L27 Lift Station Provides Reliable Wastewater Service
The L27 Lift Station replaced an existing, aging facility in Hopkins, Minnesota, which was over 40 years old, had significant condition issues, and lacked redundancy. The existing force main was constructed with Prestressed Concrete Cylinder Pipe which was susceptible to internal and external corrosion. In 2000, a corroded section of the force main collapsed within the Dean neighborhood near the project area. In addition, the existing lift station was undersized with little storage. This presented an operational limitation to address malfunctions at the lift station without causing backups to homes or spills.
Due to constraints with the existing site, a new site had been selected for L27 lift station in nearby Oakes Park. However, it was discovered that the site could not be acquired as planned. A search for a new site followed, and HR Green assisted with the evaluation of several additional candidate sites.
Ultimately, MCES purchased a site across the street from Oakes Park, in a densely populated neighborhood with several adjacent apartment buildings. The site also included wetlands, and HR Green’s team worked closely with MCES and the Minnehaha Creek Watershed District (MCWD) to develop a site plan that avoided wetland impacts and complied with MCWD and City design requirements.
Several options were assessed for response time storage for the new lift station. Storage in a large wet well was selected, in part because of the cost and risks of constructing a deep, large interceptor pipe for response time storage. The lift station was designed as a circular structure that was constructed as a caisson that was 61 feet in diameter to minimize construction excavation impacts on the tight site. The lift station’s average daily flow is 2.25 MGD with a peak of 6.3 MGD.
The new facility’s design and construction materials were selected to blend into the natural setting of the neighborhood. The improvements will provide safe and reliable wastewater service to the Hopkins area for another 50 years or more, significantly increasing long-term system reliability, protecting properties, and the local natural resources.