Releases from the Oroville Dam north of Sacramento were halted by the state Department of Water Resources after a large sinkhole formed in the dam’s spillway during the release of 55,000 cubic feet per second of water.
Too much of a good, much-needed thing for the state of California – rainfall – is causing problems this week for some of the state’s reservoirs. Rain has filled many of them to near capacity, the San Francisco Chronicle and other newspapers reported Feb. 8, and a sinkhole opened up in the spillway of Lake Oroville, which is California’s second-largest reservoir about 75 miles north of Sacramento.
The California Department of Water Resources was releasing about 55,000 cubic feet per second (cfs) from the lake through the spillway at the time the sinkhole developed. (Another 5,000 cfs was being released through a power plant at the dam.) The agency said in a news release that its employees “noticed an unusual flow pattern and erosion on the spillway, and they are investigating.”
But on Feb. 8, the agency announced it is removing trees and debris from the corridor near the dam where water would flow if an emergency spillway is needed. The emergency spillway would have no gates, and water would flow down it if the reservoir reaches its capacity of 3.5 million acre-feet at 901 feet elevation. As of the afternoon of Feb. 8, the reservoir held 3 million acre-feet of water, and inflows into the reservoir were approximately 85,000 cfs. “Enough vacant space exists in the reservoir to capture the flow of the rains expected through Friday afternoon. The dam is sound, and no imminent threat to the public exists,” it reported.
The lake was about 80 percent full as of Feb. 7 and had sufficient capacity to capture projected inflows for at least three days, according to the release, which said DWR expected to resume releases “at a rate deemed safe later today after a thorough inspection is performed.”
At federally run Shasta Lake, which is the state’s largest reservoir, more than 1.25 million acre-feet of water was released last month, the largest amount in any January in the past decade, at least, the Chronicle reported, and the federal Bureau of Reclamation raised releases there from 26,000 to 36,000 cfs this week to meet flood space regulatory requirements.
The Oroville Dam is the tallest dam in the United States at 770 feet high – 44 feet taller than Hoover Dam – and measures 6,920 feet across.
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The agency said that under the new rule, miners would benefit from “timely and rigorous” working place examinations to prevent injuries and death. Existing standards allow an examination to be conducted at any time during a shift (even at the very end of the shift) and contain no requirement that miners be notified of hazards found during an examination.
According to a fact sheet, the final rule improves safety and health of miners by requiring mine operators to:
- perform working place examinations that identify hazards before miners begin work in an area;
- promptly inform affected miners about hazardous conditions that are not corrected immediately;
- make the examination record before the end of the shift;
- record the locations examined, the name of the person conducting the examination, the adverse conditions identified, and the date of the corrective action; and
- make a copy of examination records available to MSHA and miners’ representatives upon request.
The agency estimated the final rule will result in $34.5 million in annual costs for the metal and nonmetals mine industry. The new rule, it said, will “result in benefits” due to “more effective and consistent” workplace examinations that will help to ensure conditions will be “timely identified, communicated to miners, and corrected.”
In a question-and-answer sheet, MSHA said that between January 2010 and mid-December 2015, it recorded 122 miners killed in 110 accidents at metal and nonmetal mines. It said the agency issued citations to mine operators involved in 16 accidents, in which 18 miners were killed. MSHA said it has taken “a common sense approach” with the final rule.