Oroville Dam Report Calls for Second Spillway

August 6, 2018
Ironworker ties rebar together on the lower chute of a Lake Oroville flood control spillway.

An assessment by an independent review board regarding the future operations of the Oroville Dam calls for a second spillway, seemingly the result of an independent forensic report on the spillway crisis released earlier this year. California's Department of Water Resources (DWR) hired Kiewit to rebuild and reinforce the Oroville Dam spillway after last February's close call when 188,000 residents were evacuated when the spillway failed and the dam itself was looking like it too would fail. The report criticized the “department’s tendency to be an insular organization.”

According to The Mercury News, the board released its report after visiting Oroville and meeting with representatives to gain additional insight on the project. After surveying the area, the board suggested several infrastructure changes, something the State Department of Water Resources is calling a “comprehensive needs assessment.”

According to the board’s report on July 23, the department has assigned six tasks to the reconstruction team including items such as, “restoring spillway design capacity to pass the probable maximum flood,” and “support development of alternative reservoir outflow enhancements.” The third task will assess options for making the spillway more reliable, while the fourth will consider alternatives for low-level outlets. The fifth is to analyze the reliability of and improvements to the dam embankment.

The board also said the assessment should “clearly define what is considered the spillway’s maximum flow capacity,” according to The Mercury News. The department could expect erosion when the spillway runs at full capacity, but not a breach. The assessment is set to be complete by Dec. 31, 2019.

Source: The Mercury News & Enterprise Record