The Division of Dam Safety and Inspections in the Federal Energy Regulatory Commission (FERC) issued a letter to the California Department of Water Resources (DWR) on October 25, 2018 that requires DWR to reclassify the emergency spillway at Oroville Dam as an “auxiliary spillway.” The letter also describes the need for DWR to plan for a greater volume of flood flow at Oroville Dam than DWR had previously planned for.
Unless something changes, the likely net result is that DWR will have to greatly expand the “emergency spillway” on Oroville Dam that DWR’s contractor has been rebuilding over the last year and a half, since it almost failed in February 2017 after very limited use.[1] DWR has expanded the concrete weir (or lip) at the top of the dam and constructed an “apron” (or “splash pad”) onto which water would spill as it goes over the lip when the reservoir is full and the main spillway cannot handle all the flow. The engineers at FERC are telling DWR that this isn’t enough. By definition, an “emergency spillway” is used so infrequently that it is acceptable for it to sustain significant damage during use. An “auxiliary spillway” is one that must be relied on in foreseeable circumstances. To avoid significant damage in use, the reclassified “auxiliary spillway” will need to be built out as a complete concrete spillway from the top of the dam to the bottom. Though the “apron” has added reinforcement near the top of the dam, water flowing over it would still pass over unreinforced rock and dirt to reach the bottom of the dam.
Over the past year and a half, DWR has reconstructed the main spillway, right next to the emergency spillway (see photos in the Report linked below on p. 2 and p. 11). The Sacramento Bee reported on September 6, 2018 that total construction costs were estimated to reach $1.1 billion.[2] It is reasonable to estimate that the cost for completing the auxiliary spillway could easily reach another half a billion dollars.
Thirteen years ago, Friends of the River, the Sierra Club and the South Yuba River Citizens League warned FERC in a series of filings that the emergency spillway needed to be replaced by a complete lined auxiliary spillway. A year later, CSPA supported Friends of the River’s warning in a filing of its own. In a series of filings including the above-cited Report on the Oroville spillway incident of 2017, Friends of the River, CSPA and others have advocated for a formal consideration of dam safety in relicensing. According to a just-released report from the United States Government Accountability Office (GAO),[3] FERC staff reviews dam safety during relicensing and is moving to a “risk-based” evaluation of all high-risk dams regulated by FERC. However, the GAO report suggests that FERC staff will continue the practice of not “showing its work” when it comes to public or agency comments and studies regarding dam safety.
It appears likely that filings by NGO’s in the FERC relicensing proceeding for the Oroville Facilities finally caught the eye of regulators at FERC. It is disappointing the FERC staff apparently plans to continue analysis of dam safety out of public view. However, the fact that FERC’s Division of Dam Safety and Inspections has reached what appears to be a dramatic new conclusion about the adequacy of spillways at Oroville based on a new protocol is satisfying. FERC is poised to require a crucial improvement to protect public safety and important water infrastructure.
In the world of water advocacy, persistence pays.
[1] CSPA, Friends of the River, the South Yuba River Citizens League, and American Whitewater describe the February 2017 Oroville spillway incident in a September 2017 report, The Oroville Dam 2017 Spillway Incident and Lessons from the Feather River Basin, previously posted at http://calsport.org/news/wp-content/uploads/Oroville_Lessons_2017_report_web-final.pdf
[2] https://www.sacbee.com/news/state/california/article217933520.html#storylink=cpy
[3] Available at: https://www.gao.gov/products/GAO-19-19