Watershed Project

Daniel Spera can’t point to the Prado Dam on a map, or explain the hydrological science behind a $472-million plan to raise its walls.

But the Huntington Beach office manager is acutely aware of how it affects his pocketbook. If the dam is raised, he and tens of thousands of other homeowners living in the vast Santa Ana River flood plain will no longer be required to purchase costly flood insurance.

“I pay $500 a year. That would cover a lot of Christmas presents for the kids, or a trip to the mountains,” Spera said. “It would get rid of a pretty big expense.”

The dam-raising is the final piece of the mammoth Santa Ana flood control project, a $1.3-billion effort aimed at protecting what federal officials describe as potentially the most vulnerable flood plain west of the Mississippi.

The long-delayed elevation of the dam won a big boost earlier this month when the U.S. Army Corps of Engineers agreed to pay an additional $100 million of the cost, raising its share from 30% to 50%.

The county is now optimistic the project will be built, but money is still needed from the state to fully fund the work.

The plan is to increase the storage capacity of the dam by 50%, reducing the pressures to release water into the Santa Ana River. While the river’s flow is now down to a trickle during the dry summer, the Santa Ana can run destructively wild in the rainy season and releases from the dam aggravate the problem.

Officials said the river is overdue for a great 100-year flood, which could cause an estimated $15 billion in damage and the deaths of 3,000 people.

A Amassive flood in 1938 knocked out nearly every bridge in the county, submerged much of Garden Grove, Westminster and Santa Ana and killed dozens of people.

Built in 1941, the Prado Dam sharply reduced flood dangers in central Orange County and made possible the dramatic postwar urbanization. But the corps later determined that Prado could sustain nothing greater than a 70-year flood and urged that the dam be raised.

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“To most people, this dam is a financial issue because of the insurance,” said Fountain Valley Councilman John J. Collins, whose city lies in the heart of the flood plain. “But it also gives us peace of mind.”

About 40,000 homeowners along the river are required by the Federal Emergency Management Agency to have flood insurance, far more than any other Southland county.

FEMA determines which areas must have insurance by predicting the amount of water that would accumulate during floods so severe they occur only once a century, and then overlaying these 100-year-flood depths on topographical maps to determine where flooding would be most severe. Property owners in zones that would accumulate more than a foot of water are required to have insurance.

FEMA agreed last year to reduce flood insurance rates in the flood plain by as much as 50% because the Santa Ana flood control project had reached the halfway point.

For example, the annual insurance premium on a home valued at $150,000 dropped from $690 to $326.

Eldridge said the insurance requirement would be eliminated altogether if the county can protect the flood plain against a 100-year flood--something that can only occur with improvements to the dam.

Plans call for the county to raise the elevation of the dam--off the Corona Expressway in San Bernardino County, just north of the Riverside Freeway--from 566 feet above sea level to 594.4 feet. The improvements require the acquisition of more than 1,700 acres of private property that would be flooded when the dam is raised.

Officials have encountered opposition from some environmentalists and property owners unwilling to sell their land. Still, the county hopes to have the project completed by 2005, said William L. Zaun, the public works director.

The total cost of the dam-raising is estimated at $467 million, and before the corps decided to kick in nearly $100 million of the cost, the county and state share was roughly 71% of the total, or $330 million.

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The increased federal contribution now means that the state and local portion of the bill will fall to $233.5 million, or exactly 50% of the total. Of that, the state could pay as much as $163.5 million, leaving the Orange County Flood Control District to pay $70 million.

The dam-raising, along with a massive widening of the Santa Ana River, should provide the central county with protection against the kind of flood that occurs once every 190 years--exceeding the 100-year protection FEMA said is necessary to drop mandatory flood insurance.

But officials said the extra protection is only prudent, given the unpredictable nature and catastrophic flood potential of the Santa Ana River.

“It’s not a matter of if, it’s a matter of when,” said Supervisor Jim Silva, who has lobbied state and federal officials for dam funding. “This is an investment to protect our residents against a natural disaster that is very real. It’s a small price to pay considering the damage a major flood could cause.”

Like many rivers in the West, the Santa Ana rages during the rainy season. Today, it runs in a fairly straight line from Yorba Linda south to the ocean just north of Newport Beach. But 19th century Spanish land grant maps showed the river curving west from Buena Park and emptying into the ocean near Seal Beach.

The Prado Dam was built in response to the 1938 disaster, which became known as “the flood of the century.” But in 1969, the corps determined through hydrological testing that a flood in 1862 was actually three times greater than that in 1938, and that Prado was unprepared for such a catastrophe.

Officials have been planning a dam-raising ever since, but finding adequate funding has always been the major barrier. Now, Zaun and others said they are optimistic that the full Santa Ana flood control project will be completed within the next eight to 10 years.

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Prado Plans

Increasing the height of the Prado Dam is expected to protect Orange County homes from major flooding and end the requirement that homeowners buy costly flood insurance. Improvements also include raising the height of the spillway, which would provide overflow for flood waters. A closer look at the work to be done:

1. Raise dam height from 566 to 594.4 feet

2. Move and increase dam outlet to 30,000 cubic feet per second

3. Raise height of spillway 20 feet

4. Build levee along Corona Expressway

Source: Orange County, Santa Ana River Project