Field Trip to a Dam Under Repair

By Yiyuan Zhang
Master Degree in CEE, 2017
Intern at the California Department of Water Resources

Driving 80 miles northward from Sacramento, you will meet the largest earthfill embankment dam in America, Oroville Dam. Though it may not seem as tall as it looks from far away, it is actually 770 feet high. Oroville dam is a key component of California’s State Water Project (SWP), storing more than 3.5 million acre-feet of water in Lake Oroville and bearing responsibility for flood control, water storage, and hydroelectric power generation.

I joined a group of four interns on a field trip to Oroville Dam on July 21st to get a better understanding of the SWP. Before we set off, we were all informed that the SWP is facing severe challenges from damage to the Oroville Dam’s spillway. In 2017, the dam experienced Northern California’s wettest winter in over 100 years. DWR had to open the spillway to manage the reservoir’s rising water level. After carrying high outflow for a month, a crater formed which later grew into a hole. This incident made our field trip even more meaningful.

We arrived the site at 10 o’clock, visited the drainage channel, and touched the flowing water. Water temperatures there were lower than we had expected. It is cold, not just for human beings, but also for fish. Water being pumped from Lake Oroville into a hatchery is manifesting this problem. A team in our office is working on it, and hopefully in the near future hatchery fish will have a more livable environment.

Going around the dam, we saw the damaged spillway under repair. At the end of spillway, there are four giant stone cubes serving as energy dissipaters. While they hardly seemed huge at first glance, after going around a corner, we got a better front view of the spillway, and were surprised to find large trucks looking as small as toy cars in comparison to the cubes. Our mentor, Bill Cochran, told us that the capacity of the spillway is 150,000 cubic feet per second. This flow rate is equivalent to 70 trucks passing through an intersection.

Our last stop was at the Feather River Fish Hatchery. To reduce the impact of the dam’s operations on fish, the hatchery collects salmon and steelhead, helps with egg spawning, and releases baby fish downstream when they are mature enough. Salmon and steelhead usually come in a large group before summer starts, so we were not lucky enough to view the hatchery operation, but we did see fish jumping out from the water’s surface and visitors with happy smiles.

For the Oroville spillway, the repair work is expected to be finished by November 1st, when California’s rainy season will on its way. More details on the restoration plan are available at the Department of Water Resources’ website.

Video: Oroville Spillway progress report, July 20, 2017

California Department of Water Resources

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