Metropolitan Water District of Southern California
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The Robert B. Diemer Treatmet Plant

The Robert B. Diemer Treatment Plant in Yorba Linda is one of five treatment plants in the Metropolitan Water District system.

Diemer's hilltop location is well suited for gravity-flow distribution of water to Los Angeles and Orange counties. And there's a spectacular panorama of the Los Angeles basin. On a clear day, the 830-foot elevation provides a glimpse of Catalina Island and Mt. Baldy, as well as a bird's-eye view of neighboring cities Anaheim Hills, Placentia and Brea.

From Mountain High…

Most of the water filtered through this plant originates in the mountain ranges of seven western states, travels down the Colorado River and flows through Metropolitan's 242-mile Colorado River Aqueduct.  To a lesser degree, water treated at Diemer also comes from Northern California rivers and streams that feed the State Water Project's 444-mile California Aqueduct.

One of the largest treatment plants in the United States, Diemer delivers up to 520 million gallons per day, enough water to fill the Rose Bowl every four hours.  Automated systems regulate water levels and pressures, and offer precise monitoring and surveillance capabilities.  This allows plant operators to anticipate and meet demands, and to respond rapidly to emergency situations.

...To Your Kitchen Faucet

Looking at the treatment plant's web of pipes, pumps and sophisticated electronic gadgetry, filtration appears to be complicated.  Conventional filtration, however, is surprisingly simple and effective.

Conventional filtration uses items similar to those found in any home, garden or garage.  Upstream grates and screens catch large debris and plants.  At the treatment plant, coal and sand used as filter media remove any particles left in the water; then, chlorine and ammonia are used as disinfectants.

Part of the process involves what is known as coagulation, where aluminum sulfate and other chemical additives cling to particle matter in the water.  These compounds adhere to each other, forming larger particles called floc.  Once the water and floc enter large sedimentation tanks, the floc settles to the bottom.

From the basins, water filters through the coal and sand layers, and then is disinfected to kill the few remaining microorganisms.  MWD water meets or surpasses all state and federal state water quality standards.  A project to convert Diemer from chlorine to ozone water treatment is more than 50 percent complete.

Water Power

Diemer is the only treatment plant in MWD's distribution system that has an on-site generator.  The 5.1 megawatt Yorba Linda Hydroelectric Power Plant takes advantage of the powerful force created as water rushes down the aqueducts and pipelines leading to Diemer.  The power plant is one of   16 such facilities built by MWD along its conveyance and distribution system during the 1980s) Energy from the Yorba Linda facility is used to supplement Metropolitan's overall energy needs.

The Diemer Legacy

Robert B. Diemer came to Metropolitan in 1929 with an extensive engineering career in construction of canals and dams dating back to 1911.  Under his leadership as general manager and chief engineer from 1952 to 1961, he directed the expansion program that brought the Colorado River Aqueduct to its full delivery capacity of 1 billion gallons a day.  At the time, a member of the Metropolitan board of directors representing the city of Pasadena, Diemer participated in the dedication of the Robert B. Diemer Treatment Plant on January 15, 1964.

Diemer's legacy of determination continues today with a workforce  more than 1,800 strong.  Metropolitan employees continually strive to maintain and upgrade  what has become one of the world's largest water distribution systems. Through its 26 member public agencies, MWD provides about half of the water used by more than half of Los Angeles, Orange, San Diego, Riverside, San Bernardino and Ventura counties.

The mission of the Metropolitan Water District of Southern California is to provide its service area with adequate and reliable supplies of high-quality water to meet present and future needs in an environmentally and economically responsible way.

Photo of Diemer Treatment Plant
The Robert B. Diemer Treatment Plant
3972 Valley View Ave.
Yorba Linda, CA 92886
Page updated: July 22, 2014