Kaitlin Allen is an environmental engineer working with CDM Smith. She specializes in wastewater treatment design, with an emphasis in solids handling, hydraulic modeling, headworks, and disinfection. She worked with senior engineers to design and implement many of the modifications at the Al Seier Pump Station intended to help mitigate hydraulic transients and pipe vibration. During construction of these modifications, she performed construction document review and inspection services upon completion.

The Al Seier Pump Station is an essential component of the wastewater system owned and operated by Jefferson County Environmental Services Department (JCESD) in Hoover, Alabama. The 90 MGD pump station has five vertical solids handling wastewater pumps that send flow to wastewater reclamation facilities in the system. Historically, the station has experienced hydraulic transients during operation when pumps turn off. The situation has improved since the installation of variable frequency drives (VFDs) on four of the five pumps, but the problems still exist to some extent and have been noted as moderate vibration of the pump discharge piping and occasional water hammer. The VFDs reduce the severity of the problem when they are in operation; however, a power failure or similar situation can still result in a sudden uncontrolled shut off of a pump running at full speed and thus still result in transients associated with constant speed pumps. In extreme situations, the hydraulic transients have resulted in damage to the pipe supports and structural concrete within the pump station. This paper presents the development of the hydraulic/surge model, results of the field testing of a simulated surge event for model verification, stress analysis of the pipe support system to withstand the static and dynamic forces, the transient mitigation and vibration design improvements, various process and operational improvements, and the lessons learned during construction.