning
has been inspected and approved by that Engineer.
During the placement and compaction of earth fill over the filter,
supervision by the Engineer shall be continuous. Earth fill densities
will be determined during the placement and compaction of the fill in
sufficient number to insure compliance with the specification. The
Engineer is responsible for the quality of the work and to verify that
the specifications are met.
4.020.09 Flowline
The flowline of storm sewers shall meet the following requirements:
1. The flowline shall be straight or without gradient change between the inner walls of
connected structures; that is, from manhole to manhole, manhole to junction chamber,
inlet to manhole, or inlet to inlet.
2. Gradient changes in successive reaches normally shall be consistent and regular.
Gradient designations less than the nearest 0.001 foot per foot, except under special
circumstances and for larger sewers, shall be avoided.
Revised 2/15/2015 46
3. Sewer depths shall be determined primarily by the requirements of pipe or conduit size,
utility obstructions, required connections, future extensions and adequate cover.
4. Stormwater pipes discharging into lakes shall have the discharge flowline a minimum of
three (3) feet above the lake bottom at the discharge point or no higher than the normal
water line.
5. A concrete cradle is required when the grade of a sewer is twenty (20) percent or
greater. A special design and specification is required for grades exceeding fifty
percent (50%).
6. For sewers with a design grade less than one percent (1%), field verification of the
sewer grade will be required for each installed reach of sewer, prior to any surface
restoration or installation of any surface improvements.
7. The District may require the submittal of revised hydraulic calculations for any sewer
reach having an as-built grade flatter than the design grade by more than 0.1%. Based
on a review of this hydraulic information, the District may require the removal and
replacement of any portion of the sewer required to ensure sufficient hydraulic capacity
of the system.
4.020.10 Manholes
Manholes provide access to sewers for purposes of inspection, maintenance and repair. They
also serve as junction structures for lines and as entry points for flow. Requirements of sewer
maintenance determine the main characteristics of manholes. Cast in place or precast manhole
structures are generally allowable, though the former requires approved shop detail drawings.
1. For sewers thirty (30) inches in diameter or smaller, manholes shall be located at
changes in direction; changes in size of pipe; changes in flowline gradient of pipes, and
at junction points with sewers and inlet lines.
For sewers thirty-three (33) inches in diameter and larger, manholes shall be located on
special structures at junction points with other sewers and at changes of size, alignment
change and gradient. A manhole shall be located at one end of a short curve and at each
end of a long curve.
2. Spacing of manholes shall not exceed four hundred (400) feet for pipe sewers thirty-six
(36) inches in diameter and smaller; five hundred (500) feet for pipe sewers forty-two
(42) inches in diameter and larger, except under special approved conditions. Spacing
shall be approximately equal, whenever possible.
3. When large volumes of stormwater are permitted to drop into a manhole from lines
twenty-one (21) inches or larger, the manhole bottom and walls below the top of such
lines shall be of reinforced concrete. Special structural design may be required for large
pipes and/or large drops.
4. Manholes shall be avoided in driveways or sidewalks.
5. Connections to existing structures may require rehabilitation or reconstruction of the
structure being utilized. This work will be considered part of the project being
proposed.
6. When a project requires a manhole to be adjusted to grade a maximum of twelve (12)
inches of rise is allowed if not previously adjusted. When adjustments to raise or lower
a manhole is required, the method of adjustment must be stated on the project plans and
approved by the District.
Revised 2/15/2015 47
4.020.11 Overflow/Design System
The "design" components of the drainage system include the inlets, pipe, storm sewers, and
improved and unimproved channels that function during typical rainfall events. The "overflow"
system comprises the major overflow routes such as swales, streets, floodplains, detention basins,
and natural overflow and ponding areas.
The purpose of the overflow system is to provide a drainage path to safely pass flows, which
cannot be accommodated by the design system without causing flooding of adjacent structures.
The criteria for the design of the overflow and design systems shall be as follows:
1. The "design" system shall be designed in accordance with Section 4.030.
2. The "overflow" system shall be designed for the 100-year, 20-minute event, assuming
the "design" system is completely blocked. The capacity of the "overflow" system shall
be verified with hydraulic calculations at critical cross-sections. The "overflow" system
shall be directed to the detention facility, or as approved by the District.
3. The low sill of all structures adjacent to the "overflow" system swales shall be above
the 100-year highwater elevation.
4. Where the topography will not allow for an overland flow path:
a. The storm sewer shall be designed for the 100-year, 20-minute storm, and
b. If this storm pipe is smaller than thirty-six (36) inches in diameter, a
designated ponding area shall be identified, assuming the pipe is blocked, and
c. The ponding area shall be based on the 100-year, 24-hour storm, and
d. The low sill of all structures adjacent to the ponding area shall be above the
100-year highwater elevation.
5. The "overflow" system shall be designated on the drainage area map and on the grading
plan.
6. All overflow systems will be considered on a site specific basis.
7. The stormwater design for projects within designated levee districts such as Monarch-
Chesterfield, Earth City and Riverport will be based on the Stormwater Master Plan for
these districts.
4.030 Stormwater Design Criteria
4.030.01 Flow Quantities
Flow quantities are to be calculated by the "Rational Method" in which:
Q = API
where:
Q = runoff in cubic feet per second
A = tributary area in acres
I = Average intensity of rainfall (inches per hour) for a given period and a
given frequency
P = runoff factor based on runoff from pervious and impervious surfaces
Revised 2/15/2015 48
P (Runoff Factors) for various impervious conditions are shown in Table 4-1.
P.I. values for various impervious conditions are shown in Table 4-2.
1. Rainfall Frequency
A twenty (20) year rainfall frequency is to be used in the City of St. Louis and areas of
St. Louis County where combined sewers are used. A fifteen (15) year rainfall
frequency is to be used in areas of St. Louis County where storm sewers are separated
from sanitary sewers. In the design of local storm sewer systems, a twenty (20) minute
time of concentration shall be used. Figure 4-1 gives rainfall curves for 2, 5, 10, 15, 20
and 100 year frequencies.
2. Impervious Percentages and Land Use
Minimum impervious percentages to be used are as follows:
a. For manufacturing and industrial areas, 100%*
b. For business and commercial areas, 100%*
c. For residential areas, including all areas for roofs of dwellings and garages;
for driveways, streets, and paved areas; for public and private sidewalks; with
adequate allowance in area for expected or contingent increases in
imperviousness:
In apartment, condominium and multiple dwelling areas: 75%*
In single family areas:
1/4 Acre or less 50%
1/4 Acre to 1/2 Acre 40%
1/2 Acre to 1 Acre 35%
One acre or larger Calculate impervious percentage*
Playgrounds (Non-Paved) 20-35%*
d. For small, non-perpetual charter cemeteries,
allow 30%
For parks and large perpetual charter cemeteries 5%
*NOTE: Drainage areas may be broken into component areas, with the
appropriate run-off factor applied to each component, i.e. a proposed
development may show one hundred percent (100%) impervious for paved
areas and five percent (5%) impervious for grassed areas. Use of actual
component areas may be required, however, where minimum impervious
percentages are deemed misleading, or too approximate.
The design engineer shall provide adequate detailed computations for any proposed,
expected or contingent increases in imperviousness and shall make adequate allowances
for changes in zoning use. If consideration is to be given to any other value than the
above for such development, the request must be made at the beginning of the project,
must be reasonable, fully supported, and adequately presented, and must be approved in
writing before its use is permitted.
Although areas generally will be developed in accordance with current zoning
requirements, recognition must be given to the fact that zoning ordinances can be
Revised 2/15/2015 49
amended to change the currently proposed types of development, and any existing use.
Under these circumstances the possibility and the probability of residential areas having
lot sizes changed or re-zoned to business, commercial, or light manufacturing uses
should be given careful consideration.
e. Average 20-minute values of P.I. (cfs per acre) to be used are as follows:
Percent 20 Minute Duration
Imperviousness 15 Year 20 Year
5 1.70 1.78
10 1.79 1.87
20 2.00 2.09
30 2.19 2.28
40 2.39 2.50
50 2.58 2.69
90 3.36 .. 3.50
100 3.54 3.70
*Roofs (City of St. Louis) 6.0
*Roofs 4.2 (Other than City of St. Louis)
*For Direct Connection to Sewer
3. Reduction in P.I. with Time and Area
Reduction in P.I. values for the total time of concentration exceeding twenty (20)
minutes, and for tributary areas exceeding three hundred (300) acres will be allowed only
in trunk sewers and main channels. The reduced average P.I. value for the tributary area
shall not be less than the value determined as follows on the basis of:
a. Time. As the time of concentration increases beyond twenty (20) minutes,
select the appropriate P.I. value from Table 4-1. The travel time through a
drainage channel should be based on an improved concrete section. These
reduced values shall be used unless a further reduction is allowed for area.
b. Area. As the total tributary area at any given location in a channel increases in
excess of three hundred (300) acres, the P.I. value may be further reduced by
multiplying it by an area coefficient "Ka". (The area coefficient is obtained
from data in a special study of a major storm in the St. Louis area by the U.S.
Corps of Engineers.) The average rainfall rate, for a given storm, for a given
period for the tributary area, is less than the corresponding point value as
determined from recording rainfall gauges. The curve data is as follows:
P.I. Coefficients Ka
Area (Abscissas) "Ka" (Ordinates)
300 to 449 Acres 1.00
450 to 549 Acres .99
550 to 749 Acres .98
750 to 999 Acres .97
1000 to 1280 Acres .96
1281 to 1600 Acres .95
1601 to 1920 Acres .92
1921 to 2240 Acres .91
Revised 2/15/2015 50
4.030.02 Hydraulic Grade Line for Closed Conduits
1. Computation Methods
The hydraulic grade line is a line coinciding with (a) the level of flowing water at any
given point along an open channel, or (b) the level to which water would rise in a
vertical tube connected to any point along a pipe or closed conduit flowing under
pressure.
The beginning point for hydraulic grade line computations for storm sewers shall be at
least the higher of the elevations listed in 3.030.07.1. Field-verification shall also apply.
The hydraulic grade line shall be computed to show its elevation at all structures and
junction points of flow in pipes, conduits and open channels, and shall provide for the
losses and the differences in elevations as required below. Since it is based on design
flow in a given size of pipe or conduit or channel, it is of importance in determining
minimum sizes of pipes within narrow limits. Sizes larger than the required minimum
generally provide extra capacity, however consideration must still be given to the
respective pipe system losses.
There are several methods of calculating "losses" in storm sewer design. The following
procedures are presented for the engineer's information and consideration.
It is expected that the design will recognize the reality of such "losses" occurring and
make such allowances, as good engineering judgment requires.
a. Friction Loss
The hydraulic grade line is affected by friction loss and by velocity head
transformations and losses. Friction loss is the head required to maintain
the required flow in a straight alignment against frictional resistance
because of pipe or channel roughness. It is determined by the equation:
hf =L x Sh
Where:
hf = difference in water surface elevation, or head in feet in length L
L = length in feet of pipe or channel
Sh = hydraulic slope required for a pipe of given diameter or channel of given cross-
section and for a given roughness "n", expressed as feet of slope per foot of length
From Manning's formula: Sh = [V n /(1.486 R0.667)]2
Where:
R = hydraulic radius of pipe, conduit or channel (feet)
(Ratio of flow area/wetted perimeter)
V = velocity of flow in feet per second (fps)
n = Manning's value for coefficient of roughness
Use:
n = .013 for pipes of concrete, vitrified clay, and PVC pipe
n = .012 for formed monolithic concrete, i.e., vertical wall channels, box culverts and for
R.C.P. over 48" in diameter
n = .015 for concrete lining in ditch or channel
Revised 2/15/2015 51
inverts and trapezoidal channels
n = .020 for grouted riprap lining on ditch or channel side slopes
n = .033 for gabion walled channels
Note:
"n" will have a weighted value for composite lined channels.
"n" values for unlined channels to be determined on an individual basis.
b. Curve Loss
Curve loss in pipe flow is the additional head required to maintain the required
flow because of curved alignment, and is in addition to the friction loss of an
equal length of straight alignment. It should be determined from Figure 4-2,
which includes an example.
c. Entrance Loss at Terminal Inlets
Entrance loss is the additional head required to maintain the required flow
because of resistance at the entrance. The entrance loss at a terminal inlet is
calculated by the formula:
Hti = (V2/2g)
Where: V = Velocity in flow of outgoing pipe
g = Acceleration of gravity (32.2 Ft/Sec/Sec)
d. Turn Loss
Head losses in structures due to change in direction of flow (turns) in a
structure, will be determined in accordance with the following:
Multiplier of
Change in Direction Velocity Head of
of Flow (A) Water Being Turned (K)
90 Deg. 0.7
60 Deg. 0.55
45 Deg. 0.47
30 Deg. 0.35
15 Deg. 0.18
0 Deg. 0.0
Other Angles By Interpolation
Revised 2/15/2015 52
DIAGRAM:
Formula: HL = K(VL)2/2g
Where:
HL = Feet of head lost in manhole due to change in direction of lateral flow
VL = Velocity of flow in lateral in Ft/Sec
g = Acceleration of gravity, (32.2 Ft/Sec/Sec)
K = Multiplier of Velocity Head of water being turned
e. Junction Chamber Loss
A sewer junction occurs for large pipes or conduits too large to be brought
together in the usual forty two (42) inch diameter manhole or inlet where one
or more branch sewers enter a main sewer. Allowances should be made for
head loss due to curvature of the paths and due to impact at the converging
streams.
Losses in a junction chamber for combining large flows shall be minimized by
setting flowline elevations so that pipe centerlines (springlines), will be
approximately in the same planes.
At junction points for combining large storm flows, a manhole with a slotted
cover shall be provided.
A computation method for determining junction chamber loses is presented
below:
Hj = y + Vh1 - Vh2
Where:
Hj = junction chamber loss (ft.)
Vh1 = upstream velocity head
Vh2 = downstream velocity head
y = change in hydraulic grade line through the
junction in feet
Where:
Revised 2/15/2015 53
y = [(Q2V2)-((Q1V1) + {(Q3V3Cos θ3) + (QnVnCosӨn)})]
0.5(A1+A2)g
Where:
Q2 = Discharge in cubic feet per second (cfs) at the exiting conduit
V2 = Velocity in feet per second (fps) at the exiting conduit
A2 = Cross sectional area of flow in sq. ft. for the exiting conduit
Q1 = Discharge in cfs for the incoming pipe (main flow)
V1 = Velocity in fps for the incoming pipe (main flow)
A1 = Cross sectional area of flow in Sq. Ft
for the incoming pipe (main flow)
Q3,Qn = Discharge(s) in cfs for the branch lateral(s)
V3,Vn = Velocity(ies) in fps for the branch lateral(s)
Ө3, Өn = The angle between the axes of the exiting pipe and the branch
laterals(s)
g = Acceleration of gravity (32.2 ft/sec/sec)
Where:
Ө = is the angle between the axes of the outfall and the incoming laterals
f. Losses at Junctions of Several Flows in Manholes and/or Inlets
The computation of losses in a manhole, inlet or inlet manhole with several flows
entering the structure should utilize the principle of the conservation of energy.
This involves both the elevation of water surface and momentum (mass times the
velocity head). Thus, at a structure (manhole, inlet or inlet manhole) with
laterals, the sum of the energy content for inflows is equal to the sum of the
energy content of the outflows plus the additional energy required by the
turbulence of the flows passing through the structure.
DIAGRAM:
Revised 2/15/2015 54
The upstream hydraulic grade line may be calculated as follows:
Hu = [VD2/2g]-[((QU/QD)(l-K)(VU2/2g))+((QL1/QD)(l-K)(VL12/2g))
+((QLN/QD)(l-K)(VLN2/2g))] + HD
Where:
HU = Upstream hydraulic grade line in feet
QU = Upstream main line discharge in cubic feet
per second
QD = Downstream main line discharge in cubic feet
per second
QL1-QLN = Lateral discharges in cubic feet per second
VU = Upstream main line velocity in feet per second
VD = Downstream main line velocity in feet per
second
VL1-VLN= Lateral velocities in feet per second
HD = Downstream hydraulic grade line in feet
K = Multiplier of Velocity of Water being turned
g = Acceleration of gravity, 32.2 ft/sec/sec
The above equation does not apply when two (2) almost equal and opposing flows, each
perpendicular to the downstream pipe, meet and no other flows exist in the structure. In this case
the head loss is considered as the total velocity head of the downstream discharge.
g. Transition Loss
The relative importance of the transition loss is dependent on the velocity
head of the flow. If the velocity and velocity head of the flow are quite low,
the transition losses cannot be very great. However, even small losses may be
significant in flat terrain. The sewer design shall provide for the consideration
of the necessary transitions and resulting energy losses. The possibility of
objectionable deposits is to be considered in the design of transitions.
For design purposes it shall be assumed that the energy loss and changes in
depth, velocity and invert elevation, if any, occur at the center of the
transition. These changes shall be distributed throughout the length of the
transition in actual detailing. The designer shall carry the energy head,
piezometric head (depth in an open channel), and invert as elevations, and
work from the energy grade line. Because of inherent differences in the flow,
transitions for closed conduits will be considered separately from those for
open channels.
(1) Closed Conduits
Transitions in small sewers may be confined within a manhole.
Special structures may be required for larger sewers. If a sewer is
flowing surcharged, the form and friction losses are independent of
the invert slope; therefore, the transition may vary at the slopes of the
adjacent conduits. The energy loss in a transition shall be expressed
as a coefficient multiplied by the change in velocity head (V2/2g) in
which V is the change in velocity before and after the transition.
The coefficient may vary from zero to one, depending on the design
of the transition.
Revised 2/15/2015 55
If the areas before and after a transition are known, it is often
convenient to express the transition loss in terms of the area ratios
and either the velocity upstream or downstream.
For an expansion:
HL = K(V1-V2)2/2g≈[K(V1)2/2g][1-(A1/A2)]2
in which HL is the energy loss; K is a coefficient equal to 1.0 for a sudden
expansion and approximately 0.2 for a well-designed transition and the subscripts
1 and 2 denote the upstream and downstream sections, respectively, i.e., A1 =
Area Before Transition and A2 = Area After Transition.
For a contraction:
HL = [K(V2)2/2g][(1/Cc)-1]2≈[K(V2)2/2g][1-(A2/A1)]2
in which K is a coefficient equal to 0.5 for a well-designed transition, Cc is a
coefficient of contraction, and the other terms and subscripts are similar to the
previous equation. Losses in closed conduits of constant area are expressed in
terms of (V2/2g).
The above equations may be applied to approximate the energy loss through a
manhole for a circular pipe flowing full. If the invert is fully developed, that is,
semi-circular on the bottom and vertical on the sides from one-half depth up to
the top of the pipe, for the expansion (A1/A2) = 0.88, and for the contraction
(A2/A1) = 0.88. The expansion is sudden; therefore, K = 1. The contraction may
be rounded if the downstream pipe has a bell or socket. In this case, K may be
assumed to be 0.2.
The expansion energy loss is 0.0l4 [(V1)2/2g] and the contraction energy loss is
0.010 [(V2)2/2g]. If the invert is fully developed, the manhole loss is small, but if
the invert is only developed for one-half of the depth, or not at all, the losses will
be of considerable magnitude.
(2) Open Channel Transitions
The hydraulics of open channel transitions are further complicated
by possible changes in depth. As a first approximation to the energy
loss, unless a jump occurs, the equations given above may be used
with a trial-and-error solution for the unknown area and velocity.
The K value for a well-designed expansion should probably be
increased to 0.3 or 0.4. Whether the properties of the upstream or
downstream section will be known will depend on the characteristics
of the flow and the channel, but can be determined by a profile
analysis. In transitions for supercritical flow, additional factors shall
be considered. Standing waves of considerable magnitude will be
produced in transitions. The height of these waves must be estimated
to provide a proper channel depth. In addition, in long transitions,
air entrainment will cause bulking of the flow with resultant greater
depths of the air-water mixture.
4.030.03 Hydraulic Grade Line Limits
The hydraulic grade line shall not rise above the following limits as determined by flow quantities
calculated per Section 4.030.01. Stormwater conveyance systems are usually designed for 15 year or 20
year, 20 minute rainfall frequencies per 4.030.01.1.
Revised 2/15/2015 56
1. The hydraulic grade line at any inlet or storm manhole shall not be higher than two (2)
feet below the inlet sill or top of manhole.
2. Storm sewers shall not flow with greater than three (3) feet of head.
3. The hydraulic grade line for combined sewers shall not rise above the pipe intrados.
4. The beginning point for the hydraulic grade line computations shall be the higher (i.e.
more conservative) elevation as determined below:
a. For connection to existing pipe system:
(1) Top of pipe intrados of at least two reaches downstream of the connection
point of the existing system; or
(2) The hydraulic grade line computed for the existing system.
b. For connection to channels or ditches:
(1) Top of pipe intrados of the proposed pipe, or
(2) The hydraulic grade line computed for the channel or ditch as approved
by the District.
c. For upstream system pipe connection to dry and wet detention basins:
(1) The starting hydraulic grade line for all incoming pipes shall be the 100
year-24 hour blocked low flow water surface elevation, where County
maintained streets are located adjacent to or upstream of the basins.
(2) The starting HGL for all other situations may be the 100 year – 24 hour
unblocked low flow water surface elevation, unless the local road
authority requires something higher.
5. When storm sewers are designed to convey 100 year flows, effusion at low lying inlets is
not allowed, unless 100 year ponding easements are so delineated, granted, and recorded.
Those associated temporary “ponding” easements however, should not be confused with
100 year overland flow paths, for which no conveyance area easements are presently
required. Also, such intentional effusive designs may be prohibited for St. Louis County
maintained streets or highways.
4.030.04 Inlets
Inlets function entirely as entry points for stormwater flow. They also may be constructed to serve as a
manhole on separate stormwater sewers, and are then termed inlet-manholes. Steep gradients may give
such low inlet capacities that additional inlets should be located at more favorable grade locations or
special inlets designed for steep gradients must be used. Provision must be made to control by-pass flow
and to provide additional capacity in the inlet and line affected by such increased flow. Six (6) inch open
throat inlets should be used at all times. The open throat should not be obstructed or otherwise restricted
by bars, wires or screens.
Grated inlets, without an open throat or other provision for overflow shall be avoided except under
exceptional conditions, and are prohibited in grade pockets. Any exceptions shall be used only with
District approval.
Curb inlets shall be placed at street intersections or driveways such that no part of the inlet structure or
sump is within the curb rounding.
Revised 2/15/2015 57
1. Inlets are shown in the Standard Details of Sewer Construction. The minimum depth
of a terminal inlet is four (4) feet from the top of the inlet to the flowline of the
outlet pipe. Greater depth shall be used for intermediate inlets if necessary for the
required depth of the hydraulic grade line. Trapped inlets shall have the depth
shown in the Standard Details of Sewer Construction.
2. Inlet capacity should not be less than the quantity flow tributary to the inlet and by-
pass flow shall be avoided whenever possible. “Multiple type” inlets, used in the
past, had one integral chamber shallower than the other chamber, and tops of
different size stones, as well. Use of “multiple type” inlets is prohibited for new
construction, as are bars, screens, or wires across inlet openings. Use “double inlets”
instead, if necessary for capacity. Bypass, if unavoidable, must be identified,
including amount and spread; local road jurisdiction approval must also be provided.
Inlets at low points or grade pockets should have extra capacity to compensate for
possible flow by-pass of upstream inlets.
Figure 4-3 shows inlet capacity/maximum gutter capacity with a given gutter line
grade and flow. Inlets angled in opposition to direction of vehicular travel may be
dangerous and are to be avoided.
3. Connections to existing structures may require rehabilitation or reconstruction of the
structure being utilized. This work will be considered part of the project being
proposed.
4. Grated trough drains will not be accepted for dedication to the District. Where
appended to the District curb inlet structures, design shall provide clear and
workable separation for purposes of maintenance responsibility by others for their
part of the drain.
4.030.05 Open Channels
*NOTE: This section contains some excerpts relating to design and are attributed to Open
Channel Hydraulics by Ven Te Chow, a McGraw-Hill work published in 1959.
All open channels shall meet the following requirements:
1. Size and Shape
Open channels shall not decrease in size in the direction of flow. Open channels shall be
vertical walled except in special cases where other approved materials are being
considered.
2. Materials
Channels may be constructed with reinforced concrete or other approved material.
Gabions, articulated mattresses or other systems may be approved. However, the District
shall have the right to approve or disapprove any channel material and shall select the
appropriate channel material if a proposed material is rejected. Swales shall be sodded
unless velocities are excessive (greater than 5 fps or where velocities are less than 2 fps
causing deposition of soil particles, then concrete swales may be used. Swales used as
BMP’s shall be appropriately vegetated and maintained, or otherwise stabilized in an
approved manner.
Revised 2/15/2015 58
3. Bedding
Special provisions shall be made for channels or paved swales laid over fill on non-
supportive soils to support the channel on paved swales. Pipes extended to the channel in
a fill area shall have compacted crushed limestone bedding for support.
4. Structural Considerations
Provision must be made for all loads on the channel.
5. Alignment
Open channel alignments may be limited by available easements, physical topography,
existing utilities, buildings, residential development, maintenance access and roadways.
6. Locations
Storm channel locations are determined primarily by natural drainage conditions. It is
also necessary to consider accessibility for construction and maintenance, site availability
and competing uses, and evaluating effects of easements on private property.
Storm channels shall be located:
a. To serve all adjacent property conveniently and to best advantage.
b. In easements or rights-of-way dedicated to the District.
c. In easements on common ground when feasible.
d. On private property along property lines or immediately adjacent to public
streets, avoiding crossings through the property.
e. At a sufficient distance from existing and proposed buildings and underground
utilities or sewers to avoid future problems of flooding or erosion.
f. To avoid interference between stormwater sewers and house connections to
foulwater or sanitary sewers.
g. In unpaved or unimproved areas whenever possible.
h. Crossing perpendicular to streets, unless unavoidable.
7. Flowline
The flowline of open channels shall meet the following requirements:
a. Gradient changes shall be kept to a minimum and be consistent and regular.
b. Gradient designations less than the nearest 0.001 foot per foot shall be avoided.
c. Channel and swale depths shall be determined primarily by the requirements of
the channel size, utility obstructions and any required connections.
8. Other Open Channel Considerations and Requirements
a. All natural channels and ditches shall be improved unless otherwise authorized
by the District.
Revised 2/15/2015 59
b. Drainage within private property should be controlled to prevent damage to the
property crossed. Swales, or broad shallow grass lined ditches with non-erosive
slopes, are generally located at or near rear lots and along common property
lines. If a paved gutter is utilized, then appropriate erosion protection shall be
used at both ends.
c. Drainage channels and water courses draining through a subdivision shall be
enclosed if the required pipe size does not exceed sixty (60) inches unless a BMP
plan is approved which incorporates the channel specifically. Drainage channels
originating within a project site are encouraged to be incorporated into the
development’s stormwater management plan. When it is undesirable or
impractical to enclose a channel with a pipe across a road or street, a suitable
bridge or culvert shall be required.
d. For flows greater than 4 cfs, area inlets or inlet manholes are required to intercept
the gutter or swale flow unless part of a workable, recognized and approved
BMP.
e. All improved concrete channels shall have a forty eight (48) inch chain link fence
on each side of the channel, or other protective measures as directed by the
District.
f. Channels and water courses draining large areas shall be located in rights-of-way
or easements previously approved by the District as a part of an adequate overall
plan for drainage.
9. Design Limitations
a. The flow quantity shall be calculated by the method presented in Section
4.030.01 of this manual.
b. If the channel is within an area designated in a community's flood insurance
study, then the channel shall also meet all District and the community's floodplain
requirements.
c. Other agencies of jurisdiction, for example FEMA or MoDNR, may have
requirements which must be met. A U.S. Army Corps of Engineers permit may
be required for any construction affecting a watercourse.
10. Hydraulic Grade Line
a. Computation Methods
In open channels the water surface is identical with the hydraulic grade line. The
hydraulic grade line shall be computed throughout the channel reach to show its elevation
at junctions with incoming pipes or channels and at the ends of the channel reach under
consideration. It shall also provide for the losses and differences in elevations as
required below. Since it is based on design flow in a given channel, it is of importance in
determining minimum sizes within narrow limits. The depth at which the actual flows
will occur is controlled by the two end conditions of the reach considered, and by the
relationship between the energy available and by the energy required to overcome the
losses that are encountered along the channel.
There are several methods of calculating "losses" in channel design. The following
procedures are presented for the engineer’s information and consideration.
Revised 2/15/2015 60
It is required that the design recognize the reality of such "losses" occurring and make
such allowances as good engineering judgment indicates.
(1) Control Sections
The engineer should locate all possible control sections for the reach in question.
A control section refers to any section at which the depth of flow is known or can
be controlled to a required stage. At the control section, flow must pass through
a control depth which may be the critical depth, the normal depth or any other
known depth. Three types of control sections include (a) Upstream Control
Section; (b) Downstream Control Section; (c) Artificial Control Section, which
occurs at a control structure, such as a weir, dam, sluice gate, roadway
embankment, culvert, bridges or at the confluence with a major river or stream.
(2) Friction Loss
The friction loss may be calculated by the same procedure as is presented in
(3) Flow in Curved Channels
The centrifugal force caused by flow around a curve produces a rise in the water
surface on the outside wall and a lowering of the inner wall. This phenomenon is
called superelevation. The flows tend to behave differently according to the state
of flow.
In subcritical flow, friction effects are of importance, whereby in supercritical
flow, the formation of cross-waves is of major concern.
(a) Curve Losses
Curve losses may be estimated from Figure 4-2 by replacing D, diameter,
with b, width of channel.
(b) Superelevations
In addition to curve losses, an evaluation of superelevations should be
considered and, if required, an allowance made in the top elevation of
outside wall. Equations are presented below which may be used to
determine the superelevation at channel bends.
1) Trapezoidal Channels
Subcritical Flow:
ΔHw = 1.15(V2/2grc)[b+D(ZL+ZR)]
Supercritical Flow:
ΔHw = 2.6(V2/2grc)[b+D(ZL+ZR)]
2) Rectangular Channels
Subcritical Flow:
ΔHw = (V2b/2grc)
Supercritical Flow:
ΔHw = (V2b/grc)
Where:
ΔHw = Change in water height above the
Revised 2/15/2015 61
centerline water surface elevation.
V = Average velocity of design
flow in Fps
g = Acceleration of gravity (32.2
Ft/Sec/Sec)
rc = Radius of curve on horizontal
alignment in feet
b = Base width of channel in feet
D = Depth of flow in straight channel
ZL = Left side slope (ft/ft)
ZR = Right side slope (ft/ft)
(4) Transitions
Transitions should be designed to accomplish the required change in
cross section with as little flow disturbance as possible.
The following features are to be considered in design of transition
structures.
(a) Proportioning
For a well designed transition, the following rules should be used:
1) The optimum maximum angle between the channel axis
and a line connecting the channel sides between the
entrance and exit sections is 12.5o.
2) Sharp angles in the structure should be avoided.
(b) Losses
The energy loss in a transition consists of the friction loss and the
conversion loss. The friction loss may be estimated by the
Manning Formula. The conversion loss is generally expressed in
terms of the change in velocity head between the entrance and
exit sections of the structure.
Ht = Kt ΔVH
Where:
Ht = Conversion loss
Kt = Coefficient of head loss
in transition
ΔVH = Absolute change in
velocity head
Average design values for Kt are presented in the table below:
Contracting Expanding
Type of Transition Section Section
Warped 0.10 0.20
Wedge 0.20 0.50
Cylinder-quardrant 0.15 0.25
Revised 2/15/2015 62
Straight Line 0.30 0.50
Square End 0.40 0.75
See Figure 4-4 for sketches of each type of transition.
(c) Freeboard
A transition shall have a minimum of one (1) foot of freeboard
above the hydraulic grade line.
(d) Hydraulic Jump
The existence of a hydraulic jump in a transition may become
objectionable, and the design of the transition should be checked
for such.
(e) Sudden Enlargement and Contraction
A sudden enlargement results when an intense shearing action
occurs between incoming high-velocity jet and the surrounding
water. As a result, much of the Kinetic energy of the jet is
dissipated by eddy action. The head loss at a sudden enlargement,
HLe, is:
HLe = Ke( ΔV2/2g)
Where:
Ke = Coefficient of head loss
for enlargements = 1
ΔV = Change in velocities
between incoming and
outgoing sections
g = Acceleration of gravity
(32.2 Ft/Sec/Sec)
The flow in a sudden contraction is
first contracted and then expanded
resulting in high losses as compared
to a sudden enlargement. Thus the
head loss at a sudden contraction,
HLc, is:
HLc = Kc( ΔV2/2g)
Where:
Kc = Coefficient of head loss
for contractions = 0.5
ΔV = Change in velocities
between incoming and
outgoing sections
g = Acceleration of gravity,
Revised 2/15/2015 63
(32.2 Ft/Sec/Sec)
(5) Constrictions
A constriction results in a sudden reduction in channel cross section. The effect
of the constriction on the flow depends mainly on the boundary geometry, the
discharge and the state of flow. When the flow is subcritical, the constriction will
induce a backwater effect that extends a long distance upstream. If the flow is
supercritical, the disturbance is usually local and will only affect the water
adjacent to the upstream side of the constriction. A control section may or may
not exist at a constriction. The control section, when it exists, may be at either
side of the constriction (upstream or downstream), depending on whether the
slope of the constricted channel is steep or mild. The entrance and outlet of the
constriction then acts as a contraction and an expansion, respectfully.
(6) Obstructions
An obstruction in open-channel flow creates at least two paths of flow in the
channel. Typical obstructions include bridge piers, pile trestles, and trash racks.
The flow through an obstruction may be subcritical or supercritical.
b. Hydraulic Grade Line Limits
(1) The hydraulic grade line at any point along a channel shall not be higher
than one (1) foot below the top of the channel wall.
(2) The hydraulic grade line at any point along a channel shall not cause the
hydraulic grade limits of the storm sewer system to be exceeded as stated
in Section 4.030.03 of this manual.
11. Hydraulic Jump
When flow changes from the supercritical to subcritical state, a hydraulic jump may
occur. A study should be made on the height and location of the jump, and for discharges
less than the design discharge, to ensure adequate wall heights extend over the full ranges
of discharge.
12. Open Channel Junctions
a. General
(1) Consideration shall be given in the design of open channel
junctions to the geometry of the confluence of flows in order to
minimize undesirable hydraulic effects due to supercritical
velocities.
b. Confluence Design Criteria
(1) The momentum equation can be applied to the confluence design
if the below stated criteria is used.
(2) The design water-surface elevations in the two joining channels
should be approximately equal at the upstream end of the
confluence.
Revised 2/15/2015 64
(3) The angle of the junction intersection can vary from 0-12 degrees.
(4) The width of the main channel shall be expanded below the
junction to maintain approximate flow depths throughout the
junction.
(5) Flow depths should not exceed ninety percent (90%) of the
critical depth.
13. Erosion Protection
Properly designed rock blankets, minimum one (1) foot thick, shall be required at each
end of the improved channel. The minimum length of the rock blanket shall be twenty
five (25) feet. A rock toe wall, minimum two (2) foot deep, shall be constructed at the
free end of each blanket. Alternative erosion protection products may be considered,
such as articulated block mattresses, etcetera.
14. Sanitary Sewer Crossings
The characteristics of any sanitary sewer crossing shall be given consideration in the
design of the channel floor.
4.030.06 Culverts
The design of culverts shall include consideration of many factors relating to requirements of hydrology,
hydraulics, physical environment, imposed exterior loads, construction and maintenance.
With the design discharge and general layout requirements determined, the design requires
detailed consideration of such hydraulic factors as shape and slope of approach and exit
channels, allowable head at entrance (and ponding capacity, if appreciable), tailwater levels,
hydraulic and energy gradelines, and erosion potential.
1. Hydraulic Design
The hydraulic design of a culvert for a specified design discharge involves (1) selection of a type
and size, (2) determination of the position of hydraulic control, and (3) hydraulic computations to
determine whether acceptable headwater depths and outfall conditions will result. Hydraulic
computations will be carried out by standard methods based on pressure, energy, momentum and
loss considerations.
2. Entrances and Headwalls - Outlets and Endwalls
Where an existing culvert is to be extended, the possibility for maintaining or improving existing
capacity should be investigated. Marked improvement may be obtainable by proper entrance
design. All culverts shall be designed for possible extension unless there are extenuating
circumstances.
4.040 Bridges
Bridges shall be designed to meet the current criteria of the governing agencies.
4.040.01 Waterway Capacity and Backwater Effects
Sufficient capacity will be provided to pass the runoff from the design storm determined in accordance
with principles given elsewhere in this manual.
Revised 2/15/2015 65
4.040.02 Clearance
The lowest point of the bridge superstructure shall have a (freeboard) clearance of two (2) feet above
design water surface elevation for the 15-year frequency in St. Louis County (20-year frequency in
the City of St. Louis) and one (1) foot for the 100-year frequency.
4.040.03 Waterway Alignment
The bridged waterway will be aligned to result in the least obstruction to stream flow, except that for
natural streams consideration will be given to future realignment and improvement of the channel.
4.040.04 Erosion Protection
To preclude failure by scouring, abutment and pier footings will usually be placed either to a depth of not
less than five (5) feet below the anticipated depth of scour, or on firm rock if such is encountered at a
higher elevation. Large multispan structures crossing alluvial streams may require extensive pile
foundations. To protect the channel, revetment on channel sides and/or bottom, consisting of concrete or
grouted rock blanket should be placed as required. The governing authority should be contacted
regarding their design requirements.
4.050 Outlet Erosion Protection
If outlet velocities exceed 5 fps, an appropriate erosion protection must be provided. Erosion protection may be required at
outlets where velocities are less than 5 fps if soil conditions warrant.
For paved channels a cutoff wall will be required at the termini with appropriate protection. The cutoff wall shall extend a
minimum depth of two (2) feet into the existing ground line.
4.060 Limitations on Areas Draining Across Sidewalks or Driveways [Deleted by Amendment 4]
In the City of St. Louis, per Ordinance No. 60664, up to three thousand (3,000) square feet of parking area may discharge via
a driveway to the public or private street. An additional three thousand (3,000) square feet may discharge into a public alley.
Areas larger than this must have any excess area discharge into interceptor basins as set forth in the (City of St. Louis)
Plumbing Code.
In unincorporated areas of St. Louis County, area inlets shall be required to intercept overland flows greater than 1 cfs to
prevent that flow from crossing sidewalks or curbs.
4.070 Impervious Areas - In City of St. Louis [Deleted by Amendment 4]
Any area which is to be paved, repaved, expanded or otherwise improved, that is over three thousand (3,000) square feet in
area, whether presently paved or not, shall at such time as it is to be paved, repaved, expanded or be otherwise improved, be
provided with storm water drainage facilities constructed in accordance with plans and specifications submitted to and
approved by the District.
Such approval is a pre-requisite of the City of St. Louis for acceptance of an application for the paving or any other
construction necessary to bring an impervious area into compliance with City of St. Louis Ordinance 52552 as amended. Any
impervious area, less than three thousand (3,000) square feet in area, shall not require on-site storm water drainage facilities.
The area draining toward the rear alley is counted separately from the area draining toward the street, in actual practice, if
both are receiving flow.
4.080 General Performance Criteria for Stormwater Management
4.080.01 When Required
1. The requirements of stormwater quantity and quality management shall be evaluated for all
projects submitted to the District for review and approval. Stormwater management facilities
shall be provided and designed in accordance with the requirements of this section. If another
Revised 2/15/2015 66
local jurisdiction requires more stringent design standards, then they shall govern in that locale.
A Stormwater Management Facilities (BMP) Operation and Maintenance Design Report and
Plan, including specific continuing resources, procedures and schedules to be used, shall be
submitted for approval. If required and approved, the Plan shall be included in a recorded
Maintenance Agreement by reference.
2. Stormwater quantity and quality management requirements shall be evaluated for all projects,
and specifically, will be required for projects including:
a. All new development and redevelopment projects that disturb greater than or equal to
one acre, including projects less than 1 acre that are part of a larger common parcel or
project that is greater than one acre. However, existence of downstream stormwater
problems may require quantity detention on the proposed site, where less than 2 cfs
differential is proposed.
b. Projects which have a differential runoff of 2 cfs or greater for the 15-year, 20-minute
event (in St. Louis County).The differential runoff is calculated by the Rational Method
using PI factors.
Subsequent development or redevelopment of sites without prior stormwater detention
shall provide detention or retention, when cumulative differential increase, since January
15, 2000, equals 2 cfs or greater. Projects with prior detention shall provide additional
detention or retention for increasing runoff irrespective of the 2 cfs threshold. The degree
of commonality between subsequent or concurrent projects, sites or parcels within same
watershed shall be as determined by the District for purposes of this section.
3. When existing stormwater management facilities are going to be used to accommodate additional
runoff from building or parking lot expansions or subdivision additions, the facilities shall be
retrofitted to meet the current stormwater management requirements for the drainage area, served
by the facility. Projects, which cannot meet this requirement due to physical constraints, will be
evaluated for alternatives on a case by case basis.
4. The stormwater design projects within designated levee districts such as Monarch-Chesterfield,
Earth City, Howard Bend, and Riverport will be based on the Stormwater Master Plan for these
districts. If the Stormwater Master Plan does not address water quality, the requirements of this
manual shall apply.
5. [Added by Amendment 3. See Section 16] Controls shall be designed and implemented to
prevent or minimize water quality impacts by reasonably mimicking pre-construction runoff
conditions on all “new development” projects to the maximum extent practicable. (This is a
Small MS4 NPDES Stormwater Discharge Permit requirement. It necessitates controls and
practices that reduce runoff volume through infiltration, evapotranspiration, and/or rainwater
harvesting.)
On “redevelopment” sites, controls shall be designed and implemented to prevent or minimize
water quality impacts by effectively utilizing water quality strategies and technologies, including
those that reduce runoff volume, to the maximum extent practicable. When micro-detention is
required in the combined sewer area to address sewer capacity problems, these controls should
also apply runoff reducing strategies and technologies.
Sites with 20 percent or less existing imperviousness are considered new development for
determining if the “mimicking pre-construction runoff conditions” requirement is applicable.
Any subsequent or additional development or expansion projects on those sites will also be
considered new development. Subdividing does not affect that requirement.
Revised 2/15/2015 67
4.080.02 Unified Stormwater Sizing Criteria
1. General
This section presents a unified approach for sizing stormwater Best Managements Practices
(BMP’s) to meet pollutant removal goals, reduce channel erosion and prevent flooding and pass
extreme floods. A very brief summary is listed below.
SUMMARY OF THE KEY COMPONENTS AND STORMWATER CRITERIA
Water Quality Volume
(WQv ) (acre-feet)
WQv = [(P)(Rv)(A)]/12
P = rainfall depth in inches and is equal to 1.14
Rv = volumetric runoff coefficient, and
A = area in acres
Channel Protection Storage Volume
(Cpv)
Cpv = 24 hour extended detention of post-developed
one-year, 24 hour storm event
Flood Protection Volume
(Qp2 & Qp100)
The post-developed routed peak flow from the site
may not exceed the existing routed peak flow for the
2-year and 100-year, 24-hour events, or the
allowable release rate for differential runoff greater
than 5 cfs.
The following sub-sections provide more expanded information, directories, explanations and
resource references.
2. Water Quality Volume (WQv) [See Amendment 4]
a. The Water Quality Volume (denoted as the WQv) is the storage needed to capture and
treat the runoff from 90% of the recorded daily rainfall events. In numerical terms, it is
equivalent to 1.14 inches of rainfall multiplied by the volumetric runoff coefficient (Rv)
and site area. The WQv is directly related to the amount of impervious cover created at a
site. A minimum WQv of 0.2 inches per acre shall be met at all sites where WQv is
required.
b. As a basis for determining water quality treatment volume the following assumptions may
be made:
(1) The water quality volume WQv for offsite areas is not required.
The following equations are used to determine the storage volume, WQv (in acre-
feet of storage):
WQv = [(P)(Rv)(A)]/12 P = 1.14 inches of rainfall
Where: WQv =water quality volume (in acre-feet)
Rv =0.05 + 0.009 (I) where I is percent impervious cover
A =drainage area to BMP in acres
(2) Measuring Impervious Cover: The measured area of a site plan that does not have
vegetative or permeable cover shall be considered total impervious cover.
(3) Multiple Drainage Areas: When a project contains or is divided by multiple
drainage areas, the WQv volume shall be addressed for each drainage area.
(4) Offsite Drainage Areas: The WQv shall be based on the impervious cover of the
proposed site. Offsite existing impervious areas may be excluded from the
calculation of the water quality volume requirements.
Revised 2/15/2015 68
(5)(4) BMP Treatment: The final WQv shall be treated by an acceptable BMP(s) from
the list presented in Section 4.080.05, or as approved by the District.
(6)(5) Subtraction for Non-structural Practices: When non-structural practices are
employed in the site design, the WQv volume can be reduced in accordance with
the conditions outlined in Section 4.080.06.
(7)(6) Extended Detention for Water Quality Volume: The water quality requirements
can be met by providing a 24-hour draw down of a portion of the water quality
volume (WQv) in conjunction with a stormwater pond or wetland system.
Referred to as ED, this is different than providing the extended detention of the
one-year storm for the channel protection volume (Cpv). The ED portion of the
WQv may be included when routing the Cpv.
3. Channel Protection Storage Volume Requirements (Cpv) [See Amendment 1, Chapter 16]
a. General
To protect channels from erosion, a 24-hour extended detention of the one-year, 24-hour
storm event shall be provided. The rationale for this criterion is that runoff will be stored
and released in such a gradual manner that critical erosive velocities during bankfull and
near-bankfull events will seldom be exceeded or prolonged in downstream channels.
A detention pond or underground vault is normally needed to meet the CPv requirement
(and subsequent flood protection criteria Qp2 and Qp100).
b. As a Basis for determining Channel Protection Storage Volume the following
assumptions may be made:
(1) The model TR-55 (or approved equivalent) shall be used for determining peak
discharge rates. (See 4.080.02 Paragraph 4.b.(1) for additional TR-55
information.
(2) The rainfall depth for the one-year, 24-hour storm event is 2.50 inches. Use Type
II rainfall distribution.
(3) The length of overland flow used in time of concentration (tc) calculations is
limited to no more than 100 feet for post project conditions.
(4) The 24-hour extended detention is defined as providing a 24-hour
detention lag time (T) for the one-year storm. The lag time is defined as the
interval between the center of mass of the inflow hydrograph and the center of
mass of the outflow hydrograph.
(5) A Cpv orifice diameter of less than 3.0” will require a special internal control for
orifice protection. For Cpv orifice between 3” and 1 1/2” diameter, an internally
controlled orifice shall be used with slot width less than or equal to 1/3 of orifice
diameter. Less than 1 ½” orifice will not be allowed.
(6) Cpv shall be addressed for the entire site. If a site consists of
multiple drainage areas, Cpv may be distributed proportionately to each drainage
area.
(7) Extended detention storage provided for the Cpv does not fully
meet the WQv requirement (that is Cpv and WQv should be treated separately).
Revised 2/15/2015 69
(8) The stormwater storage needed for Cpv may be provided above the WQv storage
in stormwater ponds and wetlands; thereby meeting all storage criteria in a single
facility with appropriate hydraulic control structures for each storage requirement.
(9) Infiltration is not recommended for Cpv control because of large storage
requirements. If proven effective, appropriate and desirable however, in some rare
situations it may be permissible.
c. Exemptions
To protect channels from erosion, a 24-hour extended detention of the one-year, 24-hour
storm event shall be required at all sites that do require Flood Volume Detention (Qp).
Also, the existence of downstream stormwater problems may require treatment for
channel protection (CPv), regardless of any other possible exemptions.
At some sites however, the provision of traditional extended detention (Cpv) may not be
effective or may be best achieved by other means. Specifically, the following sites may
be exempted from the channel protection storage requirement:
A.) For sites 5 acres or larger, exempt if:
1.) No detention for Flood Protection Volume (Qp) is required, and
2.) The project is a redevelopment site (at least 20% of the existing site was
impervious coverage as of January 15, 2000) and
3.) The watershed is a less sensitive, i.e. “zero increase” watershed (per
Table 4-5)
And either 4.) or 5.) below
4.) Surface BMP’s are utilized to treat the required WQv and more pervious
area is created on the site and within the tributary area.
OR
5.) Underground devices are utilized to treat the required WQv but the
proposed site will be at least 20% more pervious than the existing site.
B.) All sites less than 5 acres will normally be exempt.
C.) For all sites, regardless of size, exempt if any of the following
apply:
1.) The project site will be 100% pervious, and does not increase annual or
more frequent discharge from site (for a 1-year event per TR-55).
2.) The project is a redevelopment site (at least 20% of the existing site was
impervious coverage as of January 15, 2000) and the project reduces the
site impervious area to less than 10% of the total site area.
3.) The project is located within levee district boundaries or within the very
flat portions of the FEMA defined flood plain of the Mississippi,
Missouri, or Meramec Rivers.
4.) The project is located upstream of permanent lakes, concrete lined
channels, or enclosed pipe systems. However, the presence of any
intervening reach or downstream, natural channel which does need
extended detention channel protection may then nullify this exemption.
Revised 2/15/2015 70
a. To protect channels from erosion, a 24-hour extended detention of the one-year, 24-hour
storm event shall be provided. The rationale for this criterion is that runoff will be stored
and released in such a gradual manner that critical erosive velocities during bankfull and
near-bankfull events will seldom be exceeded in downstream channels.
A detention pond or underground vault is normally needed to meet the CPv requirement
(and subsequent flood protection criteria Qp2 and Qp100).
As a Basis for determining Channel Protection Storage Volume the following
assumptions may be made:
(2) The model TR-55 (or approved equivalent) shall be used for determining peak
discharge rates. (See 4.080.02 Paragraph 4.b.(1) for additional TR-55
information.
(2) The rainfall depth for the one-year, 24-hour storm event is 2.50 inches. Use Type
II rainfall distribution.
(3) The length of overland flow used in time of concentration (tc) calculations is
limited to no more than 100 feet for post project conditions.
(10) The 24-hour extended detention is defined as providing a 24-hour detention lag
time (T) for the one-year storm. The lag time is defined as the interval between
the center of mass of the inflow hydrograph and the center of mass of the outflow
hydrograph.
(11) Cpv is not required at sites where the one-year post development peak discharge is
less than or equal to 2.0 cfs. A Cpv orifice diameter of less than 3.0” is not
allowed.
(12) Cpv shall be addressed for the entire site. If a site consists of multiple drainage
areas, Cpv may be distributed proportionately to each drainage area.
(13) Extended detention storage provided for the Cpv does not fully meet the WQv
requirement (that is Cpv and WQv should be treated separately).
(14) The stormwater storage needed for Cpv may be provided above the WQv storage
in stormwater ponds and wetlands; thereby meeting all storage criteria in a single
facility with appropriate hydraulic control structures for each storage requirement.
(15) Infiltration is not recommended for Cpv control because of large storage
requirements. If proven effective, appropriate and desirable however, in some rare
situations it may be permissible.
4. Flood Protection Volume Requirement (Qp2 & Qp100)
a. To protect downstream areas from flooding stormwater shall be detained on site or
offsite as approved and released at a rate not to exceed the allowable release rates for
the 2-year and 100-year 24-hour events, as determined by the District for the watershed
in question. The allowable release rates have been determined by watershed modeling
(see Table 4- 5). The engineer has the option to calculate a site specific release rate
based on procedures provided by the District's Engineering Department (Volumetric
Method). Note that stormwater pipes, downstream from the control structure, shall be
sized to carry the runoff from the 15-year 20-minute design storm for the total tributary
upstream watershed. No reduction in outfall pipe size shall be permitted because of
detention.
Revised 2/15/2015 71
b. As a Basis for Determining the Flood Protection Volume the following assumptions
may be made.
(1) The 2-year and 100-year, 24-hour inflow hydrographs shall be determined by
using Technical Release 55 (TR-55), "Urban Hydrology for Small Watersheds"
from the Natural Resources Conservation Service, formerly Soil Conservation
Service (SCS). The inflow hydrograph shall be developed based on the actual
flow and timing characteristics upstream of the detention facility. The rainfall
distribution shall be Type II. The rainfall quantities to be used are from the
Illinois State Water Survey Bulletin 71, and shall be as follows: 3.1” for the 2-
year, 24-hour storm and 7.2” for the 100-year, 24-hour storm.
(2) The volume of detention may be provided through permanent detention facilities
such as dry basins or ponds, permanent ponds or lakes, underground storage
facilities or in parking lots. The engineer shall make every effort to locate the
detention facility at or near the lowest point of the project such that all of the on-
site runoff will be directed into the detention facility. Multiple use of detention
basins is encouraged. Multiple use may include parking lots, ball fields, tennis
courts, play grounds and picnic areas. This is subject to the approval of the
District.
Flows from offsite, upstream areas should be bypassed around the detention
facility to ensure that the proposed detention facility will function as designed and
will provide effective control of downstream flows with development in place. If
offsite flows are directed into a detention facility, the allowable release rates shall
not be modified without District approval. Modifying the release rate to
accommodate offsite flows may reduce or eliminate the effectiveness of the
detention facility, because it will no longer control the increased volume of runoff
during the critical time period of the watershed.
As stated in Item 4.a above, the engineer has the option to calculate a site specific
release rate based on procedures provided by the District's Engineering
Department. The engineer shall provide detailed modeling to prove that the
increase in runoff volume has been limited to existing conditions during the
critical time period of the watershed (For Volumetric Method see Appendix –
forthcoming).
(3) Detention basin volume will be based on routing the post-developed 2-year and
100 year, 24-hour inflow hydrographs through the detention facility while
satisfying the appropriate allowable release rate. The routing computations shall
be based on an application of the continuity principle, (i.e., level pool routing).
Municipalities or St. Louis County may by ordinances, have other volume
requirements. The more stringent volume requirements will govern.
4.080.03 Limits of Maximum Ponding in Stormwater Ponds
1. The maximum ponding elevation shall be calculated based on a routing of the design storm
(100-year, 24-hour event) assuming the low flow outlet is blocked with water ponded to the
overflow structure’s sill.
2. The limits of maximum ponding in dry basins or ponds and permanent lakes or ponds shall
not be closer than thirty (30) feet horizontally to any building, and not less than two (2) feet
vertically below the lowest sill elevation of any building.
Revised 2/15/2015 72
3. The limits of maximum ponding in parking lots shall not be closer than ten (10) feet
horizontally from any building and not less than (1) foot vertically below the lowest sill
elevation of any building.
4. A minimum of one (1) foot of freeboard shall be provided from the top of the basin to the
maximum ponding elevation.
5. Micro-Detention will be looked at case by case but in general the following apply:
a. 12” Freeboard Requirement
Exceptions allowed: (Freeboard 6” or less)
(1) Upper terraces of multiple in-line detention basin(s).
(2) If the basin’s outfall is directed onto a natural water way with no downstream
property to be impacted. This could be obtained by providing swales and/or
using existing swales that are around the downstream perimeter of the site and
which direct flows to natural waterways or property with no future build out
possibilities (6” freeboard still preferred).
b. Other Exceptions:
30’ Requirement for Horizontal Distance From HW Elevation
(1) If the basin is very shallow
(2) If the basin’s H.W. elevation is 2’ below the low sill of building.
It is recommended that additional construction and grading notes be put on the plans, as
well as a landscape schedule of plantings. Grading tolerances should be kept at + 0.1 and
as-builts provided. Infiltration rates should be accurate for basins without outfall structure.
Copy of maintenance and operations notes should be included on the plans.
4.080.04 General Stormwater Basin Design Requirements
1. Underground Basins’ Special Requirements:
a. Adequate access for basin maintenance and inspection shall be provided. A means of
visual inspection from the ground surface of the low flow device, overflow weir, and
outlet structure is necessary. Access shall also be provided to allow for cleaning of
the low flow device from the ground surface.
b. The basin should have sufficient volume and spillway capacity to pass/contain the
100-year 24-hour event with the low flow outlet blocked. In some situations it may be
desirable to have control structures with at least 2 outlet openings, one above the
other.
c. Underground basins shall be acceptable for non-residential projects only, except by
special municipal request, cooperation and a lack of other technical options. (See also
sub-section 4.080.05.1.c also).
d. Acceptable materials for underground basins are poured in place
reinforced concrete, RCP and aluminized CMP. The CMP gauge shall be approved
by the District prior to installation. Restricted use of other systems may be allowed in
the future.
Revised 2/15/2015 73
e. Provide immediate manhole access from ground surface for both sides of the low
flow device. Also provide a manhole at upstream end of underground basins, for
access, inspection, to facilitate maintenance and air release.
f. Adequate flowline spot elevations, sections and profiles including pipe length and
slope shall be labeled to define basin and pipe geometry.
2. General Detention Report Requirements
For detention facilities in general, the Engineer must submit 2 copies of a report sealed by
a Missouri Registered Professional Engineer containing the following for review of the
detention facility: (see 4.100 also)
a. Elevation vs Discharge tables or curves for all frequencies.
b. Elevation vs Storage tables or curves for all frequencies.
c. Inflow calculations and data for all frequencies.
d. Hydraulic gradeline computations for pipes entering and leaving the
basin for all frequencies.
e. If the embankment contains fill material a geotechnical report may be required.
f. Site plan showing appropriate design information.
g. Structural calculations for the outlet control structures (if required).
h. Cross sections defining the size, shape and depth of the detention basin shall
be required. At a minimum, three sections, one at each end and one in the
middle of the basin will be required.
3. All ends of pipes discharging into a dry basin or pond shall be connected with the low
flow pipe or control structure, by means of a permeable swale. The swale shall a
minimum 4:1 lateral (25%) slope to the center and a minimum 2.0% longitudinal slope to
ensure positive drainage. Swales shall be a minimum of six (6) inches deep and four (4)
feet wide or 1.3 times the diameter of the pipe entering the basin, whichever is greater. .
The bottom of the basin shall be sloped a minimum of two percent (2%). towards the edge
of the swale.
No concrete swales will be allowed unless approved by the District. Permanent erosion
control protection must be provided at the ends of discharging pipes. Lengths of the swale
in which the velocity exceeds 2 feet per second analyzed by the 15 year –20 minute storm
event, shall have appropriate permanent erosion control protection. Aggregate, porous
concrete blocks or appropriate vegetation are required, unless otherwise approved.
4. Railroad tie walls cannot be used where water will be in contact with the railroad tie
wall.
5. Permanent detention ponds or lakes are to be designed to minimize fluctuating lake levels.
Maximum fluctuation from the permanent pool elevation to the maximum ponding
elevation shall be six (6) feet.
6. The maximum side slopes for dry basins or ponds, and the fluctuating area of permanent
ponds or lakes shall be 3:1 (three feet horizontal, one foot vertical) without fencing.
7. Dry basins or ponds and the fluctuating areas of permanent ponds or lakes are to be
appropriately vegetated to the maximum high water elevation. . Areas above that elevation
Revised 2/15/2015 74
shall be appropriately stabilized and vegetated. Sod and mowing above that elevation may
be approved and is required for dam embankment slopes and downstream toe areas for
wet basins where riprap is not appropriate.
8. Control structures and overflow structures are to be reinforced concrete, including precast.
Only for underground proprietary or aluminized CMP basins may other approved
materials be allowed.
9. The outflow pipe shall be sized for the developed flow rate.
10. In basins with concrete walls or rip rap covered slopes, provisions should be made for
mowing equipment to reach the bottom (ramps, etc.).
11. Maximum Depths:
a. The maximum depth of water in a dry detention basin or pond shall not
exceed eight (8) feet. Projects which need a deeper basin to attain the
required detention volume due to physical constraints may be evaluated on a
case by case basis. The design and construction of dams greater than eight (8)
feet or as directed by the District must be sealed and certified by a
Professional Engineer registered in the State of Missouri with
demonstrated expertise in geotechnical engineering.
b. Parking lots used for automobiles shall have a maximum depth of eight (8)
inches of water.
c. Parking lots used for trucks or truck trailers shall have a maximum depth of
water of twelve (12) inches.
12. Detention Basin Fencing
A four (4) foot (minimum height) approved fence shall be provided around the perimeter
of any basin where the side slopes exceed 3:1 (three (3) feet horizontal, one (1) foot
vertical). Fencing such as post and rail, or fencing which prevents easy observation of
required detention basin maintenance, such as tall privacy fencing, should not be used.
13. Detention Basin Elevation
If the detention basin discharges to a piped sewer system, the low elevation of the
detention basin shall be above the 15-year, 20-minute hydraulic elevation of the
receiving storm system, or the 20 year, 20 minute hydraulic elevation of the receiving
combined systems, as applicable. Basin backflow contamination must be prevented, if
the downstream combined system is known to surcharge.
14. If the detention basin discharges to an open channel, or to a piped sewer system affected
by flood levels in a nearby downstream open channel, then the low elevation of the basin
is desirable to be above the 100-year flood elevation in the open channel as established
by the FEMA Flood Insurance Study or the District SSMIP, whichever is greater.
15. In all cases mentioned above, if the low elevation of the basin is below the receiving
system hydraulic grade or channel flood elevation, then the basin shall be sized to store
the entire design storm volume, unless directed otherwise by the District.
4.080.05 Acceptable Urban BMP Options [See Amendment 4]
1. This section sets forth five acceptable groups of BMPs that can be used to meet the
Water Quality volume criteria (WQv). The design and selection of these BMPs shall
comply with the Maryland Stormwater Design Manual, Volumes I & II (October 2000;
Revised 2/15/2015 75
effective date July 1, 2001), as prepared by the Center For Watershed Protection and
the State of Maryland Department of the Environment (MDE). Where the District
criteria or requirements are more stringent, then they shall govern. Adaption to local
Missouri environment and natural conditions should be expected but shall be as
approved by the District or a higher authority. The Manual can be purchased through
MDE’s website. A simple search for Maryland Stormwater Design Manual will provide
a direct link.
a. The acceptable BMP designs are assigned into five general categories for stormwater
quality control (WQv):
BMP Group 1 stormwater ponds
BMP Group 2 stormwater wetlands
BMP Group 3 infiltration practices
BMP Group 4 filtering practices
BMP Group 5 open channel practices
b. To be considered an effective BMP for stand-alone treatment of WQv, a design shall be
capable of:
1. capturing and treating the required water quality volume (WQv)
2. removing 80% of the TSS, and
3. having an acceptable longevity rate in the field
c. A combination of BMPs and/or credits is normally required at most development sites to
meet all three stormwater sizing criteria.
d. NOTE: Groundwater sump pump discharge may be problematic if directed towards
storm water BMPs. In general this practice should be avoided unless otherwise allowed
by the District.
1. BMP Group 1. Stormwater Ponds
a. Practices that have a combination of permanent pool, extended detention or shallow
wetland equivalent to the entire WQvs include:
P-1 micropool extended detention pond
P-2 wet pond
P-3 wet extended detention pond
P-4 multiple pond system
P-5 pocket pond
2. BMP Group 2. Stormwater Wetlands
a. Practices that include significant shallow wetland areas to treat urban stormwater but
often may also incorporate small permanent pools and/or extended detention storage to
achieve the full WQv include (Modification of existing wetland areas will require a CWA
404/401 permit: Corps 404 permit):
W-1 shallow wetland
W-2 ED shallow wetland
W-3 pond/wetland system
W-4 pocket wetland
b. U.S. Army C.O.E. Jurisdictional Wetlands shall not be used for control of water quantity
(i.e. the flood protection volume). Wetlands shall not be used for control of water
quantity (i.e. the flood protection volume).
Revised 2/15/2015 76
c. Wetlands shall be designed by a qualified and experienced team.
3. BMP Group 3. Infiltration Practices
a. Practices that capture and temporarily store the WQv before allowing it to infiltrate into
the soil over a two day period include:
I-1 infiltration trench
I-2 infiltration basin
b. Infiltration practices will be allowed on sites where it is proven that infiltration will
work. This must be supported by a soils report.
4. BMP Group 4. Filtering Practices
a. Practices that capture and temporarily store the WQv and pass it through a filter bed of
sand, organic matter, soil or other media are considered to be filtering practices. Filtered
runoff may be collected and returned to the conveyance system. Design variants include:
F-1 surface sand filter
F-2 underground sand filter
F-3 perimeter sand filter
F-4 organic filter
F-5 pocket sand filter
F-6 bioretention*
F-7 proprietary filtering system
*may also be used for infiltration
b. Filtering practices may be allowed on commercial projects. They are not allowed on
residential projects.
c. A maintenance agreement and maintenance schedule shall be required.
5. BMP Group 5. Open Channel Practices
a. Vegetated open channels that are explicitly designed to capture and treat the full WQv
within the dry or wet cells formed by checkdams or other means include:
0-1.01 dry swale
0-2 wet swale
0-3 filter strips
b. Open channel practices shall be designed with the proper plantings. They are not allowed
on single-family residential projects. They may be allowed on condominium or
apartment projects if maintenance is provided by a management company.
c. Wet swales shall be designed to drain out over time.
4.080.06 Stormwater Credits
Non-Structural BMPs are increasingly recognized as a critical feature of stormwater BMP plans,
particularly with respect to site design. In most cases, non-structural BMPs shall be combined with
structural BMPs to meet all stormwater requirements. The key benefit on non-structural BMP is that they
can reduce the generation of stormwater from site; thereby reducing the size and cost of structural BMPs.
In addition, they can provide partial removal of many pollutants. The non-structural BMPs have been
classified into seven broad categories. To promote greater use of non-structural BMPs, a series of credits
and incentives are provided for developments that use these progressive site planning techniques. Further
Revised 2/15/2015 77
details can be found in Chapter 5 of the Maryland Stormwater Design Manual, Volumes I & II (October
2000).
• natural area conservation
• disconnection of rooftop runoff
• disconnection of non-rooftop impervious area
• reserved buffers
• open channel use
• environmentally sensitive development
• impervious cover reduction
4.080.07 Easement Required
In subdivisions, the detention basin, BMP’s, access roads or paths, control structures, and outfall pipes
are to be located in easements dedicated to the subdivision trustees. Lack of appropriate easement(s) will
not relieve trustees of responsibility for required maintenance of the Stormwater Management System
BMP’s.
4.080.08 Maintenance Agreement
Prior to plan approval the property owner(s) of the Detention Basin site(s) shall execute a District
Maintenance Agreement for the urban BMPs and the detention basin or pond to insure the urban BMPs
and the detention area will be kept in working order, to the satisfaction of the District. The District will
not be responsible for maintenance of detention basins or BMPs.
Annual trustee or non-residential Property Owner’s certification and reporting of performance of required
maintenance, operation and repairs shall commence upon MSD Construction Approval of detention
facilities; final closeout of the subdivision or project SWPPP; or as otherwise specified. The annual
report will be required for those projects where the recorded Maintenance Agreement requires the
reporting directly or by reference included in the Agreement (see Sub-section 4.080.01 Item 1. regarding
need for BMP Maintenance Plan). The annual report shall be submitted to the Engineering Department,
Design Division, Development Review at 2350 Market St., St. Louis MO, 63103 (return receipt
requested).
4.090 Dam Permit Requirements
Dams with a height of thirty five (35) feet or greater will require approval from the Missouri Department
of Natural Resources.
4.100 Detention Report
1. A Detention Report shall be submitted.
2. The Detention Report shall contain a complete table of contents and a summary.
3. The Detention Report shall be signed, dated and sealed by the Missouri Professional Engineer
who is responsible for its preparation. If the report is prepared by another person, a note on the
cover shall state the preparer’s name and that he or she is under the direct supervision of the
Missouri Professional Engineer whose seal is shown.
4. The Detention Report shall be in a binder, not loose leaf.
5. The engineer shall submit two copies of the Detention Report.
6. A copy of the current “Checklist for Review of Storm Water Detention” shall be completed by
the design engineer and submitted with the reports. The checklist is shown on Exhibit 4-A
hereinafter, or on the website if updated in the future.
Revised 2/15/2015 78
EXHIBIT 4-A
Check List for Review of Stormwater Detention
The following check list is intended to provide guidance in reviewing detention designs. It is not intended to supersede any
criteria stated in the District’s “Rules and Regulations and Engineering Design Requirements for Sanitary Sewage and
Stormwater Drainage Facilities”, February 2006.
the District P-No
Project Name:
Location:
1. Check planning maps for downstream problems.
2. Check SSMIP report for downstream problems.
3. Detention required if differential runoff, per 4.080.01.2(b), is greater than 2 cfs, or if required by the
District due to flooding problems.
4. If differential runoff is greater than 5 cfs, use watershed release rates if applicable (see release rate
table, figure 4-5)
_______ 5. For building and parking lot additions, detention is required if there is existing detention. Check existing
calculations to see if addition is covered.
6. No reduction in outfall pipe size permitted because of detention.
7. Basin located at or near lowest point of site such that on-site runoff will be directed to basin.
8. Offsite flows bypassed around basin.
_______ 9. If site specific release rate is used (volumetric procedure), no increase in runoff volume during the critical
time period of the watershed.
10. Underground basin has adequate access for maintenance.
11. Provide means of visual inspection of both sides of low flow device from ground surface for
underground basin.
12. Underground basin has volume and spillway capacity to pass/contain 100-year, 24-hour event with low
flow blocked. It is further recommended that the control structure have at least 2 openings, one
above the other.
13. Check flow capacity of downstream pipe with inlet control nomographs found in Hydraulic Design of
Highway Culverts, U.S. Department of Transportation publication.
_______ 14. Check inlet control constants as entered in the analysis to match the Hydraulic Design of Highway
Culverts per US Department of Transportation.
15. Aluminized corrugated metal pipe (CMP) allowed for commercial projects only, gauge specified.
16. No underground basins allowed for residential projects, except by special municipal request, cooperation
and a technical lack of other options.
Revised 2/15/2015 79
17. TR-55 or similar SCS method used for hydrology; Type II rainfall distribution.
18. 2-year and 100-year, 24-hour rainfall amounts of 3.1” and 7.2”, respectively.
_______ 19. Legible Detention Basin Area maps showing flow paths used in time of concentration calculations and
CN values for existing and proposed conditions, 24” X 36” exhibits are preferred, (Existing
Conditions Map is not applicable to a “Fixed” Release Rate Analysis).
20. Elevations vs. Discharge table, including modeling data.
21. Elevation vs. Storage table.
22. Hydraulic gradeline calculations for incoming and outgoing pipes.
23. Provide a copy of the SCS soils map and label site.
24. Geotechnical report may be required for embankment.
25. Structural calculations may be required for control structure.
26. Details of control structure showing reinforcing.
_______ 27. Minimum of 3 cross sections through basin for as-built calculations tied to a baseline or known point or
to Property Line.
28. Incoming pipes should discharge at the toe of the slope in dry basins.
29. Earthen Pilot swale provided from incoming pipes to control structure.
30. Earthen Pilot swale is a minimum of 6 inches deep.
31. Details for permanent erosion control for earthen swales with slopes greater than 3%.
32. Minimum longitudinal slope of earthen swale is 2.0%, slope called out on plan.
33. Bottom of basin is sloped a minimum of 2% laterally towards earthen swale and called out on plan.
34. Rock blanket provided along outside of curved swale downstream of incoming pipe to prevent
erosion.
35. Concrete headwall provided around protruding low flow pipe.
36. Trash rack provided for low flow openings less than 6” wide.
37. No railroad tie walls within ponding area of basin.
38. Maximum fluctuation above permanent pool is 6’.
39. Maximum side slopes are 3:1 without fencing.
_______ 40. Dry basins and the fluctuating areas of lakes are to be appropriately vegetated to the maximum high
water elevation, call out on plan. Sod and mowing may be approved above that level and on dam slopes
(required, if not riprapped).
_______ 41. Control structures are to be reinforced concrete; no brick allowed; wall thickness is at least 8” w/one row
of steel or 10” w/two rows of steel. Underground basins, as appropriate. [Deleted by Amendment 5]
42. In basins with walls, provide access ramp.
Revised 2/15/2015 80
43. No wetland mitigation in detention basin.
44. Maximum depth of water in a dry basin is 8’ exceptions on a case-by-case basis.
45. Maximum depth of water in a parking lot is 8”, 12” for truck parking lots.
46. Maximum ponding elevation calculated with low flow blocked and water ponded to sill of overflow
structure.
_______ 47. Limits of maximum ponding are 30’ horizontally and 2’ vertically from a building; 10’ horizontally and 1’
vertically for parking lot detention.
48. Freeboard from top of berm to maximum ponding elevation is at least 1’.
49. Basin is located in common ground or easement dedicated to subdivision trustees.
50. Owners of the basin execute a District Maintenance Agreement.
51. Four foot high fence required if side slopes are steeper than 3:1.
52. Low elevation of basin is above 15-yr, 20-min hydraulic elevation of receiving system; or detain whole
storm and provide a backflow preventer (Tideflex) normally installed inside of the outfall structure.
53. Dams with a height of 35’ or greater require MDNR approval.
_______ 54. Hydraulic calculations showing 100-year flow is conveyed to basin; calculations at ditch sections, sills of
structures set above 100-yr elevation.
55. Smallest low flow opening is 3” diameter or 4” x 2” slot. However, special trashrack or opening protection
may be required.
56. Detention cannot cross watershed boundary.
57. Discharge pipe into wet basin shall be a minimum of 3’ above bottom, or flowline of pipe shall be no
higher than the normal pool elevation.
58. The report is sealed by a Missouri Professional Engineer.
59. The report has a Table of Contents, a summary and is bound.
_______ 60. The starting hydraulic grade line for all incoming pipes shall be the 100 year – 24 hour blocked low flow
water surface elevation, or an elevation approved by the District.
_______ 61. For some channel and wetlands work, a 404 and/or 401 permit may be required from the Corps and
MoDNR, respectively.
Revised 2/15/2015 81
Revised 2/15/2015 82
Revised 2/15/2015 83
Revised 2/15/2015 84
Revised 2/15/2015 85
TABLE 4-5 [See Amendment 4]
WATERSHED RELEASE RATES FOR DESIGN OF ROUTED DETENTION FACILITIES
FOR DEVELOPMENTS WITH A POST-DEVELOPMENT DIFFERENTIAL RUNOFF
GREATER THAN 5 CFS*
Note: *Differential runoff based on the 15-year, 20 minute storm. See “Rules and Regulations and
Engineering Design Requirements for Sanitary Sewage and Stormwater Drainage Facilities”, Chapter 4, Section
4.080.02. Differential runoff of 5 cfs or less, use “Zero Increase” for all watersheds and both routing frequencies.
**Differential runoff and detention routings should be computed from a completely undeveloped
condition for projects in the Harlem & Baden watersheds, Grand & Bates (March 9, 2001) sewershed, and other
sewersheds as may be directed by the District, in the City of St. Louis. System capacity has been found overcharged for
rainfall events as small as once every two (2) years. Physical limitations of the site may be considered in special cases.
**Projects which have any increase in differential runoff in the Harlem & Baden watersheds, Grand & Bates sewershed,
and other sewersheds as may be directed by the District will have stormwater management requirements as shown in
items A.) through D.) as follows:
WATERSHED FINAL ROUTED
RELEASE RATE
100-YEAR
24 HOUR STORM
FINAL ROUTED
RELEASE RATE
2-YEAR
24 HOUR STORM
VOLUMETRIC
METHOD
CRITICAL TIME
PERIOD OF
WATERSHED
Baden ** Zero Increase Zero Increase NA
Bonfils
(Cowmire)
1.0 cfs/acre 0.4 cfs/acre Hour 12.0-14.0
Bonhomme 1.8 cfs/acre 0.25 cfs/acre Hour 12.0-15.5
Caulks 1.4 cfs/acre 0.2 cfs/acre Hour 12.0-14.0
Coldwater Zero Increase Zero Increase NA
Creve Coeur 1.2 cfs/acre 0.13 cfs/acre Hour 12.0-17.2
Deer Zero Increase Zero Increase NA
Dunn 1.0 cfs/acre 0.4 cfs/acre Hour 12.0-13.0
Fee Fee 1.3 cfs/acre 0.15 cfs/acre Hour 12.0-14.1
Fenton Zero Increase Zero Increase NA
Fishpot 1.5 cfs/acre 0.3 cfs/acre Hour 12.0-14.7
Grand Glaize Zero Increase Zero Increase NA
Gravois Zero Increase Zero Increase NA
Harlem ** Zero Increase Zero Increase NA
Kiefer 2.2 cfs/acre 0.7 cfs/acre Hour 12.0-13.0
Maline Zero Increase Zero Increase NA
Martigney Zero Increase Zero Increase NA
Mattese Zero Increase Zero Increase NA
Mill 1.5 cfs/acre .13 cfs/acre Hour 11.5-15.5
River Des Peres Zero Increase Zero Increase NA
Spanish Lake 1.0 cfs/acre 0.37 cfs/acre Hour 11.0-16.0
University City Zero Increase Zero Increase NA
Watkins Zero Increase Zero Increase NA
Williams 0.7 cfs/acre 0.2 cfs/acre Hour 12.0-15.1
Yarnell 1.3 cfs/acre 0.3 cfs/acre Hour 12.0-14.0
Revised 2/15/2015 86
STORMWATER MANAGEMENT REQUIREMENTS FOR
HARLEM AND BADEN WATERSHEDS AND OTHER WATERSHEDS
AS DIRECTED BY THE DISTRICT
A.) For project differential increase 0 to < 2 cfs: Volume reduction type BMPs sized for 75% of the 90th %
rainfall 1.14” WQv calculation as shown in 4.080.02.2.b(1). In general, the minimum amount of tributary
impervious area to be treated by the BMPs shall be the acreage of added impervious area. The BMPs shall be
designed to capture 75% of the WQv from the total drainage area tributary to the BMP. The BMP shall be
designed to drain down completely in 2 days. The BMP overflow path shall be designed for the 100-year, 20-
minute storm. For an example, see MSD website BMP toolkit.
B.) For project differential increase 2 cfs or >: TR55 analysis for 2-year and 100-year events, with level pool
routing to meet release rates as specified in Table 4-5.
C.) In the case of new directly sewer connected roof area replacing existing pavement area, MSD will evaluate
these on a case-by-case basis.
D.) For all cases, where localized downstream flooding or localized downstream sewer surcharging occurs,
differential runoff calculations and detention routings shall be computed from a completely undeveloped
condition as directed by the District.
Revised 2/15/2015 87
Revised 2/15/2015 88
Revised 2/15/2015 89
Revised 2/15/2015 90
Revised 2/15/2015 91
5. FLOOD PLAIN REQUIREMENTS
5.010 Flood Plain Study/100 – Year Hydraulic Study
5.010.01 When Required
1. A flood plain study will be required for all tracts or parcels of ground located in the
100-year flood plain shown on the current Federal Emergency Management Agency's
(FEMA) Flood Boundary and Floodway Map. In incorporated areas, a letter will be
required from the municipality stating that the project is in compliance with the
municipality’s flood plain ordinance.
2. A 100 – year hydraulic study will be required for any watercourse, not identified by
FEMA, for which the 15-year, 20-minute design storm exceeds the capacity of a (60)
inch diameter sewer.
3. A flood plain study/100 – year hydraulic study will be required when development of
any type, i.e., new construction, additions to existing facilities, rehabilitation of existing
facilities, or site grading is planned within an area subject to 100-year flooding.
5.010.02 Criteria For Preparation
1. The flood plain study /100 – year hydraulic study shall be submitted by a Professional
Engineer, registered in the State of Missouri. Each page of the study shall be signed
and sealed.
a. All assumptions shall be clearly stated in the report. The modeling process,
review of existing data, necessary background, purpose, flooding potential of
the existing land, existing or previous studies, existing computer model input
and output, proposed conditions computer model input and output, 100-year
and 15-year water surface elevations, cross-sections and profiles should all be
included in the report. An electronic copy of the models shall be submitted on
a disk.
b. Sufficient hydraulic computations shall be submitted for review to verify the
100-year and 15-year water surface elevations with the proposed development
in place. The computations should also verify that the conveyance
characteristics of the water course are not restricted by the proposed
development when compared with the pre-developed conditions.
c. Flood plain elevations and design of bridges and culverts will be reviewed by
the District using the flow and elevation numbers that provide the most
protection to the public. The FEMA flow/elevation will be used for those
instances where these values will provide the most protection for the residents
and public since that is the official guide. However, since the FEMA numbers
were developed based on an empirical equation representing all the St. Louis
area and upon existing conditions at the time of the FEMA modeling (late 70’s
and early 80’s generally) they may not accurately reflect the current the
current situation and knowledge. The Stormwater System Master
Improvement Plans (SSMIP) contain more current information based upon
SWMM modeling having been performed during the 1995-1999 time period
and are based upon actual gauged or measured rainfall/runoff to calibrate the
model. Consequently, the SWMM flow/elevation numbers in several instances
provide a better estimate of actual current conditions within the watersheds.
Therefore, the District will use the more conservative flow/elevation values
for each location (either FEMA or SWMM depending on which provides the
most conservative value) on all review of future projects.
Revised 2/15/2015 92
2. A Metropolitan St. Louis Sewer District bench mark and U.S.G.S. datum shall be
referenced and shown on the study with reference made to the on-site temporary bench
mark.
3. The study shall determine the 100-year high water elevation through the site using the
elevations obtained from the most recently published Federal Emergency Management
Agency Flood Insurance Study or, if more conservative, from the District’s SSMIP
watershed studies.
4. The method used to determine the water surface elevation shall be dependent on the
stream characteristics.
a. FEMA Streams
For streams for which a detailed Flood Insurance Study has been performed
by FEMA, the water surface elevation shall be computed by the same method
as used in the FEMA Flood Insurance Study.
b. Non-FEMA Streams
The method used to determine the water surface elevation for streams for
which a hydraulic model has not been developed by FEMA, shall depend on
the conveyance characteristics of the stream.
For generally prismatic streams with a mild, constant slope, the water surface
elevation shall be computed using the direct-step method.
For non-prismatic streams with varying channel shape or slopes, the standard-
step method shall be used.
Both the direct-step and standard-step methods are described in detail in Open
Channel Hydraulics by Ven Te Chow, a McGraw-Hill work published in
1959.
5. The determination of a starting water surface elevation used in the hydraulic
computations must be stated in the study. The high water elevations shall be checked
against data showing downstream influences, such as culvert restrictions and/or flood
elevations of larger streams or rivers. The downstream and upstream study limits shall
be measured from the most downstream and upstream edges of the development. The
hydraulic computations shall extend a minimum of one hundred (100) feet beyond the
cross section where the post and pre-development water surface elevations are
coincident. There may be situations where the post and pre-development water surface
elevations are not coincident. In those situations, the post development water surface
elevation must be lower than the pre-development water surface elevation. Also, the
hydraulic slope and energy grades should not indicate a possible rise in water surface
elevation beyond the post development water surface elevation within the one hundred
(100) feet study limits. A sufficient number of cross sections should be utilized within
the study limits to accurately determine the water surface elevation. The District
reserves the right to extend the study limits.
6. If a new channel or channel realignment is proposed which would require a
FEMA map amendment, the municipality must submit to FEMA all information
required by the current FEMA "Conditions and Criteria for Floodway Revisions."
Those projects, which require map revisions, will not be approved until a conditional
letter of map revision (CLOMR) is provided by FEMA to the municipality.
Revised 2/15/2015 93
7. If the development is in an area where no discharge data exists, the Engineer shall use
the following guidelines for establishing the discharge for the study:
a. Determine the 100-year discharge value from the last known discharge, at
most upstream portion of the receiving stream, as shown in the Flood
Insurance Study (FIS).
b. Determine the 100-year discharge by using the Rational Method as
outlined in the Storm Drainage section of this manual.
c. The 100-year Rational Method discharge shall be used until that value equals
the FIS discharge determined above
d. If the 100-year discharge determined by the District’s SSMIP watershed study
is more conservative than the above value, then the SSMIP discharge shall be
used.
8. For flood plain areas not covered by FEMA regulations, the District will not
allow offsite rise in the 100-year water surface elevation due to an encroachment in the
channel or overbanks.
5.010.03 Filling in Flood Plain Areas
1. If a tract of land, located in the flood plain, has been the subject of unauthorized fill, the
flood plain study shall be based on ground conditions prior to placement of
unauthorized fill.
2. Placement of fill shall be in accordance with FEMA guidelines as allowed by
the governing municipality's flood plain ordinance and consistent with any other
governmental restrictions. In Unincorporated St. Louis County, the floodway fringe
may be filled without providing equivalent storage in the flood plains of the Missouri
River, the Mississippi River and the Meramec River. However, there may be the need
for wetland delineation first, since flood plain areas have high probability for wetlands.
3. Placement of fill, roadway embankments or placement of buildings may occur within
areas designated as a floodway on the Flood Insurance Floodway maps, but only as
allowed by municipal Floodplain Ordinance and supported approved calculations.
5.010.04 Detention Basins in Flood Plains
Detention basins will be allowed in flood plain areas if all other flood plain requirements are
satisfied.
5.010.05 Bridges in Flood Plains
1. Bridges, culverts, roadway embankments or any encroachment planned in the
floodway shall not increase the 100-year water surface elevation adjacent to or beyond
the project site.
2. Bridges in flood plain areas shall be designed on a 100-year storm frequency
and shall provide a minimum of one (1) foot of freeboard between the bottom of the
superstructure and the 100-year water surface elevation.
5.010.06 Parking Lots in Flood Plains
1. No parking lots will be allowed within the 15-year flood plain.
Revised 2/15/2015 94
5.010.07 Site Plan Requirements
1. The site plan shall show existing and proposed contours, existing and
proposed 100-year floodway limits, and existing and proposed 100-year high water
elevations as a minimum. The contour interval shall be two (2) feet or less. The site
plan shall also show locations of the proposed encroachment and structure(s), together
with existing topography.
2. The site plan shall show the entire flood plain (not just the project site area) a
minimum of two hundred (200) lineal feet downstream and upstream of the proposed
project.
3. Cross section locations and alignment shall be shown on the site plan. The sections
should be located perpendicular to the flow in both the channel and overbanks. The
sections shall be taken and plotted left to right looking downstream. The flood profile
shall be plotted for inclusion in the study.
4. Cross sections shall show the following items:
a. 100-year water surface elevation.
b. Manning's "n" values
c. Top of bank locations
d. Horizontal stationing, vertical elevations
e. Existing and proposed ground lines
f. Existing and proposed sewers
g. Cross section identification as it relates to the site plan and hydraulic study
h. Existing or proposed structures
i. Floodway limits
5. Crossroad culverts in the flood plain shall be designed on a 100-year storm
frequency and provide a minimum of two (2) feet of freeboard at the road shoulder line.
6. Basement elevations, with the exception of walkouts, must be one (1) foot above the
100-year flood elevation. Basements outside the flood plain limits may be below the
100-year flood elevation if a sanitary pump is installed in the basement with the
outgoing plumbing located above the 100-year elevation.
7. The lowest finished floor elevation of all new or redevelopment structures, including
slab on grade, shall be minimum of one (1) foot above the 100-year flood elevation. .
The low sill of all structures in or adjacent to the floodplain shall be a minimum of two
(2) feet above the 100-year flood elevation.
8. Channel and overbank (flood plain) velocities should generally not increase by more
than fifty percent (50%) over pre-developed conditions. Velocities in excess of five (5)
feet per second (fps) in channels shall require erosion protection.
Revised 2/15/2015 95
6. RECOUPMENT RULES AND REGULATIONS
6.010 General
Any owner or owners of real property within the District and within the area to be sewered may make application to the
District for the private construction of sanitary sewers, combined sewers, pumping station, sewage disposal plants and any
other sewer facilities which will herein-after be known as "sewer facility" for purposes of those recoupment rules and
regulations. The Board of Trustees of the District shall decide whether or not it is in the public interest to proceed with such
private construction under the recoupment program.
6.020 Contract Between District and Owner(s)
If the Board finds it is in the public interest to privately construct the sewer facility, the Director shall have the power to
contract with the owners of the real estate for the construction of the sewer facility to serve the area in which the real estate is
located, and such other area as can be efficiently served by the sewer facility to be constructed. Approval of the contract by
the Board of Trustees is necessary to make it binding.
6.030 Recoupment Provisions
Any contract discussed in Section 6.020 shall also provide for the reimbursement to the owners by any owner of real estate
who directly or indirectly taps into or uses the same and did not contribute to the original cost of the sewer facility. The
reimbursement amount shall be the fair pro-rata share of the cost of construction of said sewer facility, subject to such
reasonable rules and regulations as the Director may provide, before plan approval by the District. Construction inspection
and final inspection shall be performed on all construction of recoupment sewer facilities.
The recoupment is only for the additional cost of sewer facilities built larger, i.e. greater in size, than the minimum size
required for the project outfall. An 8” diameter sanitary sewer is the normal minimum size of pipe for a project. However, a
very large project could require a larger size minimum diameter. No guarantee is made of full recovery within the term of the
contract. The contract has a 10-year term and is non-interest bearing. It is paid out of 75% of the connection fee collected by
MSD from subsequent, tributary development by others, if any during the life of the contract.
The costs as described in Section 6.040 shall be furnished to the District and certified by the Owner for approval as further
described in Section 6.040.
6.040 Recoupment Procedures and Project Costs
A formal letter requesting recoupment must be initiated by the owner. Plans, specifications and three competitive sealed bids
of the complete cost of construction or a copy of the proposed contract for the construction and a tributary area map must be
submitted to and receive the approval of the District before plan approval by the District. Construction inspection and final
inspection shall be performed on all construction of recoupment sewer facilities.
Certified costs actually expended for labor and materials, obtaining rights-of-way, permit and inspection fees, insurance,
bond premiums, legal and engineering fees, and other costs essential to the construction of the sewer facility shall be
furnished to the District for approval. Proof of payments are required. The Executive Director shall examine these costs and
upon his approval, as rendered or as adjusted, they shall be certified by him as the complete construction costs of the facility.
6.050 Objections to Certified Completed Construction Costs
Any person objecting to the amount of the approved total construction costs of the sewerage facility, as certified by the
Executive Director, may appeal to the Board of Trustees of the District by filing, in writing, with the Secretary of said Board
the specific objections to said costs. Upon receiving such appeal, the Board of Trustees will consider the matter, and after
consideration of all the facts will finally certify the approved total construction costs of the sewerage facility.
6.060 Recoupment Fees
Recoupment fees shall be determined by applicable ordinances of the District. They shall be payable to the District and/or its
Agents or Assigns.
Revised 2/15/2015 96
6.070 Areas Served by More Than One Sewer Facility Under Recoupment
For properties served by two or more sewer facilities constructed under separate recoupment agreements, charges
shall be divided proportionately between the builders of the facilities based upon the ratio of the actual cost of each
recoupment agreement to the total actual cost under all agreements.
6.080 Connection to Recoupment Sewer Facility
The District shall not approve any plan or issue any permit for a connection to the sewer facility until payment has been made
to the District or its Agents or Assigns, of the pro-rate share of the certified cost of the sewer facility.
6.090 Reports of Owner of Sewer Facility
6.090.01 Annual
Each year, on or before January 31, a report shall be filed with the District giving the correct
name and address of the owner of the sewer facility, and a record of all payments received for
connections to said sewer facility prior to January 1 of the year for which the report is filed,
along with a statement of the remaining balance. Failure to file this report shall cause the District
to send by registered mail, a notice to the last recorded address of the owner of the sewer facility
registered with the District. If the owner fails to file the required report within the designated
time noted in said notice, the recoupment contract shall then become null and void and no further
recoupment fees shall be collected.
6.090.02 Interim
If at any time the Executive Director has probable cause to suspect that the owner of any
recoupment sewer facility is not performing any of the covenants of the recoupment agreement,
he may make demand, by registered mail, for a report giving the information required in the
annual report, for that portion of the calendar year prior to the date of such demand. If the owner
fails to file such report within the designated time noted after the date of such demand, the
recoupment contract shall then become null and void and no further recoupment fees shall be
collected.
6.100 Extent of and Time Limits of Recoupment
The right to recoup construction costs shall continue until the total amount of all pro-rata shares collected from all parcels
connected to the sewer facility, excluding interest where applicable, equals the certified construction cost of the sewer facility
as approved by the District. This recoupment period shall last for a period of time to be established by the District.
Revised 2/15/2015 97
7. EASEMENTS
7.010 General
All sewers shall be constructed in easements with working room. Existing easements without working room may only be
used if revised to include working room. All public sewers, storm drains and open channels shall be constructed in public
rights-of-way or in easements. No permit for construction or improvement of any public sewer, drain or storm channel will
be issued without the provision of suitable permanent easements. Easements required shall be acquired and submitted to the
District except for recorded subdivision plats. The District shall record all easements before plans will be approved.
Recording fees are paid by the Developer and not the District, for private development and municipal projects. Easement
plats shall be prepared in full accordance with the District's *Plan Preparation Guidelines
(http://www.stlmsd.com/Contractors/PlanPrepGuide/PlanPrepGuide.asp), latest edition. The District may also require
stormwater discharge easements and ponding easements where applicable.
7.020 Use of Existing Easements
Every existing easement to be used shall be shown on the plans submitted for review and approval. The information on the
plans shall include the City or County book and page numbers of the recorded instrument.
All restrictive clauses as to the use of the easements, i.e. for utility purposes, storm sewers only, sanitary sewers only, etc.
shall be noted on the plan adjacent to the pertinent easement. Construction of a sewer in the same easement with a water or
gas main will not be approved unless the easement is of such size that the locations of the sewer and utility relative to each
other comply with dimensional clearances required by the regulatory authorities.
7.030 Location of Easements
In locating easements, consideration shall be given to the property owner's interests. Undue splitting and angling across
property shall be avoided. Easement locations shall be fixed by distances to known property lines or public right-of-way
lines and, where necessary, by angles.
7.040 Width of Easements
The width of the easement shall be sufficient to allow proper access for maintenance of the sewer. Easement widths shall
provide a two (2) feet minimum clearance between outside limit of structures to easement line with a ten (10) foot minimum
width. All easements shall include additional space adjacent to the right-of-way so granted as may be required for working
room.
7.050 Wording of Easements
Easements should be prepared on the District standard forms, which carry the proper wording for the easement dedication.
There are various forms, some for easements on property owned by an individual or individuals, and some for corporate
owners. Examples of which forms to use and how to fill them out can be found in the District’s Plan Preparation Guidelines
(http://www.stlmsd.com/Contractors/PlanPrepGuide/index1.html). A sample of the cover sheet required by the Recorder’s
offices can be found also. Variations in wording are acceptable only where necessary, and approved by the District. Print
and original signatures and initialing shall be in black or dark blue ink. Easement Plat "Exhibit A" shall also be initialed and
dated in ink by grantor(s).
7.060 Easement Plat Preparation Information Guidelines
7.060.01 Label Established Lines Affecting Tract and/or Mentioned in its Legal Description:
The following lines shall be shown, where pertinent:
1. Lot lines
2. Subdivision lines (affected, adjacent, or near)
3. Section lines (or sub-section lines)
Revised 2/15/2015 98
4. U.S. Survey lines
5. Street, road, highway and alley right-of-way lines with widths
Property is to be located in relation to known corners along the above listed established lines.
7.060.02 Identify Parcel or Tract:
The following written information shall be shown, where pertinent:
1. Legal subdivision name, with Lot and Block, Plat Book and Page; if in a recorded
subdivision
2. For metes and bounds described parcels, the current owner with Book and
Page labeled across tract; add N/F (Now or Formerly) preceding owners'
names.
3. Fully dimension owner's property (or as much as shown)
4. Show "North" arrow and scale with "North" to top or side of plat
5. Above owner's name indicate property locator number per current assessor’s records
7.060.03 Provide Accurate Title Box Information:
The following information shall be shown, where pertinent:
1. Label as "Easement Plat"
2. Describe only where easement is sought, not wherein all the owner's land lies
3. Use as applicable in St. Louis County:
a. Subdivision name, Lot Number, Block Number, and Plat Book Number
and Page Number, followed by municipality (if incorporated), followed by
"St. Louis County, MO", OR
b. Section Number (or fractional section), followed by Township and Range,
followed by Municipality (if incorporated), followed by "St. Louis County,
MO" OR
c. U.S. Survey No., followed by Township and Range, followed by Municipality
(if incorporated), followed by "St. Louis County, MO"
4. Within the City of St. Louis use as applicable City Block Number, Outlot Number,
Subdivision Name, Lot Number (if within subdivision), Block Number, Plat Book
Number, and Page Number, followed by "City of St. Louis, MO."
7.060.04 Easement Plat Drafting Guidelines
(Refer to current Plan Preparation Guidelines
(http://www.msd.st-louis.mo.us/Contractors/PlanPrepGuide/index1.html)
that elaborate on the following:)
1. General
Revised 2/15/2015 99
a. The standard blank plat labeled "Exhibit A" is to be used in
preparation of easement plats or temporary construction
licenses. Mylars will not be accepted.
b. Use line weights, symbols, style, and size of lettering in uniform direction that
will make an uncluttered, easy-to-read plat; i.e. show all that is necessary, but
nothing extraneous.
For clarity purposes, dark blue or black lettering and lines should be used.
(1) No lettering shall be smaller than (8) point print or #80 "Leroy" lettering
guide, assuming easement is not to be reduced when recorded.
(2) The resultant easement plat or temporary construction license should be
easily understandable by property owners and portray all information
necessary for a surveyor, with adequate field notes, to stake it out on the
ground.
c. No title blocks of any kind, other than shown in examples, shall
be used.
d. At the top left hand corner, outside of plat border, indicate the District's exact
project name and reference number as appropriate.
e. In the bottom left hand corner outside of the plat border, indicate the date of
the most recent version of the Easement Plat.
2. Show complete location and alignment of Easement required with:
a. Distances along intersected property line to nearest property corners
b. Bearing (or angle) and distance for each course of easement across property
c. All calculated and set distances are to be to the nearest hundredth of a foot
and bearings to the nearest second
d. Indicate easement width(s), and information so that a metes and
bounds description for the easement could be written and the area calculated.
Show existing easements and indicate appropriate Deed Book and Page, or
Plat Book and Page
e. Show only pertinent information. Do not show items such as building lines,
sewers, areas, etc.
7.070 Vacation of Easements [See Amendment 5]
The District shall consider vacating its rights within an easement or public right-of-way when it determines that the
easement or right-of-way is not required for any existing or future sewer or drainage facility.
The vacation of an easement or the District's rights within a public right-of-way can only be accomplished with the
approval of the Director. by the passage of an Ordinance by the District's Board of Trustees. In order to determine
if the easement or right-of-way can be vacated, and to prepare the vacation document, Ordinance, the following
information must be provided to the District:
1. A letter from the petitioner stating the reason or the request to vacate.
2. A legal description of the area to be vacated, prepared by a registered land surveyor, and an Easement
Vacation Plat, prepared in the format outlined in Section 7.06.
Revised 2/15/2015 100
If the District determines that there is no future need for the easement or right-of-way in question, a
vacation document an Ordinance will be prepared. for consideration and adoption by the Board of
Trustees.
If the easement to be vacated is part of a project still under review or construction, a vacation document an
Ordinance will not be prepared or presented for consideration and adoption by the Board of Trustees until
such time as the project has received construction approval or by special permission of the Director. The
exhibit A Easement Vacation Plat however will still be reviewed as part of the Plan Review process.
In certain situations, if as-built/construction approval is being delayed, easement vacation may proceed by
special approval of the Director.
Upon the Director’s approval of the vacation, passage of the Ordinance, the petitioner will be required to
submit the recording fee, payable to MSD the "Recorder of Deeds" for the recording of the vacation.
Ordinance.
Should the District determine that it is necessary to retain its rights within the easement or public right-of-
way in question; the petitioner will be notified in writing that the request has been denied.
7.080 Easement Encroachment [See Amendment 5]
Easement encroachments, especially for buildings or other such structures are to be strongly discouraged; are
undesirable to the District for private development projects, and are an undesirable position for both future project
Owners and the District to be put in. Sewer location and alignment requirements of sub section 3.020.07, 3.020.085,
4.020.06 and 4.020.07 are consistent with and intended to reduce the need for such encroachments.
The District shall consider allowing the encroachment of a structure over or onto an easement in which it has rights,
only in cases when there is no reasonable way to relocate the existing sewer or drainage facility or relocate the
proposed structure or other encroachment.
The District may require that the structure which would encroach over or onto an easement be constructed with a
pier and grade beam foundation design, with the piers extending a minimum of 2 feet below the flowline of the
sewer or drainage facility.
In some situations, casing pipe may be used. The casing pipe must be sized adequately to allow the “carrier pipe” to
be properly placed within, and to accept the designed load on the casing pipe. The length of the casing pipe will
extend beyond the geogrid or similar reinforcement of the modular block retaining wall. After the casing pipe is in
place, the pipe within the casing pipe shall be placed on and supported by steel rails or other approved supports.
Both ends of the casing pipe shall be sealed.
In addition, the District may require that the sewer or drainage facility be structurally rehabilitated before allowing
such encroachment. All costs associated with this rehabilitation will be the responsibility of the petitioner.
The following information must be submitted before the District will consider an encroachment:
1. A letter of request from the petitioner stating the reason for the encroachment.
2. Three (3) sets of plans showing the existing sewer or drainage facility, the existing easement, the
proposed structure, and the proposed foundation design in plan and profile relative to the sewer.
The foundation design calculations must also be submitted.
Upon receipt of this information, the existing sewer will be inspected to determine its condition.
Based on this inspection and a review of the plans, the District will determine if the
encroachment will be allowed and what, if any, sewer rehabilitation, will be required.
If the encroachment is to be allowed, the property owner will be required to enter into an
"Encroachment Agreement" with the District. The property owner will also be required to
Revised 2/15/2015 101
submit a recording fee, payable to MSD the "Recorder of Deeds" for the recording of this
document.
If the encroachment is denied, the petitioner will be notified in writing of this denial.
7.090 Indemnity Agreement
The District will consider entering into an Indemnity Agreement with the property developer when the developer is
unable to acquire a stormwater discharge easement from the adjacent property owner, for the discharge of
stormwater onto the adjacent property.
The property developer must submit the following items for the District's consideration:
1. A letter of request to enter into an Indemnity Agreement in lieu of acquiring the Stormwater
Discharge Easement.
2. Adequate documentation verifying that reasonable effort was made to acquire the Stormwater
Discharge Easement.
3. A site plan indicating the proposed location of the stormwater outfall structure and energy
dissipater (as required). Hydraulic calculation for the energy dissipater design will be required.
Revised 2/15/2015 102
8. APPROVAL AND DEDICATION OF PROJECTS WITH PUBLIC SEWERS [Amended. See Section 16]
8.010 General
The District will accept for dedication, all public sewers, pump stations and sewerage treatment facilities within easements
dedicated to the District that have been constructed to the District standards and for which the requirements stated herein
have been met.
The maintenance of these public facilities will remain the responsibility of the project Owner until such time that they have
been accepted for dedication by the District.
8.020 Requirements for Plan Approval and Issuance of Permits
8.020.01 Agreement to Dedicate
An executed "Agreement to Dedicate" will be required for projects involving construction of
public sewer facilities. The District will provide two (2) copies of this document to the Owner
as part of the plan review process. These forms must be executed by the record Owner and
returned to the District. The District will execute the documents and return one (1) copy to the
Owner. Plan Approval will not be given for a project having public sewer facilities until the
"Agreement to Dedicate" has been executed by both parties.
An "Agreement to Dedicate" will not be required from the State of Missouri, any incorporated
municipality, the City of St. Louis or St. Louis County or other tax supported government utility
(school/fire district). All Projects submitted by these entities will be dedicated at the time
construction approval is issued by the District.
8.020.02 Construction Escrow Deposit and Cash Deposit Agreement [See Amendment 2 & 3]
Prior to the issuance of construction permits, a Construction Deposit for all public facilities, as
well as an As-Built Deposit will be required as stated in Chapter 9. In addition, the project
Owner will be required to execute a Construction Deposit Agreement Guaranteeing Completion
of Sewer Improvements. Two (2) copies of this document will accompany the Plan Approval
Notice to the Owner. The agreements must be executed and returned to the District before
construction permits will be issued. One original will be returned to the Owner upon execution
by the District.
8.020.03 Conditional Plan Approval [Amended. See Section 16]
Conditional plan approvals may be issued in very limited instances, with a written agreement
with the District. In such cases an additional Construction Deposit in the amount of $10,000.00,
may be assessed upon compliance with all requirements as noted in the “Conditional Plan
Approval” the District will release the Deposit within fourteen (14) days of review/approval by
the Plan Reviewer.
8.020.04 Flexibility for BMP Permitting and Inspection [Added by Amendment 2]
Developments with BMPs placed on each lot but for which no new public sewers are constructed
may be divided into individual “P#’s” for the purpose of tracking BMP inspections and
collecting and releasing the BMP deposits. The Developer’s Engineer shall indicate the
Developer’s interest to do this prior to plan approval. Once plans are approved, these requests
cannot be accommodated.
Additional administrative costs are required to provide for this flexibility. These costs will
generally include a submittal fee and review fee proportional to the level of effort required to set
up each individual “P#”, the amount to be determined on a case-by-case basis.
Revised 2/15/2015 103
8.030 Requirements for Construction Approval
8.030.01 Construction Inspection
All public sewer facilities must be inspected by the District. It is the responsibility of the
Owner's Contractor to contact the District's Construction Department to arrange for this
inspection. The District will not grant Construction Approval for any public sewer facilities,
which were not constructed in accordance with approved plans and with the District inspection.
The District will not allow the physical connection of the new public sanitary sewer construction
to the existing system until construction approval has been given. Occupancy permits will be
withheld by St. Louis County or the local municipality until Construction Approval is given.
8.030.02 Field Changes and Plan Revisions
It is the intent and purpose of "Field Change" approvals to minimize the need for a formal plan
revision for minor changes to the approved plans, and to minimize delays in construction. The
following are the general procedures for processing a Field Change.
1. Initial requests for a change may be made verbally to the Engineering Department by the
Owner, the Owner's Engineer or the Owner's Contractor, and followed up with a letter of
request for file documentation. The petitioner should state the requested changes and the
reason for the change.
2. Upon receipt of the request, the District will evaluate the proposed change to determine if it
is to be allowed. In addition, if the request is made by someone other than the Owner's
Engineer, the District will formally contact the Engineer to obtain authorization for the
change, and request a letter of authorization for file documentation.
3. If determined to be necessary, revised hydraulic calculations may be required from the
Owner's Engineer.
4. If the change is allowed, the Owner's Engineer will be required to submit the “required
number” sets of the plan sheet(s) indicating the change. These plans may be copies of the
original plans with the change noted in red. On occasion 11” X 17” excerpts of the original
plan sheet(s) may be allowed. They should be to original scale and sealed.
5. The Engineering Department will notify the Construction Department of the approved field
change and send copies of the changed plans to the appropriate District personnel, the
Owner, Engineer, Contractor and municipal agencies.
6. The Contractor will be responsible for payment of all inspection fees associated with the
change prior to Construction Approval.
7. Field changes must be indicated on the "As-Built" drawings.
Significant change(s) to the HGL; the need for additional special structure(s), or additional
permit(s) or significant fees or deposits; or, significant revisions to the project or missing
requirements will preclude use of a “field change” format. In that case a formal plan revision will
be necessary, instead.
8.030.03 As-Built Drawings
As-built drawings and State Plane Coordinates, certified by a Land Surveyor or Engineer
registered in the State of Missouri, must be submitted to the District for review and acceptance
prior to construction approval. As a minimum, the following information shall be provided for
the As-Builts:
Revised 2/15/2015 104
1. Storm, Sanitary and Combined Sewers
As-built drawings and State Plane Coordinates shall indicate the vertical and
horizontal location of the storm, sanitary and combined sewers and structures
in plan and profile view, including any and all changes from the Approved
Plans and “Field Changes”. Special attention shall be paid to situations where
sewers have moved out of easements. In those cases, additional easement(s) to
be obtained must be so shown and so labeled.
2. Detention Basin
a. A field survey of the basin shall be made to confirm the basin's location, size,
shape and depth. As a minimum the as-built drawings and State Plane
Coordinates shall include:
(1). As-built cross-sections of the basin plotted over the design cross-
sections.
(2) Spot elevations shown in plan, defining the location and elevation of
the basin berm and overflow spillway.
(3) Location, length, size, shape and flowline elevation of the detention
basin concrete swale.
(4) Control and overflow structure location, configuration, size,
elevations, and any other information relevant to the proper
operation of the structure (i.e.; opening size; low flow and outlet pipe
size, slope and flowline and sill, orifice, weir elevations; etc.).
b. Based on the field survey information, an elevation vs. storage table or curve
of the detention basin should be submitted.
c. Should the District be concerned that the as-built detention basin varies
significantly enough from the approved basin design that it may not function
as designed the District will require that new detention calculations be
submitted for review. Based on this review, modifications to the detention
basin may be required before acceptance of the as-built plans and release of
any escrow.
3. Pump Station Construction
a. As-Built Drawings and State Plane Coordinates shall indicate the physical
location of the pump station, retention, access road force main, tuned locator
markers and other related structures.
b. Shop Drawings of all structures.
c. Equipment manuals and pump operating curves for any items which differ
from the original design as a result of a field change.
d. For the pump(s) actually installed, and at the end of the job and in addition to
the Manual and pump curve(s) from the equipment supplier, also provide the
District Pump Station Division with pump serial number(s), model number,
impeller trim, et cetera.
Revised 2/15/2015 105
e. The pump(s) will need to be run under actual conditions. Actual discharge
pressures will then be used to determine actual operating point on the curves.
Pumps running at the end of the curve will not be accepted.
4. Subdivision Plats
A recorded copy of the subdivision plat must be submitted with the As-Built drawings.
5. Geotechnical Engineer's Certification
Geotechnical Engineer's Certification will be required verifying that all work associated
with the treatment of sinkholes, placement of compacted fill, and other soils-related
work was completed in accordance with the approved Geotechnical Report.
6. State Plane Coordinates
State Plane Coordinates as detailed below, are required on all improvements
requiring As-built Drawings by the District.
a. Horizontal Data
All horizontal data provided on facilities will be in State Plane Coordinates –
Missouri East Zone, NAD 83(HARN). All horizontal coordinates provided
shall have an accuracy of 50mm.
b. Vertical Data
All vertical data provided on facilities will be according to the NGVD29 (St.
Louis County & St. Louis City Benchmark Books Datum). All vertical data
shall have an accuracy of 60mm.
c. Deliverables
An electronic points file of all state plane information will be required. The
electronic points file shall be delivered as electronic media along with as-built
drawings. The format for the electronic points file should be as follows:
Electronic points file: Comma delimited text file with the extension of file type
of ASC. The format of the file should be:
Point, Northing, Easting, Elevation, Description (P, N, E, Z, D)
Point: Survey point number
Northing: Horizontal Data for Northing of State Plane coordinate
Easting: Horizontal Data for Easting of State Plane coordinate
Elevation: Vertical Data for Elevation of Top of Structure, Manhole Lid, etc.
Description: Identifying number assigned to structure or location that
corresponds with the plans.
Example: File name: P-12345-00.ASC
Sample: 22, 1020432.283, 850432.952, 501.82, MH 23
23, 1020641.663, 850350.877, 503.96, MH 24
24, 1022447.353, 848806.986, 507.24, MH 25
Revised 2/15/2015 106
8.030.04 Stormwater Quality Management Facilities and Construction Cash Deposit Agreement
[Added by Amendment 2, Amended by Amendments 3 and 5]
Construction of Stormwater Quality Management Facilities is not required for construction
approval. However, prior to the issuance of construction approval items a.) and b.) below shall
be completed:
a. The project owner shall execute a "Construction Deposit Agreement Guaranteeing
Completion of Stormwater Quality Management Facilities". Two (2) copies of this
document will accompany the Plan Approval Notice to the Owner. This document
must be executed and returned to the District before construction approval will be
issued. One original will be returned to the Owner upon execution by the District.
b. The project owner shall provide a construction deposit for all stormwater quality
management facilities, as stated in Chapter 9.
c. BMP permits shall be obtained prior to BMP construction. The permittee shall
apply for all stormwater BMP permits. The owner executed “Construction Deposit
Agreement Guaranteeing Completion of Stormwater Quality Management
Facilities" and associated deposit shall be provided to MSD before stormwater
BMP permits are issued. [Modified by Amendment 5]
8.030.05 Notification of Construction Approval [See Amendment 2]
The District will notify the Owner and the Owner's Contractor when construction approval is
given. In addition, St. Louis County or the local municipality will be notified that occupancy
permits may be released.
8.040 Requirements for District Approval of Stormwater Quality Management Facility Construction [Added by
Amendment 2]
8.040.01 Construction Inspection [See Amendment 3]
All permitted stormwater quality management facilities must be inspected by the District. It is the
responsibility of the Owner's Contractor to contact the District's Construction Department to
arrange for this inspection.
The District will issue a “BMP Construction Completion Letter” when its inspection indicates
that stormwater quality management facilities were constructed satisfactorily and in compliance
with approved plans. The District will not issue a BMP Construction Completion Letter for any
facilities which were not constructed in accordance with approved plans and without District
inspection. No portion of the Stormwater Quality Management Facilities Construction Deposit
will be released without the District issuing the BMP Construction Completion Letter.
Stabilization of the drainage area tributary to stormwater quality management facilities is very
important to the facility’s function. The District will also perform an inspection of the drainage
area tributary to stormwater quality management facilities. The District’s determination of
drainage stability will be determined when the drainage area’s final landscape cover is
established. Any vegetated covers should provide a uniform, evenly distributed final vegetative
cover with a minimum density of 80 percent. MSD reserves the ability to require additional site
stabilization measures, where construction sediment or other construction materials are affecting
BMP performance.
8.040.02 Field Changes and Plan Revisions
Revised 2/15/2015 107
Requirements for field changes and plan revisions for stormwater quality management facilities
are the same as those listed in 8.030.
8.040.03 As-Built Drawings [See Amendment 2, Section 16]
As-built drawing requirements for stormwater quality management facilities are similar as those
listed in 8.030 for detention basins. As-built drawings shall be submitted to the District for
review and acceptance prior to issuance of the BMP Construction Completion Letter.
MSD may waive as-built drawings for stormwater BMPs on a case-by-case basis. In general, this
waiver will be limited to smaller surface BMPs that serve small, controlled drainages (e.g.,
bioretention fed by roof downspouts). This waiver, when applicable, will be noted by MSD on
approved plans.
8.050 Dedication and Release of Construction Deposit [See Amendment 2 & 3]
8.050.01 Residential and Commercial Subdivisions, Apartments and Condominiums [See
Amendment 2]
B. Initial Dedication Inspection
Upon completion of fifty percent (50%) of the lots in the total residential or commercial
subdivision, or fifty percent (50%) of the buildings in an apartment or condominium
development, the District will perform a dedication inspection upon receipt of a written
request from the Owner.
1. If there are no deficiencies, the District will release one-half of the monies
held in deposit within fourteen (14) days of the receipt of a properly executed
"Sewer Dedication Agreement" form.
2. If deficiencies are noted within the system, the Owner has ninety (90) days to
correct these deficiencies.
a. If the deficiencies are not corrected within this period, the District
will contact St. Louis County or the local municipality and request
that all unissued building permits and occupancy permits be withheld
until the deficiencies are corrected. Extensions may be granted for
inclement weather or other extenuating circumstances.
b. Upon correction of the deficiencies, the Owner will be responsible
for requesting a reinspection of the system.
c. The District will release one-half of the within fourteen (14) days of
the second inspection, provided all deficiencies have been corrected
to the District's satisfaction and receipt of a properly executed
"Sewer Dedication Agreement" form.
B. Final Dedication Inspection
Upon completion of one hundred percent (100%) of the lots in the total residential or
commercial subdivision, or one hundred percent (100%) of the buildings in an
apartment or condominium development, and within three (3) years of the execution of
the Cash Deposit Agreement, the District will perform a final dedication inspection
upon receipt of a written request from the Owner.
Revised 2/15/2015 108
1. If there are no deficiencies, the District will release the remaining
Deposit within fourteen (14) days of the inspection, provided both
the Owner and the District execute a Sewer Dedication Agreement
(if not already executed at the fifty percent (50%) completion stage).
2. If deficiencies are noted within the system, the Owner must correct
these deficiencies before the remaining monies will be released.
a. Upon correction of the deficiencies, the Owner will be
responsible for requesting a reinspection of the system.
b. The District will release the remaining Deposit and within
fourteen (14) days of the second inspection, provided all
deficiencies have been corrected to the District's
satisfaction, and the Sewer Dedication Agreement is
executed by both the Owner and the District (if not already
executed at the fifty percent (50%) completion level).
c. Fees for multiple inspections will be required as stated in
sub-section 8.040.03.
3. If the development is not completed within three (3) years of the
execution of the Cash Deposit Agreement, the remaining Deposit
will not be returned to the Owner and will be used by the District, at
its discretion and in any manner the District sees fit, to complete any
improvements or correct deficiencies.
8.050.02 Sewer Extensions and Single Lot Developments [See Amendment 2]
The District may release fifty percent (50%) of the Deposit for small sewer extensions and single
lot commercial and residential developments at the time of construction approval, provided the
“Sewer Dedication Agreement" is executed by both the Owner and the District.
The remaining fifty percent (50%) would be released as stated in 8.040.01.B - Final Dedication
Inspection.
8.050.03 Dedication Inspection Fees [See Amendment 2]
A. All projects with public sewer facilities will receive a total of four (4) dedication
inspections (four (4) for Pump Station inspections) by the District without charge as
follows:
1. The first inspection and the reinspection at the fifty percent (50%)
development completion.
2. The first inspection and the reinspection at the one hundred percent (100%)
development completion.
3. One inspection and one reinspection at each stage of the pump station
construction.
Inspection fees, as determined by the District, will be required for each additional inspection.
The amount of these fees will be deducted from the Deposit to be released to the Owner.
8.060 Pump Stations [See Amendment 2]
Revised 2/15/2015 109
Pump Stations will be accepted for dedication upon Construction Approval of the project. The “Sewer Dedication
Agreement” for pump stations constructed as part of a subdivision, apartment or condominium project will not be executed
until all items in 8.040.01 have been completed.
The District will release the Pump Station Deposit upon completion of the two stages of the pump station construction as
described below.
The Owner must submit a written request to the Escrow Section of the Engineering Department for inspection and release of
the Pump Station Deposit. Only one (1) inspection may be requested within a thirty (30) day period.
The inspection and release of the Deposit will be made only if the District agrees that the necessary work is complete and no
discrepancies have been identified.
Pump Station Deposit Account:
A. Stage One
1. “Fifty percent (50%) Inspection” and Release of Deposit
a. One hundred percent (100%) of the construction of the pump station structure, storage
tank, force main and pump bases. This inspection requires the wet well floor to be dry.
B. Stage Two
1. “One hundred percent (100%) Inspection” and Release of Deposit
a. All electrical and mechanical equipment installed and in operating condition. All
paving, fencing, site restoration, and any additional easement requirements completed
and written notice of Construction Approval. Operation of the pumps must be within
acceptable limits of pump curves. Flow into station must be less than or equal to
projected flow. Flow must be free from excessive grease and other foreign substances.
b. Letter of completion from installing paving contractor, guaranteeing all pavement and
pavement subsurfaces have been installed per the District Pump Station Design
Requirements document.
8.070 Abandonment of Work [See Amendment 2]
Upon receipt of a written statement from the Owner that further work on the project has been abandoned, the District shall
determine whether or not the uncompleted work is required to ensure the public health, safety and welfare. Should it be
determined that completion of the work is necessary, the District shall utilize the monies deposited in the Construction
Deposit for the project to complete this work.
Should the District determine that the completion of the work is not required; the Construction Deposit shall be released in
accordance with Section 8.040.
8.080 Release of Stormwater Quality Management Facilities Construction Deposit [Added by Amendment 2,
Amended by Amendment 3]
The District will release up to seventy-five percent (75%) of the deposit upon issuance of BMP Construction Completion
Letter. For sites with multiple (more than four (4)) permitted BMPs, the District will consider proportionally releasing the
deposit at twenty-five percent (25%) and fifty (50%) percent of the total number of BMPs constructed.
Where dedication of public sewers is not required, the District will also perform an inspection of the drainage area tributary
to stormwater quality management facilities. MSD will hold the balance of the stormwater quality management facility
deposit until the BMP drainage areas (for which the developer has disturbed or has reasonable control over) is sufficiently
stable for stormwater quality management facility operation and all BMPs are functioning properly.
Revised 2/15/2015 110
Where dedication of public sewers is required, the District will perform the inspection of the drainage area tributary to
stormwater quality management facilities as part of the dedication inspection process. The balance of the BMP deposit will
be released as part of the dedication process.
Revised 2/15/2015 111
9. FEES AND DEPOSITS REQUIRED BEFORE PLAN APPROVAL AND ISSUANCE OF CONSTRUCTION
PERMITS
9.010 Fees Required Before Plan Approval
The District will require that certain fees be paid prior to the acceptance of the plans for review, or the subsequent
approval of these plans. Failure to submit the fees in a timely manner could delay the review and approval of the
plans. No plans will be approved until all required fees have been paid.
Since the amount of these fees are subject to change, no amount for these fees is given herein. Please contact the
District for a current list of fees.
9.010.01 Submittal Fee
A submittal fee in the amount indicated on the District Engineering Form E.2 must be submitted
along with the plans and Form E.2. Failure to submit this fee, Form E.2 or the appropriate
number of plans, will result in the rejection of the plans for review.
9.010.02 Review Fee
The District will charge a fee to review the project based on the acreage of the development.
This fee will be determined by the District, and the Owner will be notified of the amount as part
of the review process. The Review Fee must be paid with the second (2nd) submittal of Plan sets.
Review of second submittal will not begin until after receipt of Review Fee.
9.010.03 Connection and System Development Fees
A Connection Fee will be required for all projects, which require sanitary sewer service. This fee
will be based on the domestic water tap size for the project in accordance with the District
Ordinance 9346, or successor.
In addition, a System Development Fee may be required if the project is located in an area where
a subdistrict, impact area or recoupment area has been established by Ordinance.
These fees will be determined by the District, and the Owner will be notified of the amount as
part of the review process.
9.010.04 Recording Fees [See Amendment 5]
The Owner will be responsible for paying the recording fees for all documents to be recorded
with the Recorder of Deeds for St. Louis County or the City of St. Louis. Checks are to be made
payable only to MSD. the appropriate Recorder. Documents are to be reviewed by the District
prior to execution. After execution and notarizations, the documents are to be delivered to the
District for transport to the Recorders Office and MSD will then pay the Recording Fees along
with the Recording Fees. (Subdivision plats are not recorded by the District for private
development projects).
9.020 Deposits Required Before Issuance of Construction Permits [See Amendment 2 & 3]
For projects with public sewer facilities, detention facilities or private facilities requiring the District construction inspection,
certain deposits will be required prior to the issuance of construction permits. All Construction Deposits, Stormwater Quality
Management Facility Deposits, and Conditional Plan Approval Deposits must be in the form of cash, a cashier’s check, wire
transfer, or letter of credit. No vouchers or Letters of Credit will be accepted. As-Built deposits may be cash, cashier
checks, corporate checks personal checks or wire transfer. The Construction Deposit, Stormwater Quality Management
Facility Deposit, and As-Built Deposit must be remitted from the Owner, not the Contractor or Engineer.
Revised 2/15/2015 112
9.020.01 As-Built Deposit
An As-Built Deposit will be required for projects with public sewers which are to be dedicated to
the District, and for projects with detention facilities. The As-Built deposit will be released to
the Owner upon Construction Approval of the project and review and approval of the As-Built
drawings by the District.
9.020.02 Construction Deposit [See Amendment 2 & 3]
The Owner will be required to submit to the District a Construction Deposit. When the deposit is
in the form of cash, the amount of the deposit shall be ten percent (10%) of the estimated
construction cost of the public sewers and private facilities to be constructed under the District
inspection, not including stormwater quality management facilities (see 9.020.05 for BMP
deposits). When the deposit is in the form of a letter of credit, the amount is also ten percent
(10%), however, the minimum amount of the letter of credit shall be $30,000. The Deposit
amount will be computed by the District at the time of request for required number of plans.
Release of the Construction Deposit will be made as stated in Chapter 8.050.
9.020.03 Pump Station Escrow Deposit
The Owner will be required to submit to the District a Pump Station Deposit in the amount of
one hundred percent (100%) of the estimated construction cost of the pump station, force main
and storage system. The Deposit amount will be computed by the District at the time of request
for required number of plans.
Release of the Pump Station Deposit will be made as stated in Chapter 8.070.
9.020.04 Conditional Plan Approval Deposit
The owner will be required to submit to the District a Conditional Plan Approval Deposit. The
Deposit amount will be determined by the District at the time a request for a Conditional Plan
Approval is made.
Release of the Conditional Plan Approval Deposit will be made as stated in Chapter 8.020.03.
9.020.05 BMP Deposit [Added by Amendment 2 and amended by Amendment 3 and 6]
The Owner will be required to submit to the District a BMP Deposit (Stormwater Quality
Management Facility Deposit) in the amount of fifty percent (50%) of the estimated construction
cost of the stormwater quality management facilities constructed under the District inspection.
When the deposit is in the form of a letter of credit, the minimum amount of the letter of credit
shall be $30,000. The Deposit amount will be computed by the District at the time of request for
required number of plans.
Release of the BMP Deposit will be made as stated in Chapter 8.080.
It is noted that the BMP deposit can be paid later in the construction process (i.e. after MSD
permits have been issued for sewer construction). However, the BMP deposit must be paid
prior to:
a.) issuance of MSD BMP permits, and
b.) MSD construction approval for sewer construction
Revised 2/15/2015 113
10. CONSTRUCTION PERMITS
10.010 General
10.010.01 Permits Required
Any person, firm or corporation desiring to construct, install, relocate, connect or reconnect any
sanitary, combined, or stormwater sewer or drainage facility, whether public or private, within
the boundaries of the District shall cause plans and specifications therefore to be prepared by a
registered professional engineer, licensed in the State of Missouri, and shall cause the same to be
submitted to the District for examination, revision, and approval according to the design
standards of the District. Such approval shall be a condition precedent to the issuance of a permit
for the construction of such facilities, and no such facilities shall be constructed without a permit
therefore from the District. All such plans and specifications shall be prepared in such form and
manner as may be prescribed by the District.
10.010.02 Defaults
No person shall be entitled to a permit while such person is in default in the performance of any
of the obligations to the District with respect to a previous permit issued to such person by the
District.
10.020 Permittee [See Amendment 2]
Excluding certain aboveground stormwater quality best management practices, all applications for permits for construction of
sewer and drainage facilities, for connection to such facilities and for repair of a connection to such facilities shall be made
by a master drainlayer having a certificate of qualification or other applicable license to perform work as a master drainlayer
issued in his name by the Board of Examiners of Plumbers and Drainlayers of the City of St. Louis or of St. Louis County or
other applicable licensing authority.
For permit application for aboveground stormwater quality best management practices: where the permittee is not a master
drainlayer, the permittee shall provide MSD a certificate of General Liability Insurance meeting the requirements of Section
10.090.01 and 10.090.02 before permits are issued
All applications for permits for construction of sewer and drainage facilities, for connection to such facilities and for repair of
a connection to such facilities shall be made by a master drainlayer having a certificate of qualification or other applicable
license to perform work as a master drainlayer issued in his name by the Board of Examiners of Plumbers and Drainlayers of
the City of St. Louis or of St. Louis County or other applicable licensing authority.
10.030 Performance Bond [See Amendment 4]
Excluding permits for certain above ground stormwater quality best management practices, no construction or
connection permit shall be issued unless the applicant shall first have filed with the District a cash or corporate bond in
an amount not less than Ten Thousand Dollars ($10,000.00). Such bond shall run to the District and shall be
conditioned as follows:
That the permittee, his agents and servants, shall comply with all of the terms, conditions, provisions,
requirements and specifications of the District's applicable Rules and Regulations and Standard Construction
Specifications.
A permittee may elect to maintain such bond with respect to all permits issued hereunder during the period of
the bond or with respect to a single permit.
Before acceptance, all bonds shall be approved by the Director or a designee thereof. All bonds must be executed by a
surety or insurance company satisfactory to the District with the following qualifications:
• Duly authorized to transact business in Missouri as evidenced by a Certificate of Authority granted by the Insurance
Commissioner, Department of Insurance, State of Missouri.
Revised 2/15/2015 114
• Having a financial strength rating of "A" or better and a financial size category of Class V or higher per AM Best
Company.
If a cash bond is offered, it shall be deposited with the Secretary-Treasurer, who shall give his official receipt therefore,
reciting that the cash has been deposited in compliance with and subject to the provisions of applicable Rules and
Regulations.
No construction or connection permit shall be issued unless the applicant shall first have filed with the District a cash or
corporate bond in an amount not less than Ten Thousand Dollars ($10,000.00). Such bond shall run to the District and shall
be conditioned as follows:
That the permittee, his agents and servants, shall comply with all of the terms, conditions, provisions, requirements and
specifications of the District's applicable rules and regulations.
A permittee may elect to maintain such bond with respect to all permits issued hereunder during the period of the bond or
with respect to a single permit.
Before acceptance, all bonds shall be approved by the Appointing Authority. All bonds must be executed by a surety
company satisfactory to the District and duly authorized to transact business in Missouri as evidenced by a Certificate of
Authority granted by the Insurance Commissioner, Department of Insurance, State of Missouri. The surety company must
have a policyholder's rating of "A" or better and a financial rating of Class V or higher in BEST'S KEY RATING GUIDE,
latest edition. If a cash bond is offered, it shall be deposited with the Secretary-Treasurer, who shall give his official receipt
therefore, reciting that the cash has been deposited in compliance with and subject to the provisions of applicable rules and
regulations.
10.040 Construction and Connection Permit and Fees
In addition to the fees stated in Chapter 9, the following fees, deposits, or escrows may be required prior to the issuance of
the Construction and Connection permits.
10.040.01 Connection Permit and Fee
Each applicant for a connection permit shall, at the time of filing an application, pay to the
District a permit fee as applicable. No refunds will be given for connection permit fees. If the
permittee is unable to locate a wye according to the measurements given on the permit, the
District's Permit Office shall be contacted. Indiscriminate tapping in any sewer line is not
permitted. District ordinance prohibits leaving any sewer connection "... open, unsealed, or
incomplete in a manner which permit stormwater, ground water, or surface water to enter any
District sanitary sewer.” Any person found guilty of violation is subject to fine and/or
imprisonment.
10.040.02 Construction Permit and Fee
Each applicant for a construction permit shall, at the time of filing an application, pay to the
District a fee for the issuance of a construction permit.
10.040.03 Machine Tap Permit and Fee [Amended by Amendment 6]
In all cases where a connection is to be made to an existing sewer, at a point where an existing
stub or “wye” is not available, the physical connection to such existing sewer shall be made by
the permittee only when District personnel are present to inspect the work. In cases where the
permittee is not using a tee saddle, inserta tee or “rolling in” a wye, MSD will furnish a saddle
and apparatus for connections up to twenty-four (24) inches in diameter. The permittee shall
furnish the labor and the balance of materials required at the site, including the connecting sewer
pipe. Fees are assessed when the permit is applied for.
Revised 2/15/2015 115
In all cases where a connection is to be made to an existing sewer, up to twenty-four (24) inches
in diameter, at a point where an existing stub or "wye" is not available, the physical connection to
such existing sewer shall be made only by the District. The District shall furnish the saddle,
apparatus and labor to perform such connection, the permittee to furnish the balance of materials
required at the site, including the connecting sewer pipe. Fees are assessed when permit is
applied for.
10.050 Inspection Fee Deposit
Each applicant for a construction permit shall, at the time of filing application, deposit with the District an estimated
inspection fee. If the sum so deposited shall exceed the inspection costs as finally fixed, and the permittee has complied with
District requirements, the excess amount of such deposit over costs shall be refunded upon written notice of Construction
Approval. If the sum so deposited shall be less than the inspection costs as finally fixed, the permittee shall pay to the
District the amount of the deficiency.
10.060 Expiration and Extension of Permits and Approved Plans
10.060.01 Approved Plans
Plans approved for construction, for which construction permits have not been issued, shall be
held by the District for no more than one year, at which time the documents shall be destroyed.
New plans, and the appropriate submittal and review fees, must be submitted for review and
approval before permits will be issued.
10.060.02 Construction and Connection Permits
1. Construction Permits for which work has not been started within ninety (90) days after the
issuance of the permit shall become void unless a written request is made prior to the
expiration date.
2. Connection Permits for which work has not been started within ninety (90) days after the
issuance of the permit shall become void unless a written request is made prior to the
expiration date.
3. Reinstatement of an expired permit will be granted providing a written request for the
reinstatement is received by the District within the period for which an extension could be
granted.
4. Written requests for an extension or reinstatement shall be addressed to the Permit Section
of the Engineering Department.
5. Not more than one extension shall be granted on any permit without showing cause and the
approval of the Appointing Authority.
10.070 Cancellation of Permits and Refunds of Fees and Deposits
10.070.01 Prior to the Start of Work
A refund of the permit and inspection fees and cancellation of the construction permit will be
made for any permit which has not expired upon receipt of a written statement from the Owner
that the project has been abandoned. The construction permit must be submitted with the written
statement.
Revised 2/15/2015 116
No refund of the permit and inspection fees shall be made for construction permits, which have
expired.
Written statements should be sent to the attention of the Permit Section of the Engineering
Department.
10.070.02 After the Start of Work
A partial refund of the inspection fee for construction permits may be given after the start of the
work upon receipt of a written statement from the Owner that further work on the project has
been abandoned, and the District agrees that the work is not required. The construction permit
must be submitted with the written statement.
Upon receipt of the written statement, the cost of the inspection of work completed shall be
determined by the District. Inspection fees paid to the District in excess of the actual cost shall
be refunded. No refund shall be made for any portion of the permit fee.
Written statements should be sent to the attention of the Permit Section of the Engineering
Department.
10.070.03 Connection Permits
No refunds will be given for connection permit fees.
10.080 Final Determination of Construction Inspection Fees
Upon completion of construction of a project, receipt of final as-built documents, and after the permittee has complied with
all other terms of these rules and regulations, the District shall compute the actual inspection fee based on field
measurements. The District shall be paid therefore, or refund shall be made to the permittee, as the case may be. All
outstanding fees must be made before Construction Approval is given.
10.090 Minimum Insurance Requirements for Off Site Construction [See Amendment 4]
The District may require proof of insurance when projects require off site sewer construction. The need for insurance will be
noted on the Approved Project Plans.
If proof of insurance is required, the permittee must provide a copy of an executed Certificate of Insurance on ISO ACORD
25 form indicating that the permittee has obtained and will continue to carry commercial general liability and comprehensive
automobile liability.
The permittee shall carry and maintain adequate commercial general liability insurance for bodily injury, personal injury and
property damage with a company satisfactory to the District and which is:
1. Licensed to do business in the State of Missouri (Admitted) with a financial strength rating of “A-” or
better and a financial size category of Class VI or higher per AM Best Company; or
2. Not licensed in the State of Missouri (Non-admitted) with a financial strength rating of “A” or better and a
financial size category of Class IX or higher per AM Best Company.
The insurance company will be acceptable regardless of the above requirements if the insurance company furnishes a bond
guarantee or policy containing a provision (commonly referred to as a “cut-thru” endorsement) giving all claimants
thereunder a direct right of recovery against the company’s reinsurer, provided the reinsurer meet one of the qualifications
listed above.
The limits of liability shall not be for less than the amounts listed below and shall be in larger amounts if such are required by
the District.
Revised 2/15/2015 117
10.090.01 Comprehensive Business Automobile Liability:
Insurance shall apply to all owned, non-owned and hired vehicles.
$1,000,000 Liability Coverage each occurrence
-and-
$5,000,000 Excess (Umbrella) 1
1Limits of Excess (Umbrella) coverage for Projects less than $100,000 may be reduced to
$2,000,000.
10.090.02 Commercial General Liability (occurrence form):
The Commercial General Liability (CGL) policy shall include the following:
1. Premises – Operations Liability
2. Blanket Contractual Liability
3. Completed Operations Liability
4. Contractor’s Protective Liability (Independent Contractors)
5. Personal Injury Liability
6. Broad Form Property Damage Liability Endorsement
7. Coverage for explosion, collapse and underground hazards (XCU)
8. Blasting (provided that blasting coverage may be excluded if not to be performed in
connection with the work)
A specific endorsement may be needed if non-standard coverage is provided.
The following wording must be stated in the Description of Operations section of the Certificate:
“No amendments to the ISO Commercial General Liability policy have been made (with the
exception of: _______________)”. The District shall be named as an Additional Insured with
respect to the Project.
Required Limits of Liability
$1,000,000 Combined Single Limit per occurrence per project
$1,000,000 Personal Injury
$1,000,000 General Aggregate per project or location
-and-
$5,000,000 Excess (Umbrella) 2
2Limits of Excess (Umbrella) coverage for Projects less than $100,000 may be reduced to
$2,000,000.
The District reserves the right to require additional commercial general liability insurance as
deemed necessary.
10.090.03 Cancellation & Replacement Policy
Should any of the required insurance coverage be cancelled prior to the expiration date, the
contractor/permittee must provide at least sixty (60) days written notice to the District prior to
the cancellation. For policy cancellation for non-payment of premium, the contractor/permittee
must notify the District at least ten (10) calendar days prior to the cancellation.
Revised 2/15/2015 118
Should any of the required insurance coverage be cancelled, terminated or materially altered, the contractor/permittee will
send written notice to MSD at least sixty (60) days prior to the effective date of said cancellation, termination or alteration.
Upon receipt of any notice of insurance cancellation, termination or alteration, the contractor/permittee shall within thirty
(30) days procure other policies of insurance identical in all respects to the policy or policies about to be cancelled,
terminated or altered and shall provide the District with evidence of coverage before the cancellation or termination date; and
if the contractor/permittee fails to provide, procure and deliver acceptable policies of insurance and satisfactory certificates
or other evidence thereof, the District may obtain such insurance at the cost and expense of the contractor/permittee without
notice to the contractor/permittee and elect to pursue any other remedy permitted by law and/or the applicable contract.
The District may require proof of insurance when projects require off site sewer construction. The need for insurance will be
noted on the Approved Project Plans.
If proof of insurance is required, the permittee must provide a copy of an executed Certificate of Insurance on ISO Accord
25s form indicating that the permittee has obtained and will continue to carry commercial general liability and
comprehensive automobile liability.
The permittee shall carry and maintain adequate public liability insurance for Property Damage with a company, which is:
1. Licensed to do business in the State of Missouri (Admitted) with a policyholder’s rating of “B+”
or better and a financial rating of Class VI or higher in Best’s Key Rating Guide, most recent
addition;
2. Not licensed in the State of Missouri (non-admitted) with a policyholder’s rating of “A” or better
and a financial rating of Class IX or higher in Best’s Key Rating Guide, most recent addition;
3. Organized pursuant to Missouri Insurance Company Act (R.S.Mo 287.900 to 287.920)
The insurance policy will be acceptable regardless of the above requirements if the insurance company furnishes a bond
guarantee or policy containing a provision (commonly referred to as a “cut-thru” endorsement) giving all claimants
thereunder a direct right of recover against the company’s reinsure, provided the reinsurer meet one of the qualifications
listed in the above.
The limits of liability shall not be for less than the amounts listed below and shall be in larger amounts if such are required by
the District.
10.090.01 Comprehensive Automobile Liability:
$500,000 per occurrence: Combined Single Limit
1. All owned (Symbol 2) vehicles, and (provided, that if Contractor owns less than four vehicles,
the District may permit Contractor to provide scheduled (Symbol 7) vehicle coverage for each
owned vehicle and provide an accompanying letter listing all the vehicles owned and
guaranteeing that prior to the Contractor’s acquisition of any additional vehicle, the Contractor
will provide notice to the District and obtain appropriate coverage).
2. Non owned and hired vehicles used in connection with the work (Symbols 8 and 9).
10.090.02 Commercial General Liability (occurrence from):
The minimum required commercial general liability shall be as follows:
$500,000 Combined Single Limit each occurrence
$1,000,000 Annual Aggregate
$1,000,000 Annual Aggregate (per job)
Revised 2/15/2015 119
The District reserves the right to require additional commercial general liability insurance as
deemed necessary.
The following wording must be stated in the Description of Operations section:
“No amendment to the ISO Commercial General Liability policy have been made (with the
exception of: _______________) and the District shall be named as an Additional Insured with
respect to the project.”
Insurance policy will not be acceptable if any of the following coverages are excluded from the
ISO Commercial General Liability policy:
1. Premises – Operations Liability
2. Blanket Contractual Liability
3. Completed Operations Liability
4. Contractor’s Protective Liability (Independent Contractors)
5. Personal Injury Liability
6. Broad Form Property Damage Liability Endorsement
7. Coverage for explosion, collapse and underground hazards (X.C.U.)
8. Blasting [provided that blasting coverage may be excluded if blasting is not to be
performed in connection with the work].
10.090.03 Cancellation
The Cancellation Provision in the Certificate shall read as follows:
(Items in parentheses should be removed)
Should any of the above described policies be cancelled before the expiration date, thereof, the
insuring company will (ENDEAVOR TO) mail thirty (30) days written notice to the certificate
holder named to the left (BUT FAILURE TO MAIL SUCH NOTICE SHALL IMPOSE NO
OBLIGATION OR LIABILITY OF ANY KIND UPON THE COMPANY, IT’S AGENTS OR
REPRESENTATIVES).
Any insurance certificate which contains the above cancellation provision will not be deemed
unacceptable for including an additional limitation of only ten (10) days notice for cancellation
for non-payment of premium.
Revised 2/15/2015 120
11. INSPECTION
11.010 General
Before approval of the construction of any sewerage or drainage works, a field inspection will be made by the District
personnel, to verify that such works have been installed and constructed in accordance with the plans, designs and
specifications approved by the District before the start of the construction.
Before final approval or acceptance of any dedication to the District of a completed sewerage or drainage facility, the District
shall determine whether or not all requirements due under terms of any and all permits issued by and contracts with the
District with respect to such sewerage to drainage facilities have been satisfied.
11.020 Privately Constructed Sewers and Treatment Facilities
All privately constructed sewers and sewage treatment facilities shall have obtained the proper permits and shall have had
District inspection during construction, supplemented by a final inspection before approval as either a recoupment facility or
for dedication acceptance upon completion. These sewers and facilities shall have had "As-built" plans submitted for final
review and approval before dedication or acceptance for recoupment.
11.030 Maintenance and Operation Inspection
Operation and maintenance of any private, semi-public or industrial sewage disposal, pump station or treatment facility shall
be subject to inspection by the District at all times.
11.040 Fees
For house connections and industrial connections, and for the repair of house connections and industrial connections, the
inspection fee is combined with the permit fee.
No permits will be issued for construction or repair of house and industrial connections, or for construction of sewerage and
sewage disposal, pump station or treatment facilities until the required inspection fee or inspection fee has been paid to the
District.
11.050 Inspection
His/Her agent must notify the District 24 hours prior to commencing construction of permitted work. Failure to notify the
District may result in the removal and replacement of the uninspected sewer and/or appurtenances.
Revised 2/15/2015 121
12. REGULATION AND CORRECTION OF IMPROPER PRIVATE SEWER FACILITIES
12.010 General
Some buildings within the District's boundaries have leaking or failing septic tanks, sanitary lines which connect into storm
sewers or discharge on open ground, broken or improper sanitary sewers, and other improper sewerage facilities, which
constitute a public nuisance. Further, it is frequently impossible or impractical to persuade the Owner of such property to
repair such sewers or to make a connection of such improper sewer facilities to a public sewer when such public sewer is
available. Consequently, the following procedures and regulations are followed by the District.
12.020 Notification to Owner
Whenever the District determines that any building has improper sewerage facilities which are creating a public nuisance and
the use of such improper sewerage facilities is a menace to public health, the District shall send a notice to the owner or his
agent by mail, informing him of such condition and permitting him a period of 30 days after date of such notice to correct
such condition by making repairs or making such connection to a public sewer. The time of thirty (30) days can be extended
at the discretion of the District.
12.030 Expiration of Period Without Work Being Done
If the corrective work is not done within the thirty (30) day period given in Section 12.020 or the authorized extension
thereof, the owner or his agent may appear before the Executive Director or his representative on the day and hour given in
the notification (see Section 12.020) and show cause why the District should not make such repairs or make such connection
with its own forces and assess the costs thereof as a tax against the property for which such work is done.
12.040 District to Proceed with Work
Within 10 days after the owner or his agent have appeared to show cause why the District should not make such repairs or
such connection, the Executive Director shall make his decision regarding such work. If, in his opinion, the owner or his
agent have failed to show cause why such repair or construction should not be made, he shall direct the Director of
Operations to estimate the probable cost of the work, and if such estimated cost does not exceed $5,000, to cause such work
to be done under his direction and to his satisfaction, and an accurate account kept of the cost of all labor, including
supervision, and material entering into such work.
12.050 Cost of Work - A Lien
Upon completion of such work as is authorized as set out in Section 12.040, the District shall determine the actual total cost
of the work, which shall be assessed as a special lien against each lot or ground chargeable therewith in the name of the
owner thereof. Such assessments shall become a lien upon the property charged therewith upon filing with the Recorder of
Deeds of the City of St. Louis or of St. Louis County, as the case may be.
12.060 Appeal from Decision to Proceed with Work
Should the property owner or his agent be dissatisfied with the decision or order of the Executive Director or his authorized
representative, to proceed with the repairs or construction, he may appeal the decision or order to the Board of Trustees of
the District, by filing a written notice of appeal, which shall be served on the Executive Director within ten (10) days after
such decision or order has been given. The Board of Trustees will then set the matter down for hearing within thirty (30)
days.
Should the Board, after a full and complete hearing, uphold the decision of the Executive Director or his authorized
representative, then he may proceed as indicated in Section 12.040 and 12.050.
Should the owner or his agent be still dissatisfied, he may appeal from such order or decision to the appropriate Circuit Court
as set forth in Section 12.110 of the PLAN OF THE DISTRICT, except that the proceedings upon such order as appealed
from the decision of the Board shall not be stayed unless a restraining order shall be granted by a court of competent
jurisdiction.
Revised 2/15/2015 122
13. SEWAGE PUMPING STATIONS
13.010 General
A sanitary sewage pump station will only be considered where a thorough study of all alternatives clearly indicates a gravity
collection and disposal system is not practical or feasible. The minimum size of a pump station dedicated to the District shall
have an average daily flow rate influent of 6 gallons per minute (GPM) or greater. In residential terms, this is 20 homes or
more. Where the construction of a sanitary sewage pump station is being considered, the current guidelines regarding plan
review procedures, construction drawing preparation, easements, specifications and acceptance will be provided by the
District in a document called Pump Station Design Requirements (PSDR). Reasonable variances to the PSDR may be
granted by the District. Variance requests must be made in writing and must clearly state why the variance is necessary. A
brief summary of the plan review procedure is described below:
13.020 Pump Station Plan Review Procedure
The following material must be submitted to the District Engineering Department for review.
13.020.01 Design Report
1. The Pump Station Design Report shall be typed and bound in 8½ inch by 11
inch booklet form.
2. The following information shall be included in the report:
a. Title page
b. Sewer system information
c. Pump station and force main design calculations
d. Cycle times/Detention Pipe Design Calculations
e. Summary of results from design calculations
f. Manufacturer's specifications for the mechanical and electrical
components
g. Pump performance curves
13.020.02 Design Drawings
1. The design drawings shall be individual 24 Inch by 36 Inch Design Plan
Sheets
2. The following information shall be included on the drawings:
a. Cover sheet
b. General site plan (Scale 1” = 50’)
c. Pump station site plan (Scale 1/4 inch = 1 foot)
d. Force main plan and profile (Scale 1” = 10’ vertical, 1” – 50’
horizontal?)
e. Gravity sewer plan and profiles with elevations for the building
lateral and the lowest finished floor connection indicated
f. Pump station structure sheet (Scale ½ inch = 1 foot)
g. Pump station mechanical sheet (Scale 1” = 1 foot)
f. Electrical plans and details
h. Miscellaneous details (service panels, alarm towers, etc.)
i. Pump station design requirements
(*Note-Thrust Blocks are no longer required since change to certain approved mechanical joint restraints.)
Revised 2/15/2015 123
13.020.03 Required Submittal
For any project utilizing a pump station, three (3) additional sets of plans and a total of four (4) sets of pump station
design report must be submitted to the Engineering Department. Refer to Section 1.040.02 of this manual for further
information. Incomplete sets will not be reviewed by Engineering or the Pump Station Division and shall be returned to
the Engineer with a request for missing material.
13.030 Low Pressure Sewer Systems (LPSS)
13.030.01 General
A sanitary sewage low pressure sewer system will only be considered where a thorough study of all alternatives clearly
indicates a gravity collection and disposal system or a sewage pump station is not practical or feasible. This will include
developments requiring pumping but fall below the 6 GPM average daily flow rate. Where the construction of a sanitary low
pressure sewer system is being considered, the current guidelines regarding plan review procedures, construction drawing
preparation, easements, specifications and acceptance will be provided by the District in a document called Low Pressure
Sewer System Design Requirements. Additional protection of the existing downstream gravity system (e.g. coatings, linings)
and odor control/treatment facilities may also be required. A brief summary of the plan review procedure is described below.
13.030.02 LPSS Plan Review Procedure
The following material must be submitted to the District Engineering Department for review:
1. Low Pressure Sewer System Design Report:
a. The Low Pressure Sewer System Design Report shall be typed and bound in 8-1/2” x 11” booklet
form.
b. The following information shall be included in the report:
(1) Title page
(2) Sewer system information
(3) Pump station and force main design calculations
(4) Downstream pump station detention pipe design calculations
(5) Summary of results from design calculations
(6) Pump performance curves
2. Design Drawings:
a. The design drawings shall be individual 24” x 36” design plan sheets
b. The following information shall be included on the drawings:
(1) Cover sheet
(2) General site plan
(3) Force main plan and profile
(4) Miscellaneous details
13.030.03 Required Submittal
For any project utilizing a low pressure sewer system, three (3) additional sets of plans and a
total of four (4) sets of the low pressure sewer system design report must be submitted to the
Engineering Department. Refer to Section 1.040.02 of this manual for further information.
Incomplete sets will not be reviewed by Engineering or the Pump Station Division and shall be
returned to the Engineer with a request for missing material.
Revised 2/15/2015 124
14. APPENDIX – VOLUMETRIC METHOD
Introduction
The volumetric design procedure is to be used in cases where detention cannot be designed using the simple
maximum release rate procedure and involves detailed modeling of the local tributary drainage system. The
volumetric approach would be necessary to do the following:
• Determine the release rate when there are off-site upstream flows that cannot be bypassed around the
detention facility.
• Determine whether a detention rate less than the prescribed watershed release rate might meet the
planning criteria.
• Evaluate “interim” conditions when a regional detention facility is planned.
• Determine the detention basin release needed to compensate for development areas that cannot be
drained to the detention pond.
The volumetric procedure has been demonstrated to lead to detention basin designs that are consistent with the
objectives and criteria established for the Stormwater System Master Improvement Plan (SSMIP).
Procedures
Regulatory Requirements and Approach
Prior to conducting the analysis, the regulatory requirements for the watershed should be determined. This is
best accomplished by meeting with MSD staff. At the meeting, the following information can be obtained:
• Planning watershed available information.
• MSD regulatory release rate.
• MSD special requirements due to special watershed problem or capacity limitations.
• Availability of MSD SWMM model at the project location.
The meeting will assist the engineer in determining whether the volumetric approach is required and which
computer model strategy is appropriate. An appropriate model such as SWMM, HEC-1, or TR-55 plus a
routing package must be used.
Analysis
The following steps outline the basic modeling procedure to develop or verify a volumetric-based release rate for a
detention facility. Some of this information may not be needed for simple cases:
1. Delineate sub-basins
a. Proposed development area draining to pond.
b. Proposed development area not draining to pond (should be minimized).
c. Off-site areas draining to proposal pond.
d. Off-site areas draining to proposed bypass.
Revised 2/15/2015 125
2. Define hydrologic parameters, such as area, % impervious, curve number, sub-basin width and time of
concentration. Requirements depend on whether SWMM, HEC-1, or TR-55 is being used. Determine
parameters for:
a. Existing land use.
b. Post development land use.
3. Determine design rainfall distributions for the 2-year and 100-year 24-hour storm events using the
SCS TYPE II distribution.
4. Run Model for 100-year rainfall and obtain the following runoff hydrographs:
a. Existing land use hydrograph for area to be developed plus off-site upstream area draining to
detention basin.
b. Future land use hydrograph for development plus off-site areas (using existing conditions)
draining to detention basin.
c. Future land use hydrograph for area to be developed but not draining to detention basin.
d. Future conditions flow to be bypassed.
5. Determine Critical Time Period
The critical time period will be based on SWMM model results developed during the MSD watershed
planning. The critical time period will be determined by MSD using the following definitions:
a. Start of Critical Time Period is the time of peak runoff from the proposed development under
future land use conditions
b. End of the critical time period is the peak of the existing conditions hydrograph at the
downstream outlet of the watershed or as determined by previous study.
If the SWMM watershed model is not yet available then an approximate critical time period will be defined as
starting at the time of peak rainfall intensity with a duration equal to the time of concentration for the planning
watershed.
6. Determine Critical Time Period outflow volume.
This is the existing conditions runoff volume from the area to be developed plus any runoff from
offsite area that will be routed through the detention basin. The volume is computed based on flow
during the Critical Time Period from the hydrograph in step 4a. above. The runoff volume during the
critical time period must be limited to this volume using detention.
7. Obtain first estimate of the release rate.
The Critical Time Period outflow volume divided by the length of the critical time period in seconds is
the average release rate allowed during the critical time period.
8. Obtain first estimate of required storage.
The required storage is the difference between average release rate in 7. above and overall future
hydrograph. (The overall future hydrograph may the sum of hydrographs 4b and 4c).
9. Conduct analysis of future detention.
Revised 2/15/2015 126
The hydrograph from step 4b. is routed through the proposed detention basin. The detention basin
outflow is then combined with hydrograph from step 4c. if there is one. This is the proposed site
outflow hydrograph. The site outflow volume during the critical time period must be less than or equal
to the existing conditions volume for the same drainage area. Adjust outlet structure and storage
volume until site outflow volume during critical period is equal to existing conditions target volume.
10. Repeat step 4 for the 2-year, 24-hour storm hydrograph. Adjust the outlet design as needed to limit
2-year flows to the prescribed maximum release.
11. Plot performance results
Plot hydrographs of existing conditions flow (4a.) and proposed site outflow (routed pond outflow
plus additional site runoff). The plot should show the critical time period and the target volume
expressed as an average outflow.
Revised 2/15/2015 127
15. Reserved (for future index)
Revised 2/15/2015 128
16. AMENDMENTS TO RULES AND REGULATIONS