Regulators Failed to Regulate and Inspect

Sep 8, 2017

California’s Oroville Dam had design defects dating back to its construction in 1969. The dam’s spillway failed in February and caused the evacuation of 200,000 residents. An initial inspection report showed 24 possible reasons why the Oroville Dam’s spillway failed. Some reasons cited were inadequate maintenance, thin concrete slabs, poor drainage, and the use of weathered rock. State and federal officials who reviewed the dam relied on visual inspections. The second interim report said that a “serious dam and infrastructure review should have reviewed blueprints, construction records and other documents.” Records as far back as the 1970s detail cracks in the concrete right after the dam opened in 1969. Other records show uneven thickness of the spillway’s slab and drains were “improperly designed to handle their rated water-flow capacities.” In 2007 the dam failed a 50-years extension and has been operating “on temporary one-year regulatory extensions” for the last decade. The state spent $275 million in emergency repairs to the main and emergency spillways. But the dam’s numerous defects remain.