HomeMy WebLinkAbout8A - Watershed Outlet Project
16200 Eagle Creek Avenue S.E.
Prior Lake, MN 55372-1714
CITY COUNCIL AGENDA REPORT
DATE:
AGENDA #:
PREPARED BY:
AGENDA ITEM:
SEPTEMBER 7, 2004
SA
STEVE ALBRECHT, CITY ENGINEER
PRIOR LAKE OUTLET CHANNEL IMPROVEMENTS
PROJECT PRESENTATION
PRESENTATION:
Shannon Lotthammer, District Administrator of the Prior Lake
Spring Lake Watershed will be presenting information regarding the
proposed Outlet Channel Improvements. She will provide an
overview of the proposed project along with the redesign of the lake
outlet structure. Shannon will also address the status of the
Environmental Assessment Worksheet (EAW) for the project.
G: \Agenda\Agenda04\Lotthammer Presentation. DOC
www.cityofpriorlake.com
Phone 952.447.4230 / Fax 952.447.4245
Prior Lake Outlet & Channel
Improvement Project
Prior Lake City Council
September 7, 2004
Prior Lake Oudet & Channel
Improvement Project -- Background
. Prior Lake has natural overflow at 918.0 feet
. Outlet constructed in the early 1980s
. Channel connected and improved to carry water
from lake to :Minnesota River
. Watershed District operates outlet and
completes maintenance/repairs
. System has worked well for last 20+ years
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Changing Uses, Future Needs
. Shift from flood mitigation to storm-water
conveyance
. Increasing pressures:
. Current development
. Approved future development plans
. 20 years of "wear and tear"
. 2003 Prior Lake Outlet Channel and Lake Volume
Management Study
. Five management strategies
Outlet & Channel Improvement
Project
. Restoration and enhancement of system
. Need for the project:
. Current system is expensive to operate and maintain
. Erosion from 20 years of use
. Flow in some segments is inefficient
. Future development pressures (increased runoff):
. Additional channel stabilization
. More efficient outlet
Outlet Box Improvements
. Replace existing box with new struc
. Same elevation (902.5')
. Allow outlet to reach maximum capacity at lower
lake elevations
. Proposed Operating Plan changes:
. Allow fall outletting between lake levels of 902.0'
and 902.5' under certain conditions
. Allow up to 30 cfs discharge during spring and fall
discharge period
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Impacts & Benefits of Improvements
. Less maintenance during operation
. Larger structure, enhanced aesthetics
. Greater efficiency, no change in overall capacity
. Potential for slightly higher volumes discharged
. More likely to reduce intensity of discharge during
high water events without increasing total volume
. Prior Lake water quality is relatively good, so
effect on downstream waters is minimal or
beneficial
Channel Restoration &
Enhancement
. Increase easement to 75 feet (minimum)
. Remove accumulated sediment
. Re-slope channel banks to enhance stability and
increase capacity in some areas
. Stabilize banks through combined approach:
. Traditional engineering using rocks and boulders
. Bioengineering using native plants such as willows,
dogwoods and grasses
Impacts & Benefits of Outlet
Channel Improvements
. Decreased potential for future erosion
. Increased habitat
. Greater compatibility with greenway
. Enhanced water quality (less erosion, wider buffer)
. May impact wetlands; work in wetlands will be
minimal
. Outlets, channel side slopes and "toe protection"
. Reduced erosion, increased habitat, reduced bounce
. Winter construction to minimize potential impacts
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Project Costs & Financing
. Overall cost estimated at $3.7 million
. Cooperative effort ofWD, cities of Prior Lake
and Shakopee, and possibly the Shakopee
Mdewakanton Sioux Community
. Watershed District share proposed at $1.7 million
. Watershed-wide levy, due to watershed-wide
benefits
. District likely to issue bonds for at least part of
the project costs
Next Steps
. Voluntary EA W - comment period extended
. Other permits: DNR, WCA, Corps of
Engineers, Cities, MPCA
. Revision of Joint Powers Agreement
. Plan to advertise bids this fall for first segment
Geffers), and smaller project just south of CR 16
. Construction during winter
. Planting during spring
. Future segments as agreements, funding allow
Questions?
Comments?
Thank YOU!
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