Questions Raised on Use of Basin for Park, Commuting

When the Sepulveda Basin flooded Monday, federal water engineers noted with satisfaction that it was functioning as designed.

But the close call for the scores of people who had to be rescued from the floodwaters resurrected long-simmering questions about using a flood plain as a city park and commuter shortcut.

From an urban drainage perspective, the 2,150-acre basin’s metamorphosis into an instant lake is the carefully crafted alternative to allowing the flooding of residential areas in the San Fernando Valley and downstream in downtown Los Angeles.

“A (storm) centered over the Sepulveda Basin dropped several inches of rain and filled the pool behind the Sepulveda Dam--and that’s really what (the basin) is supposed to do,” said Bob Armogeda, spokesman for the Los Angeles district of the U.S. Army Corps of Engineers.

The corps built the dam in the 1940s precisely to concentrate floodwaters in the West Valley--which then was only sparsely populated.

Even with additional rain, there is little chance of water breaching the dam, Armogeda said. It was holding back no more than 7,000 acre-feet late Monday, he said, and was built to hold more than 17,000. The Army Corps was so confident that the flooding would not spread beyond the flood control basin that it did not open its emergency center, he said.

But the basin’s other use was clearly disrupted--at least temporarily. Most of the acreage is leased to the city for a park, which attracts more than a million visitors annually. A large, and growing, sewage treatment plant also sits on 40 acres there.

The Donald C. Tillman sewage treatment plant was closed Monday after it flooded, said Harry Sizemore, assistant director of the city’s Bureau of Sanitation.

Sizemore said that about 10 million gallons of treated but unchlorinated sewage had been released into the basin and that people should avoid contact with the basin’s water.

Questions lingered, too, about why motorists were caught by rising floodwaters, despite gates that are supposed to block the commonly used streets through the basin during a flood.

Whether the manually operated gates are closed is the decision of the Army Corps, although in emergencies city park officials can use their own keys to lock them, said Phillip Manzi, senior ranger for the city parks’ Valley Region.

Manzi said the gates were not closed until about noon because the late-morning storm swept in so quickly and so furiously, depositing more than six inches of rain in the West Valley.

“Instead of acting, we were reacting,” he said. “Usually we have two to three hours notice.”