with CalOSHA to hire a third-party expert to improve the safety of the river valve outlet system (RVOS) and make it operational again. In 2014, DWR embarked on an accelerated refurbishment program to respond to concerns about operational needs during the ongoing drought. The system was mostly refurbished and was used during 2014 and 2015 to meet Endangered Species Act temperature requirements for the Feather River. Some additional refurbishments were being made to portions of the RVOS and were expected to conclude in early 2017. 2013, 2015 spillway cracks and inspection The spillway cracked in 2013. A senior civil engineer with the DWR was interviewed by the Sacramento Bee, and explained, "It’s common for spillways to develop a void because of the drainage systems under them", and "There were some patches needed and so we made repairs and everything checked out." In July 2015, the state Division of Safety of Dams inspected the dam spillway visually "from some distance" and did not walk it. 2017 spillway failure Initial spillway damage The rainy season of 2016–2017 was Northern California's wettest winter in over 100 years. Heavy rainfall resulted in record inflows from the Feather River, and the spillway was opened in January to relieve pressure on Oroville Dam. After a second series of heavy storms in February, the spillway flow was increased to , and on February 7, DWR employees noticed an unusual flow pattern. This halted spillway outflow, and DWR brought engineers onto the spillway to inspect its integrity. The engineers found a large area of concrete and foundation erosion. This erosion feature was too massive to repair without diverting water to the emergency spillway, and halted outflow along the main spillway for a period to fix the hole. High inflows to Lake Oroville forced dam operators to continue using the damaged spillway, causing additional damage. The spillway hole continued to grow. Debris from the crater in the main spillway was carried downstream, and caused damage to the Feather River Fish Hatchery due to high turbidity. Although engineers had hoped that using the damaged spillway could drain the lake enough to avoid use of the emergency spillway, they were forced to reduce its discharge from to due to potential damage to nearby power lines. Emergency spillway use and evacuation Shortly after 8:00 pm on February 11, 2017, the emergency spillway began carrying water for the first time since the dam's