The Department of Water Resources (DWR) continues work on the Oroville Dam spillway. The main spillway suffered major damage in February 2017 when heavy rains and snowmelt caused significant inflow, eroding the foundation and a portion of the spillway. The main spillway was shut down, but the water continued to rise, eventually testing the dam's emergency spillway. This caused further erosion, which threatened nearby residents and forced evacuations in Butte County. The DWR jumped into action on repair efforts and controlled the situation in a short period of time.
Working with a sense of urgency to reconstruct the spillway before the upcoming winter, the DWR used both structural and roller-compacted concrete (RCC), as it is very quick to roll out. The intention is to replace much of the RCC with structural concrete in 2018. RCC and structural concrete plants exist at the site, enabling quick and efficient relocation of heavy materials. These plants served to be vital in the on-time completion of the project's first phase.
“I think this is a...phenomenal feat that has been done this summer,” State Water Project (SWP) Deputy Director Joel Ledesma said at a meeting of the California Water Commission in Sacramento earlier this month. “I believe, in talking to even some of the experts that are helping us, that nobody's constructed the spillway this fast ever before.”
The DWR, along with contractors, finished building a new spillway and completed phase one of the project on November 1. The new spillway’s reinforcement is capable of conveying over 100,000 cubic feet of water per second (CFS). According to Ledesma, the structural concrete used in the construction was enough for a five-and-a-half-foot-wide sidewalk to be laid out and stretched from Sacramento to Los Angeles.
The next phase will include construction of a new emergency spillway, a cement buttress built up against the weir, and a wave suppression wall to safeguard against the force of rushing water. The hope is that the new emergency spillway will never need to be used, and will better withstand the issues of future erosion. A comprehensive analysis is currently underway by the DWR which will identify the particular needs of additional infrastructure at the Orville Dam moving forward.
Another focus of attention with the SWP is a study on subsidence of the California Aqueduct conducted by Don Walker from the Division of Operations and Maintenance for the DWR. The study shows that the aqueduct is dropping in several places. Survey records dating back as far as 50 years were used in the study, as well as radar satellite mapping provided by NASA to determine rate and location of subsidence for the study area — just west of the San Joaquin Valley. The study looked at the effects that subsidence is having on water deliveries, amongst other things, and identifies short-to-long-term suggested actions to ensure the safe and functional future operation of the aqueduct. The actions call for the restoration of some of the lost capacity in the next two to four years. In the meantime, the safe operation of the aqueduct is a top priority for the DWR.
Included in the updates presented to the California Water Commission was the current status of greenhouse gas reduction. The DWR introduced the Greenhouse Gas Emissions Reduction Plan in 2012 to reduce greenhouse gas emissions in all of its operations, including the SWP and parts of the State Plan of Flood Control managed by the DWR. The goals set forth in the plan are to reduce greenhouse gas emissions by 50 percent by 2020 and 80 percent by 2050, based on levels recorded in 1990. The DWR is attacking this challenge from multiple angles, and already achieved the 2020 reduction target goal by the end of 2016.
In 2013, the DWR discontinued the use of a coal-fired power plant in Nevada named the Reid Gardner Generating Station. This reduced greenhouse gas emissions by about 800,000 to 900,000 metric tons annually. To put that into perspective, the DWR's 1990 greenhouse gas emissions levels were 2,746,000 metric tons.
“We didn't just go after the low-hanging fruit,” said Andrew Schwarz, Senior Engineer with the DWR's Climate Adaptation Office. “We have best management practices for our construction activites, [and] even though it's a very small contribution to our footprint, the emissions that come from the lights and computers in our business practices, we've gone after reducing those emissions as well.”
The DWR is currently analyzing the greenhouse gas emissions that resulted from the Orville spillway efforts like the diesel burned from heavy equipment, and preliminary estimates show only an additional 200,000 metric tons in a two-year span, keeping the goal of an 80 percent reduction by 2050 in sight.