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0 of 3 Premium Clicks used this month SUBSCRIBE Print + Online Subscriber Activation | Register x Forgot Password | Need an Account? e-edition | subscribe | newsletter | deals Classifieds Jobs Autos Real Estate FEATURED » NEWS NOW Emergency services, Oct. 16 ... Since You Asked: Park resurfacing delayed during winter ... SOU training gives tips on what to do if there's an active shooter ... Emergency services, Oct. 16 ... Since You Asked: Park resurfacing delayed during winter ... SOU training gives tips on what to do if there's an active shooter ... SINCE YOU ASKED Since you Asked: Lost Creek Dam is earthquake-resistant The U.S. Army Corps of Engineers expects the Lost Creek Dam to weather severe earthquakes, but plans to study the impacts of a 9.0 quake. Comment MailTribune.com Writer Posted Aug. 5, 2015 at 12:01 AM Posted Aug. 5, 2015 at 12:01 AM » Social News I am curious what magnitude earthquake the Lost Creek Lake Dam was built to withstand? And after this magnitude 9 earthquake, what is the expected time frame to escape up into the hills should it break and release the captured water behind? — Jolene, Shady Cove The U.S. Army Corps of Engineers looks at forces on dams in terms of ground acceleration instead of using the Richter scale that measures the strength of earthquakes, according to Scott Clemans, spokesman for the Corps' Portland District, which includes the Rogue Basin. At the time the Lost Creek dam was finished in 1977, it was built to withstand 0.1 G of peak ground acceleration. (Gravity measures 1.0 on the G scale.) The earthquake potential for our area was considered to be in the 0.06 to 0.08 range, according to Corps data. However, that was before scientists gained more understanding about the West Coast's Cascadia subduction zone, which can cause massive earthquakes with ground acceleration of 0.17 G to 0.19 G in the Lost Creek area. In 2014, the Corps planned to study the impacts of an earthquake measuring 9.0 on the Richter scale on Lost Creek Dam. But money for such studies is spent first on higher risk dams, and the Lost Creek dam study has been postponed to the fiscal year that begins in October, Clemans said. When Japan experienced a quake in 2011 that measured 9.0 on the Richter scale, only one dam collapsed and a handful suffered damage out of approximately 250 dams in the area. The damaged dams still held back their water, Clemans said. "The historical performance of dams across the world in earthquakes has been incredibly good," he said. More research will be done, but preliminary screening shows the Lost Creek dam would not collapse and send water rushing downriver if a major earthquake strikes, said Matt Craig, a Corps dam safety manager. "We do not expect a catastrophic release of the pool. We do not expect it to fail catastrophically," Craig said. The Corps has recently updated its maps showing which areas would be inundated if the dam did fail. That information will be presented at meetings from 6:30 to 8 p.m. on Sept. 21 in Shady Cove and on Sept. 22 in Grants Pass. The location of the Shady Cove meeting is yet to be determined, while the Grants Pass meeting will be at the Anne G. Basker Auditorium, 604 N.W. Sixth St. Portions of Rogue River communities — including Shady Cove, the town of Rogue River, and Grants Pass — would be inundated under the unlikely dam-failure scenario, said David Tucker, operations section chief for the Corps' Rogue River Basin Project. Information presented at the meetings will include water depth and water arrival time. Those factors vary for each area based on topography, distance from the river and a host of other criteria, Tucker said. "The inundation maps portray the worst case scenario of rapid and widespread collapse of the dam structure itself," Clemans said. "We don't expect that to happen in an earthquake." But understanding the worst-case scenario can help residents and emergency managers prepare for less serious events, he said. Although Lost Creek dam is unlikely to collapse, it could suffer damage that could cause problems like a spillway gate malfunction, Clemans said. "Folks downriver could see higher water levels after an earthquake in that case," he said. Send questions to “Since You Asked,” Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by email to [email protected]. To see a collection of columns, go to mailtribune.com/youasked . We’re sorry, but the volume of questions received prevents us from answering all of them. MailTribune.com Writer Posted Aug. 5, 2015 at 12:01 AM » Comment or view comments Reader Reaction » STAY INFORMED Email NewsLetter Sign Up Today Sign up for our newsletter and have the top headlines from your community delivered right to your inbox. 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