In 2008 the WRA retained consulting engineer HDR to provide planning, permitting, design, construction, and start-up services for a high-rate CSO treatment facility called the Combined Sewer Solids Separation Facility or CSSSF. The goal was to store and/or treat CSO flows during wet weather. The facility was to be capable to reduce the adverse impacts of wet weather flows to the existing nearby wastewater reclamation facility. HDR, working in conjunction with Electric Pump, Inc., the local Flygt representative, and with technical assistance from Xylem-Flygt, evaluated several preliminary sump design concepts. The result was an innovative two-stage wet well and sump design concept incorporating a low-flow sump and high-flow pump wet well. The high-flow pump arrangement incorporated new Formed Suction Intakes (FSI) that reduced the size of the wetwell.
Flygt engineers evaluated the original design concept and recommended converting the two side-by-side pump stations into a single sump design concept. This design not only brought both stations together by using standard sump design concepts for the centrifugal pumps and the axial flow pumps, but also included FSIs for each of the axial flow pumps to provide an additional reduction in the overall width of the pump station.