Birdland Pump Station Increases Hydraulic Capacity and Eliminates Sewer Overflow

The City of Des Moines previously owned and operated the old Birdland Pump Station (BPS) constructed in 1964, which is located adjacent to the Des Moines River and serves combined sewers. The current BPS does not have the capacity to handle peak combined sewer flows resulting in sewer overflows during wet weather. Elimination of this combined sewer overflow will require an increase in pumping and conveyance capacity of the existing BPS. The WRA agreed to construct a new BPS to handle peak flows while eliminating the overflow per a DNR Consent Decree.

HR Green was retained by the WRA to provide engineering services (design, bidding, and construction phases) for the project improvements. HR Green started with the conceptual design of several improvement alternatives, including reusing the existing BPS vs. constructing a completely new pump station. In order to establish design flow rates during wet weather, HR Green established a hydraulic model that was calibrated based on existing flow meter data and rainfall data. Additionally, HR Green worked with a subconsultant to provide a condition assessment of the existing 24-inch cast iron pipe force main that serves the existing BPS. The condition assessment was completed using a highly sensitive acoustical tool that traveled through the pipeline collecting information to identify leaks and air pockets which are obvious areas of potential concern.

The alternative of reusing the existing BPS was ruled out due to the inadequate size of the wet well and dry well. The selected alternative included replacement of the existing BPS with all new facilities. Attached to the new pump station building will be a screen building to remove large debris from the influent flow stream that could potentially damage the pumps. The mechanical bar screens will discharge into a roll-off dumpster located above the operating level. Post-screening, the wastewater will flow into a common channel before being routed into individual pump wet wells compliant with the Hydraulic Institute Confined Wet Well design. The pump arrangement includes four pumps overall, two normal duty (70 hp), and two wet weather (420 hp) pumps that provide a total capacity of 25 mgd. Due to the extreme peaking factors, the normal duty pumps convey flow into an 18-inch force main while the wet weather pumps convey flow into the existing 24-inch force main. The project also includes extensive site improvements to protect the new pump station from river flooding. The pump station architecture was designed with input from local residents to match the neighborhood aesthetics and includes odor control provisions due to proximity to commercial and residential properties. A surge analysis was conducted to evaluate how to protect the piping system from transient pressures conditions, and the recommended design includes surge relief valves and strategically located combination air valves. The design also included a comprehensive construction sequence which was needed to minimize disruption to surrounding residents, allow the existing pump station to operate throughout construction, and ensure feasibility of construction on a very limited site footprint adjacent to the river. The project involved extensive permitting coordination with the Iowa DNR, US Army Corps of Engineers, and City of Des Moines.

The new Birdland Pump Station will meet the projected needs of the combined sewershed while eliminating a sewer overflow that discharges raw wastewater directly into the Des Moines River. The new pump station will provide reliable and safe operations while improving the site’s aesthetics to the neighborhood. The project wrapped up construction in January 2025 with Substantial Completion.