Strengthening Gate Arms at Rocky Reach Dam | 3.6.2012
The spillway gates at Rocky Reach Dam, on the Columbia River in Washington, are similar in size, design, age and environment to those used at Folsom Dam, on the American River in California. Thus, the spillway gate failure experienced at Folsom Dam in July 1995 caught the attention of Rocky Reach Dam owner Chelan County Public Utility District.
The failure resulted in nearly 40% of Folsom Lake draining through the broken gate. The freshwater that reached San Francisco Bay altered the migration habits of some salmon and striped bass. A year-long investigation by the Bureau of Reclamation attributed this failure to a design flaw. According to the report, gate pivot bearings seized up when the gate was lifted and lateral loading stressed support beams to their yield point and the structure buckled.