The Folsom Dam auxiliary spillway project is in its last phase and on schedule to finish by October, according to the U.S. Army Corps of Engineers, Sacramento District. The $900 million structure, which runs parallel to Folsom Lake Crossing, has been in construction since 2008 and is a joint project between several federal and state agencies: the U.S. Army Corps of Engineers, U.S. Bureau of Reclamation, State of California and Sacramento Area Flood Control Agency. The Corps of Engineers built the dam, while the Bureau of Reclamation excavated the spillway chute and will operate the dam when it is finished. “The majority of construction work is coming to completion,” said Corps of Engineers project manager Kristine Des Champs. “There’s still some remaining restoration work that the Corps will be working on, and we’re also working on commissioning the structure.”
The spillway project was split into five phases. Phase four ended in December, and the final phase involves removing equipment routes and restoring natural drainage to the area. Commissioning the structure will require running a series of tests to make sure the spillway is capable of handling its capacity of 312,000 cubic feet per second. “That’s equivalent to four Olympic-size swimming pools per second,” Army Corps spokesman Rick Brown said. Brown said that there have been questions about whether the new spillway could be used now, in light of all the rain the area has received. He said the project needs to be tested first under controlled
conditions, and since multiple agencies have been working on the spillway, the Corps of Engineers cannot make the final call on running it early.
The spillway project consists of three main pieces: an approach channel within Folsom Lake, a six-gate control structure and a 3,027-foot long spillway chute and stilling basin, which is intended to slow water down to safe speeds before it re-enters the river. Des Champs said though the elevation of the spillway is the same as the main dam, the new spillway’s gates are 50 feet lower than those of the dam proper. “Essentially what this project does is allow for safer releases ahead of a storm coming in,” Des Champs said. Brown added that the project helps prevent water spilling over the main dam if the lake gets too full. Des Champs said the spillway will help both federal agencies meet their goals. The Corps of Engineers is aiming to reduce flood damage in the area, while the Bureau of Reclamation is working on dam safety. “This project accomplishes both of those missions because we’re able to release water sooner out of the auxiliary spillway,” she said. According to an email from Todd Plain, a spokesman for the Bureau of Reclamation, reservoir releases are typically administered to manage flood conditions, satisfy regulations and ensure adequate water supply for both people and wildlife.
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