Sweeney Lake Water Quality Improvement Project

Golden Valley

Project Number: SL-8

Project Status   |  Active

The BCWMC officially ordered this project at their meeting on September 19, 2019 after a public hearing. (There were no public comments regarding this project received during the hearing.) The federal grant for this project was approved and a grant agreement was executed in January 2020. A survey of aquatic plants and an herbicide treatment of curly-leaf pondweed took place in spring 2020. Carp management in Sweeney Lake and Schaper Pond, including removing carp with baited box nets, took place summer 2020. The first treatment with alum was applied in late October and early November 2020. A second alum treatment slated for fall 2022.

Project Funding   |   Grant Funded

Estimated project costs are $568,080. Partial funding of $238,080 is proposed to come from the BCWMC’s Capital Improvement Program funds through 2020 and 2021 ad valorem property taxes collected by Hennepin County on property within the Bassett Creek Watershed. The remainder of project costs will be paid by a Federal Clean Water Act Section 319 grant awarded to the BCWMC through the Minnesota Pollution Control Agency.

Project Description

This project will significantly reduce phosphorus, improve water quality, and support a balanced aquatic ecosystem in Sweeney Lake by performing an alum treatment and managing carp in Schaper Pond (just south of the lake) and/or in Sweeney Lake. Sweeney Lake is a 67-acre lake with a maximum depth of 25 feet and an average depth of 12 feet. The lake provides recreational value for fishing, boating, and swimming; and it harbors a variety of panfish, a limited game fishery, and an average plant community. The lake receives runoff from a 2,400-acre fully developed watershed with nearly all of the flow entering through the Sweeney Branch of Bassett Creek. The creek flows from the south and through Schaper Pond which is immediately upstream of Sweeney Lake. Despite numerous best management practices installed or implemented in the lake's watershed over the years, water quality in Sweeney Lake has not improved significantly. Regular monitoring from 1985 to the present indicates that total phosphorus concentrations exceeded the state standard of 40 ug/L 74% of the time. Further, the lake has a history of Harmful Algae Blooms, negatively impacting the lake’s recreational usability.

The combination of curly-leaf pondweed control in Sweeney Lake, carp management in Schaper Pond and Sweeney Lake, and an alum treatment in Sweeney Lake is expected to reduce total phosphorus by 350 pounds per year, effectively “flipping” this lake from a eutrophic, algae dominated system, to a healthy, clear water system that can fully support aquatic recreation and a balanced ecosystem for aquatic biota.

Project Announcements

Activities in 2022

  • Electrofishing: On three occasions during the summer Carp Solutions surveyed carp to assess how/if populations rebounded after the carp removal activities in 2020. Surveys included electrofishing in Schaper Pond and Sweeney Lake. The data gathered during this survey will help identify long term carp management needs.
  • Panfish Stocking in Schaper Pond: In late May, 1,000 bluegills were released into Schaper Pond to reduce the carp population by eating carp eggs. We highly suspect Schaper Pond is used as a carp nursery where eggs are laid and young fish become established. The panfish stocking approved through a DNR permit.
  • Sweeney Lake Monitoring all summer: Water quality samples were collected Sweeney Lake north and south basins on multiple occasions this summer to assess conditions and get ready for this fall's alum treatment.
  • October Alum Treatment: During the week of October 16th SOLitude Lake Management added aluminum sulfate (alum) to Sweeney Lake over a 5-day period. The weather cooperated and the treatment went well.

Results from all activities will be available spring 2023.

More Information

Sweeney Lake Water Quality Improvement Project 2020 Activities and Outcomes Report for results from 2020.

2020 Carp Removal Results: Technical Memo

Curly-leaf Pondweed Treatment Areas (May 2020) ~ Wisconsin DNR Fact Sheet on Herbicide Diquat

Open House Presentation (April 8, 2020) Questions & Answers from Open House

Report and Presentation on Results of Carp Population Survey in Sweeney Lake and Schaper Pond

Resolution 19-09 Ordering Project (Sept 19, 2019)

319 Grant Workplan & Budget

Related Studies and Reports: