No Bursting at the Streams

Mild-mannered most of the year, the Santa Ana River reminded its neighbors last week of the wrath it can unleash with little warning.

With a history of such calamities as the 1938 flood that killed dozens of people, the 96-mile-long river -- once considered the biggest flood threat west of the Mississippi -- has long been a force to be reckoned with. Beginning in 1990, county and federal agencies have banded together to undertake a massive $1.3-billion worth of improvements to prevent flooding across Orange County and the Inland Empire.

By the middle of last week, the Santa Ana River Project looked successful as rainwater washed to the sea and not into the streets.

But before dawn Friday came evidence that the work is far from over and that the river is never without surprises. Residents were urged to evacuate and emergency flood control work began when engineers detected seepage from Prado Dam, the 64-year-old structure in Corona that regulates the river’s flow.

Corona police spokesman Jesse Jurado said Saturday that some residents were returning home as word spread that the water had receded and the Army Corps of Engineers had repaired the dam.

“Officially, we still have a voluntary evacuation,” Jurado said, but “the concern is diminishing.”

Officials said they were pleased with how well the river had held up -- even at its highest volume since 1969.

“So far, the river has performed exactly like we’ve hoped it would,” said Herb Nakasone, director of Orange County Public Works. “That doesn’t mean we’re not going to have occasional street flooding, but that’s not the serious kind of floods that put people out of their homes.”

The project, which is two-thirds finished, has three main parts: widening river channels through Orange County, building the Seven Oaks Dam in San Bernardino County and raising Prado Dam. Without the fortified dams and river channels, authorities said the region is at risk for a flood that could engulf 110,000 acres, kill 3,000 people and cause $15 billion in damage

Flood control officials said improvements to the lower Santa Ana River -- finished three years ago -- kept it from experiencing the problems of San Juan Creek, which threatened to flood hundreds of homes in San Juan Capistrano last week after rushing water tore away large chunks of concrete banking.

Before its makeover, the Santa Ana River looked much like the San Juan Creek -- an earthen-bottomed stream with concrete sides.

But the concrete walls weren’t set deep enough, and officials worried that strong waters would erode the river bottom and undermine the walls’ foundation.

So the Army Corps of Engineers spent years widening the channel and building stabilizers into the river. South of 17th Street in Santa Ana to Adams Street in Costa Mesa, the river is lined with concrete. North of Santa Ana, the banks are lined with rock and concrete but the bottom is earthen.

Spaced every half-mile or so, the stabilizers help prevent sediment erosion. When the water cascades off each 12- to 15-foot-tall step, it hits concrete bumps, or “baffles,” that help slow the flow. The result is water slowly traveling down several level planes rather than a single continuous slope.

Standing on the bank overlooking a stabilizer near Anaheim, Peter Dalquist, a county engineer who has kept an eye on the Santa Ana River for 25 years, said he was amazed at how well the river held up during this month’s deluge.

“I’ve seen panels destroyed, rocks moved around and erosion ... but, oh, it just held up beautifully,” Dalquist said.

The $1.3-billion project is “definitely money well spent. The cost savings are millions just from this storm,” he said.

“You may get a little water over the top on some of the local channels, but you’re not going to get the city-by-city flooding that was possible before.”

Miles upstream, the Seven Oaks Dam was also doing its part. Completed in 1999, the dam helps regulate the water behind Prado Dam and protects parts of San Bernardino and Riverside counties from flooding.

The final phase of the project includes raising Prado Dam and building new outfall gates that will triple the amount of water that can be released. Construction crews are two years away from finishing the Prado Dam phase, according to the Army Corps, but their work was stymied after storm flows last week overtook a temporary dam protecting the site.

When water began seeping through weakened portions of Prado Dam on Friday, Corona officials evacuated 2,300 residents. Saturday, some residents returned, but others were too shaken.

“Who needs to take a chance?” asked Susanne Mittelstaedt, 48, a single mother of two who returned to her home Saturday for a few hours before leaving again. “We’ve got one [engineer] saying nothing is going to happen, but at the same time, they make the comment that if something does happen, it would only take 15 minutes to drown us. I’d rather play it safe.”

Lois Southard, 39, said she returned home because, “I’d take the engineer’s advice before I take the mayor’s” suggestion to stay away. “But I’ll always be a little leery now about the dam.”

Eric Glazier, 38, and his wife had mixed feelings. “She thinks there’s a big huge crack that’s going to blow, and I’m more believing the engineers [that the leak stopped]. But we still have our bags packed in the back of the car in case they call and tell us to get our butts out of here.”

The Army Corps said there was no imminent danger, but as a precaution they increased their releases to 10,000 cubic feet per second. Thanks to the improvements, the additional water flowed smoothly out to sea.

The federal government and Orange County have shared funding for the project, with Washington picking up about three-quarters of the total. So far, Congress has provided $822 million.

Rep. Christopher Cox (R-Newport Beach), who helped secure the congressional funds, said the recent record rainfall serves as a reminder.

“It is gratifying when Mother Nature cooperates and postpones the inevitable until we’ve taken the necessary precautions,” he said. “If there’s a silver lining to all this rain and flooding, it is that it will raise awareness in Congress about the urgent need to complete this project.”