Crisis underscores peril at nation's aging dams

FILE - In this April 14, 2010, file photo the auxiliary spillway, right, is under construction at Folsom Dam, in Folsom, Calif. Twelve years ago, widespread destruction from Hurricane Katrina on the Gulf Coast helped compel federal engineers to spend nearly $1 billion constructing the auxiliary spillway at Folsom Dam, scheduled to be completed in 2017.
FILE - In this April 14, 2010, file photo the auxiliary spillway, right, is under construction at Folsom Dam, in Folsom, Calif. Twelve years ago, widespread destruction from Hurricane Katrina on the Gulf Coast helped compel federal engineers to spend nearly $1 billion constructing the auxiliary spillway at Folsom Dam, scheduled to be completed in 2017.

LOS ANGELES -- Nearly 12 years ago, widespread destruction from Hurricane Katrina on the Gulf Coast helped compel federal engineers 2,000 miles away in California to remake a 1950s-era dam by constructing a steel-and-concrete gutter that would manage surging waters in times of torrential storms.

The nearly $1 billion auxiliary spillway at Folsom Dam, scheduled to be completed later this year, stands in contrast to the troubles 75 miles away at the state-run Oroville Dam, where thousands of people fled last week after an eroded spillway threatened to collapse and potentially send a 30-foot wall of floodwater gushing into three counties.

The two dams illustrate widely diverging conditions at the more than 1,000 dams across California, most of them decades old. The structures also underscore the challenge of maintaining older dams with outdated designs.

"Fifty years ago, when we were evaluating flood risk, the fundamental assessment was the climate was stable, not changing. We now know that is no longer true," said Peter Gleick, chief scientist with the Pacific Institute, a California-based think tank specializing in water issues.

"We need to look at the existing infrastructure with new eyes," he said.

In 2005, Katrina's deadly path became an arguing point for Rep. Doris Matsui, D-Calif., who was among those pushing Washington for improvements at Folsom Dam, perched 25 miles from 500,000 people living in Sacramento, the state capital.

"I used that, vigorously, to say we are the second-most at-risk river city in the nation," Matsui said, after the Category 5 storm swept through New Orleans.

State officials now face questions about maintenance at Oroville Dam, the nation's tallest at 770 feet, and why a decade ago they dismissed warnings from environmentalists that more needed to be done to strengthen its earthen emergency spillway.

After years of drought, Northern California became waterlogged this winter from heavy rain and snow. Oroville Lake is brimming, and water managers have been using the main spillway, which is lined with concrete, to lower the water level.

The emergency spillway is a brush-covered hillside below a masonry lip and had never been used until last weekend. When water gushed onto it, the ground began eroding, and it was feared that the intake lip could collapse and water would surge down the hill.

John France, vice president and technical expert on dams for the engineering consulting firm AECOM, said the problems at Oroville should raise alarms across the country.

"Most of the dams in the United States are over 50 years old, when we didn't understand floods as well as we do now. So we have a number of dams in the U.S. that have spillways that aren't large enough for the floods that they should be designed for," France said.

At Oroville, opened in 1968, construction crews in recent years patched cracks on the main spillway, and a state inspector called the repairs "sound" in a February 2015 report. However, a hole ripped open on that spillway two weeks ago, leading to the use of the emergency spillway and evacuation orders for nearly 200,000 people.

Since then, crews dumped thousands of tons of rocks to shore up the damaged spillways, and residents were allowed to return home Tuesday, after the lake level dropped.

Butte County Supervisor Bill Connelly, whose district includes the dam, has criticized dam managers for years.

"They never spend money unless they have to," he said. "If we were a federal facility, you don't see this happening."

A concrete-and-steel chute being constructed by the Army Corps of Engineers is expected to add as much as 40 percent capacity to the main spillway that controls water flowing from the reservoir behind it.

Information for this article was contributed by Rebecca Boone of The Associated Press.

A Section on 02/20/2017

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