Project
KLJ’s study revealed numerous system deficiencies in the old system, primarily caused by excessive length of small diameter force main and minimal volume within the lift station wet well. The force main limitations generated excessively high head levels (TDH) which caused the pumps to operate dangerously near the shutoff head and created significant water hammer effect at shutdown. Furthermore, pumps capable of operating at an acceptable efficiency level were not readily available. Additional deficiencies included lack of air release valves, insufficient pump submergence depth and insufficient wet well volume.
Solution
KLJ recommended construction of a new lift station, installation of a 6-inch diameter force main parallel to the existing 4-inch force main, rerouting the gravity sewer to the new lift station, and demolition of the old lift station.
KLJ provided a variety of services during this project which included civil design, electric design, surveys, and construction administration. The civil design included hydraulic calculations of the pumping system, extension of gravity flow sanitary sewer, force main sizing and routing, street and shared-use path repairs, facility site planning and demolition of the old lift station. Electrical design included power supply, system controls, interior building electrical, and exterior site lighting. Structural design included building footings, foundations, and interior concrete floor. Survey work included topographic survey, preparation of easement documents, and preparation of a plat of irregular description. Construction services included construction administration, construction observation, construction staking, and project coordination.
Results
Completed in 2016, the new lift station utilizes recessed impeller pumps capable of operating at an acceptable efficiency level through the new 6-inch force main, the old 4-inch force main or both force mains in parallel. The pump motors were provided with soft starters to minimize water hammer effect and air release valves were installed at high point in the force main to eliminate potential for air locking. The lift station controls are housed in a single piece, pre-fabricated fiberglass structure which will require minimal maintenance throughout the lifetime of the system.
