Construction on the largest dam removal project in California history completed this week in Carmel Valley, CA. The $83-million San Clemente Dam and Carmel River Reroute Project officially finished with a June 6 celebration, featuring project team members from California American Water, the owners and operators of the dam; the California State Coastal Conservancy; and Granite Construction, the design-builder.
The 106-ft San Clemente Dam was built in 1921 and removed last summer. The project involved removal of the antiquated dam and implementation of a watershed restoration process to "bring the Carmel River back to life."
Project goals included providing a long-term solution to the public safety risk posed by the potential collapse of the outdated San Clemente Dam in the event of a large flood or earthquake which would have threatened 1,500 homes and other public buildings; and provide unimpaired access to more than 25 miles of essential spawning and rearing habitat for the endangered steelhead trout.
The project also sought to restore the river’s natural sediment flow to help replenish sand on Carmel Beach and improve habitat downstream of the dam for the steelhead; reduce beach erosion that contributed to destabilization of homes, roads, and infrastructure; re-establish a healthy connection between the lower Carmel River and the watershed above San Clemente Dam; and improve habitat for threatened California red-legged frogs.
Before its removal, the reservoir no longer provided significant water storage for the community, says project officials. Over time, 95% of its space had become filled with more than 2.5 million cu-yards of sediment, leaving a remaining water storage capacity of only about 70 acre-ft.
The project, developed through a Public Private Partnership (PPP), included an innovative engineering approach of rerouting the river around accumulated sediment.
“Our approach avoided the environmental impact of releasing or transporting sediment,” said California American Water President Rob MacLean in a press release. “The river reroute makes this dam removal unique from a technical and engineering point of view."
Granite Construction was selected through a competitive procurement process to design and build the three-year construction project. Now that the job is complete, Granite will also perform five years of post-construction monitoring and maintenance activities to ensure that the project objectives are met and the restoration project is successful.
The dam removal project was team effort between California American Water, the California State Coastal Conservancy, and NOAA’s National Marine Fisheries Service. The $83 million cost of the project was made up of $49 million from California American Water, and $34 million from federal, state and private sources, including the State Coastal Conservancy and the National Marine Fisheries Service, as well as The Nature Conservancy, the Wildlife Conservation Board, and the California Department of Fish and Wildlife.