Asbestos Complicates Oroville Dam Cleanup
Naturally occurring asbestos has been found in the air and in rock formations near the damaged Oroville Dam main spillway.
The California Department of Water Resources said in a news release Thursday (March 16) that while the risk to workers and the surrounding community is “minimal,” they are working with the Butte County Air Quality Management District to increase dust-control operations and monitor air quality at the work site and nearby neighborhoods.
Quick History
On Feb. 7, officials discovered a massive hole, estimated at 250 feet long, in the main spillway. The spillway’s capacity had to be reduced so that the damage could be addressed, and to prevent further erosion that the DWR said could threaten nearby power lines.
But heavy rains—weather records show Oroville got more than 3 inches of precipitation between Feb. 6 and Feb. 10—meant rising levels in the reservoir, which is California’s second-largest. By Feb. 11, the water level had reached 901 feet above sea level, the level at which water begins to flow over a concrete weir and into the emergency spillway.
Flow was finally stopped altogether on the main spillway on Feb. 27, revealing the full extent of the damage. Water flow was reduced from about 50,000 cubic feet per second down to zero over a six-hour period.
Since then, crews have been working to remove sludge and debris from the bottom of the spillway.
Asbestos Impact
The DWR said that asbestos was found in “limited areas” during debris removal. However, the amount of asbestos is irrelevant, said assistant air pollution control office Bob McLaughlin.
“Absolutely any time there’s potential for public exposure to asbestos it’s a concern,” he said. “It’s either there, or it isn’t. If it’s there, you do everything you can to minimize dust emissions. You have to assume it’s everywhere (at the site). ... You need to be very diligent and proactive in protecting public health.”
While asbestos is a commonly found mineral in California, it is a human carcinogen, so “out of an abundance of caution,” DWR has submitted a dust-control and air monitoring plan to the Air Quality Management District.
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The DWR said that asbestos was found in “limited areas” during debris removal. However, the amount of asbestos is irrelevant, said assistant air pollution control office Bob McLaughlin. |
Control measures already include wetting the soil, using wet-drilling methods and utilizing rumble strips on roads to reduce dirt collection on equipment. Additional plans include washing trucks and tires, using personal air monitors and increasing how many air samples are collected.
McLaughlin said the Air Quality Management District is working with DWR on additional minoring to determine if there are “ambient levels of asbestos that would be a concern.”
Spillway Flushing
Just a day after the asbestos announcement DWR released water down the main spillway for the first time in three weeks. At about 50,000 cubic feet per second, water flowed down new repairs.
"The idea is to make sure nothing moves around while we go through the spill event," DWR Acting Director, Bill Croyle said. "We believe we've done everything we can and more."
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Just a day after the asbestos announcement DWR released water down the main spillway for the first time in three weeks. At about 50,000 cubic feet per second, water flowed down new repairs. |
Since the water stopped flowing in late November, the dam water levels have increased more than 20 feet, which is why an estimated three flushings (between now and Juine 1) will take place—to make room in the reservoir for future snow melt and rain.
Officials said they hoped to use the spillway for about five days, or until they reach the reservoir’s target elevation of 835 feet.
"As long as we don't see a catastrophic loss of a lot of concrete, then we're going to need to roll through this," Croyle said.
At the corresponding media briefing officials announced their estimated cost of repairs so far has amounted to $100 million.
