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Summary of Proposed Solutions (EIR)
The San Clemente Dam and Reservoir was built in 1921 to store water from the Carmel River and San Clemente Creek. At the time of construction, little was known about building for earthquake safety. Between 1980 and 1992, initial studies were preformed to determine the safety of the San Clemente Dam in the event of an earthquake on the nearby Tularcitos fault, or a flood caused by a large storm.
These studies found that the dam was not safe according to current standards. In 1992 the Division of Safety of Dams (DSOD) required that California American Water, as the current owner and operator of the San Clemente Dam, upgrade it to comply with current seismic safety standards. This project is known as the San Clemente Dam Seismic Retrofit, even though one of the alternatives currently being considered is total removal.
Between 1992 and 2006, various studies were done of alternatives for upgrading the dam to be seismically safe. During that time, the reservoir became almost completely filled with sediment, rendering its original purpose as storage obsolete. The April 2006 draft Environmental Impact Report (EIR/EIS) covers each alternative in detail, including potential impacts on geology and soils, hydrology and water resources, water quality, vegetation and wildlife, wetlands, air quality, and noise. It also considers total cost as these costs would be passed on to California American Water’s ratepayers, unless other funding is obtained.
Alternatives Considered
The alternatives considered by the EIR/EIS include the project as proposed by California American Water (dam strengthening) as well as 3 alternatives that achieve the required safety objectives. The final alternative, no project, is included for comparison purposes.
- Dam strengthening (thickening)
- Dam notching (to approximately EL. 506 feet)
- Dam removal (with sediment excavation)
- Carmel river reroute and dam removal (sediment storage in place)
- No project (no action)
The preferred alternative is dam strengthening, which includes the following key features.
- Thicken downstream face of dam and replace fish ladder
- No sediment removal impacts
- Manage sediment with sluice gates
- Tularcitos access route
- Eliminates dam safety issue
- Fish barrier remains, but new ladder
- Least impact to frogs/other biological resources
- Least costly action alternative
- Construction period: 4 years permit to completion
See Fixing the Dam Problem for more information, or read the complete draft EIR/EIS for the San Clemente Dam Seismic Retrofit Project.
Pros/Cons of Other Alternatives
Dam Notching
- Notch dam to elevation 506 feet and replace fish ladder
- Remove 930 AF of sediment via conveyor belt
- Existing access below dam/Cachagua access above dam
- Fish barrier remains but lower new ladder
- Manage sediment with sluice gate
- Large impacts to frogs/other biological resources
- New water intake
- 2nd most costly action alternative
- Construction period: 4 years permit to completion
Dam Removal
- Demolish and remove dam
- Remove 1,555 AF of sediment via conveyor belt
- Existing access below dam/Cachagua access above dam
- Restore free-flowing river – natural sediment flow
- Eliminate dam safety issues
- Eliminates fish barrier
- Red legged frog habitat temporarily removed
- Water supply point of diversion moved
- Most costly action alternative
- Construction period: 5 years permit to completion
Carmel River Reroute and Dam Removal
- Demolish and remove dam
- Bypass about 2500 feet of Carmel River and store sediment in bypassed reach
- Reroute Carmel River into San Clemente Creek and restore free-flowing river
- Existing access below dam/Cachagua access above dam
- Eliminates dam safety issue
- Minimal sediment storage impacts
- 2nd least costly action alternative
- Construction period: 4 years permit to completion
No Project (No Action)
- Dam left in place, fish ladder replaced
- Continued risk of dam failure and potential loss of life and property
- Least impacts to frogs/other biological issues
- Fish barrier remains, but new ladder
- Sediment in = sediment out
- Water supply point of diversion unchanged
- Least cost
- Construction period: 1 year permit to completion
EIR/EIS Timeline
The complete EIR/EIS process includes the following, with a final EIR/EIS anticipated by September 2006.
- Scoping (public/agency meetings November 2004)
- Alternatives description (March 2005)
- Environmental studies (September 2005)
- Preliminary draft EIR/EIS (October 2005)
- California responsible agencies review (January 2006)
- Draft EIR/EIS (April 2006)
- Public hearing (May 2006)
- Public comment period (April 21 – July 3, 2006)
- Final EIR/EIS (September 2006)
- CEQA findings/certification (October 2006)
- NEPA record of decision (2007)
Excerpts from the EIR/EIS
The following short sections from the full draft EIR/EIS are included as additional information.
Description of Dam and Reservoir
This thin arch concrete dam is located 18.5 miles upstream from the mouth of the Carmel River, below its confluence with San Clemente Creek. The reservoir was constructed as a water supply project and provides a physical diversion point on the Carmel River from which water flows to the Carmel Valley Filter Plant and is distributed to the Carmel Valley Village area and other down-gradient areas. The San Clemente Dam initially impounded a reservoir of about 1,425 acre-feet at the spillway elevation of 525 feet. More than 2.5 million cubic yards of sediment have accumulated behind the dam since it was constructed in 1921.
The dam includes a fish ladder that allows steelhead trout, a Federally listed threatened species, to ascend 68 feet over the dam to use the watershed above the dam. The California red-legged frog, another Federally listed threatened species and a California State species of special concern, also uses habitat at the reservoir and along the river and creek.
Project Purpose, Need & Objectives
The need for the San Clemente Dam Seismic Safety Project is to increase dam safety to meet current standards for withstanding a Maximum Credible Earthquake (MCE) and passing the Probable Maximum Flood (PMF) at the dam. The purposes and objectives for the project are to:
- Meet current standards for withstanding a MCE and PMF at the San Clemente Dam.
- Provide fish passage at the dam.
- Maintain a point of diversion to support existing water supply facilities, water rights and services.
- Minimize financial impacts to CAW rate payers.
CAW's Proponent’s Proposed Project and the alternatives to it that are evaluated in this EIR/EIS meet the need of eliminating safety risks associated with the MCE and PMF at the dam and the other objectives stated above.
Abstract
This EIR/EIS analyzes the Proponent’s Proposed Project (dam strengthening) and the following alternatives: Alternative 1 (dam notching with partial sediment removal), Alternative 2 (dam removal with full sediment removal), Alternative 3 (Carmel River reroute and dam removal with in-place sediment stabilization), and Alternative 4 (No Project).
Date of Implementation
Depending on the alternative selected, the San Clemente Dam Seismic Safety Project would be implemented within three to five years after project approval, including environmental review, permitting, design, infrastructure improvements, and all aspects of construction or demolition.
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