Woodland Ave/ Hartley Park Green Infrastructure benefitting Tischer Creek

The Woodland Ave/Hartley Park Green Infrastructure project will improve water quality and aquatic habitat in Tischer Creek, a cold-water trout stream that begins in the wetlands of the City of Rice Lake, eventually cascading down the Duluth hillside and emptying into Lake Superior at Glensheen Mansion. The project will treat urban runoff from 110-acres of a residential and commercial area that is intercepted by the Woodland Avenue storm sewer and currently discharged, untreated, from a 3' diameter pipe directly into the Creek, resulting in a visible sediment plume. Tischer Creek is listed by the Minnesota Pollution Control Agency (MPCA) and the Environmental Protection Agency (EPA) as impaired for E. coli (bacteria), with total suspended solids (TSS) levels just below the water quality standard. The project will also help maintain cold baseflow to the creek and an associated tributary during drought conditions, restore pre-development hydrology and reduce "flashiness" that can lead to stream bank erosion. The project would implement an action (treat urban runoff) that is called for in several watershed plans.

Treatment will be provided via a 212,096 cubic foot capacity green infrastructure system to be constructed on City of Duluth property. To divert runoff into the treatment area, St. Louis County will reconstruct a portion of the storm sewer under Woodland Avenue as part of a 2024 road project. After pre-treatment via a sedimentation vault near the road, runoff will flow into a sedimentation basin and marsh followed by a series of bio-infiltration basins. The last basin includes biochar for bacteria removal. Basins and surrounding areas will be planted with native vegetation appropriate for the site. The project will include at least three years of vegetation maintenance, invasives control and re-planting by a qualified contractor. The project makes use of a previously farmed area that was ranked #1 by a City study of potential sites for adding green infrastructure.

In addition to capturing 11.3 tons/year of sediment and associated bacteria, trash and other pollutants, the green infrastructure is designed to maximize recharge of groundwater to support nearby wetlands and baseflow to Tributary 7 to Tischer Creek. Bio-infiltration basin design includes 12? of course aggregate below the drain tile to help cool water and allow for recharge of shallow groundwater, while the final discharge is designed to diffuse flow into an existing wetland adjacent to Tributary 7.

The project offers multiple opportunities to leverage other funding sources as well as significant contributions of time and expertise by County and City staff.
oThe County has secured federal funding to cover 75% of design and construction costs. This request would cover the 25% match during construction. Project design has used federal funds with the County covering 25% match. The project will be ready to go to bid winter 2023/24.
oCosts to rebuild storm sewer under Woodland Ave to divert flow, estimated at $115,000, will be covered by the County's road project budget. In addition, during the BMP project design phase, St. Louis County covered the 25% match (approx. $50,000, half via staff time).
oThe City-County partnership pools resources of both jurisdictions to achieve the best project at lowest cost with highest potential for long-term success. After starting conceptual design of a smaller system in the road right-of-way, the project was expanded in 2022 via a formal agreement with the City of Duluth to build the project in a portion of Hartley Park that was once farmland and is currently dominated by invasive, non-native vegetation. The City of Duluth will own, operate and maintain the BMPs after construction is complete. St. Louis County Public Works, which typically implements $60 million/yr. of construction projects, is taking the lead on design, funding, bidding, contracting and construction oversight.