The City of Duluth owns, operates, and maintains 53 wastewater pumping stations within its 80.2 square-mile limits, including five storage facilities, the majority of which have been designed by MSA. Leveraging this long-standing relationship, the City once again called upon MSA engineers for an important assignment: the relocation and replacement of Lift Station No. 15. This project was an important first step in one of the largest infrastructure projects in Duluth’s history — the three-year, $200 million Twin Ports Interchange project which overhauls the I-35/I-535/Hwy 53 “Can of Worms” exchange.
The existing Lift Station No. 15 was located near the intersection of 22nd Avenue W. and W. Michigan Street, in direct conflict with the upcoming interchange project’s overpasses and support abutments. It was also past its typical life span and in a severe state of deterioration with structural, mechanical and safety concerns tied to its original 1960s age. The City of Duluth and Minnesota Department of Transportation (MnDOT) worked collaboratively to coordinate the necessary upgrades and to deliver an aesthetically pleasing facility to mirror what would soon be a newly reconstructed and publicly prominent highway project. This positive relationship, aided by the receipt of federal funding, led to the project’s successful completion for both parties.
The proposed site for the lift station had a number of challenges including environmentally compromised soils from a prior user that required Phase I and II Environmental Site Assessments and the ultimate removal and disposal of approximately 2,700 tons of asbestos-containing material and 75 tons of petroleum-impacted soil before construction could commence. The soils were also not structurally competent to support the new lift station, resulting in MSA utilizing a deep steel H-pile system to provide the necessary foundation for the project.
MSA’s design for the new facility included a new 5,000-gpm lift station, 36-inch sanitary sewer extension, and new 20-inch sanitary force main. The station features a new lifting cast-in-place concrete wet well and brick/block control building, with an exterior aesthetic designed to blend into the surrounding neighborhood. The station also includes a new raw wastewater grinder, 60-hp VFD-controlled submersible pumps, 16-inch DIP process piping and flow meter.
The process piping provides access for sewer pig launching for long-term operations and maintenance and the system discharges into a new 20-inch HDPE SDR 17 force main constructed on an engineered base that supports the pipeline and connects to an active Western Lake Superior Sanitary District (WLSSD) interceptor structure. The station’s process controls and instrumentation have been seamlessly integrated into the City’s existing SCADA system and runs on 480V power along with a natural gas standby engine generator.
MSA worked closely with the City and other stakeholders in the planning, design and construction of Lift Station No. 15. The project required close coordination with other city-led utility relocations as well as the design and construction of a new multiuse trail happening concurrently. The Lift Station No.15 relocation project required numerous specialists and trades to address and design for the numerous challenges. The project was constructed on schedule and on budget, complete with site restoration, native plantings, and landscaping.