HomeMy WebLinkAbout10D - PW Design Manual
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Cn~ 16200 Eagle Creek Avenue S.E.
U W'" Prio' Lake, MN 55372-1714
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MEETING DATE:
AGENDA #:
PREPARED BY:
AGENDA ITEM:
DISCUSSION:
CITY COUNCIL AGENDA REPORT
OCTOBER 2, 2006
10 D
ROSS BINTNER, WATER RESOURCES ENGINEER
CONSIDER APPROVAL OF SECTION 6 OF THE PUBLIC WORKS DESIGN
MANUAL HYDROLOGY APPENDIX.
Introduction
The purpose of this agenda item is for the City Council to approve Section 6 of
the Public Works Design Manual Hydrology Appendix.
Historv
At its June 26, 2006 meeting the Prior Lake City Council considered and
approved revisions to the Public Works Design Manual Hydrology Appendix
with the exception of Section 6, Wetlands pending further review.
Within the municipal boundary of the City of Prior Lake are two water
management entities, the Prior Lake Spring Lake Watershed District (WD) and
the Scott Water Management Organization (WMO). Each of these
organizations has authority for management of water resources within their
respective boundaries. However the rules and approaches of the WMO and
WD vary.
Current Circumstances
Currently the City of Prior Lake follows the WD standard for creation of buffer
zones around wetland areas citywide; however, with the creation of the Scott
WMO and recent implementation of its rules, the City of Prior Lake chose to
revise its own rules and consolidate review authority.
When first proposed, the Rules attempted to mix the requirement of both the
WMO and WD to make a standard that was uniform over the entire City. The
approach was abandoned after the Scott WMO refused to accept the City's
uniform proposal. In the new rule the goal of uniformity was dropped in favor
of allowing the WMO and WD rules to vary.
Current Rules
Currently the City of Prior Lake requires a 30 foot average width buffer with a
minimum of 20 feet. This means that a developer can chose to decrease the
buffer width in one area where space is tight but must expand the buffer in
another to make up the difference in area so the average is 30 feet. In the
Watershed District areas, a conservation easement is required in addition to
the City drainage and utility easement over all buffer areas. Currently no
conservation easement is required in Scott WMO areas.
Prooosed Rules
Because of Scott WMO's position, the City is mandated to recommend
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Phone 952.447.4230 / Fax 952.447.4245
ISSUES:
FINANCIAL
IMPACT:
ALTERNATIVES:
when development occurs within the WMO. The following table shows existing
and proposed average buffer widths, minimum buffer widths, setbacks and no-
grade zones for both the WMO and WD.
Buffer
Requirement
Average Buffer
Width (ft)
Scott WMO
Current
Watershed
District
30
25-65
*Dependanton
wetland quality
25
30
Minimum Buffer
Width (ft)
Minimum No-
Grade Zone (ft)
Foundation 20 20 35
setback (ft) recommended from buffer from wetland
* The Scott WMO rule requires that the average buffer width vary dependant
on the quality of the wetland with width ranging from 25, 30, 50 and 65 feet.
20
20
o
10
25
In addition to drainage and utility easements, conservation easements will be
required over buffer areas in both WMO and WD properties.
The City has the choice to implement standards less restrictive than the WMO,
however the Scott WMO would then be free to take over permitting authority
and issue permits for land developing within the City. The City has avoided
this result in the past and is moving away from this "dual track" attempting to
consolidate permitting authority in the effort to provide a single point of contact
and better customer service.
However, by adoption two standards the City could be exposed to equal
protection claims from property owners and developers. Two standards also
complicate administration of those requirements as staff will have to be sure of
property location before reciting buffer requirements. Two standards are not
the staff's preference but neither is the confusion created by the City issuing
permits in the WD and the Scott WMO in the WMO. From a staff perspective,
it would be inappropriate to implement new standards for developments
already underway. Therefore to afford the pUblic with the opportunity to initiate
development before the new standards take place, the Section 6 of the new
appendix would become effective for any development action submitting a
complete preliminary plat application after January 1, 2007.
A copy of the revised wetland rule is attached.
This rule is revenue neutral for the City to implement given the fact that buffer
rules are already enforced within the City and this is only a change to specific
provisions of the rules. This rule may have an effect on density in the WMO
area and could affect land value.
1. Approve a resolution approving Section 6 of the Public Works Design
Manual Hydrology Appendix.
2. Deny this item for a specific reason and provide staff with direction.
3. Table this item until some date in the future.
RECOMMENDED
MOTION:
Alternative #1.
Reviewed by:
Frank BOYler:J.J.~
.f47h
Steve Albrecht, Public Works Director/City Eng.
Rule Aqel"':da F\dpofi,dGC
A RESOLUTION APPROVING SECTION 6 OF THE CITY OF PRIOR LAKE PUBLIC
WORKS DESIGN MANUAL HYDROLOGY APPENDIX.
Motion By:
Second By:
WHEREAS, Section 6 sets forth rules within the City of Prior Lake governing wetlands; and
WHEREAS, A public and stakeholder comment period was conducted; and
WHEREAS, On the June 26, 2006 the City Council approved the Public Works Design Manual with
the exception of Section 6, pending the results of further study by outside parties; and
WHEREAS, The Scott WMO approved the Local Surface Water Management Plan and Public
Works Design Manual contingent on equivalent wetland rules being in place by
October 2006; and
WHEREAS, All complete preliminary plat applications submitted after the effective date of the
Rules must comply with the rules laid out in the Public Works Design Manual
Hydrology Appendix;
NOW THEREFORE, BE IT HEREBY RESOLVED BY THE CITY COUNCIL OF PRIOR LAKE,
MINNESOTA as follows:
1. The recitals set forth above are incorporated herein.
2. Section 6 of the Public Works Design Manual Hydrology Appendix, is hereby approved.
3. Section 6 will become effective for on January 1, 2007.
PASSED AND ADOPTED THIS 2ND DAY OF OCTOBER 2006.
YES
NO
, HauQen
I Dornbush
I Erickson
LeMalr
Millar
Haugen
Dornbush
Erickson
LeMalr
Millar
Frank Boyles, City Manager
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Phone 952.447.4230 / Fax 952.447.4245
City of Prior Lake
Public Works Design Manual- Hydrology Appendix
SECTION 6:
WETLANDS
Procedure
For developments near wetlands, the following procedure is dependent on which Watershed the
wetland falls. Some requirements, common to both WMO and WD are listed under "both." To
determine which watershed a project is in, refer to Figure 2.
Stormwater susceptibility is determined from the results of a MnRAM to determine if a wetland is
eligible for stormwater utilization.
Both:
The applicant must submit a wetland delineation and a MnRAM 3.0 wetland assessment, these
documents are then reviewed by the City.
If impacts are proposed to any wetland, the procedure follows the requirements of the Wetland
Conservation Act and these rules.
A wetland is given a functional classification dependent on the value for vegetative diversity
determine by the MnRAM 3.0. Rankings are: Exceptional, High, Medium, and Low.
Reouirements
PLSLWD:
Wetland replacement for impacts occurring within the PLSLWD must take place within the District
at a rate of 0.5:1 (New Wetland Credit per acre impacted.)
Both:
The City must review and approve of the wetland delineation and Minnesota Routine Assessment
Version 3.0, (MnRAM) (as amended).
Any drainage, fill, excavation or other alteration of a public waters or wetlands is regulated by the
Wetland Conservation Act (WCA), State Statutes 1 03G.245 and regulations adopted thereunder.
The City is the Local Governing Unit (LGU) under these rules.
A conservation easement is required over all buffers.
Stormwater Susceptibility.
Both:
Highly Susceptible: A wetland is considered highly susceptible if:
. Forty percent or more of the wetland complex has highly susceptible wetland communities
as shown in Table 6.1 and;
. Highly susceptible wetland communities have medium to exceptional floral
diversity/integrity.
Moderately Susceptible: A wetland is considered moderately susceptible if:
. Forty percent or more of the wetland complex has a moderately susceptible wetland
communities shown in Table 6.1 and;
. Moderately susceptible wetland communities have medium to exceptional floral
diversity/integrity.
G:IWater ResourcesILSWMP\2006 LSWMPIPWDM Hydrology AppendixlWetIand Rule.doc
1
City of Prior Lake
Public Works Design Manual - Hydrology Appendix
Least Susceptible: Wetlands with low floral diversity, as determined by MnRAM, were considered to
be least susceptible wetlands.
Slightly Susceptible: Wetlands that do no fall under the high, moderate or least susceptible
categories are considered slightly susceptible.
Table 6.1
Wetland Community Susceptibility to Stormwater Impacts
Highly Susceptible Wetland Communities. Moderately Susceptible
Wetland Communities.
Sedge Meadow Low Prairies Shrub-Carrs
Bogs Coniferous Swamps Alder Thickets
Coniferous Bogs Hardwood Swamps Fresh (wet) Meadows
Open Bogs Seasonally Flooded Basins Shallow Marsh
Calcareous Fens Deep Marsh
. Wetland communities determined using key provided in MnRAM Version 3.0.
Stormwater Utilization:
Hydroperiod
Standard
100-year Storm
Bounce
Discharge Rate
Highly
Susceptible
Existing
Table 6.2
S "0 rmwate r Utilization
Moderately
Susceptible
Existing + 0.5 ft
Slightly
Susceptible
Existing + 1.0 ft
Least
Susceptible
No Limit
Existing
Section 4:
Wetland
Standard (1)
Existing + 1 Day
Section 4:
Wetland
Standard (1)
Existing + 2 Days
Section 4:
Wetland
Standard (1)
Existing + 7 Days
1 & 2 year NRCS
event Inundation
10 yr NRCS Existing Existing + 7 Days Existing + 14 Existing + 21
event Inundation Days Days
(2) Outlet Control None: Note None: Note 0 - 2 ft additional 0 - 4 ft additional
Elevation OE/HWL on Map OE/HWL on Map storage storage
(1) Rates shall be held to the rate control spelled out in section 4, alternate rate control
standard for wetlands, unless obtaining these rates is prevented by inundation period
requirement.
(2) Outlet Control Elevation changes can be made to mitigate volume storage as required in
Section 5.
Buffer & No-Grade Zone Requirements
Existing
PLSLWD:
The following are the buffer and minimum no-grade zone requirements for each functional
classification. The tiered buffer requirement is based on a functional classification of; exceptional,
high, medium or low, and can be found using the results of the MnRAM vegetation assessment as
described above
G:IWater ResourcesILSWMP\2006 LSWMP\PWDM Hydrology AppendixlWetIand Rule.doc
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City of Prior Lake
Public Works Design Manual- Hydrology Appendix
Table 6.3
PLSLWD Buffer, Setback and No-Grade Matrix
Buffer Exceptional High Medium Low
Requirement
Average Buffer 30 30 30 30
Width (ft)
Minimum Buffer 20 20 20 20
Width (ft)
Minimum No- 10 10 10 10
Grade Zone (ft)
Foundation 20 20 20 20
setback from
Buffer
Scott WMO:
The following are the buffer and minimum no-grade zone requirements for each functional
classification. The tiered buffer requirement is based on a functional classification of; exceptional,
high, medium or low, and can be found using the results of the MnRAM vegetation assessment as
described above.
Buffer
Requirement
Average Buffer
Width (ft)
Minimum Buffer
Width (ft)
Minimum No-
Grade Zone (ft)
Foundation
setback from
wetland
Table 6.4
Scott WMO Buffer, Setback and No-Grade Matrix
Exceptional High Medium
Low
65
50
30
25
25
25
25
25
25
25
25
25
35
35
35
35
Both:
Grade changes or other disturbances are not allowed in No-Grade Zones with the following
exceptions: Pipe Outlets and associated riprap, reseeding or soil amendments, embankment and
impacts associated with an approved CIP transportation corridor, grade changes adjacent to
approved WCA impacts to wetlands, approved wetland or flood storage mitigation areas and
temporary impacts associated with utility installation.
A buffer width may vary using "Buffer Averaging." Buffer width may be reduced to the minimum
buffer width, but the overall buffer area must be equal in area to a hypothetical fixed width average
buffer around the same wetland. This means that while one side of a buffer is reduced in width, the
buffer must be increased in width in another area to make up for the loss of area.
G:IWater ResourcesILSWMP\2006 LSWMPIPWDM Hydrology AppendixlWetland Rule.doc
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0.75 0.375 0 0.75
Miles
BOUNDARIES
I I PL I SL WATERSHED DISTRICT
_ SCOTT WMO
FIGURE 2
W+E
S