Sioux Falls Main Pump Station Increases Collection Capacity

Challenge: The City of Sioux Falls aging Main Pump Station (MPS), originally constructed over 35 years ago, presented several limitations with no built-in provisions for expansion. The MPS is a critical infrastructure facility that serves 90% of Sioux Falls. Recognizing the need for essential upgrades, the city aimed to enhance its flow capacity, streamline maintenance access, improve overall functionality, ensure reliable standby power, and enhance safety measures.

Solution: HR Green successfully managed the design, bidding, and construction phases of the MPS Replacement Project. The newly upgraded Lift Station has a peak design capacity of 65 million gallons per day (MGD) with the flexibility to accommodate an additional pump, pushing the flow capacity to 90 MGD. This lift station features two mechanical screens, a bypass channel, and even provisions for future expansion with the addition of more screens to further boost capacity.

The station is equipped with four robust dry-pit pumps, each designed to handle a peak flow of 15,000 gallons per minute at 128 feet of total dynamic head (TDH). These pumps are driven by 600 horsepower motors, which are controlled by variable frequency drives. The pump room is thoughtfully designed to facilitate maintenance, complete with a bridge crane and an open mezzanine for easy access to the piping header. The site design also considered maintenance access for tractors at the wet well and snow removal.

During the design process, HR Green conducted a thorough evaluation of multiple sites and conducted hydraulic modeling of a no-rise condition for grading impacts to the floodplain. The deep excavation required a large area along with major staging and staff trailers. The electrical design includes a standby generator to ensure uninterrupted operation. Additionally, the site grading safeguards the Main Lift Station, elevating it above the 500-year floodplain elevation. A surge analysis was carried out to protect the piping system from both high and low-pressure conditions, with the design incorporating surge tanks and surge relief valves.

Benefit: By increasing the station’s capacity, the new lift station has enhanced the city’s ability to manage wastewater effectively and accommodate potential growth. Additionally, the design considerations for easy maintenance and floodplain protection contribute to the long-term reliability of the station, reducing service disruptions and maintenance costs.