The San Clemente Dam is located just downstream of the confluence of the Carmel River and San Clemente Creek, approximately 100 miles south of San Francisco, California. The dam, which has blocked both the river and San Clemente Creek for 94 years, was put out of commission after being declared a seismic hazard by the California Department of Water Resources in 2002. California American Water, which owns the dam, agreed that the possible risk of collapse and the catastrophic implications to the 1,500 homes and local businesses downstream necessitated the removal of the dam, and a plan was quickly developed.
This endeavor became known as the Carmel River Reroute and San Clement Dam project and is the largest dam removal project ever to occur in California and one of the largest to occur on the West Coast. This groundbreaking project sets precedence for other dam removal and river restoration projects in California and nationwide.
The project, when completed, will remove the 106 foot high antiquated dam and implement a watershed restoration process that will bring the Carmel River back to life. The channeling of the Carmel River into a carefully engineered river bed was designed to bypass the tons of sludge behind the 106-foot-tall dam. Removal of the dam without a suitable diversion channel would send an estimated 2.5 million cubic yards of sediment downstream, jeopardizing the entire 25 mile river ecosystem.
Engineers estimated that removal of the sediment behind the dam would cost between $30 million and $75 million and involve many months of trucks rumbling through local communities. An alternative plan needed to be developed to effectively remove the sediment without the prolonged and costly disruption.
The solution, which was first suggested by the dam caretaker, was to dig a new half-mile channel leading to the dam and divert the entire river through that channel, allowing the Carmel to join San Clemente Creek approximately a mile upstream from the dam. Ideally, planned construction would then be able to leave all the accumulated sediment in place - building berms to retain the sediment. Excavated material would be used to construct these berms, enabling the growth of native plants while turning the old river bed into a natural part of the landscape.
The 3-year-project began in 2013. Granite Construction Company was able to dynamite a mountain and dig out a million cubic yards of earth. The new channel constructed diverts the river past the dam, allowing water to continue to flow through the sluice gates until next year when the sediment field is expected to be dry and stable and the dam structure can then be removed.
Contech Engineered Solutions worked in conjunction with Granite Construction to supply pipe product for the diversion channel needed to reroute the Carmel River around the dam. With over 3,000 LF of ULTRA FLO® corrugated metal pipe (CMP) needed to accomplish this, Contech employed the use of their local plant to manufacture and ship the pipe locally to help expedite the process and keep the project on schedule. ULTRA FLO's unique spiral rib profile provides one of the most hydraulically efficient storm sewer systems and was an ideal solution for the diversion line.