HomeMy Public PortalAbout07-10-2018 POSTED IN CITY HALL July 5, 2018
PLANNING COMMISSION AGENDA
TUESDAY, JULY 10, 2018
7:00 P.M.
CITY HALL (2052 County Road 24)
1. Call to Order
2. Public Comments on items not on the agenda
3. Update from City Council proceedings
4. Planning Department Report
5. Public Hearing - Ordinance Amendment – Chapter 8 of the City Code
related to Stormwater Management Regulations
6. Approval of May 8, 2018 Planning Commission Minutes
7. Council Meeting Schedule
8. Adjourn
Planning Department Update Page 1 of 2 July 3, 2018
City Council Meeting
MEMORANDUM
TO: Mayor Mitchell and Members of the City Council
FROM: Dusty Finke, Planning Director; through City Administrator Scott Johnson
DATE: June 28, 2018
SUBJ: Planning Department Updates – July 3, 2018 City Council Meeting
Land Use Application Review
A) Woods of Medina Final Plat –710 Shawnee Woods Road and 4412 County Road 116 –
4412 JKP LLC has requested final plat for a 16-lot subdivision on approximately 8.25 acres.
Staff is conducting a preliminary review and will schedule for City Council when complete,
tentatively at the July 17, 2018 meeting.
B) Ditter Concept Plan – Jim Ditter, Tom Ditter, and Ditter Properties have requested review of a
concept plan related to the potential subdivision of four existing parcels totaling approximately 25
acres into six lots. Two of the existing parcels are served by City sewer and included within the
urban service area but all the property is zoned rural residential. The applicants requested that the
City consider rezoning the two parcels served by city sewer to Suburban Residential, allowing the
parcels to be reduced in size to create additional rural lots. The Planning Commission held a public
hearing at the May 8 meeting and feedback was generally supportive of what was proposed. The
Council reviewed on June 19 and raised questions whether designating the property as LDR was
consistent with the objectives of the Comp Plan.
C) Deer Hill Preserve 2nd Addition – Property Resources Development Company has requested final
plat for the 2nd phase of Deer Hill Preserve, to include 5 lots in the northwest portion of the site. The
City Council granted final plat approval at the May 15 meeting. Staff will work with the applicant
on the conditions of approval prior to construction beginning.
D) Reiser lot line rearrangement – 1425 County Road 24 and PID 23-118-23-32-0002 – The
John H. Reiser Trust and Philip W. Reiser Trust have requested approval of a lot line
rearrangement between two 10-acre parcels. The City Council adopted a resolution
approving the rearrangement at the April 17, 2018 meeting. Staff will work with the
applicant to finalize the rearrangement with Hennepin County.
E) Maxxon Site Plan Review – 900-920 Hamel Road – Maxxon has requested a site plan review for a
4,854-square foot addition between the two existing buildings on their property. The applicant
proposes to convert existing bituminous to pervious surfacing because no more hardcover can be
added as a result of the Elm Creek Shoreland Overlay District. The Planning Commission reviewed
at the January 18 meeting and recommended approval. The Council granted approval on February
20. Staff will work with the applicant on conditions of approval before construction begins.
F) School Lake Nature Preserve CD-PUD – Wally and Bridget Marx have requested final plat
approval for their conservation design subdivision of 6 lots and conservation of 70 acres (11.76
buildable). The Council granted final approval at the February 20 meeting. Staff will work with the
applicant on the conditions of approval.
G) Lunski Final Plat – Lunski, Inc. has applied for final approval of the subdivision related to
the development of 83 units of mixed senior housing and 24,000 s.f. of office north of
Highway 55 and west of Mohawk Drive. The Council adopted a resolution of approval at
the November 16 meeting. Staff will work with applicant on conditions of approval before
construction begins.
Planning Department Update Page 2 of 2 July 3, 2018
City Council Meeting
H) Reserve of Medina Second Addition – Toll Brothers has requested approval of the second
phase of the Reserve of Medina project. The City Council adopted approval documents on
September 19. Staff will work with the developer related to the conditions of approval.
I) Johnson ADU CUP, Dykhoff Septic Variance, Hamel Brewery, St. Peter and Paul Cemetery – The
City Council has adopted resolutions approving these projects, and staff is assisting the applicants
with the conditions of approval in order to complete the projects.
J) Hamel Road Thirty Two, Hamel Haven subdivisions – These subdivisions have received final
approval. Staff is working with the applicants on the conditions of approval before the plats are
recorded
Other Projects
A) Comprehensive Plan – Met Council staff has verbally indicated that the City’s 2020-2040 Plan
Update is now complete for review. Met Council staff continues to raise questions related to the
staging of high density residential property. Council members Martin and Anderson, City
Administrator Johnson and myself met with Metropolitan Council Member Katie Rodriguez and
relevant committee chairs who informed us that there would be no flexibility on the staging. The
City Council directed staff to update the Staging Plan to stage the high density residential property
after 2021. This adjustment was resubmitted on June 8, along with a letter stating the City’s strong
preference to stage the property for development immediately and requesting that the Met Council
allow it.
B) Stormwater Ordinance and Design Guide –staff met with Engineering staff to discuss the scope and
workplan for reviewing the City’s stormwater regulations to conform with the City’s surface water
management plan and current practices. The Planning Commission and City Council held a
workshop on the regulations at the May 15 meeting. Staff intends to present the design guide for
review and the ordinance for a public hearing at the July 10 Planning Commission meeting
C) Mixed Residential zoning district – the City held an open house on June 12 and received feedback
on the regulations which will ultimately apply to the Mixed Residential land use. Staff will use this
feedback to draft an ordinance for a public hearing at the August 15 Planning Commission meeting.
D) Safety Training – staff took part in annual safety training.
E) Long Lake Subwatershed Partnership – Scott and I took part in a phone conference related to the
next steps for the partnership following Orono’s decision not to take part in the carp study. The
Minnehaha Creek Board is scheduled on July 12 to discuss contributing to the project to add
additional data collection.
1
CITY OF MEDINA 1
PLANNING COMMISSION 2
DRAFT Meeting Minutes 3
Tuesday May 8, 2018 4
5
1. Call to Order: Chairperson White called the meeting to order at 7:00 p.m. 6
7
Present: Planning Commissioners Aaron Amic, Dino DesLauriers, Kerby Nester, Robin 8
Reid, Janet White, and Rashmi Williams. 9
10
Absent: Planning Commissioner Todd Albers. 11
12
Also Present: City Planner Dusty Finke. 13
14
2. Public Comments on Items not on the Agenda 15
16
No comments made. 17
18
3. Update from City Council Proceedings 19
20
Finke reported that the Council met recently to consider the lot rearrangement for the Riser 21
family, approving the rearrangement. He noted that the Council also reviewed the draft 22
Comprehensive Plan from Loretto. He stated that staff is currently reviewed the Plan from 23
Orono. He noted that the Council received an update on City wells and the irrigation policy 24
of the City which prohibits new development from connecting lawn irrigation systems to the 25
City water system. He explained that lawn irrigation is then either supplied by water reuse or 26
supplemented by private wells. He stated that this change has resulted in less demand in the 27
City’s water infrastructure. He reported that the Council also reviewed the ordinance 28
regarding LED lighting and tabled the ordinance directing staff to clarify language. He noted 29
that the Council also authorized $10,000 for the City to participate in the Long Lake 30
Subwatershed Partnership, which is developing a study to determine the impact of Carp on 31
Long Lake. 32
33
DesLauriers referenced the water runoff pond at Hamel Legion Park and asked if the reuse of 34
that water has been successful. 35
36
Finke reported that the water from that pond is used for irrigation of the fields and also used 37
to supply irrigation water to the Enclave development. 38
39
DesLauriers asked if the wells near the landfill were monitored as part of the well study. 40
41
Finke stated that he did not believe that was part of the study, but noted that he could reach 42
out to the MPCA. 43
44
White asked if there was anything that stands out in the Plan from Loretto. 45
46
Finke stated that Loretto only plans to add 40 homes in the next ten years. He noted that 47
Loretto does plan to abandon their sewage treatment plant and plans to hook up to the 48
Metropolitan Council’s regional system through Medina. 49
50
51
2
4. Planning Department Report 52
Finke provided an update. 53
54
5. Public Hearing – Ditter Properties – 2032-2052 Holy Name Drive – Concept 55
Plan Review of Potential Rezoning and Subdivision 56
57
Finke presented a concept plan review which includes four parcels that would be proposed to 58
be subdivided into six parcels. He stated that two parcels are currently connected to the 59
City’s water/sewer utilities, although all parcels are currently zoned rural residential. He 60
stated that the request, should it move forward, would include a Comprehensive Plan 61
amendment. He displayed an aerial of the 25-acre site and the four lots within that property. 62
He noted that some of the lots are fairly odd shaped and identified adjacent uses. He 63
identified the location of the newly proposed lots, noting that the two lots currently connected 64
to the sanitary sewer system would be shrunk to match the size of a suburban residential 65
property that is served by utilities. He noted that the excess property would then be combined 66
with the remaining property to create additional lots that would remain rural residential. He 67
stated that the basic question is if this seems appropriate to guide the area served by sanitary 68
sewer to low-density residential. He stated that the applicant is not proposing new sewered 69
lots, but to shrink those properties served by municipal utilities and combine the remainder of 70
the land with the other rural residential property. He stated that the proposed lots would meet 71
the requirements of the zoning districts proposed. 72
73
White opened the public hearing at 7:19 p.m. 74
75
No comments made. 76
77
White closed the public hearing at 7:20 p.m. 78
79
Reid stated that this seems like a logical solution and she would support the request. 80
81
DesLauriers asked for clarification on the language proposed on the MUSA. 82
83
Finke explained that the MUSA is required to be mapped for the Metropolitan Council and 84
noted that the current map includes the two parcels connected to the sanitary sewer. He noted 85
that if those parcels are made smaller, the MUSA map would then reflect that smaller area. 86
87
DesLauriers stated that this makes sense and the applicant has met all the technical aspects. 88
He stated that he is also intrigued with restoring and protecting the first home, as the 89
applicant has stated in their documentation. 90
91
White asked if each new lot would have a septic and whether that would impact Holy Name 92
Lake. 93
94
Mr. Ditter stated that there is sufficient land and suitable soils to provide septic sites for those 95
rural residential lots. 96
97
Finke noted that more details on septic systems will be provided if this continues to move 98
forward. He provided additional details on the lots that were bailed out in the past, noting 99
that those sites were typically about one acre in size. 100
101
Amic asked the location of Mr. Ditter’s home. 102
103
3
Mr. Ditter replied that his home is on what would be lot four. And his mother has a life estate 104
on lot one. 105
106
Amic agreed that this seems to make sense. 107
108
Finke stated that there would be perhaps one other example that would be able to follow 109
down this path, but noted that each case would need to stand on its own. He noted that other 110
than those two cases, this would not really be applicable throughout the City. 111
112
Nester asked for details on the existing driveway location. 113
114
Finke provided additional details on the path the existing driveway travels. He noted that the 115
Council will review this concept plan at their meeting on May 15th. 116
117
6. Reminder Special Meeting – Tuesday, May 15, 2018 at 6:00 p.m. 118
119
White reminded the Commission of an upcoming special meeting on Tuesday, May 15th at 120
6:00 p.m. 121
122
7. Approval of the April 10, 2018 Draft Planning Commission Meeting Minutes. 123
124
Motion by Reid, seconded by Amic, to approve the April 10, 2018, Planning Commission 125
minutes as presented. Motion carries unanimously. (Absent: Albers) 126
127
8. Council Meeting Schedule 128
129
Finke advised that the Council will be meeting the following Tuesday and White volunteered 130
to attend in representation of the Commission. 131
132
White noted that Reid has put together a website detailing the history of the Independence 133
Beach neighborhood. 134
135
9. Adjourn 136
137
Motion by DesLauriers, seconded by Nester, to adjourn the meeting at 7:36 p.m. Motion 138
carried unanimously. 139
Stormwater Management Ordinance/ Page 1 of 2 July 10, 2018
Design Guide Planning Commission Meeting
MEMORANDUM
TO: Planning Commission
FROM: Dusty Finke, Planning Director
DATE: July 5, 2018
MEETING: July 10, 2018 Planning Commission
SUBJ: Public Hearing: Stormwater Management Ordinance; Design Guide
Background
At the May 15 joint worksession the Planning Commission and City Council began review of the
City stormwater management requirements. The Commission and Council reviewed
introductory information from the City Engineer (attached for reference) and provided policy
direction.
The regulations are being reviewed for the following primary reasons:
1) The City updated its Surface Water Management Plan (SWMP) in connection with the
Comprehensive Plan last year, and watersheds had updated their requirements the prior
year. The City needs to ensure that regulations are in line with these updates.
2) Stormwater management practices have evolved significantly in the past decade, and this
new information should be incorporated into City guidance documents.
The “Goals and Policies” chapter of the SWMP is attached for reference, which provides
guidance for the City’s regulations. The SWMP in its entirety can be found on the City’s
website: (https://medinamn.us/wp-content/uploads/2016/09/Final-Draft-121217-Part-1.pdf)
Proposed amendments to the City’s stormwater management ordinance are attached for review.
A draft of the updated Stormwater Design Guide is also attached for information. The Planning
Commission should hold a public hearing on the ordinance prior to review and recommendation.
The Commission is not required to act on the Design Guide, but Commissioners are encouraged
to provide feedback.
Summary of Primary Changes
The requirements for Volume Control, Rate Control, and Water Quality are not proposed to be
changed significantly and are generally similar to those commonly required by other
jurisdictions. Even if the City did not have these requirements in place, new development would
be subject to the requirements through watershed review. The City could adopt more stringent
requirements, but has previously adopted the standards shared by most jurisdictions.
Volume Control
The primary change is that the Design Guide proposes to increase the Volume Control
requirement for new development from 1.0 inch to 1.1 inch to be consistent with watershed
requirements.
Stormwater Management Ordinance/ Page 2 of 2 July 10, 2018
Design Guide Planning Commission Meeting
The Design Guide proposes to require that any new development include management practices
designed to keep the first 1.1 inches of precipitation on the site. This requirement is proposed to
be increased from 1.0 inch to be consistent with watershed requirements.
The Design Guide is proposed to add descriptions of additional means to meet the Volume
Control standard. The practice which will likely be used most commonly will be re-use of
stormwater for lawn irrigation. Other practices include credit for preservation of natural areas,
creation of larger buffers, tree planting, or soil corrections.
Triggers/Threshold for Management Practices
While the requirements are similar to the watersheds and other jurisdictions for the sake of larger
developments, it is important to note that the existing regulations are triggered by comparatively
smaller construction projects.
Currently, the City requires stormwater management practices if more than 5000 square feet of
impervious surface is proposed to be added.
Staff has recommended language exempting residential projects which result in less than 20%
total impervious surfaces on a site. Projects adding more than 1/3 acre of hardcover (14,520
square feet) would be required to provide stormwater management even if under 20% total
impervious surfaces.
The thought behind this exemption is that this amount of hardcover should not significantly
impact drainage off the site, provided it can dissipate on the site. In cases where the runoff
cannot dissipate on the site before draining onto neighboring property or into a wetland or lake,
stormwater management would be required.
Action Requested
The Planning Commission should hold a public hearing on the proposed ordinance amendment.
Following the hearing, the Planning Commission should provide feedback on the ordinance and
design guide. Once review is complete, the following motion would be appropriate:
Move to recommend adoption of the ordinance related to stormwater management with
the changes noted by the Commission.
Attachments
1. Draft ordinance
2. Design Guide
3. Goals and Policies from SWMP
4. City Engineer memo from 5/15 Worksession
Ordinance No. ### 1
DATE
CITY OF MEDINA
ORDINANCE NO. ###
AN ORDINANCE REGARDING STORMWATER MANAGEMENT;
AMENDING CHAPTER 8 OF THE CITY CODE
The City Council of the City of Medina ordains as follows:
SECTION I. Section 828.33 of the code of ordinances of the City of Medina is amended by
deleting the struck through language and adding the underlined language as follows:
Section 828.33. Stormwater Management
Subd. 1. Purpose
Land development projects, and associated increases in impervious cover, alter the
hydrologic response of local watersheds. Increases in stormwater runoff rates and
volumes, flooding, erosion, sediment transport and deposition, and water-borne pollutants
can be controlled and minimized through the regulation of stormwater runoff.
The purpose of this ordinance is to protect and safeguard the health, safety, and welfare
of the public by regulating stormwater runoff in order toto protect local water resources
from degradation. This ordinance seeks to meet this purpose through the following
objectives:
(a) minimize increases in stormwater runoff rates from any development in order toto
reduce flooding, siltation and erosion and in order toto maintain the integrity of
stream channels,
(b) minimize increases in nonpoint source pollution caused by stormwater runoff
from development which would otherwise degrade local water quality,
(c) minimize the total annual volume of surface water runoff that flows from any
specific site during and following development so as not to exceed the
predevelopment hydrologic regime to the maximum extent practicable,
(d) ensure that these management controls are properly maintained and pose no threat
to public safety, and
(e) implement stormwater management controls to help meet current and future total
maximum daily load (TMDL) goals, to address the need to improve water quality,
and to meet objectives in the Local Surface Water Management Plan.
Subd. 2. Incorporation by Reference
The Medina Stormwater Design Manual, dated November 15, 2011, as it may be
Ordinance No. ### 2
DATE
amended from time to time, is hereby incorporated into this ordinance as if fully set forth
herein. The Manual shall serve as the official guide for stormwater principles, methods,
and practices for proposed development activities.
Subd. 3. Definitions
For the purpose of this ordinance, the following definitions describe the meaning of the
terms used in this ordinance:
(a) "Applicant" means a property owner or agent of a property owner who has filed
an application for a stormwater management approval.
(b) "Channel" means a natural or artificial watercourse with a definite bed and banks
that conducts continuously or periodically flowing water.
(c) "Impervious Area" means those surfaces that cannot effectively infiltrate rainfall
(e.g., building rooftops, pavement, sidewalks, gravel, driveways, decks,
swimming pools, etc.).
(d) "Land Disturbance Activity" means any activity that changes the volume or peak
discharge rate of stormwater runoff from the land surface. This may include the
grading, digging, cutting, scraping, or excavating of soil, placement of fill
materials, paving, construction, substantial removal of vegetation, or any activity
that bares soil or rock or involves the diversion or piping of any natural or
fabricated watercourse.
(e) "Maintenance Agreement" means document recorded against the property which
provides for long-term maintenance of stormwater treatment practices.
(f) RESERVED “Major Expansion Project” means any construction, alteration, or
improvement which disturbs one acre or more in area or which increases the
Impervious Area by one-half acre or more and where the existing land use is
commercial, industrial, institutional, or multi-family residential. For the purposes
of this section, the area of disturbance when repaving or reclaiming an existing
paved surface shall only include those areas where soil beneath the existing gravel
base is disturbed.
(g) RESERVED “Major Single-family Residential Project” means:
(i) Any subdivision, as defined by law, which result in one or two additional
single-family detached lots; or
(ii) Any construction, alteration, or improvement which: 1) disturbs one acre or
more in area and increases Impervious Area by more than 1,000 square feet;
or 2) increases Impervious Area by more than 5,000 square feet.
(h) RESERVED “Minor Expansion Project” means any construction, alteration, or
improvement which increases the Impervious Area by more than 5,000 square
feet and less than one-half acre where the existing land use is commercial,
industrial, institutional, or multi-family residential.
(i) RESERVED“New Development” means:
(i) Any subdivision, as defined by law. For the purposes of this section, a
subdivision creating less than three new single-family detached lots shall not
be considered New Development, but should instead be considered a Major
Single-family Residential Project.
(ii) Construction of a principal structure on an existing vacant lot. For the
Ordinance No. ### 3
DATE
purposes of this section, construction of a detached single-family home shall
not be considered New Development.
(iii)Redevelopment of a property which results in the removal of more than 50
percent of the market value of the principal structure and such removal is
followed by reconstruction. For the purposes of this section, redevelopment
of a single-family detached home shall not be considered New Development.
(j) "Nonpoint Source Pollution" means pollution from any source other than from
any discernible, confined, and discrete conveyances, and shall include, but not be
limited to, pollutants from agricultural, silvicultural, mining, construction,
subsurface disposal and urban runoff sources.
(k) "Off-Site Facility" means a stormwater management measure located outside the
subject property boundary described in the permit application for land
development activity.
(l) “Responsible Party” means the entity which will be responsible for ownership and
maintenance of Stormwater Treatment Practices.
(m) “Site” means:
(i) For New Development any tract, lot or parcel of land or combination of
tracts, lots, or parcels of land, which are in one ownership, or are contiguous
and in diverse ownership, where development is to be performed as part of a
unit, subdivision, or project.
For a Major Expansion Project, Minor Expansion Project or Major Single-
family Residential Project the area of new construction, as shown on an
approved site plan, or the original parcel. Final determination of the
applicable area for stormwater management shall be made by the City.
(n) "Stop Work Order" means an order which requires that all construction activity on
a Site be stopped.
(o) "Stormwater Management" means the use of structural or non-structural practices
that are designed to reduce stormwater runoff pollutant loads, discharge volumes,
and/or peak discharge rates.
(p) “Stormwater Management Plan” means a set of drawings or other documents
submitted by a person as a prerequisite to obtaining a stormwater management
approval, which contains all of the required information and specifications
pertaining to Stormwater Management.
(q) "Stormwater Runoff" means flow on the surface of the ground, resulting from
precipitation.
(r) "Stormwater Treatment Practices (STPs)" means measures, either structural or
nonstructural, that are determined to be the most effective and practical means of
preventing or reducing point source or nonpoint-source pollution inputs to
stormwater runoff and waterbodies.
(s) "Water Quality Volume (WQ v )" means the runoff storage volume needed to treat
the specified phosphorus loading as determined in the Medina Stormwater Design
Manual.
(t) "Watercourse" means a permanent or intermittent stream or other body of water,
either natural or fabricated, which gathers or carries surface water.
(u) “Watershed” means the total drainage area contributing runoff to a single point.
Ordinance No. ### 4
DATE
Subd. 4. Applicability
(a) This ordinance shall apply to the following circumstances:
(i) New Development, as defined herein;
(ii) Major Expansion Projects, as defined herein;
(iii)Minor Expansion Projects, as defined herein; and
(iv) Major Single-family Residential Projects, as defined herein.
(b) The following activities shall be exempt from the stormwater performance criteria
of this ordinance:
(i) Agricultural activity.
(ii) Repairs to any Stormwater Treatment Practice deemed necessary by the
City.
(iii)Emergency actions as declared by the City.
Land Disturbance Activities which do not meet the thresholds described for New
Development, Major or Minor Expansion Projects, or Major Single-family Residential
Projects as described herein.RESERVED
Subd. 5. Performance Criteria for Stormwater Management
(a) Unless determined by the City to be exempt or granted a waiver, all site designs for the
following development, redevelopment, construction, or land disturbance activities shall
establish Stormwater Management Practices to control the peak flow rates, volume of
flow, and pollutants of stormwater discharge associated with specified design storms and
runoff volumes, as detailed in the Medina Stormwater Design Manual.
(i) Any land development, redevelopment, or construction on a Site which increases
impervious surface by 5,000 square feet or greater, except as described in (iv)
below.
(ii) Any land development, redevelopment, or construction on a Site which disturbs
more than one acre of land, except:
(1) if the total amount of existing and proposed impervious surfaces is
less than 20% of the Site and the proposed grading does not channelize
stormwater discharge off of the property or towards wetland, lake,
waterbody, or area of slopes in excess of 4:1; or
(2) if the activity results in a reduction of existing impervious surfaces
by 10% or greater.
(iii)Any subdivision of property.
(iv) Notwithstanding (i) above, land development, redevelopment, or construction on
a Site which increases impervious surface by 5,000 square feet or greater but less
than 14,520 square feet may be exempt from establishing STPs if all of the
following conditions are met:
(1) The activity occurs on residential property; and
(2) The total amount of existing and proposed impervious surfaces is
less than 20% of the Site; and
(3) The drainage from 5,000 square feet or more of the additional
impervious surfaces are not directed towards one of the following features
within 100 feet: a wetland, lake, waterbody or area of slope in excess of
Ordinance No. ### 5
DATE
4:1; and
(1)(4) The drainage from the additional impervious surfaces are not
channelized onto neighboring property, rights-of-way or waterbodies.
(b) New Development: Rate Control, Volume Control, and Water Quality standards
shall apply to all New Development. The City Council may waive strict
adherence with Rate Control, Volume Control, and Water Quality standards for
redevelopment and new development which results in less than one acre of Land
Disturbance. Best management practices addressing the potential water resource
impacts associated with the proposed activity shall be incorporated to limit
creation of impervious surface, maintain or enhance on-site infiltration, control
peak flow rates, and limit pollutant generation on and discharge from the Site.
Best management practices may include site design and structural and non-
structural practices.
(c) Major Expansion Projects: Rate Control, Volume Control, and Water Quality
standards shall apply to all Major Expansion Projects.
(d) Minor Expansion Projects: Rate Control, Volume Control and Water Quality
standards shall apply to all Minor Expansion Projects. As an alternative to
meeting relevant Volume Control and Water Quality standards, an Applicant may
install a raingarden or similar stormwater improvement as described in the
Medina Stormwater Design Manual. Provisions shall also be required to control
the rate of run-off if determined to be necessary by the City Engineer.
(e) Major Single-family Residential Projects: Rate Control, Volume Control and
Water Quality standards shall apply to all Major Single-family Residential
Projects. As an alternative to meeting relevant Volume Control and Water
Quality standards, an Applicant may install a raingarden or similar stormwater
improvement as described in the Medina Stormwater Design Manual. Provisions
shall also be required to control the rate of run-off if determined to be necessary
by the City Engineer.
Subd. 6. (b) Approval Required Prior to Permit or Subdivision
No landowner or land operator shall receive a building permit, grading permit, or
subdivision approval for any project involving Land Disturbance Activities subject to
this ordinance until first meeting the requirements of this ordinance prior to
commencing the proposed activity.
(c) Exceptions. The following activities shall be exempt from the stormwater
performance criteria of this ordinance:
(i) Agricultural activity.
(ii) Repairs to any Stormwater Treatment Practice deemed necessary by the
City.
(iii) Emergency actions as declared by the City.
(iv) Land Disturbance Activities which do not meet the thresholds described
in this section.
Subd. 7. Application Requirements
Ordinance No. ### 6
DATE
Unless otherwise exempted by this ordinance, an application for stormwater
management approval shall include the following as a condition for its consideration:
(a) a Stormwater Management Plan;
(b) a Maintenance Agreement.
The Stormwater Management Plan shall be prepared to meet the requirements of Subd.
5 of this ordinance; the Maintenance Agreement shall be prepared to meet the
requirements of Subd. 10 of this ordinance.
In lieu of preparation of a Stormwater Management Plan, Major Single-family
Residential Projects and Minor Expansion Projects may install a raingarden or similar
stormwater improvement as described in the Medina Stormwater Design Manual.
Subd. 8. Application Requirements
Applications shall include the following: five copies of the Stormwater Management
Plan, three copies of the Maintenance Agreement, and any required review fees.
Subd. 9. Waivers for Providing Stormwater Management
Every Applicant shall provide for Stormwater Management, unless a waiver is granted.
Requests to waive the Stormwater Management requirements shall be submitted to the
City for approval.
The minimum requirements for Stormwater Management may be waived in whole or in
part upon written request of the Applicant, if the City determines that at least one of the
following conditions applies:
(a) It can be demonstrated that the proposed Land Disturbance Activity will not
impair attainment of the objectives of this ordinance.
(b) Alternative minimum requirements for on-site management of stormwater
discharges have been established in a Stormwater Management Plan that has been
approved by the City.
(c) Provisions are made to manage stormwater by an Off-Site Facility. The Off-Site
Facility is required to be in place, to be designed and adequately sized to provide
a level of Stormwater Management that is equal to or greater than that which
would be afforded by on-site practices and has a legally obligated entity
responsible for long-term operation and maintenance of the stormwater treatment
practice.
In instances where at least one of the conditions above applies, the City may grant a
waiver from strict compliance with Stormwater Management provisions that are not
achievable, if acceptable mitigation measures are provided.
Subd. 10. Stormwater Treatment Maintenance Plan and Agreement
During the application process, the City shall determine who the Responsible Party will
be for ownership and maintenance of all Stormwater Treatment Practices.
Ordinance No. ### 7
DATE
The Responsible Party shall enter into a Maintenance Agreement with the City that
documents all responsibilities for operation and maintenance of all Stormwater
Treatment Practices. Such responsibility shall be documented in a maintenance plan
and executed through a Maintenance Agreement. The Maintenance Agreement shall be
executed and recorded against the parcel.
(a) Maintenance Agreement
The stormwater Maintenance Agreement shall be in a form approved by the City, shall
describe the inspection and maintenance obligations of this section and shall, at a
minimum:
(1) Designate the Responsible Party, which shall be permanently responsible for
maintenance of the structural or nonstructural measures.
(2) Pass responsibility for such maintenance to successors in title.
(3) Grant the City and its representatives the right of entry for the purposes of inspecting
all Stormwater Treatment Practices as described in Subd. 10(b) below.
(4) Allow the City the right to repair and maintain the facility, if necessary maintenance
is not performed after proper and reasonable notice to the Responsible Party as
described in Subd. 10(d) below.
(5) Include a maintenance plan that contains, but is not limited to the following:
(i) Identification of all structural Stormwater Treatment Practices.
(ii) A schedule for regular inspection, monitoring, and maintenance for each
practice. Monitoring shall verify whether the practice is functioning as
designed and may include, but is not limited to quality, temperature, and
quantity of runoff.
(iii)Identification of the Responsible Party for conducting the inspection,
monitoring, and maintenance for each practice.
(6) Identify a schedule and format for reporting compliance with the Maintenance Plan to
the City.
(b) Inspection of Stormwater Facilities
Inspection programs shall be established on any reasonable basis, including but not limited
to: routine inspections; random inspections; inspections based upon complaints or other
notice of possible violations; inspection of drainage basins or areas identified as higher than
typical sources of sediment or other contaminants or pollutants; inspections of businesses or
industries of a type associated with higher than usual discharges of contaminants or
pollutants or with discharges of a type which are more likely than the typical discharge to
cause violations of state or federal water or sediment quality standards or the National
Pollutant Discharge Elimination System (NPDES) stormwater permit; and joint inspections
with other agencies inspecting under environmental or safety laws. Inspections may include,
but are not limited to, reviewing maintenance and repair records; sampling discharges,
surface water, groundwater, and material or water in drainage control facilities; and
evaluating the condition of drainage control facilities and other stormwater treatment
Ordinance No. ### 8
DATE
practices.
When any new Stormwater Treatment Practice is installed on private property, or when any
new connection is made between private property and a public drainage control system,
sanitary sewer, or combined sewer; the property owner shall grant to the City the right to
enter the property at reasonable times and in a reasonable manner for the purpose of
inspection. This includes the right to enter a property when the City has a reasonable basis to
believe that a violation of this ordinance is occurring or has occurred, and to enter when
necessary for abatement of a public nuisance or correction of a violation of this ordinance.
(c) Records of Installation and Maintenance Activities
The Responsible Party shall make records of the installation and of all maintenance and
repairs of the stormwater treatment practices, and shall retain the records for at least three (3)
years. These records shall be made available to the City during inspection of the Stormwater
Treatment Practice and at other reasonable times upon request.
(d) Failure to Maintain Practices
If a Responsible Party fails or refuses to meet the requirements of the Maintenance
Agreement, the City, after reasonable notice, may correct a violation of the design standards
or maintenance needs by performing all necessary work to place the Stormwater Treatment
Practice in proper working condition. In the event that the Stormwater Treatment Practice
becomes a danger to public safety or public health, the City shall notify the Responsible
Party in writing. Upon receipt of that notice, the Responsible Party shall have thirty days to
perform maintenance and repair of the facility in an approved manner. After proper notice,
the City may specially assess the owner(s) of the Stormwater Treatment Practice for the cost
of repair work and any penalties; and the cost of the work shall be assessed against the
property and collected along with ordinary taxes by the county.
Subd. 11. Financial Security
(a) The City shall require the submittal of a letter of credit or other financial security in a
form acceptable to the City in order toto insure that the Stormwater Treatment Practices
are installed by the permit holder as required by the approved Stormwater Management
Plan. The amount of the security shall be 150% of the total estimated construction cost
of the Stormwater Treatment Practices approved, with the exception of Major Single-
family Residential Projects, which shall be 50% of the total estimated construction cost.
The performance security shall contain forfeiture provisions for failure to complete work
specified in the Stormwater Management Plan.
(b) The security shall be released in full only upon submission of "as built plans" and written
certification by a registered professional engineer that the Stormwater Treatment Practice
has been installed in accordance with the approved plan and other applicable provisions
of this ordinance. The City will make a final inspection of the Stormwater Treatment
Practice to ensure that it complies with the approved plan and the provisions of this
ordinance. Provisions for a partial pro-rata release of the security based on the
completion of various development stages may be done at the discretion of the City.
Ordinance No. ### 9
DATE
Subd. 12. Notice of Construction Commencement
The Applicant must notify the City in advance before the commencement of construction.
Regular inspections of the Stormwater Treatment Practice construction shall be
conducted by the staff of the City or certified by a professional engineer or their designee,
and the Applicant shall be responsible for the costs of such inspections. All inspections
shall be documented and written reports prepared that contain the following information:
(a) the date and location of the inspection,
(b) whether construction is in compliance with the approved Stormwater
Management Plan,
(c) variations from the approved construction specifications,
(d) any violations that exist.
If any violations are found, the Applicant shall be notified in writing of the nature of the
violation and the required corrective actions. No added work shall proceed until any
violations are corrected and all work previously completed has received approval by the
City.
Subd. 13. As Built Plans
All Applicants are required to submit actual "as built" plans for any Stormwater
Treatment Practices located on-site after final construction is completed. As-built plans
must show the final design specifications for all Stormwater Treatment Practices, and the
plans must be certified by a professional engineer. A final inspection by the City is
required before the release of any performance securities can occur. The City may waive
certain requirements for the as built plans in the case of a Major Single-Family
Residential Project or a Minor Expansion Project, provided the Applicant provides
sufficient information to verify that the alternative improvements were installed as
designed.
Subd. 14 Violations
Any person who commences or conducted Land Disturbance Activity contrary to this
ordinance is guilty of a misdemeanor and may be prosecuted as such, restrained by
injunction or otherwise abated in a manner provided by law.
(a) Notice of Violation
When the City determines that an activity is not being carried out in accordance with the
requirements of this ordinance, it shall issue a written notice of violation to the owner
of the property. The notice of violation shall contain:
(1) the name and address of the owner or Applicant,
(2) the address when available or a description of the land upon which the violation
is occurring,
(3) a statement specifying the nature of the violation,
(4) a description of the remedial measures necessary to bring the development
activity into compliance with this ordinance and a time schedule for the
completion of such remedial action,
(5) a statement of the penalty or penalties that shall or may be assessed against the
person to whom the notice of violation is directed, and
Ordinance No. ### 10
DATE
(6) a statement that the determination of violation may be appealed to the City by
filing a written notice of appeal within fifteen (15) days of service of notice of
violation.
(b) Stop Work Orders
Persons receiving a notice of violation will be required to halt all construction activities.
This Stop Work Order will be in effect until the City confirms that the Land
Disturbance Activity is in compliance and the violation has been satisfactorily
addressed. Failure to address a notice of violation in a timely manner may result in
civil, criminal, or monetary penalties in accordance with the enforcement measures
authorized in this ordinance.
(c) Civil and Criminal Penalties
In addition to or as an alternative to any penalty provided herein or by law, any person
who violates the provisions of this ordinance shall be guilty of a misdemeanor and
subject to prosecution. Such person shall be guilty of a separate offense for each day
during which the violation occurs or continues.
(d) Restoration of Lands
Any violator may be required to restore land to its undisturbed condition. In the event
that restoration is not undertaken within a reasonable time after notice, the City may
take necessary corrective action, the cost of which may, after notice and opportunity
for hearing, be specially assessed against the property and collected along with the
ordinary taxes by the county.
Subd. 15. Holds on Occupancy Permits
Occupancy permits will not be granted until all Stormwater Treatment Practices have
been installed and accepted by the City, or a financial guarantee in a form acceptable to
the City has been submitted to ensure completion.
Subd. 16. Duration of Approval; Revocation of Approval
(a) Approved plans issued under this section shall be valid from the date of approval through
the date the City notifies the owner that all stormwater treatment practices have passed
the final inspection required under approved conditions, or the approval is revoked.
(b) Revocation of the stormwater approval may be made by the City if requirements within
this ordinance are not fulfilled, or the owner or Applicant is unable to fulfill the ordinance
requirements. If an approval is revoked, the Applicant must resubmit a Stormwater
Management Plan prior to proceeding with any subsequent Land Disturbance Activity.
Subd. 17. Appeals
Any person aggrieved by the action of any official charged with the enforcement of this
ordinance, as the result of the disapproval of a properly filed application for approval,
issuance of a written notice of violation, or an alleged failure to properly enforce the
ordinance in regard to a specific application, shall have the right to appeal the action to
the City.
(a) The Applicant shall submit the appeal in writing and include supporting
Ordinance No. ### 11
DATE
documentation.
(b) City staff shall make a decision on the appeal within 15 business days of receipt of a
complete appeal application.
(c) The Applicant may appeal the decision of city staff to the city council. This appeal
must be filed with the City within 30 days of City staff’s decision.
Subd. 18 Compatibility with Other Permit and ordinance Requirements
This ordinance is not intended to interfere with, abrogate, or annul any other ordinance,
rule or regulation, statute, or other provision of law. The requirements of this ordinance
should be considered minimum requirements, and where any provision of this ordinance
imposes restrictions different from those imposed by any other ordinance, rule or
regulation, or other provision of law, whichever provisions are more restrictive or impose
higher protective standards for human health or the environment shall take precedence.
Subd. 19. Severability
If the provisions of any article, section, subsection, paragraph, subdivision or clause of
this ordinance shall be judged invalid by a court of competent jurisdiction, such order or
judgment shall not affect or invalidate the remainder of any article, section, subsection,
paragraph, subdivision or clause of this ordinance, which shall remain in full force and
effect.
SECTION II. This ordinance shall become effective upon its adoption and publication.
Adopted by the Medina city council this __ day of ________, 2018.
______________________________
Bob Mitchell, Mayor
Attest:
___________________________________
Jodi M. Gallup, City Clerk
Published in the Crow River News on the ___ day of ______, 2018.
Stormwater
Design Guide
for the City of Medina
DRAFT July 2018
Project Number: 011705-000
TABLE OF CONTENTS
Stormwater Design Manual Table of Contents
City of Medina, MN
WSB Project No. 011705-000
1. DESIGN OVERVIEW ........................................................................................................................ 1
2. DEFINITIONS .................................................................................................................................... 1
3. PROCEDURE FOR REVIEWING STORMWATER MANAGEMENT PLANS .................................. 3
4. SUBMITTAL REQUIREMENTS ........................................................................................................ 4
5. LIST OF ACCEPTABLE PRACTICES .............................................................................................. 7
6. BASIC SIZING CRITERIA ................................................................................................................. 8
6.1. Volume Control Requirements ...................................................................................................... 8
6.2. Volume Control Calculations ......................................................................................................... 8
6.3. Water Quality Control .................................................................................................................. 10
6.4. Rate Control ................................................................................................................................ 11
6.5. Wetlands ..................................................................................................................................... 12
6.6. Freeboard .................................................................................................................................... 12
6.7. Floodplain Management .............................................................................................................. 13
6.8. Long-term Inspection and Maintenance of Stormwater BMPs ................................................... 13
7. STORMWATER TREATMENT PRACTICE DESIGN STANDARDS .............................................. 13
7.1. Storm Sewers .............................................................................................................................. 13
7.2. Outlet and Inlet Pipes .................................................................................................................. 14
7.3. Channels and Overland Drainage ............................................................................................... 15
7.4. Ponds .......................................................................................................................................... 15
7.5. Infiltration/Filtration Practices ...................................................................................................... 16
7.6. Emergency Overflow Paths ......................................................................................................... 17
8. DESIGN EXAMPLES ...................................................................................................................... 17
9. STORMWATER TREATMENT PRACTICE DETAIL DRAWINGS ................................................. 17
10. CONSTRUCTION SPECIFICATIONS ............................................................................................ 17
11. CHECKLISTS .................................................................................................................................. 17
LIST OF TABLES
APPENDICES
Appendix A – Construction Sediment and Erosion Control Checklist
Appendix B – Maintenance Agreement Template
Appendix C – BMP Operation and Maintenance Requirements
Appendix D – Standard Details
Appendix E - Ramsey-Washington Metro Watershed District Stormwater Reuse Calculator
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 1
1. DESIGN OVERVIEW
The City of Medina’s Local Surface Water Management Plan (LSWMP) identifies the goals and policies
that define the City’s stormwater management program. The goals and policies are implemented via the
City Stormwater Management ordinance and this Design Manual. Medina’s stormwater requirements
were written to meet the City’s goals to preserve, protect, and manage its water resources as well as to
meet federal, state, and watershed stormwater regulations and to meet the following objectives:
A. Minimize increases in stormwater runoff rates from any development in order to reduce flooding,
siltation, and erosion and in order to maintain the integrity of stream channels.
B. Minimize increases in nonpoint source pollution caused by stormwater runoff from development
which would otherwise degrade local water quality.
C. Minimize the total annual volume of surface water runoff that flows from any specific site during
and following development so as not to exceed the predevelopment hydrologic regime to the
maximum extent practicable.
D. Ensure that these management controls are properly maintained and pose no threat to public
safety.
E. Implement stormwater management controls to help meet current and future total maximum daily
load (TMDL) goals, address the need to improve water quality, and meet objectives in the
LSWMP.
2. DEFINITIONS
For the purpose of this Design Manual, the following definitions describe the meaning of the terms used in
this manual:
a) Applicant means a property owner or agent of a property owner who has filed an application for
a stormwater management approval.
b) Applicability means any land disturbing activity requiring a Stormwater Management Plan as
defined in City Code Chapter 8-1200 Surface Water Management.
c) Best Management Practice (BMPs) means measures, either structural or nonstructural, that are
determined to be the most effective and practical means of preventing or reducing point source or
nonpoint-source pollution inputs to stormwater runoff and waterbodies.
d) Channel means a natural or artificial watercourse with a definite bed and banks that conducts
continuously or periodically flowing water.
e) Impervious Area means those surfaces that cannot effectively infiltrate rainfall (e.g., building
rooftops, pavement, sidewalks, driveways, swimming pools, etc.). Gravel areas will be considered
impervious.
f) Land Disturbance Activity means any activity that changes the volume or peak discharge rate
of stormwater runoff from the land surface. This may include the grading, digging, cutting,
scraping, or excavating of soil; placement of fill materials; paving; construction; substantial
removal of vegetation, or any activity that bares soil or rock; or involves the involves the
maintenance, repair, improvement, diversion, or piping of any natural or man-made watercourse.
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 2
g) Maintenance Agreement means document recorded against the property which provides for
long-term maintenance of stormwater treatment practices.
h) Municipal Separate Storm Sewer System (MS4) means a conveyance or system of
conveyances (roads with drainage systems, municipal streets, catch basins, curbs, gutters,
ditches, man-made channels, storm drains, etc.) that is also:
a. Owned or operated by a public entity (which can include cities, townships, counties,
military bases, hospitals, prison complexes, highway departments, universities, etc.)
having jurisdiction over disposal of sewage, industrial wastes, stormwater, or other
wastes, including special districts under State law such as a sewer district, flood control
district or drainage districts, or similar entity, or an Indian tribe or an authorized Indian
tribal organization, or a designated and approved management agency under section 208
of the Clean Water Act that discharges to waters of the United States;
b. Designed or used for collecting or conveying stormwater;
c. Which is not a combined sewer; and
d. Which is not part of a publicly owned treatment works.
i) New Development Project means any new construction, alteration, or improvement which
increases the impervious area by more than 5,000 square feet.
j) Nonpoint Source Pollution means pollution from any source other than from any discernible,
confined, and discrete conveyances, and shall include, but not be limited to, pollutants from
agricultural, silvicultural, mining, construction, subsurface disposal, and urban runoff sources.
k) Off-Site Facility means a stormwater management measure located outside the subject property
boundary described in the permit application for land development activity.
l) Redevelopment means any construction, alteration, or improvement that has a site size of
greater than one acre and disturbs more than 40% of the site’s existing hardcover. If total
impervious area is reduced by more than 10%, no stormwater management plan is required. For
the purposes of this design manual, the area of disturbance when repaving or reclaiming an
existing paved surface shall only include those areas where soil beneath the existing gravel base
is disturbed.
m) Responsible Party means the entity which will be responsible for ownership and maintenance of
Stormwater Treatment Practices.
n) Single-family Residential Project means any construction, alteration, or improvement which
occurs on a single lot with a designated land use of single-family residential that increases
impervious by more than 5,000 square feet. An exemption for a stormwater management plan will
occur if the impervious cover is less than 20% of the overall property size.
o) Site means any tract, lot, or parcel of land or combination of tracts, lots, or parcels of land, which
are in one ownership or are contiguous and in diverse ownership, where development is to be
performed as part of a unit, subdivision, or project. Final determination of the applicable area for
stormwater management shall be made by the City.
p) Stop Work Order means an order which requires that all construction activity on a site be
stopped.
q) Stormwater Management means the use of structural or non-structural practices that are
designed to reduce stormwater runoff pollutant loads, discharge volumes, and/or peak discharge
rates.
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 3
r) Stormwater Management Plan means a set of drawings or other documents submitted by a
person as a prerequisite to obtaining a stormwater management approval, which contains all of
the required information and specifications pertaining to Stormwater Management.
s) Stormwater Runoff means flow on the surface of the ground, resulting from precipitation.
t) Water Quality Volume (WQ) means the runoff storage volume needed to treat the specified
phosphorus loading as determined in the Medina Stormwater Design Manual.
u) Watercourse means a permanent or intermittent stream or other body of water, either natural or
fabricated, which gathers or carries surface water.
v) Watershed means the total drainage area contributing runoff to a single point.
3. PROCEDURE FOR REVIEWING STORMWATER MANAGEMENT
PLANS
The general review process, from the submittal of the concept and final plans to the issuance of the
Stormwater Management Plan approval, is summarized in the following seven steps.
1) Determine if the project triggers the City of Medina threshold requirements under a New
Development Project, Redevelopment Project, or Single-Family Residential Project, defined in
Section 2.
o Additional activities that are exempt from completing a Stormwater Management Plan
include:
Linear projects completed by the City that do not trigger stormwater permits from
the watershed agencies.
Installation of fence, sign, telephone, and electric poles and other kinds of posts
or poles.
Emergency work to protect life, limb, or property.
2) What non-City permits, or approvals, are required for the project site, and what waivers and/or
exemptions are applicable? (MCWD, PSCWMC, ECWMC, DNR, USACE, MPCA NPDES, WCA,
etc.)
3) Are the selected practices appropriate for this site?
4) Are the practices designed to meet the minimum performance criteria?
5) Does the Stormwater Management Plan meet other resource protection requirements as
specified in the City of Medina Code and LSWMP?
6) Are provisions for long-term maintenance adequate, including access and methods of
maintenance defined?
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 4
4. SUBMITTAL REQUIREMENTS
Requirements for Stormwater Management Plan Approval
Stormwater Management Plan Required
To be completed with ordinance language.
The Stormwater Management Plan must be signed by a licensed professional engineer in the State of
Minnesota, who will verify that the design of all stormwater management practices meet the submittal
requirements outlined in the Stormwater Management Plan Requirements of this section. No building
permit, grading permit, sediment control permit, or subdivision approval shall be issued until a satisfactory
final Stormwater Management Plan, or a waiver thereof, shall have undergone a review and been
approved by the City after determining that the plan or waiver is consistent with the requirements of this
design manual.
Stormwater Management Conceptual Plan Requirements (Optional)
A stormwater management concept plan submittal is optional, but highly encouraged. A concept plan
identifies basic site information, locations of proposed development features, and preliminary locations
and sizing of BMPs. The concept submittal has a greater chance of identifying major obstacles and can
facilitate alternative stormwater management arrangements in a timely fashion. If a concept plan is
submitted for review, it should include sufficient information (e.g., maps, basic hydrologic and water
quality calculations, etc.) to evaluate the environmental characteristics of the project site. This
information should show the potential impacts of all proposed development of the site, both present and
future, on the water resources, and show the effectiveness and acceptability of the measures proposed
for managing stormwater generated at the project site. The intent of this conceptual planning process is
to determine the type of stormwater management measures necessary for the proposed project, to
ensure adequate planning for management of stormwater runoff from future development, and to identify
major issues prior to completing final plans. The concept plan is generally less time consuming and
provides a more efficient process in evaluating proposed development plans and BMPs.
The final plan provides more detailed design information for the proposed BMPs and includes final design
detail in terms of hydrologic conditions and site features.
For redevelopment occurring on a previously developed site, within the concept plan an applicant should
include measures for controlling existing stormwater runoff discharges from the site in accordance with
the standards of this Manual to the maximum extent practicable. After review of the concept plan and
modifications deemed necessary by the City are made, a final Stormwater Management Plan may be
submitted for approval.
Stormwater Management Plan Requirements (Required)
The final Stormwater Management Plan shall include all the information listed below.
Record drawings are required for all projects that impact wetlands and/or the floodplain, require the
construction of BMPs, have significant grade changes, and/or have other unusual circumstances. Record
drawings must be certified by a professional land surveyor or civil engineer. Record drawings should not
include temporary erosion control measures.
Plan Details
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 5
Contact information including name, address, email/telephone number of all persons having a
legal interest in the property, and the tax reference number and parcel number of the property or
properties affected.
North arrow, street names, and lot and block numbers for property or subdivision.
Location of benchmark based on the City/County benchmark system.
Key with all line types, symbols, shading, and cross-hatching denoted.
Illustration key showing symbols for all information pertaining to lot and building design, including
grades, easements, lot and block, setbacks, etc.
Plan scale (shown graphically on a bar scale) of: 1 inch = 20 feet, 1 inch = 30 feet, 1 inch = 40
feet, 1 inch = 50 feet, or 1 inch = 100 feet. Plans in other scales will not be reviewed.
Total area of subject property, with subtotals of disturbed and undisturbed areas (tabulation
permitted).
Subject property’s boundary lines, lot lines, and right-of-way lines.
All existing and proposed drainage and utility easements.
All man-made features, including existing and proposed buildings, structures, and paved areas.
All existing storm sewer facilities within 150 feet of the subject parcel.
All proposed storm sewer facilities (include grades and size of structures).
All existing and proposed natural features including, but not limited to, significant trees and tree
lines, wetlands, ponds, lakes, streams, drainage channels, and floodplain.
Show setbacks and buffers for wetlands, ponds, lakes, streams, and floodplains.
All adjacent plats, parcels, rights-of-way, section lines, extended a minimum of 150 feet beyond
the subject parcel in all directions.
Topography
A 1" = 200' topographic base map of the site which extends a minimum of 50 feet beyond the
limits of the proposed development and indicates existing surface water drainage including
streams, ponds, culverts, ditches, and wetlands; current land use including all existing structures;
locations of utilities, roads, and easements; and significant natural and manmade features not
otherwise shown.
Topography details in a minimum of two-foot contour intervals with existing contours as dashed
lines and proposed contours as dark, solid lines labeled at each edge of the plan and at other
appropriate locations.
Standard lot benching detail, where appropriate (maximum slopes: 3:1).
Direction arrows indicating swales and lot drainage patterns (show percent grades along
drainage swales on plan).
Elevation Information
Proposed top of curb elevations at lot corners and driveway or entrances.
Finished spot elevations at all high and low points including flow path arrows.
Proposed elevations at garage and lowest floor for proposed buildings.
Proposed finished ground elevations around structures for final grading.
Hydrologic and Hydraulic Analysis
Hydrologic and hydraulic design calculations for all structural components of the stormwater system (i.e.,
storm drains, open channels, swales, management practices, etc.) for the predevelopment and post
development conditions must be submitted. Such calculations shall include:
Existing and proposed condition analysis for runoff rates, volumes, velocities, and water surface
elevations showing methodologies used, design parameters, and supporting calculations. Atlas
14 rainfall data and MSE 3 distributions must be used.
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 6
Final sizing calculations for structural stormwater management practices including contributing
drainage area, storage, normal and high-water levels, peak inflow and outflow, and outlet
configuration. Drainage areas must include any offsite drainage.
Stage-discharge or outlet rating curves and inflow and outflow hydrographs for storage facilities
(e.g., stormwater ponds and wetlands).
Analysis, computations, and supporting materials indicating that volume control, water quality,
and water quantity design criteria are being met.
Final analysis of potential downstream impact/effects of project, where necessary.
Dam breach analysis, where necessary.
Existing and proposed structural elevations (e.g., invert of pipes, catch basins, etc.).
Structural details of outlet structures, embankments, spillways, stilling basins, grade control
structures, conveyance channels, etc.
Soils information including Hennepin County Soil Survey or logs of borehole investigations that
may have been performed along with supporting geotechnical report.
Temporary Erosion Control Best Management Practices (BMPs)
Show location of all structural erosion control measures (with standard detail plates and
maintenance information for each), including, but not limited to:
Temporary rock entrance/exit for all vehicle access points.
Perimeter silt fence: silt fence and/or bale checks should also be placed along swales or slopes
greater than 50 feet in length (flare ends of silt fence up slope).
Storm sewer inlet filters (indicate type and show graphically on plan at each location).
Temporary sediment basins.
Erosion control mats, fiber blankets, netting, temporary seed, or temporary mulch. All exposed
soil areas must be stabilized as soon as possible to limit soil erosion, but in no case later than 14
days after the construction activity if that portion of the site has temporarily or permanently
ceased, and no later than seven days after construction activity in that portion of the site where
construction has temporarily or permanently ceased and discharge points on the project are
within one mile of a special or impaired water, as well as flows to that special or impaired water.
Soil stockpile areas (indicate temporary stabilization measures).
Street sweeping required: plans must include a note indicating that all adjacent streets will be
swept daily, or as directed by the City, to remove all accumulated materials. Failure to perform
any street sweeping within six hours of notice by the City will result in the work being performed
by the City and all associated costs billed to the contractor. The City also requires removal of
accumulated materials on streets during winter.
Maintenance and Repair Plan
The design and planning of all stormwater management facilities shall include detailed maintenance and
repair procedures to ensure their continued function. These plans will identify the parts or components of
the BMP that need to be maintained and the equipment and skills or training necessary. Provisions for
the periodic review and evaluation of the effectiveness of the maintenance program and the need for
revisions or additional maintenance procedures shall be included in the plan. The maintenance and repair
plan must include:
Name, address, and phone number of responsible parties for maintenance.
Description of annual maintenance tasks
Maintenance easements. Access to all stormwater treatment practices at the site for the purpose
of inspection and repair must be assured by securing all the maintenance easements needed on
a permanent basis. Maintenance easements will be recorded with the plat and will remain in
effect even if the title of the property is transferred to a new owner.
Landscaping plan that includes a detailed plan for management of vegetation associated with
stormwater features after construction is finished.
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 7
Maintenance agreement that is binding on all subsequent owners of land served by an on-site
stormwater management measure in accordance with the requirements of this manual.
Description of funding source
Minimum vegetative cover requirements
Access and safety issues
Testing and disposal of sediments that will likely be necessary
5. LIST OF ACCEPTABLE PRACTICES
When developing the BMP appropriate for the development or redevelopment, infiltration/abstraction is
the most important practice to apply in the design. Filtration is warranted when site conditions do not
allow for an effective infiltration facility or other abstraction method. For flooding or rate control, detention
systems are typically the preferred practice. Low Impact Design (LID) practices are encouraged when
they can be functionally incorporated into the design. Alternative practices may be approved at the
discretion of the City Engineer.
Designers are expected to follow the nine-step screening process for BMP selection detailed in
the Minnesota Stormwater Manual; BMPs will be scrutinized using these same matrices. Deviations from
recommended guidance in the Minnesota Stormwater Manual will require detailed written explanation.
Approval of any deviation from the Minnesota Stormwater Manual guidance will be at the discretion of the
City.
Green infrastructure options shall be the preferred BMPs for accomplishing stormwater management
goals. The following green infrastructure options should be considered and must be consistent with
zoning, subdivision, and PUD requirements.
1. Preserving natural vegetation.
2. Preserving and utilizing natural upland swales, depressions, and upland storage areas in the
post-development condition to the degree that they can convey, store, filter, and retain
stormwater runoff before discharge. Preservation requires that no grading or other construction
activity occurs in these areas.
3. Eliminating barrier curb and gutter where practicable and using vegetated swales or equivalent.
4. Minimizing impervious surface.
5. Minimizing parking facility size.
6. Installing permeable pavement.
7. Maximizing open space while incorporating smaller lot sizes to conserve natural areas and
reduce the amount of stormwater runoff generated at the site (0.75 inches over preserved forest
or grassland towards volume reduction requirement)
8. Utilizing vegetated areas to filter sheet flow, remove sediment and other pollutants, and increase
time of concentration.
9. Disconnecting impervious areas by allowing runoff from small impervious areas to be directed to
pervious areas where it can be infiltrated or filtered.
10. Increasing buffers around streams, steep slopes, and wetlands to protect from flood damage and
provide additional water quality treatment.
11. Installing green roofs.
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City of Medina, MN
WSB Project No. 011705-000 Page 8
12. Using irrigation ponds/systems, cisterns, and related BMPs to reuse stormwater runoff.
13. Planting of trees as a stormwater BMP (0.5 x % Interception x tree canopy area x 1 inch of
rainfall).
14. Utilizing a soil amendment/decompaction process after site disturbance.
6. BASIC SIZING CRITERIA
Proposed Stormwater Management Plans must incorporate Volume Control, Water Quality Control, and
Rate Control as the basis for stormwater management in the proposed development plan. Proposed
BMPs must fulfill Volume Control, Water Quality, and Rate Control sizing requirements, as defined in
Section 1.
6.1. Volume Control Requirements
Volume control measures are required on projects to meet the water quality criteria of the City of
Medina’s LSWMP. Volume control shall be required for proposed new impervious area greater
than 5,000 square feet or redevelopment that disturbs more than 40% of the existing impervious
area on a one acre or greater site. If an applicant can demonstrate that the volume control
standard has been met, then the water quality sizing criteria shall be considered satisfied.
6.2. Volume Control Calculations
Depending on applicability, a proposed development shall capture and retain onsite 1.1 inches of
runoff from the net new impervious surfaces in post-construction conditions. Infiltration facilities
and stormwater reuse will receive full credit towards the volume control requirement. Acceptance
of infiltration or stormwater reuse will be determined on a site-by-site basis subject to the approval
of the City Engineer.
The use of infiltration techniques is prohibited in areas where the BMP will receive discharge
from, or be constructed in, any of the following areas:
Where the industrial facilities are not authorized to infiltrate industrial stormwater under
an NPDES/SDS Industrial Stormwater Permit issued by the MCPA.
Where vehicle fueling and maintenance occurs.
Where there is less than three vertical feet of separation from the bottom of the infiltration
BMP to the elevation of the seasonally saturated soils or the top of bedrock.
Where high levels of contaminants in soil or groundwater will be mobilized by the
infiltrating stormwater.
The use of infiltration techniques shall be restricted and subject to additional city review where the
infiltration BMP will be constructed in any of the following areas:
Where predominantly Hydrologic Soil Group C or D soils (clay) exist
Where soil infiltration rates exceed 8.3 inches per hour
Within a Drinking Water Supply Management Area (DWSMA) as defined in Minnesota R.
4720.5100, subp. 13.
Where site factors listed above limit the construction of infiltration systems, the proposed project
shall provide appropriate documentation to the City regarding the limitations. If the City
determines that infiltration is restricted or prohibited on-site, the applicant may construct the
alternative BMPs described below and/or utilize stormwater reuse.
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City of Medina, MN
WSB Project No. 011705-000 Page 9
Partial volume control credit will be given for the following BMPs if infiltration or stormwater reuse
is not feasible for the site.
90% credit for using an iron-enhanced sand filter
70% credit for using an iron-enhanced sand filter wrapped draintile (See standard detail)
60% credit for using stormwater ponds without water reuse
50% credit for using standard filtration
Additional credit towards the volume control requirement can be met by using the following best
management practices. Volume credits will be based on the amount of impervious surface that
drains to each feature.
Increasing buffers around streams, steep slopes, and wetlands in excess of minimum
requirements. The applicant may compute a credit of 0.5 inches over the excess buffer
area and apply that toward the abstraction volume requirement.
Preserving undisturbed forest or grassland conservation areas. Conservation areas must
remain undisturbed during construction and must be protected by a permanent
conservation easement prescribing allowable uses and activities on the parcel and
preventing future development. A long-term vegetation management plan describing
methods of maintaining the conservation area in a natural vegetative condition must be
submitted with the stormwater management plan. The applicant may compute a credit of
0.75 inches over the conservation area and apply that toward the abstraction volume
requirement.
Disconnecting impervious surface by redirecting runoff across a pervious surface or into
an engineered bioinfiltration facility. Impervious disconnection must be designed to
prevent any reconnection of runoff with the storm drain system. The applicant may
subtract the disconnected impervious surface area from the total impervious surface
area used to compute the required abstraction volume.
Planting of additional trees. Credit will be calculated as follows:
0.5 x % Interception x tree canopy area x 1 inch of rainfall
Percent rainfall interception shall be determined using results from the City of
Minneapolis, Minnesota Municipal Tree Resource Analysis. Percentages for
the species studied are listed below. If desired tree species is not listed, the applicant
shall use the median value provided below or provide documentation by a
certified arborist to support a different percent interception. Tree canopy area must be
documented as part of the permit application submittal.
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 10
6.3. Water Quality Control
For new development, the water quality control standard shall be considered satisfied if
the volume control standard has been satisfied. If it is infeasible to meet the volume control
standard due to contaminated soils, site constraints, or other factors, the proposed BMP will need
to detain and treat a sufficient volume of stormwater to achieve a phosphorus load reduction of
20% from existing conditions using an approved BMP.
The 20% reduction requirement does not apply to land use classifications for meadow, forested,
open space, or wetland land use (see Table 1). These areas are considered natural condition
areas, and no additional phosphorus reduction is needed from these areas. Water quality
treatment for these natural condition areas shall be controlled to existing phosphorus loading
conditions only. Approval of a waiver from the Volume Control or Water Quality requirement will
be evaluated on a case-by-case basis. Demonstration that the water quality criteria have been
met shall be done using P8, MIDS, PondNet, or other approved water quality modeling method.
If using PondNet, then the event mean concentrations found in Table 1 shall be used. Curve
numbers for each land use can be found in Table 2.
Table 1: Event Mean Concentrations for PondNet Modeling
Land Use Phosphorus (P) Runoff
Concentration (PPB)
Row Crop Agriculture 540
Pasture 350
Meadow* 200
Rural Residential 255
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 11
Urban Residential 450
Forested* 200
Commercial, Industrial 600
Open Space* 200
Golf Course 550
Right-of-Way 400
Wetland* 200
* - Natural Condition Area
A Microsoft Excel™ version of PondNet can be made available upon request to the City
6.4. Rate Control
Post development discharge rates must be less than or equal to existing conditions discharge
rates for the 2-year (2.5-inch), 10-year (4.3-inch), and 100-year (7.3-inch) Atlas 14 MSE 3, 24-
hour storm events. In some cases where there is the potential for adverse downstream impacts,
the rate control requirement may be more stringent than the existing conditions standard.
Ultimately, the stormwater system will be managed so that development, redevelopment, and
other infrastructure projects do not overburden the existing downstream system for the design
event. On sites that do not require volume control, the need for rate control best management
practices will be determined by the City if any downstream impacts are identified.
All runoff calculations shall be according to the methodology described in the Natural Resources
Conservation Service’s Technical Release 55, Urban Hydrology for Small Watersheds (commonly
referred to as TR-55). Example acceptable modeling software includes HydroCAD and XP-
SWMM. Other methodology may be used with prior approval by the City. Composite curve
numbers shall not be used; instead, proposed contributing areas shall be broken into one of the
cover types in Table 2.
Curve numbers for each land use shall be chosen based on Table 2.
Table 2: Curve Numbers for Use in Hydrologic Computations
Hydrologic Soil Group
Cover Type A B C D
Open Water 100 100 100 100
Pasture 68 79 86 89
Meadow 30 58 71 78
Forested 55 55 70 77
Developed Open Space1 61 61 74 80
Impervious Areas2 98 98 98 98
Agricultural Land3 Peak Growth Formula
Row Crop - Fallow 77 86 91 94
Row Crop – Average 72 81 88 91
Gravel Road 76 85 89 91
Wetlands 98 98 98 98
1 Lawns, parks, golf courses, other grassy areas, etc.
2 Streets, parking lots, roofs, driveways, etc.
3 Where existing conditions are characterized by agricultural land use, the “peak growth” curve
number should be utilized. Calculation of the peak growth curve number is based on the
following formula:
CN average = ½ * (CN peak growth + CN fallow), or
CN peak growth = 2 * (CN average) - CN fallow
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City of Medina, MN
WSB Project No. 011705-000 Page 12
For example, for row crop agriculture and hydrologic soil group B, the peak growth curve
number is 76. This is based on average and fallow curve numbers of 81 and 86,
respectively.
An Atlas 14, MSE 3 24-hour rainfall distribution with average antecedent moisture conditions
should be utilized for runoff calculations.
The recommended minimum outlet diameter is six inches due to plugging susceptibility
and may supersede the rate control requirement for the 2-year event.
Infiltration will not be considered when determining rate control or freeboard.
Waterbodies should be modeled with the starting water level at their normal water level
and/or outlet elevation. City standard detail plates should be utilized for pond outlet
structures. It is recommended that outlet structures be designed in three phases with a
primary outlet structure and secondary overflow structure routed to the storm sewer and
a defined emergency overflow as the tertiary outlet structure.
6.5. Wetlands
Bounce of water level within the wetlands shall be maintained according to the following table:
Table 3: Bounce Restriction for Runoff Directed Through Wetlands
Protection
Classification
Additional Protection Requirements for
Bounce (Change in water level due to runoff event)
Preserve Maintain bounce at or below existing conditions
Manage 1 Maintain bounce at or below existing conditions plus 0.5 feet
Manage 2 Maintain bounce at or below existing conditions plus 1.0 feet
Manage 3 No quantity requirement
The following items shall be considered in the management of landlocked basins:
The flood levels established for landlocked basins shall take into consideration the effects
of water level fluctuations on trees, erosion, and property values. Steeply sloped
shorelines subject to slope failure and shoreline damage should not be in contact with
floodwaters for extended periods.
The capacity of proposed outlets to landlocked basins should not be so small as to cause
extended duration of high water levels that would result in damage to upland vegetation.
Exceptions to this policy include basins that are strictly regional stormwater management
basins and not formerly wetlands. Exceptions also include wetlands converted to
regional stormwater management basins through mitigation of the affected wetland
areas.
6.6. Freeboard
Elevation separations of buildings with respect to ponds, lakes, streams, and stormwater features
shall be designed as follows:
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City of Medina, MN
WSB Project No. 011705-000 Page 13
1. At least two feet of vertical separation is required from an area's emergency overflow
elevation to the lowest opening of a structure. In areas where this separation is not or
cannot be provided, additional analysis is required to show that the 100-year back-to-
back storm event does not affect adjacent homes.
2. Drainage easements and outlots for ponds, lakes, wetlands, streams, and other features
shall encompass an area to the calculated one foot above the 100-year high water level
(HWL).
6.7. Floodplain Management
The City prohibits filling activities within the 100-year floodplain that will cause an increase in the
stage of the 100-year or regional flood, or cause an increase in the flood damages in the reach
affected unless compensatory storage is provided and/or channel improvement is provided that
will not result in the flood stage. Compensatory storage for any filling in the 100-year floodplain
shall be at a 1:1 ratio.
Filling within the floodway is prohibited unless the filling meets FEMA, DNR, and watershed
district requirements, and City Code Chapter 826.74 – 826.97.
6.8. Long-term Inspection and Maintenance of Stormwater
BMPs
No private storm water facilities may be approved unless a maintenance plan is provided that
defines how access will be provided, who will conduct the maintenance, the type of maintenance
and the maintenance intervals. At a minimum, all private stormwater facilities shall be inspected
annually and maintained in proper condition consistent with the performance goals for which they
were originally designed and as executed in the stormwater facilities maintenance agreement.
All stormwater facilities must be inspected annually and maintained as necessary. The applicant
shall obtain all necessary easement or other property interests to allow access to the facilities for
inspection or maintenance for both the responsible party and the City of Medina.
All settled materials including settled solids shall be removed from ponds, sumps, grit chambers,
and other devices and disposed of properly.
7. STORMWATER TREATMENT PRACTICE DESIGN STANDARDS
7.1. Storm Sewers
Requirements include:
1. Manhole spacing shall not exceed 400 feet.
2. Where more than one pipe enters a structure, a catch basin/manhole shall be used.
3. Storm sewer pipe should match top of pipe to top of pipe unless grade constraints
prevent this. In that case, hydraulic calculations will be necessary to verify that excessive
surcharging will not occur.
4. Stormwater pipes shall be designed utilizing the Rational Method. Channel design shall
be hydrograph method only. All methods are subject to the City Engineer’s approval.
5. Lateral systems shall be designed for the 10-year 24-hour Atlas 14 rainfall using the
Rational Method. State Aid roadway storm sewer shall be designed per the State Aid
requirements.
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City of Medina, MN
WSB Project No. 011705-000 Page 14
6. The minimum full flow velocity within the storm sewer should be 3 feet per second (fps).
The maximum velocity shall be 10 fps, except when entering a pond, where the
maximum velocity shall be limited to 6 fps.
7. Trunk storm sewer should be designed at a minimum to carry 100-year pond discharge in
addition to the 10-year design flow for directly tributary areas. The following table shall
be used for the calculation of peak rates using the Rational Method:
Table 4: Rational Method Runoff Coefficients for Storm Sewer Design
Cover Type 10-Year Runoff Coefficient
Single-family Residential 0.4
Multi-family Residential 0.5
Commercial 0.7
Industrial 0.7
Parks, Open Space 0.2
Ponds, Wetlands 1.0
8. For storms greater than the 10-year event, and in the case of plugged inlets, transient
street ponding will occur. For safety reasons, the maximum depth in streets should not
exceed 1.5 feet at the deepest point.
9. To promote efficient hydraulics within manholes, manhole benching shall be provided to
half the diameter of the largest pipe entering or leaving the manhole.
10. Vaned grate (3067V) catch basin castings shall be used on all streets.
11. The maximum design flow at a catch basin for the 10-year storm event shall be 3 cubic
feet per second (cfs), unless high capacity grates are provided. Catch basins at low
points will be evaluated for higher flow with the approval of the City Engineer.
12. All structures located in the street are to be a minimum of four feet deep (rim to invert)
and a minimum of three feet deep elsewhere. Two-by-three catch basins are to be four
feet deep.
13. The last structure in the street prior to discharging into a pond is to be a minimum of five
feet deep with a four-foot deep sump, where appropriate.
7.2. Outlet and Inlet Pipes
Requirements include:
1. Inlet pipes of stormwater ponds shall be extended to the pond normal water level (NWL)
whenever possible.
2. Outfalls with velocities greater than 4 fps into channels, where the angle of the outfall to
the channel flow direction is greater than 30-degrees, require energy dissipation or stilling
basins.
3. Outfalls with velocities of less than 4 fps, that project flows downstream into a channel in
a direction 30-degrees or less from the channel flow direction, generally do not require
energy dissipaters or stilling basins, but will require riprap protection.
4. In the case of discharge to channels, riprap shall be provided on all outlets to an
adequate depth below the channel grade and to a height above the outfall or channel
bottom. Riprap shall be placed over a suitably graded filter material and filter fabric to
ensure that soil particles do not migrate through the riprap and reduce its stability. Riprap
shall be placed to a thickness at least 2.5 times the mean rock diameter to ensure that it
will not be undermined or rendered ineffective by displacement. If riprap is used as
protection for overland drainage routes, grouting may be recommended.
5. Discharge velocity into a pond at the outlet elevation shall be 6 fps or less. Riprap
protection is required at all inlet pipes into ponds from the NWL to the pond bottom.
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 15
6. Where outlet velocities to ponds exceed 6 fps, the design should be based on the unique
site conditions present. Submergence of the outlet or installation of a stilling basin
approved by the City is required when excessive outlet velocities are experienced.
7. Submerged outlet pipes from ponds are not allowed.
7.3. Channels and Overland Drainage
Requirements include:
1. Overland drainage routes where velocities exceed 4 fps should be reviewed by the City
Engineer and approved only when suitable stabilization measures are proposed.
2. Open channels and swales are recommended where flows and small grade differences
prohibit the economical construction of an underground conduit. Open channels and
swales can provide infiltration and filtration benefits not provided by pipe.
3. The minimum grade in all unpaved areas shall be 2%.
4. Maximum length for drainage swales shall be 400 feet.
5. Channel side slopes should be a maximum of 4:1 (horizontal to vertical) with gentler
slopes being desirable.
6. Riprap shall be provided at all points of juncture, particularly between two open channels
and where storm sewer pipes discharge into a channel.
7. Open channels should be designed to handle the expected velocity from a 10-year
design storm without erosion. Riprap may need to be provided.
8. Periodic cleaning of an open channel is required to ensure that the design capacity is
maintained. Therefore, all channels shall be designed to allow easy access for
equipment.
7.4. Ponds
1. Maximum allowable pond slopes above the outlet elevation are 3:1.
2. All constructed ponds and wetland mitigation areas shall have an aquatic or safety bench
around their entire perimeter. The aquatic bench is defined as follows:
a. Cross-slope no steeper than 10:1.
b. Minimum width of 10 feet.
c. Located from pond outlet elevation to one foot below pond outlet elevation.
3. All constructed ponds shall be provided a maintenance access from an adjacent
roadway. The maintenance access shall be provided in the form of an easement no
narrower than 20 feet. The maintenance access shall have a longitudinal slope no
steeper than 6:1 and minimal cross slope. Maintenance access routes, due to their extra
width, also serve well as emergency overflow (EOF) routes.
4. All constructed ponds and wetland mitigation areas shall have a maintenance access
bench around sufficient perimeter to provide access to all inlets and outlets. The
maintenance bench shall be located within a designated outlot or within a permanent
easement. The maintenance bench shall extend from the outlet elevation to one foot
above the outlet elevation and its cross slope shall be no steeper than 10:1. The
maintenance bench shall connect to the maintenance access.
5. Maximum pond wet volume depth is eight feet.
6. Mean depth for wet ponds shall be a minimum of four feet. If the pond is smaller than
three acre-feet in volume, mean depths of three to four feet may be used. Mean depth is
defined as the area at outlet elevation divided by the wet volume.
7. All ponds shall be graded to one foot below design bottom elevation. This “hold down”
allows sediment storage until site restoration is complete.
8. The top berm elevation of ponds shall be a minimum of one foot above the 100-year
pond HWL.
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 16
9. Grading shall not block or raise emergency overflows from adjoining properties unless
some provision has been made for the runoff that may be blocked behind such an
embankment.
10. To prevent short circuiting, the distance between the major inlets and normal outlet shall
be maximized.
11. All ponds shall have a protected EOF.
12. Stormwater ponds shall not be constructed within protected wetland buffers.
7.5. Infiltration/Filtration Practices
Requirements include:
1. Sizing of filtration/infiltration practices, or BMPs, shall be in conformance with the volume
control requirements of this manual and the Minnesota Stormwater Manual.
2. When designing an infiltration practice for volume control and water quality management,
on-site testing and detailed analysis are required to determine the infiltration rates of the
proposed infiltration facility. Documented site-specific infiltration or hydraulic conductivity
measurements (double-ring infiltrometer) completed by a licensed soil scientist or
engineer is required. In the absence of a detailed analysis, the saturated infiltration rates
listed in the Minnesota Stormwater Manual shall be used. A piezometer shall be installed
to ascertain the level of the local groundwater table and demonstrate at least three feet of
separation between the bottom of the proposed facility and the groundwater. The soil
boring is required to go to a depth of at least five feet below the proposed bottom of the
BMP. The soils shall be classified using the Unified Soil Classification system. The least
permeable soil horizon will dictate the infiltration rate. Infiltration practices shall be
designed to infiltrate the required runoff volume within 48 hours.
3. Pretreatment in the form of ponds, forebays, filter strips, or other approved methods shall
be provided for all infiltration areas. Pretreatment upstream of volume management
practices is a key element in the long-term viability of infiltration areas. The level of
pretreatment varies largely depending on the BMP and drainage area. Local watershed
district, City staff, and Minnesota Stormwater Manual recommendations shall be utilized
for determining the appropriate level of pretreatment on a case-by-case basis.
4. Vegetation of infiltration/filtration practices shall be as shown in the City of Medina
Standard Details. A plan for the management of vegetation shall be included in the
Stormwater Management Plan and/or Storm Water Pollution Prevention Plan.
5. Subgrade soils for infiltration/filtration practices shall be as presented in the City of
Medina Standard Details. Assume a 40% void ratio for the purposes of volume
calculations.
6. For infiltration benches adjacent to ponds, benches shall have slopes no steeper than 5:1
over the proposed infiltration zone. A slope of 10:1 is preferred. The Minnesota
Stormwater Manual cites concerns with locating infiltration features immediately adjacent
to ponds. To address this, benches shall be located to maintain hydraulic separation
from the saturated zone of the pond in order to minimize the loss of infiltration potential
over time.
7.6. Water Reuse
1. Required design submittal packages for water reuse BMPs must include:
a. An analysis using Ramsey-Washington Metro Watershed District Stormwater Reuse
Calculator. An example of the Calculator can be found in Appendix E. The full
spreadsheet can be requested from the City.
b. Documentation demonstrating adequacy of soils, storage system, and delivery
system; and
c. Operations and maintenance plan.
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 Page 17
2. Approved capacity of an irrigation practice will be based on:
a. An irrigation rate of 1.0 inches per week over the irrigated pervious area(s) or the
rate identified through the Stormwater Reuse Calculator (whichever is less); or as
approved by the City; and
b. No greater than a 26 week (April 15th to October 15th) growing season.
3. Design of the irrigation system must include, but is not limited to, the following items.
Each system will be reviewed and approved by the City on a site-by-site basis.
a. Plumbing code review, adherence, and permitting, if applicable.
b. Water reuse pump system design including supply line, intake, meter, and pump
c. Electrical and controls design
d. Construction drawings, specifications, and system integration
7.7. Emergency Overflow Paths
1. EOFs shall be sized with a minimum bottom width of five feet and 4:1 side slopes.
2. The maximum flow depth in EOFs shall be less than or equal to one foot as calculated for
a 100-year back-to-back storm event.
8. Design Examples
The design process for each of the acceptable Best Management Practices is detailed in the Minnesota
Stormwater Manual.
9. Stormwater Treatment Practice Detail Drawings
Please refer to the City of Medina Engineering Standard Details in Appendix D.
10. Construction Specifications
Construction specifications and details are found in the Minnesota Stormwater Manual for each of the
acceptable BMPs, unless otherwise restricted by this Manual.
11. Checklists
Checklists for Construction Inspection
Construction Inspection Checklists for each of the approved Best Management Practices are available in
Appendix D of this Manual.
Checklists for Operation & Maintenance
Operations & Maintenance Checklist for each of the approved Stormwater Treatment Practices are
available in Appendix D of this Manual.
APPENDIX A
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 APPENDIX A
APPENDIX A
Construction Sediment and Erosion Control Checklist
APPENDIX B
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 APPENDIX B
APPENDIX B
Maintenance Agreement Template
APPENDIX C
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 APPENDIX C
APPENDIX C
BMP Operation and Maintenance Requirements
APPENDIX D
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 APPENDIX D
APPENDIX D
Standard Details
APPENDIX E
Stormwater Design Manual
City of Medina, MN
WSB Project No. 011705-000 APPENDIX E
APPENDIX E
Ramsey-Washington Metro Watershed District Stormwater Reuse Calculator
SECTION 5
5. GOALS AND POLICIES
5.1. Summary
The primary goal of Medina's SWMP is to provide a framework for effective surface water
management and to bring the City into statutory compliance. This includes guiding redevelopment
activities and identifying and implementing retrofits to the existing system. These retrofits consist
of both projects and programs. Additionally, the plan provides clear guidance on how Medina
intends to manage surface water in terms of both quantity and quality.
The goals and policies described in this section are intended to incorporate the foundation of
several regional, state, and federally mandated programs. They are not meant to replace or alter the
regional, state and federally mandated programs, rules and regulations, but to serve as an
enhancement and provide some general policy guidelines. The goals address the management
strategies of each watershed management commission, Pioneer -Sarah Creek, Minnehaha Creek
and Elm Creek, and are consistent with the objectives set forth in the State Wetland Conservation
Act (WCA) and the Federal Nationwide Urban Runoff Program (NURP) Cooperation,
collaboration, and partnering results in projects that are less likely to conflict with the goals of the
affected entities, are better able to meet long-term goals, and are generally more cost-effective.
In addition to the goals and policies contained in this section, the City will annually review and
update its Storm Water Pollution Prevention Plan (SWPPP) to effectively manage its stormwater
system and be in conformance with the NPDES MS4 Program. Refer to Appendix B for the most
recent version of the City SWPPP.
This section outlines the goals and policies specific to surface water management in Medina. Goals
and policies are grouped by their relationship to the key issues listed below:
• Section 5.2 - Land Development, Redevelopment, and City Projects
• Section 5.3 - Water Resource Management
• Section 5.4 - Management of Floodplains, Shorelands, and Natural Areas
• Section 5.5 - Citywide Program Elements
• Section 5.6 - Support of Other Agencies
5.2. Land Development, Redevelopment, and City Projects
Overall Goal
Manage land disturbance and increased impervious surfaces to prevent flooding and
adverse impacts to water resources.
Overall Policies
1. Medina will pursue a non -degradation policy in regard to runoff volume, runoff
rate, and nutrient loading from development projects. Low Impact Development
(LID) techniques are Medina's preferred method of controlling runoff volume and
nutrient loading. Medina considers LID techniques as complementary to pipes,
ponds, and wetlands for its flood control system.
Surface Water Management Plan
City of Medina Section 5
WSB Project No. 2714-940 Page -1
SECTION 5
2. Medina will consider redevelopment and linear projects as an opportunity to
retrofit non -degradation to previously developed areas and infrastructure.
3. Medina will amend or modify its ordinances and/or engineer standards to facilitate
stormwater quantity and quality performance measures identified in its Local
Surface Water Management Plan.
4. Medina will consider water quality retrofits on existing City properties as a means
of providing treatment to currently developed areas without treatment.
5. Medina will reference the following documents as guidance for Best Management
Practices in the City: The Minnesota Pollution Control Agency's Protecting
Water Quality in Urban Areas and its Minnesota Stormwater Manual, and the
Metropolitan Council's Minnesota Urban Small Sites BMP Manual.
5.2.1.Runoff Volume Management
Goal: Maintain existing runoff volumes so that runoff from development does not increase
volume loading to wetlands, lakes and streams.
Policy: Any site that requires an NPDES construction site permit will be required to implement
permanent volume management such that existing runoff volumes are maintained. Sites that do not
require an NPDES construction site permit shall maintain existing runoff volumes to the extent
practical.
Policy: Medina's preferred water quality strategy is to reduce the volume of its runoff through
infiltration or reuse projects. If volume control is not feasible due to site conditions, the City will
establish alternatives to achieve relevant volume control goals. Volume control calculations will be
consistent with Medina's Stormwater Design Manual.
Policy: Redevelopment and linear projects will implement runoff volume management practices
for net new impervious surfaces. Redevelopment and linear projects will consider whether
additional runoff volume management practices might feasibly be incorporated for existing
impervious surfaces also.
5.2.2.Runoff Rate
Goal: Control the rate of stormwater runoff from development to reduce downstream flooding
and erosion and protect water resources.
Policy: Future peak rates of discharge from new development and redevelopment will not exceed
existing peak rates of discharge for the 1-yr or 2-yr, 10-yr and 100-yr 24 -hour storm events using
Atlas 14 rainfall values. MSE-3 distribution shall be used.
Policy: New storm sewer systems shall be designed using the following guidelines:
Surface Water Management Plan
City of Medina Section 5
WSB Project No. 2714-940 Page -2
SECTION 5
New lateral storm sewer systems shall be designed to accommodate discharge rates for the 10-yr
critical storm event using Atlas 14 rainfall values. Trunk storm sewer should be designed as a
minimum to carry 100 -year pond discharge in addition to the 10 -year design flow. New storm
sewer systems shall be designed to match the inside top elevation of adjacent pipes. The maximum
velocity shall not exceed 10 feet per second, except when entering a pond, where the maximum
velocity shall be limited to 6 feet per second.
Policy: New storm sewers and open channels shall be designed using the Rational Method or other
technical method approved by the City. Runoff Coefficient "C" shall be in accordance with the
guidelines provided in the Stormwater Design Manual.
Policy: The City will base all drainage system analyses and designs on proposed full development
land use patterns.
Policy: Where development occurs upstream of a known flood -prone area, the City may seek
additional rate control as a means to mitigate this flooding.
Policy: When off -site regional ponding is available and this off -site ponding accomplishes the
rate control requirement, then the rate control requirement can be waived for a particular site.
5.2.3. Flood Prevention
Goal: Provide adequate storage and conveyance of runoff to protect the public safety and
minimize property damage.
Policy: Building low floor elevations within the City of Medina shall be required to be at least 2
feet above the emergency overflow elevation. In areas where this separation is not or cannot be
provided, additional analysis is required showing that the 100 -year back-to-back storm event does
not affect adjacent homes.
Policy: Flood storage for those landlocked depressions with no outlet present must accommodate
the volume generated by back-to-back 100-yr, 24 -hr storm events or the 100-yr, 10 -day snowmelt
event, whichever generates the higher calculated HWL.
Policy: The City will encourage, to the extent practicable, implementation of Low Impact
Development techniques and mitigation of stormwater runoff volume within development and
redevelopment areas draining to landlocked depressions.
Policy: The City shall require that rate control structures and stormwater drainage ways are
included in a drainage or utility easement.
Policy: The City will require compensatory storage for any filling in the 1% (100 -year) floodplain
at a 1:1 ratio.
Policy: Medina will amend or modify its Floodplain Management Ordinance to incorporate the
policies identified in its Local Surface Water Management Plan.6
Surface Water Management Plan
City of Medina Section 5
WSB Project No. 2714-940 Page -3
SECTION 5
5.2.4.Nutrient and Sediment Loading
Goal: Reduce the nutrient and sediment loads over current conditions.
Policy: Medina's minimum standard is water quality treatment that meets the requirements of the
NPDES construction site permit. Under no circumstances shall overall treatment fall below the
requirements of this permit.
Policy: Any site that requires a NPDES construction site permit will be required to reduce
phosphorus loadings over current conditions. The water quality control standard shall be
considered satisfied if the volume control standards has been satisfied, as defined in the City's
Stormwater Design Manual. If volume control is infeasible due to site constraints, a 20% reduction
in phosphorus loading over existing conditions will be required for redevelopment projects. In
cases where existing land cover is natural, the maintenance of existing loading rates is acceptable if
the minimum requirements identified in the policy above are met.
Policy: Medina will institute a standard practice of evaluating all development, redevelopment,
and linear projects for opportunities to retrofit water quality treatment to areas without significant
existing treatment.
Policy: Guidelines for the design of water quality ponds and infiltration/filtration practices will
follow the requirements listed in the City's Stormwater Design Manual.
Policy: The City will require outlet skimming in all water quality ponds. Skimming shall occur
for up to the 10 -year, 24 -hour event. The City shall not allow the use of submerged pipes to provide
skimming.
Policy: The City will require the use of its standard outlet structure (Appendix G) for new water
quality ponds.
5.2.5.Erosion and Sediment Control
Goal: Prevent sediment from construction sites from entering the City's surface water resources.
Policy: The City will enforce the Construction Site Storm Water Runoff Control Ordinance as
outlined in Chapter 8 of the City Code; Section 828 Performance Standards and Enforcement.
Policy: Erosion control must meet the requirements outlined in the Minnesota Pollution Control
Agency's NPDES General Permit to Discharge Stormwater from Construction Sites and the
following criteria. A copy of the most recent requirements can be found at www.mpca.mn.us.
Policy: The City will periodically review its Construction Site Storm Water Runoff Control
Ordinance to maintain conformance with the NPDES construction permit, the City's MS4 permit,
guidance from Metropolitan Council and the requirements of the watershed management
organizations.
Surface Water Management Plan
City of Medina Section 5
WSB Project No. 2714-940 Page -4
SECTION 5
5.3. Water Resource Management
Overall Goal
Protect the City's wetlands, lakes, streams and groundwater to preserve the functions and values of
these resources for future generations.
Overall Policies
1. The City will protect water resources through implementation of the Wetland Conservation Act,
groundwater protection rules and TMDL studies.
2. The City will look to retrofit rate control, water quality treatment, and runoff volume reduction
upstream of existing water bodies, as these opportunities arise. Medina considers Low Impact
Development techniques as the preferred means of retrofitting water quality treatment and runoff
volume reduction.
5.3.1. Wetland Management
Goal: Protect and preserve wetlands to maintain or improve their function and value.
Policy: The City will continue to administer WCA responsibilities within the City to ensure no
net loss of wetland functions and values.
Policy: The City will administer their WCA responsibilities using technically trained staff. At a
minimum the trained staff will be certified by the Minnesota Wetland Delineator Certification
Program and/or a comparable program.
Policy: The City will work collaboratively with the relevant WMO in the application of City and
WMO policies and performance standards for wetlands.
Policy: The City will implement the Wetland Protection Ordinance, City Code 828.43, which
incorporates the results of the City's Wetland Inventory and Assessment.
Policy: The City will require that, prior to development activities or public projects, a wetland
delineation must be completed, including a field delineation and report detailing the findings of the
delineation.
Policy: The City requires through its wetland ordinance that future development proposals
include natural buffer zones around wetlands and streams. Buffer areas should not be mowed or
fertilized, except that harvesting of vegetation may be performed to reduce nutrient inputs.
Policy: The City requires that runoff be pre-treated prior to discharge to wetlands. Wetlands may
not be considered as treatment areas for the purposes of meeting Medina's stormwater
management standards. Direct roof runoff that is discharged to a wetland without pretreatment will
be reviewed by the City.
5.3.2.Lake Management
Surface Water Management Plan
City of Medina Section 5
WSB Project No. 2714-940 Page -5
SECTION 5
Goal: Manage lakes to improve water quality and protect resource values.
Policy: The City will begin implementing the TMDL Implementation Plans listed in Section 2.
Through its annual reporting, the City will report progress toward meeting this phosphorus load
reduction.
Policy: The City will cooperate with the Three Rivers Park District, Pioneer -Sarah Creek
Watershed, Elm Creek Watershed, and Minnehaha Creek Watershed to identify possible activities
to improve water quality in impaired waterbodies.
5.3.3.Stream Management
Goal: Improve water quality, provide wildlife habitat and protect the resource value of streams.
Policy: The City will work with the ECWMC to facilitate implementation of the outcomes of the
Elm Creek Channel Study.
Policy: The City will cooperate with the PSCWMC and the ECWMC to remove deadfall from
creeks within the City.
Policy: The City will require a 50 foot buffer for land disturbance projects along Elm Creek.
5.3.4. TMDL Implementation
Goal: Address target pollutants identified in TMDL studies to improve the quality of impaired
waters.
Policy: The City will implement the pollutant reduction strategies identified in the SWPPP.
Policy: The City will incorporate completed TMDL studies and relevant implementation
projects.
Policy: The City will use the findings of the TMDL studies to guide development review.
Policy: The City will consider Low Impact Development techniques as the primary means of
meeting load reductions identified in TMDL implementation plans.
5.3.5. Groundwater Recharge and Protection
Goal: Protect groundwater resources and groundwater dependent resources.
Policy: The City will cooperate with Hennepin County, MDH, and other state and federal
agencies to identify areas of groundwater resources critical to protect.
Policy: The City will use the guidance developed in the Minnesota Stormwater Manual for
locating infiltration BMPs in vulnerable Wellhead Protection Areas.
Surface Water Management Plan
City of Medina Section 5
WSB Project No. 2714-940 Page -6
SECTION 5
5.4. Management of Floodplains, Shorelands, and Natural Areas
Overall Goal
Manage the City's floodplains, shorelands and natural areas to preserve the functions and values of
these resources for future generations.
Overall Policy
The City will manage these areas through implementation of local zoning codes and agency
regulations.
5.4.1.Floodplain Management
Goal: Control development in flood prone areas to protect the public safety and minimize
property damage.
Policy: The City will regulate land development within the Floodplain District to ensure that
floodplain capacity and flood elevations are not adversely impacted by development, and that new
structures are protected from damage.
Policy: The City will update the Floodplain Management Ordinance, City Code 826.74 as
required by FEMA and the MnDNR, or as needed, to ensure adequate protection for structures and
eligibility for flood insurance programs.
5.4.2.Shoreland Management
Goal: Conserve and protect the scenic, historical and cultural resources of the waterbodies
within the City and maintain a high standard of environmental quality.
Policy: The City will regulate land development within the Shoreland Overlay District to
minimize impacts as specified in the City Code 827.01.
5.4.3.Natural Area Management
Goal: Protect and enhance natural areas within the City to provide wildlife habitat and water
resource benefits.
Policy: The City will review land use and development decisions with the intent to preserve
natural resources, connect environmental corridors and provide buffers for streams, wetlands and
lakes. Existing MLCCS coverage and other data sources will guide decisions regarding natural
area preservation. Figure 18 shows parcels owned by the City. These parcels will be reviewed to
possibly enhance natural areas and provide water resource benefits.
Policy: The City will support programs to maintain and restore the resource value of natural
areas.
Policy: The City will continue to implement its Open Space Plan and will coordinate with the
Surface Water Management Plan
City of Medina Section 5
WSB Project No. 2714-940 Page -7
SECTION 5
Parks Department on future development.
Policy: The City will cooperate with the MCWD to implement conservation practices for those
areas identified in the MCWD CWRMP as Key Conservation Areas.
Policy: The City will coordinate conservation efforts with other agencies, such as watersheds,
Hennepin County, Three Rivers Park and non -governmental bodies, like the Minnesota Land
Trust, Embrace Open Space and Pheasants Forever.
Policy: The City will require permanently conserved land to be held in an easement by an outside
agency, such as the Minnesota Land Trust, a watershed district or similar entities.
5.5. City Wide Program Elements
Overall Goal
Manage water resources and drainage systems on a citywide scale.
Overall Policies
1. The city wide surface water management program will include monitoring and maintenance of
drainage systems, targeted pollution prevention, public education, system reconstruction
projects and equitable collection of supporting funds.
2. The City will actively implement the NPDES Stormwater Pollution Prevention Plan as stated
in the MS4 permit.
3. The City will work with the Watershed having jurisdiction and applicable LGU to resolve any
intercommunity drainage issues that may arise.
5.5.1.Pollution Prevention
Goal: Detect and address urban pollutants discharged to storm sewers.
Policy: The City will address pollutant sources through enforcement of codes and public
education.
Policy: The City will develop and maintain an effective spill response plan.
Policy: The City will continue to develop and update their storm sewer system on an annual basis.
Policy: The City will complete employee training in the operation, maintenance and inspection of
stormwater facilities, as included in the SWPPP.
Policy: The City will monitor storm sewer outfalls for pollutants as outlined in the City's NPDES
permit.
5.5.2.Monitoring and Maintenance
Surface Water Management Plan
City of Medina Section 5
WSB Project No. 2714-940 Page -8
SECTION 5
Goal: Maintain the function and effectiveness of stormwater management structures through
monitoring and maintenance.
Policy: The City will continue to conduct annual street sweeping of City owned streets. Rural
road sections will be swept at least once annually and the urban road sections will be swept at least
three times annually.
Policy: The City will inspect and monitor the construction and installation of all new stormwater
facilities and require that such facilities be surveyed to create as -built drawings.
Goal: Ensure the long term operation and maintenance of stormwater management BMPs.
Policy: The City will require that all ponds constructed as part of a common plan of development
be placed on outlots.
Policy: The City will require that all ponds be returned to their original design capacity prior to
acceptance by the City and that an as -built design be submitted to verify that the pond meets the
original design capacity.
Policy: The City will require developers to provide a minimum one-year guarantee that
stormwater management facilities are properly installed, maintained and functioning.
Policy: The City will require that an operation and maintenance plan for the proposed stormwater
management BMPs be submitted for all development and redevelopment projects.
5.5.3.Public Education
Goal: Inform and educate residents about stormwater pollution, the effects of urban runoff and
the need to protect natural resources.
Policy: The City will implement a public education and outreach program as identified in the
City's NPDES permit.
Policy: The City will develop and maintain a public education program for landowners to
promote reduction of nutrient, sediment, and bacteria loading to water bodies. The City will
encourage residents and landowners to practice environmental friendly lawn care and to encourage
the use of native plantings or natural landscapes, where practical.
Policy: The City will coordinate public education work with the local WMOs.
Policy: The City will promote citizen and volunteer efforts to protect, restore and enhance local
water and natural resources.
Policy: The City will use available opportunities through its public meetings, website, City
newsletter, Comprehensive Plan, or interpretive elements at parks and open space sites to inform
its residents about the value of local water resources, the effects of stormwater runoff, and
opportunities for stewardship of water and natural resources.
Surface Water Management Plan
City of Medina Section 5
WSB Project No. 2714-940 Page -9
SECTION 5
5.5.4. Funding
Goal: Secure adequate funding to support implementation of the surface water management plan.
Policy: The City will cost effectively manage the plan to balance surface water goals with available
resources.
Policy: The City will seek grant funds or other resources to assist with special projects or
implementation of plan goals.
Policy: The City will utilize the Stormwater Utility Fund to pay for stormwater management
projects and implementation activities.
5.6. Support of Other Agencies
Overall Goal:
Coordinate local surface water management with the work of watershed management organizations
and state agencies.
Overall Policy:
The City will cooperate and collaborate with the local water management organizations in their efforts
to maintain and improve water quality in the city.
Goal: Facilitate WMO review of development projects and enforcement of watershed standards.
Policy: Policy: Medina will coordinate development review activities with the watershed
organizations with jurisdictions overlapping that of the City.
Goal: Cooperate with other organizations to complete and implement management plans and
studies for water resources in Medina.
Policy: The City will work with local watershed management organizations, Hennepin County,
and others when appropriate and as resources are available to participate in resource management
plans or studies that benefit water and natural resources.
Policy: The City will work with the local watershed management organizations to jointly
implement the LSWMP.
Goal: Cooperate with other organizations working to protect groundwater resources.
Policy: The City will cooperate with the County and water management organizations to
implement the recommendations of the Hennepin County Groundwater Plan, to protect
groundwater quality by reducing the potential for transport of stormwater pollutants into the
groundwater, and maintaining the functions of groundwater recharge areas.
Policy: The City will support well -sealing programs developed by Hennepin County and the
Minnesota Department of Health.
Surface Water Management Plan
City of Medina Section 5
WSB Project No. 2714-940 Page -10
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K:\011705-000\Admin\Docs\Summary Memo for Council.docx
Memorandum
To: Dusty Finke, AICP, City of Medina
From: Stephanie Hatten, EIT, WSB & Associates
Earth Evans, PE, WSB & Associates
CC: Scott Johnson, City of Medina
Steve Scherer, City of Medina
Jim Stremel, PE, City of Medina
Date: May 10, 2018
Re: Medina Stormwater Design Guide Update
WSB Project No. 011705-000
Introduction
The City is currently in the process of updating their Stormwater Design Guidelines that identify
requirements needed for approval of development projects. These Design Guidelines are a
supplementary document to the City’s Surface Water Management Plan, which was finalized in early
2018. The Surface Water Management Plan is a planning tool for the City to identify specific policies such
as rate control, volume control, water quality, nutrient reduction, and total maximum daily load (TMDL)
compliance. Stormwater Design Guidelines and related ordinances are a way for the City to implement
these policies on a day-to-day basis as development occurs.
The scope of the Stormwater Design Guidelines update includes reviewing and revising the following
components:
• Minimum thresholds for compliance with the City’s stormwater design criteria
• An infiltration standard and flexible stormwater treatment options that suits the City’s clay soils
• Alternative methods for achieving the volume control requirement, similar to the regulating
watersheds (i.e., stormwater reuse for irrigation, credit for impervious disconnection, iron
enhanced sand)
• Clarification on specific design standards for developers
Need for the Design Guidelines Updates
The City’s Stormwater Design Guidelines are being updated to remain consistent with the Elm Creek
Watershed Management Commission, Pioneer-Sarah Creek Watershed Management Commission and
Minnehaha Creek Watershed District stormwater management permitting rules. The Guidelines are also
going to be updated to provide an emphasis on water reuse for irrigation and to provide greater flexibility
in stormwater best management practices to treat new and redeveloped impervious surfaces. The new
Guidelines will simplify the stormwater management requirements based on impervious cover, rather than
land use type. Attachment A provides examples of stormwater treatment options that the City will
encourage as options to meet triggered requirements.
Mr. Finke
May 10, 2018
Page 2
K:\011705-000\Admin\Docs\Summary Memo for Council.docx
Summary of Existing Guidelines
The current City guidelines are as follows:
• Threshold
o New development – Any subdivision greater than 3 single family lots or a major
expansion that disturbs 1 acre or more or increases impervious area by half an acre.
o Redevelopment – Removal of more than 50% of the market value of the principal
structure followed by reconstruction
o Single family – Disturbs 1 acre or more and increases impervious by 1,000 square feet or
increases impervious by 5,000 square feet
o Minor expansion – Increased impervious by 5000 square feet and less than half an acre
for commercial, industrial, institutional, or multi-family.
• Volume Control/Water Quality
o Infiltration – 1.0 inches of runoff off new impervious. Water reuse can replace this
requirement.
o Filtration – Volume required for infiltration multiplied by 1.5
o Exception for minor expansion and single family homes to construct a rain garden
o Water quality- If infiltration is not feasible, total phosphorus must be removed to at least
20% of existing.
Recommendations
• Threshold
o New development – Increase in new impervious of 5,000 square feet. Includes all land
uses.
o Redevelopment – If a site area is greater than 1 acre and more than 40% of the site’s
hardcover is disturbed. If impervious area is reduced by 10%, no stormwater
management is required.
o Single family – Exemption for single family if the proposed impervious cover is less than
20% of the overall property size.
The recommended thresholds differ from the existing in that a focus is placed on the amount of
impervious cover added versus the disturbed area. The site classifications were also simplif ied to
new development, redevelopment, and single family lots to limit confusion in land use type.
Establishing thresholds for volum e control and water quality sets the basis for development and
must not be set too high or too low. If the threshold is set too high, it becomes a challenge for the
City to meet their objectives to improve water quality and maintain volume control from an
increase in impervious surfaces. If the threshold is set too low, high costs are added to property
owners in implementing stormwater improvements.
• Volume Control/Water Quality
o Infiltration – 1.1 inches of runoff off new impervious. Water reuse can replace this
requirement.
o Variety of options to meet the volume control requirements including increased natural
buffer areas around wetlands, preserving undisturbed forest and grassland, planting of
trees, and disconnecting impervious area. Credit is given for iron enhanced sand filters
(75%), stormwater ponds (60%), and filtration basins (50%).
o Water quality- If infiltration is not feasible, maintain existing total phosphorus. If the
existing land use is agricultural, existing total phosphorus must be removed to at least
20%.
The recommended infiltration requirement of 1.1 inches is consistent with the three watershed
districts that have jurisdiction in Medina. The stormwater treatment options were modeled after
Elm Creek Watershed Management Commission and allows for a greater flexibility to provide
better water quality treatment on a site-by-site basis.
Attachment A – Best Management Practice (BMP) Examples
Stormwater reuse for irrigation
Stormwater ponds can be used as the storage component of a stormwater reuse system. These ponds
are multi-purpose, providing stormwater retention, sedimentation, and storage for later use. In this way,
stormwater reuse systems can be part of a treatment train approach for stormwater management and
provide irrigation to residential developments. Existing ponds can also be retrofitted to serve as a water
source for a reuse system.
Infiltration basin
Infiltration practices are applicable to sites with naturally permeable soils and a suitable distance to the
seasonally high groundwater table, bedrock or other impermeable layer. They may be used in residential
and other urban settings where elevated runoff volumes, pollutant loads, and runoff temperatures are a
concern. In applications where the stormwater runoff has a particularly high pollutant load or where the
soils have very high infiltration rates, a significant amount of pre-treatment should be provided to protect
the groundwater quality. Infiltration basins can have various different aes thetic features, with plantings
ranging from native flowering plants, to green grass, to prairie grasses.
Iron enhanced sand
Iron-enhanced sand filters are filtration Best Management Practices (BMPs) that incorporate filtration
media mixed with iron. The iron removes several dissolved constituents, including phosphate, from
stormwater. Iron-enhanced sand filters may be particularly useful for achieving low phosphorus levels
needed to improve nutrient impaired waters. Iron-enhanced sand filters could potentially include a wide
range of filtration BMPs with the addition of iron; however, iron is not appropriate for all filtration practices
due to the potential for iron loss or plugging in low oxygen or persistently inundated filtration practices.
Filtration basin (Bio and sand)
Filtering practices include media filters (surface, underground, perimeter), vegetative filters (filter strips,
grass channels), and combination media/vegetative filters (dry swales). Media and media/vegetative
filters operate similarly and provide comparable water quality capabilities as bioretention. Filtering
practices have widespread applicability and are suitable for all land uses, as long as the contributing
drainage areas are limited (e.g., typically less than 5 acres). Media filter s are not as aesthetically
appealing as bioretention, which makes them more appropriate for commercial or light industrial land
uses or in locations that will not receive significant public exposure. Media filters are particularly well
suited for sites with high percentages of impervious cover (e.g., greater than 50 percent). Media filters
can be designed with an underdrain, which makes them a good option for treating potential
stormwater hotspots (PSHs). They can also be installed underground to prevent the consumption of
valuable land space (often an important retrofit or redevelopment consideration). Vegetative filters can be
incorporated into landscaped areas, providing dual functionality.
Filtration Structure (underground)
Stormwater Pond
Generally speaking, the term “stormwater pond” may refer to any constructed basin that is built for the
purpose of capturing and storing stormwater runoff, either temporarily or for an extended period of time, in
order to prevent or mitigate downstream water quantity or quality impacts. Several distinct structure types
(wet ponds, dry ponds, etc.) are included in this general category.
**All descriptions were pulled from the Minnesota Stormwater Manual
Existing City Standards Proposed City Standards Elm Creek Watershed Management Commission Pioneer-Sarah Creek Watershed
Management Commission Minnehaha Creek Watershed District NPDES Permit Minimal Impacts Design Standards (MIDS)
Infiltration
1.0 inch of runoff off new impervious.
Water reuse for irrigation counts for full
credit.
1.1 inches of runoff from new impervious. 1.1 inches of runoff from new impervious. Water
reuse counts as abstraction.
1.1 inches of runoff from new
impervious. Water reuse counts as
abstraction.
First 1 inch of rainfall from the site's impervious
surface. Where infeasible, abstraction must be to
the greatest extent feasible and at least 0.5 inches
and TP removal that would occur from the
abstraction of the 1 inch of rainfall. Must provide
an Abstraction Analysis.
1 inch of runoff from new impervious
surfaces
1.1 inches from new/reconstructed impervious
For linear, 0.55 inches off new/reconstructed or 1.1 off net
increase in impervious, whichever is greater
Filtration Volume required for infiltration x 1.5
85% credit for using iron enhanced filter
60% credit for using stormwater ponds
50% credit for using standard filtration
Where infiltration is not possible, biofiltration is
required.
Where biofiltration is infeasible, at a minimum filtratio
n through a medium that incorporates organic materi
al, iron fillings, or other material to reduce soluble pho
sphorus must be provided.
Same as Elm Creek 50% volume abstraction credit
No specific filtration credit. If
infiltration is not feasible, any BMP can
be used.
No specific filtration credit.
Options In-Lieu of
Infiltration
*Minor expansion projects and major single
family projects are only required to
construct a raingarden onsite. Rain garden
size must be 0.0733 x area of new
impervious (sf)
*Water reuse for irrigation counts for full
credit
*Natural buffer areas around new
impervious (20-30 feet) in excess of
required wetland buffers Using MIDS
calculations based on slope, length, and soil
type. Portion will go towards volume
reduction credit
*Preserving undisturbed forest or grassland
(0.75 inches over saved area towards
volume reduction requirement)
Planting of trees (0.5*%Interception*tree
canopy area * 1 inch of rainfall)
*Meeting post construction soil quality and
amendment depth requirements
*Preserving undisturbed forest or grassland
conservation areas
*Providing wetland buffers in excess of min
requirements
*Disconnecting impervious surface
*Connecting to a downstream regional facility that
has sufficient capacity
Same as Elm Creek
*Soil amendments
*Preservation/planting of new trees
*Enhancement of pervious area
Any type of BMP may be used if
infiltration is not feasible.
If infiltration is not feasible, must follow the flexible treatment
option flow chart.
FTO 1
1.a. Achieve at least 0.55” volume reduction goal, and
1.b. Remove 75% of the annual TP load
FTO #2
2.a. Achieve volume reduction to the maximum extent
practicable
(as determined by the Local Authority), and
2.b. Remove 60% of the annual TP load
FTO #3
Off-site mitigation
For Alternative #2, the applicant is encouraged to use BMPs that
reduce volume. Secondary preference is to employ filtration
techniques, followed by rate control BMPs
Water Quality
If infiltration is not feasible, new
development TP must be removed to at
least 20% from existing conditions with any
type of BMP.
If infiltration/water reuse is not feasible,
new development TP must be removed to
at least 20% from agricultural existing land
use with any type of BMP. Other existing
land uses must maintain existing TP loading.
No net increase in total phosphorus and total
suspended sediment annual loads Same as Elm Creek
No net increase in phosphorus. Where an
applicant demonstrates that it is infeasible to
meet the one inch abstraction requirement
through use of volume control, must provide for
abstraction of runoff to the greatest extent
feasible, and at least 0.5 inches, and phosphorus
control in an amount equivalent to that which
would be achieved through abstraction of one
inch of rainfall from the site’s impervious surfaces.
Water quality BMPs shall be designed
for 1 inch of runoff from new
impervious surfaces
Water quality is considered met if the abstraction requirement
is met. See Flexible Treatment options for requirements.
Volume Control/Water Quality Requirements