HomeMy WebLinkAbout1C Emerging Issues - Markley Lake - Work Session Report
Phone 952.447.9800 / Fax 952.447.4245 / www.cityofpriorlake.com
4646 Dakota Street SE
Prior Lake, MN 55372
CITY COUNCIL WORK SESSION REPORT
MEETING DATE: JULY 15, 2019
PREPARED BY: ANDY BROTZLER, PUBLIC WORKS DIRECTOR/CITY ENGINEER
PETE YOUNG, WATER RESOURCES ENGINEER
PRESENTED BY: ANDY BROTZLER AND PETE YOUNG
AGENDA ITEM: 1C EMERGING ISSUES – MARKLEY LAKE DISCUSSION
ACTION
REQUESTED:
Review and Provide Direction to Staff
INTRODUCTION: Markley Lake is a landlocked water body approximately 22 acres in size.
Portions of the City of Prior Lake and Credit River Township are within
the Markley Lake watershed. The Scott Watershed Management
Organization (WMO) is responsible for watershed management in this
area of the City.
Background
The City, County, and Township were jointly sued by Township property
owners in the mid-1990s after septic systems on private properties were
inundated by high water levels on Markley Lake. The parties reached a
settlement agreement, the terms of which outlined an interim plan that
relied on pumping Markley Lake to reduce water levels. The interim plan
was followed during a high water event in 1999. The cost to implement
the plan was approximately $17,000. The cost was split between the
City, Township, and County with the City contributing about $10,000. An
additional item in the settlement agreement directed the City to
implement other controls as a solution to high water issues, thereby
eliminating the need for an interim plan.
The City completed the Markley Lake Study (2010) to guide
implementation of practices with the goal of keeping the lake at pre-1991
water levels under developed conditions. The Markley Lake Study,
based on modeling, concluded that adding 20 ac-ft of compensatory
flood storage in the Markley Lake watershed would achieve the lake level
goal.
The City completed 16 ac-ft of compensatory flood storage for Markley
Lake between the Welcome Avenue project and a diversion within the
Eagle Creek Estates development. This amount is proportional to the
amount of land under City jurisdiction within the watershed. An additional
4 ac-ft of flood storage would be needed in Credit River Township when
additional areas within the Markley Lake watershed are developed.
2
Current Conditions
Markley Lake is currently exhibiting high water levels. This area has seen
seven consecutive years of above-average precipitation and 2019 will
likely also be above-average. Lake levels have seen an increasing trend
since bottoming out in 2010. Residential properties in Credit River
Township have wet yards/landscaping but no structural impacts. Higher
water levels could affect existing mound septic systems for two Township
properties (16506 and 16523 Whitewood Avenue); the City does not
have elevation data for these systems. Higher water levels could affect
homes starting at a lake level of approximately 899.8 feet (about 2 feet
above today’s levels). All impacts to City properties are confined to
existing Drainage and Utility Easements in the Markley Lake Woods
development; vegetation and a City trail have been affected.
Discussion
Staff has received several complaints about high water affecting the City
trail system, damage to lawns and landscaping, and the potential for
future septic system or home impacts in the Township. Because Markley
Lake has no outlet, there are few short-term options available to address
high water levels. The primary short-term option would be to implement a
lake drawdown by pumping water to the Credit River, similar to the
drawdown that was last completed in 1999.
City Council direction is requested to address the following question:
1. Should the City pursue a partnership with the Scott WMO and
Credit River Township to draw down Markley Lake by pumping to
the Credit River?
Issues
The following should be considered for a potential lake drawdown:
• Costs
o There is no existing cost-share agreement between City,
Township, and WMO
o Costs include staff time, materials, and fuel
o Viability of old Met Council sanitary line – jetting
o Total estimated cost between $30,000 and $50,000
• Timing
o Pumping 24 hours per day or during limited hours
o A minimum of 45 days would be required to draw down the lake
to the ordinary water level of 893.2; this assumes no additional
rainfall and continuous operation
• Noise
o The City’s diesel pump is extremely loud
o City staff noted that noise complaints were received during 1999
pumping operations; notification would be required
o Possible structure to attenuate noise
• Permitting
o DNR permit process is well-defined and likely to be quick
o W ould need to determine applicant – WMO (cross-jurisdictional)
may be in best position; County was applicant in 1999