Rehabilitation of a 1960s-Era Sanitary Lift Station

A municipal sanitary lift station built in 1965 required extensive rehabilitation to enable future operations. Three pumps of antiquated design needed to be replaced. Piping penetrations into the wet well were leaking, and repeated attempts to remedy had failed. Electrical feeds and pumps station controls needed to be upgraded. Piping and valves needed to be replaced. Flows had increased into this facility over the years, and flow metering in this critical facility was needed for improved control.During rehabilitation, the lift station was required to remain in operation at all times. Several design objectives were identified. The two original discharge lines needed to be consolidated into a single pipe. Reliability and redundancy of pumps, valves, and piping was needed. Because of the small wet well volume, the operation of the station could be improved by flow matching with variable frequency drive controls on the pump motors. A primary system of level control using a transducer was developed, with a secondary system using float devices. Three dimensional drafting techniques were used to plan the construction sequence, minimize bypass pumping, and expedite the rehabilitation.Since completion of the rehabilitation, operational data spanning one year has demonstrated the value of this project. Performance of the station during both dry and wet weather has shown efficient handing of the flows. An analysis of lessons learned from the project will be presented.