Santa Clara Valley’s longest operating treatment plant

An aerial view of the treatment plant taken in 2012.

In 1967, the Santa Clara County Flood Control and Water Conservation District – the precursor to today’s water district – completed the valley’s first water treatment plant on 40-acres in the hills above Los Gatos.

Getting it built, however, wasn’t easy. It took two bond votes – in 1962 and 1963 – before voters approved funding for the treatment plant that also included dollars for the South Bay Aqueduct linkup and conveyance and distribution facilities. The plant was to serve as a hub where distribution systems would take treated water to Cupertino, Santa Clara and Campbell. Water would reach the plant from the South Bay Aqueduct on the valley’s east side through a 72-inch pipeline laid across the valley floor.

Workers in the midst of construction on the Rinconada plant.
Workers in the midst of construction on the Rinconada plant.

Dedicated as the Rinconada Water Treatment Plant, it had a capacity to treat 80 million gallons of water a day from supplies imported from the State Water Project, a water storage and delivery system of reservoirs, aqueducts, power and pumping plants that stores and distributes water to urban and agricultural water suppliers in northern California, the San Francisco Bay, the San Joaquin Valley, the Central Coast and Southern California.

Among other things, it housed a 1,280-square foot laboratory for testing water quality, utilized four 20-feet deep and two million gallon clarifier basins.

Today, the plant’s major facilities include an operations and administration building, four upflow clarifiers, six dual media filters, residual management facilities, two clearwells and one treated water reservoir. The laboratory relocated in 2009 to the district’s Almaden campus, gaining more space – it now has more than 18,000-square feet to work with – and better equipment to deal with new regulations.

Rinconada is the oldest of three treatment plants built by the water district. The Santa Teresa and Penitencia treatment plants are located on the East Pipeline have the luxury of serving as back-ups to each other, a benefit not shared by Rinconada, the sole supplier of drinking water to customers in the western areas of Santa Clara County, including San Jose Water Company, the California Water Service, the City of Mountain View Public Works, the City of Santa Clara Water Department and the City of Sunnyvale Public Works Department. Given the low level of flexibility in the West Side Distribution System, the plant is taken offline from its 24-hour operation for maintenance only for short periods of time and during low-demand periods in the winter.


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