McMahon Lake Outlet Project

Project Description

McMahon Lake is a land-locked basin with no natural or constructed outlet.  Water levels on McMahon Lake in Cedar Lake and Spring Lake Township have been rising over the past several years reaching an elevation of 967.66 or 2.6 feet over the Lake’s Ordinary High Water Level (OHW) in the fall of 2019. This has created a situation where much of the public Department of Natural Resources (DNR) boat launch was under water all season causing roadway safety issues with the public still launching boats; with high water causing significant shoreline erosion, threatening the longevity of the shoreline stabilizations that have been completed with landowners, water levels reaching within feet of septic systems and accessory structures, inundating and threatening numerous trees around the lake as well as within a few feet of the low point on Mushtown Road and County Road 8.

The primary goal of the proposed flood improvement project is to control lake levels to protect infrastructure of roads, homes and septic systems and the recently improved water quality of the lake.  An outlet on McMahon Lake would consist of installing a permanent water level control structure at one of the identified locations in the feasibility study completed in May 2019 by WSB. 

Project Funding

Funding for this project is being provided by the following organizations and grant award:

• Minnesota Department of Natural Resources Flood Hazard Mitigation Grant: $385,000 award
• Scott County: $210,000
• Scott Watershed Management Organization:  $175,000

Engineering & Design

The Request for Proposals for the McMahon Outlet engineering & design was published on Tuesday, August 17, 2021 on the Scott County Bids page and Association of Minnesota Counties' RFP page.

Pre-Proposal Conference virtual meeting via Zoom was scheduled for Wednesday, August 25, 2021 at 1:00 p.m. Engineering proposal deadline was September 17, 2021.

Project Updates

Update 12/1/21

• We have received the grant funding agreement from the DNR and it is currently under review with the county attorney and risk management.
• We are in negotiations with an engineering firm, and will finalize that decision this month.
• The Environmental Assessment Worksheet is about 80% complete.