Marin Municipal ordered to review three dams in response to Oroville

08/17/2017

Per a mandate issued by state regulators last month, Marin Municipal Water District will evaluate three of its seven dams for potential structural inadequacies. The Peters, Seeger and Soulajule Dams are on a list of 93 for which the California Department of Water Resources ordered a review after the failure of the Oroville Dam spillway in the Sierra Nevada foothills in February. After torrential winter storms, that spillway crumbled on one side, leading to the evacuation of 200,000 people. The department’s dam division, hoping to avoid a similar disaster, ordered operators to perform immediate reviews to determine how well the spillways will hold up during flood events, and to make any necessary repairs by winter. The complete list, which was selected based on the age, height, storage capacity, hazard potential downstream, design, geologic conditions and maintenance records of the dams, was released to the public in late July. “It will not be known which spillways, if any, will need repairs until the comprehensive assessments are completed and reviewed by [this agency],” the department’s Division of Dams and Safety said. Marin Municipal submitted a work plan that will guide its evaluation of the three dams. According to resources provided by spokeswoman Emma Detwiler, that plan will include a structural assessment of the spillways, a site investigation of spillway linings (including maps of repairs, cracks and erosion and the identification of potential geologic hazards) and a performance evaluation of drainage systems. After the assessment is completed and approved by the state dams division, the district will request proposals from contractors to complete any work that needs to be done. Peters Dam, built in 1954, is built across Lagunitas Creek and forms Kent Lake. Seeger Dam was built over Nicasio Creek in 1961 to form Nicasio Reservoir and Soulajule Dam, built after a severe drought in 1976, runs over Arroyo Sausal stream near the Marshall-Petaluma Road. The list released by the Department of Water Resources also includes some of the largest dams in California, such as the New Exchequer Dam on the Merced River, New Bullards Bar on the Yuba River and the Lake Almanor Dam on the Feather River. Each of those three holds back reservoirs roughly the size of Folsom Lake, which can store about 977,000 acre-feet of
water.

This article was corrected on Aug. 21.