Located off Interstate 215 in the city of Riverside, Mills sits near the Box Springs foothills at an elevation of 1,650 feet the highest of the five plants. Mills supplies treated water, via gravity flow, throughout most of Eastern Municipal Water District's and Western Municipal Water District of Riverside County's service areas.
From Mountain High…
The water filtered through this plant originates in northern California's mountains, rivers and streams, and flows through the Sacramento-San Joaquin Delta before entering the State Water Project's 444-mile California Aqueduct. In emergencies, water from the Colorado River that flows through Metropolitan's 242-mile Colorado River Aqueduct can also be treated at Mills. Under a three-year multimillion dollar expansion project, Mills will see the construction of two additional filtration modules, a second 25 million gallon treated water storage reservoir and plant control structures. Since its dedication in May 1978, Mills has been upgraded from 150 million gallons per day to 326 million gallons per day. At capacity the plant will clean enough water to fill the Rose Bowl every 72 minutes. Automated systems regulate water levels and pressures. These precise monitoring and surveillance capabilities allow plant operators to anticipate and meet demands, and to respond rapidly to emergency situations.
…To Your Kitchen Faucet
Looking at the plant's web of pipes, pumps and sophisticated electronic gadgetry, filtration appears to be a complicated process. Conventional filtration, however, is surprisingly simple and effective.
Items used are similar to those found in any home, garden or garage. Upstream grates and screens catch large debris and plants. At the filtration plant, coal and sand used as filter media remove any particles left in the water. Then, chlorine and ammonia are used as disinfectants.
Conventional filtration 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 basins, 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 water quality standards.
Wildlife Protection
An endangered species, the Stephen's kangaroo rat inhabits land outside the perimeter of the Mills plant. If you look closely; you can spot a knee-high "K-rat" wall that encourages the nocturnal rodent to live and nest within protected areas.
Insuring the safety of the kangaroo rat is just one example of how Metropolitan continues to mitigate environmental impacts in order to protect threatened and endangered wildlife ecosystems.
Mills The Man
On March 1, 1967, Henry J. "Hank" Mills became the general manager of the Metropolitan Water District. By the time he retired some four and half years later, he was wrapping up a 41-year career with Metropolitan. As general manager, Mills was popular with district employees because he was one of their own--an aqueduct builder who walked the same ground they now walk. His Metropolitan career began on a survey crew, plotting routes for the Colorado River Aqueduct. From there he worked his way up the ranks to assistant chief engineer, chief engineer, and finally, general manager leaving Metropolitan a legacy difficult to match.
Today, more than 1,800 Metropolitan employees strive to maintain and upgrade what has become one of the world's largest water distribution systems.