The Mayfield booster pump station (BPS) was originally constructed in 1970 and had reached the extent of its expected service life. California American Water (CAW) had decided to replace the BPS with a modern premanufactured below-ground pump station that would alleviate several of the issues that were identified in the BPS condition assessment. The new BPS provides for more efficient operation with variable frequency drive (VFD) domestic water pumps; additional fire flow capacity to meet county requirements; emergency generator; ventilation; sound attenuation; and greater accessibility for maintenance. 

WHB Engineers provided preliminary engineering services that included hydraulic analysis of the closed-loop service area using the Water CAD model and projected demands; surveying, geotechnical investigation; and development of a Basis of Design Memorandum that identified several options and associated cost estimates. Close coordination with premanufactured vendors, USEMCO and EFI, resulted in a preferred installation with little impact to the surrounding residential area.   

Both premanufactured vendors were solicited for bids based on performance specifications and preliminary engineering drawings. WHB Engineers provided bid support review and recommendations for purchase by CAW. In the Final design phase, WHB Engineers provided construction documents for the civil, structural, electrical, and traffic control improvements to support the installation of the BPS. Construction support services included attendance at meetings, response to requests for information (RFI), and submittal review. 

One of the major challenges in the project were the existing site constraints. The original BPS had been located within a small 12ft x 15ft easement between two residential properties on a steep slope with relatively shallow rock bed. In 1991 and 1995 electrical improvements were made to the BPS that extended beyond the easement property lines. The new BPS required a greater area to support the additional pumps, emergency generator, and greater accessibility for maintenance.

During preliminary design an alternative was developed to relocate the pump station to the adjacent street and allowing for the existing easement to be used for the new emergency generator. The alternative design minimized impact to the existing residents by not requiring additional easement acquisition and still allowed for the installation of the new larger BPS within the street right-of-way (ROW) with all the CAW desired features.

Description: The Otay Crossings Commerce Park Sewage Pump Station will service the new Otay Crossing development located in East Otay Mesa. The lift station includes a 7700 gallon wet well with a 15,000 gallon emergency storage manhole and two 15 HP lift pumps each capable of 275 gpm of sewage flow.

WHB Engineers provided electrical and control systems design, including power, controls, site lighting, grounding, and maintaining County SCADA standards to maintain consistency across all facilities.