Good project, as reported by the Sacramento Bee, but best one is to build the Auburn Dam.
“At the ripe old age of 64, Folsom Dam is about to hit a growth spurt.
“Federal crews have begun a five-year effort to raise the height of the dam by 3.5 feet to increase flood protection for 440,000 downstream residents in metropolitan Sacramento, including areas of Arden-Arcade, Rosemont and many areas in the city of Sacramento as far south as the Pocket area and north to upper Natomas.
“The Sacramento region, much of built on low-lying land at the confluence of two major rivers, is considered one of the highest urban flood-risk areas in the country.
“The Folsom Dam Raise project is one of several flood protection upgrades at the dam and along the lower American River after major storms in 1986 and 1997 forced dam operators to discharge dangerously high water flows into the river, threatening to burst the levees that protect much of the metropolitan area.
“At the time of the 1986 and 1997 incidents, officials feared the fast-rising reservoir water could over-top the dam, which in fact is not one dam but instead a series of eight earthen dikes or dams that flank a central concrete dam. To avoid that, they released unprecedented flows of water from the dam into the American River channel below at levels that were thought to be higher than the levees at the time could handle. Officials were able, though, to reduce the flows before a levee break occurred.
“The dam-raise work involves packing rock, gravel, dirt and pavement on top of the earthen portions of the Folsom dam and dike system, which is several miles long, boosting the height from 340 to 344 feet. The concrete central portion of the dam itself already is taller than the adjacent dikes and will not be raised, but will have seals added to the top of the row of outlet gates near its brim to allow for more water storage.
“The project, expected to cost nearly $400 million, will allow the federal Bureau of Reclamation to hold an additional 43,000 acre feet of water in Folsom reservoir annually if needed during heavy rains. That’s 4 percent more capacity.
“The project also will bolster the earthen dike portions of the dam against potential failure in the event of high-water storm wave action in the reservoir.
“The dam raise follows on the heels of another modernization project at the dam, completed in 2017, that rebuilt the facility’s emergency spillway, lowering the top of the spillway some 50 feet to allow dam operators to release more water at lower lake levels.
“The dam raise builds on flood risk management benefits that were derived from (previous work),” said Army Corps project manager Gerry Slattery. “We are going to further reduce that risk with the dam raise.”
“As a secondary benefit, officials said, the dam raise will allow federal dam managers to hold more water behind the dam to be used for water supply when drought years are expected. The reservoir water is used as drinking water by many downstream communities.
“Rep. Doris Matsui, D-Sacramento, a federal flood control advocate who secured the federal funding portion for the project, will be at the dam with other federal and local officials on Tuesday at an invitation-only event to commemorate the formal start of the project. Some work has been underway, though, for several months.” Retrieved January 21, 2020 from https://www.sacbee.com/news/local/article239329138.html