Department of Ecology News Release - August 22, 2014

Heavy rains in fire area collapse dams
Two of four Wenner lake dams fail in Okanogan County

TWISP – Heavy rains overnight collapsed two of four public and private dams holding water in the Wenner lakes on Benson Creek six miles southeast of Twisp.

Personnel from the Okanogan County Department of Emergency Management are on the scene with dam inspectors from the Washington Department of Ecology.

The dams collapsed in one of the burn areas from this summer’s fires and a high volume of stormwater run-off may have caused the breaches. Thursday night a storm cell settled over the area which received about two inches of rain. The fires have scoured vegetation from ground that would have held back the stormwater and dead trees from the fires and debris from last night’s storm may have also clogged spillways raising waters levels beyond the dams’ capacity to hold it. The spillways normally should have been able to carry the stormwater downstream.

The Okanogan County Sheriff’s Department is notifying downstream residents of the dam breaches and will advise residents if they should evacuate.

The county’s Department of Emergency Management is evaluating the dams which have not breached to determine if water should be released from them to relieve pressure on the earthen structures. The Wenner lakes hold irrigation water and are used for recreation.

The dams that collapsed were not due for inspection by Ecology this year and earlier this summer, Ecology’s Dam Safety Office advised owners of all dams in burn areas of Central Washington to inspect their structures for damage from the fires that would put their dams at risk of collapse.

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Contacts:

Dan Partridge, Ecology communications manager, 360-480-5722, dan.partridge@ecy.wa.gov

Scott Miller, Okanogan County emergency management, 509-846-6039