Rubber Dams Ready to Restrain Runoff

When the winter rains finally come, the Orange County Water District will be ready with its rubber rafts--not to escape but to salvage storm water.

The water agency, known for its innovative efforts to bolster local water supplies, has installed a 320-foot-long, seven-foot-high rubber dam near Imperial Highway along the Santa Ana River and plans to install another one upstream of Ball Road.

The dams can be inflated within 30 minutes to help hold river runoff back so that it seeps into Orange County’s ground-water basin instead of flowing into the ocean. When water rises so near the top of the rubber dams that it could cause flooding, the dams automatically deflate within 45 minutes.

The underground basin fed by the Santa Ana River supplies about three-quarters of the water used by residents in the northern half of the county. As much as 3 billion gallons of storm water a year can be conserved by using inflatable dams, the district estimates.

The Orange County Water District has spent about $40 million on improvements, including new pumps and pipelines, to ensure that as much river runoff is captured as possible.

The district’s improvements helped save enough runoff during the Dec. 7 storm to serve 100,000 people for a year. Water rushed down the river at half a million gallons per minute, and the agency’s pumps siphoned much of it into a series of reservoirs in Anaheim. The runoff comes from the 100-mile-long river’s massive flood plain in Riverside and San Bernardino counties.

William R. Mills. Jr., general manager of the Orange County Water District, said the cost of the improvements can be recovered by capturing one season’s worth of storm flows, which would save millions of dollars in the cost of imported water.

“After six straight years of drought, Northern California has no surplus to export, and the cost of Colorado River supplies is rising. We have to be innovative in developing ways to conserve more of our local water resources,” Mills said.