DeCola Ponds B & C Improvement Project

Golden Valley

Project Number: BC-2,3,8

Project Status   |  Active

At their meeting on September 21, 2017, the Bassett Creek Watershed Management Commission approved a proposal from the Commission Engineer (Barr Engineering) to perform a feasibility study for the project which began in October 2017 and continued through the winter.

In November 2017 and April 2018, a public open houses were held to gather resident input about the area, answer questions and understand their concerns.

The feasibility study was completed and approved by the BCWMC in May 2018. The BCWMC took action to pursue Concept #3 from the feasibility study which aims to balance maximizing flood storage while preserving trees and improving wetland and upland habitats.

A public hearing was held by the BCWMC on August 16, 2018 - no comments were received during the hearing. Immediately following the hearing, the BCWMC adopted a resolution officially ordering the project, certifying costs to Hennepin County for tax collection, and approving an agreement with the City of Golden Valley to design and build the project.

An Environmental Assessment Worksheet was completed and approved in January 2019. A public open house was held on February 6th with displays of the 50% design plans. The 50% designs were approved by the BCWMC at their meeting in February 2019. 90% designs were approved by the BCWMC April 18, 2019. Construction began fall 2019 and was completed summer 2020. A final project report is expected by the end of 2020.

Project Funding   |   Grant Funded

The estimated cost for this project is $4.1 million (-10%/+20%). The BCWMC will use an ad valorem tax levied on all watershed residents by Hennepin County to fund approximately $1.53 million (over two years) for this project. The remainder of the funding will come from a variety of sources, including Clean Water Funds from the MN Board of Water and Soil Resources, the City of Golden Valley, Hennepin County, Minnesota Department of Natural Resources (MnDNR) Flood Damage Reduction Grant program, and other sources (e.g. other grants, as appropriate).

Project Description

The project will improve flood storage volumes within the project area, develop additional water quality treatment volume, and remove accumulated sediment that has collected in the north end of DeCola Pond B. The project will help alleviate local flooding around Medicine Lake Road, and downstream at DeCola Ponds A, B, C and D, and will improve water quality downstream by trapping sediment in the new forebay pond, thus minimizing sediment passing downstream to DeCola Ponds B and C (which are DNR Public Waters) and Bassett Creek. The project will also improve ecology and wildlife habitat, enhance active and passive recreation opportunities, and provide educational opportunities.

The project develops approximately 24 acre-feet of additional flood storage for the 100-year flood frequency event, which brings the 100-year flood elevation on the Medicine Lake Road low point from 3.1 feet of depth to approximately 1.8 feet of depth. This flood depth reduction on Medicine Lake Road is close to achieving the goal outlined in the Medicine Lake Road Winnetka Avenue Long Term Flood Mitigation Plan (Barr, 2016) and will allow passage of emergency vehicles during large, intense rain events. Additionally, lowering the 100-year flood elevation eliminates one structure (12-unit condominium on Rosalyn Court) from being at-risk of flooding and improves access to Rosalyn Court during the 100-year design storm event). There are also reductions in the flood elevations on DeCola Ponds A, B, C, and D. With the combination of the Liberty Crossing Flood Mitigation Project and the recommended DeCola Ponds B and C Improvement Project, a total of six structures (two commercial properties and four 12-unit condominiums) would no longer be at-risk of flooding during the 100-year event.

Additionally, the concept project will increase the phosphorus load reduction by 10.8 pounds per year. The expansion of flood storage will result in the removal of trees in low-lying areas of the project. However, the restoration plan includes the planting of hundreds of new high-quality native trees and shrubs and restoration of 2.9 acres of wetlands and upland habitat.