Project Number: BC-7
After a detailed feasibility study, in May 2020 the BCWMC approved implementation of the project to dredge all 3 lagoons to a depth of 6 feet (Alternative 2-all). A public hearing was held September 17, 2020; there was no public input and the project was officially ordered by resolution. The project is being implemented (designed and constructed) by the BCWMC in close coordination with the Minneapolis Park and Rec Board. Project design at the 50% phase were approved in December 2021. 90% designs were approved in June 2022. Construction began in early January 2023 and is expected to continue through the winter.
The total cost of this project is estimated at $2,759,000 including feasibility study, design, construction, landfill disposal of contaminated sediment, and administration. Project costs are likely to be paid from a variety of sources including grant funds, ad valorem property taxes collected over multiple years by Hennepin County on property within the Bassett Creek Watershed, and up to $800,000 in BCWMC Closed Project Account funds.
Clean Water Grant Funding of $250,000 from the MN Board of Water and Soil Resources was awarded in late 2020. A $74,000 Hennepin County Opportunity Grant was awarded in 2021.
This project will remove sediment that has collected in three of the seven “lagoons” created along the Main Stem of Bassett Creek in Wirth Park, between Golden Valley Road and Highway 55. These lagoons were originally created in the mid-1930s by Civilian Conservation Corps crews. A 2015 study found that the lagoons remained relatively unchanged until the early 1990s, when large amounts of sediment began to appear in the lagoons. The sedimentation appeared to slow or stop by the mid-1990s. The sedimentation in Lagoon “E” (immediately to the east of the chalet and parking area) is of concern to City of Minneapolis and Minneapolis Park and Recreation Board (MPRB) staff because the sedimentation may be contributing to flooding of the parking lot and a short section of Theodore Wirth Parkway. The sedimentation has resulted in the creation of new “islands” in the creek/lagoons that reduce the flow capacity and floodplain storage of the creek.
In addition to improving flow capacity and floodplain storage, the project will improve habitat for fish and macroinvertebrates and will improve downstream water quality by trapping sediment in the lagoons, thus minimizing sediment and nutrients passing downstream within Bassett Creek and on to the Mississippi River. The project will result in a reduction of approximately 600 pounds of total phosphorus and 156,000 pounds of total suspended solids per year that currently flows downstream in the creek and into the Mississippi River.
Almost 40,000 cubic yards of accumulated sediment will be removed through this project. Due to high levels of toxic substances in the sediment, all dredged material is likely to require landfill disposal. Disposal of contaminated sediment is very expensive, resulting in the high cost of the project. Despite the high cost, however, the cost per pound of total phosphorus removal (one measure often examined when considering project implementation) is extremely low at $270/pound of total phosphorus removed.
Construction got underway in early January 2023 including preparing access routes to the ponds, dredging the ponds, and hauling the sediment to a certified landfill. Minimal disruption to trails and roads is expected. A project flyer, including map of impacted areas, is available here. More detailed FAQs are available here.
EAW Findings of Fact and Record of Decision (Jan 2022)
Environmental Assessment Worksheet (Nov 2021)
Resolution Ordering the Project (Sept 2020)
Feasibility Study Report (no appendices) (May 2020)
Feasibility Study Report Appendices (May 2020)
Presentation of Feasibility Study (May 2020)
Feasibility Study Proposal (approved July 2019)