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Lower Cavanee Pump Station Upgrade,
San Jose Water Company, San Jose, CA

Existing Pump House with Sand Box in Foreground

New Submersible Pumps Installed

Water Works Engineers designed a retrofit pump station for the San Jose Water Company’s (SJWC) Lower Cavanee Pump Station. The existing pump station included a diversion dam, leaf screen, sand box, and pump house with a single 3500 gpm vertical turbine pump with a variable frequency drive. The goal of the project was to increase the capacity of the pump station to 5000 gpm, with the ability to reduce flows to as low as 500 gpm to take full advantage of SJWC’s water rights on Cavanee Creek. During preliminary design activities, three alternative pump station layouts were developed:

  1. Submersible pumps inside existing sand box,
  2. Vertical turbine pumps suspended over sand box, and
  3. Vertical turbine pumps in new building.

The approach used to develop these alternatives was heavily focused on meeting the SJWC’s aggressive construction schedule while minimizing construction cost and meeting the operational goals of the project.

A hydraulic model was developed using AFT Fathom software to evaluate the full range of possible flow scenarios from the creek and the SJWC’s other water diversions, and for pump selection and power cost estimation. The 20-year net present value of these three alternatives were estimated, and Alternative 1 was selected based on the ability to construct the project within the current year, reuse existing facilities, and the ability of submersible pumps to handle high solids loadings and debris. In addition to pump station hydraulics and layout, the selected design included raising the walls of the sand box and installing a new metal roof to replace the aging wooden roof, installation of a new belt on the leaf screen to minimize headloss at the higher design flows, and all new instrumentation and controls housed in the existing CMU pump house.

The highly detailed 90 percent design drawings and specifications were used as the basis for construction, with close coordination between Water Works Engineers, SJWC and the contractor through construction. Construction was completed on schedule and the pump station is currently in operation.

Pump/System Curves at Operation Extremes