Pumping Station Modifications to Comply with ANSI/HI 9.8 improve performance while lessening O&M Requirements — Two Case Studies

Abstract

Oversized wet wells in wastewater pumping stations lead to the accumulation of grit, sludge and floatable materials. Trench-type wet wells in compliance with ANSI/HI 9.8, the American National Standard for Pump Intake Design, minimize wet well volume and facilitate wet well cleaning through periodic pump down operations. Two pumping stations, the Cross-Irondequoit Pump Station (CIPS), Monroe County, New York, and the Metropolitan Council Environmental Services (MCES) L-65 Lift Station, South St. Paul, Minnesota, were modified to more closely comply with ANSI/HI 9.8. Both stations were initially constructed in the 1970s, prior to the adoption of ANSI/HI 9.8 as a consensus standard. In addition to the wet well modifications, four of the original pumps at the CIPS were removed and replaced with new pumps with improved foundations to address vibration problems and provided with revised suction piping to comply with the pump inlet requirements of ANSI/HI 9.8. The L-65 Lift Station underwent a complete renovation, with all pumps, piping, electrical and mechanical systems upgraded while keeping the lift station in service at all times during construction.Modifications to the wet well and the improved pump foundations have eliminated grit accumulation and vibration problems at CIPS. The trench-type wet well provided at L-65 has been used by MCES operations staff during pump down operations to fluidize and remove floatables that accumulate on the wet well, greatly simplifying cleaning operations.