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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.
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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.
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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.
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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.
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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.