Project Title:

Urban Stormwater Sediment Demonstration Project
US EPA-GLNPO: GL96514601-0

Grantee:

City of Duluth, Dept. of Public Works, Utility Operations/Stormwater Utility
520 Garfield Ave, Duluth MN 55802

Award Date:
January 2004    Project Completion Date:    September 2006
Abstract:

Minnesota Slip located in the Duluth Harbor at the mouth of the St. Louis River (a Great Lakes Area of Concern [AOC]) has been identified as an area for remediation due to contaminated sediment. The remediation is a priority project that could be addressed under the Great Lakes Legacy Funding. However, before remediation can be successfully completed an identified source of on-going pollution (urban non-point sediment) must be controlled.

The problem to be addressed is the control of the sediment source -3 culverts conveying stormwater from approximately 300 acres of steep hillside in a highly developed urban area discharging at the foot of the slip. Although with construction of the Interstate 35 expressway, sediment traps were installed addressing some of the sediment discharge, recent sediment work done by the MPCA indicates that a problematic level of sediment discharge continues.

Visual observations of the slip indicate movement of debris and garbage in and out of the three City outfalls. The sources and characteristics are difficult to determine because the the major outfalls are below the water level prior to entering the slip. The observations are further complicated by the seiche that pushes water back into the outfalls at regular intervals.

Removal of the sediment source will offer a challenge because of the cold climate and the velocity of water coming off a slope that drops 500 feet in eight blocks. Sources of sediment include sand used in winter snow control, erosion of steep slopes, and garbage and debris from urban road usage.