Notice of Intent To Prepare a Draft Environmental Impact Statement for the Proposed San Clemente Dam Seismic Hazard Remediation Project-Carmel Valley, Monterey County, CA

AGENCY:

U.S. Army Corps of Engineers, DoD.

ACTION:

Notice of Intent (NOI).

SUMMARY:

The U.S. Army Corps of Engineers (USACE) has received an application for Department of the Army authorization from California-American Water Company (CAW) to deposit approximately 3,200 cubic yards of fill material into wetlands and other waters of the U.S. in association with remediating the safety hazards of an existing Dam on the Carmel River. This application is being processed pursuant to the provisions of Section 404 of the Clean Water Act (33 U.S.C. 1344) and in accordance with the National Environment Policy Act (NEPA) of 1969 (42 U.S.C. 4321 et seq.). In accordance with NEPA, USACE has determined that the proposed action may have a significant impact on the quality of the human environment and, therefore, requires the preparation of an Environmental Impact Statement (EIS). A combined Environmental Impact Report (EIR)/EIS will be prepared with the USACE as Federal lead agency and the California Department of Water Resources, San Joaquin District (DWR) as the State lead agency under the California Environment Quality Act (CEQA). The basic purpose of the proposed actions is to provide Dam safety. The overall project purpose is to have San Clemente Dam meet current standards for withstanding a Maximum Credible Earthquake (MCE) and the Probable Maximum Flood (PMF) while providing fish passage at the Dam; maintaining a point of diversion to support existing water supply facilities, water rights and services; and minimizing impacts on CAW rate payers.

DATES:

A public scoping meeting for this project will be held on November 4, 2004, from 6:30 to 8:30 p.m. at the Rancho Canada Golf Club, 4860 Carmel Valley Road, Carmel Valley, California. A public agency scoping meeting for this project will be held on November 9, 2004, 10 a.m. to 12 p.m. at the same location. You may mail comments to: Phelicia Thompson, U.S. Army Corps of Engineers, Regulatory Branch, 333 Market Street, 8th Floor, San Francisco, California 94105-2197.

FOR FURTHER INFORMATION CONTACT:

Phelicia Thompson, 415-977-8452, or electronic mail: Phelicia.M.Thompson@spd02.usace.army.mil.

SUPPLEMENTARY INFORMATION:

1. Background: Approximately 2.4 million cubic yards of sediment have accumulated behind San Clemente Dam since it was constructed in the early 1920s. Engineering studies of San Clemente Dam were conducted in the 1990s to evaluate seismic safety at the request of the California Department of Water Resources Division of Safety of Dams (DSOD). These studies concluded that at the maximum water surface elevation of 537 feet (the height of the Dam's crest), the Dam might not be stable under the MCE. The Dam could suffer severe structural damage leading to the potential loss of the reservoir during a MCE. In addition, under the PMF the Dam could overtop and the downstream abutment area would be susceptible to excessive erosion, leading to a risk of Dam failure. Based on these findings, DSOD has required that the San Clemente Dam be brought into safety compliance to withstand seismic loading from a MCE on nearby faults and safely pass the PMF.

2. Description of the Proposed Action: Dam Strengthening. CAW has proposed to meet seismic safety needs for the Dam and protect against the effects of a PMF by thickening the downstream face of the Dam with concrete. A concrete batch plant would be installed on-site to manufacture the concrete needed. Sediment accumulated behind the Dam would be left in place. However, minor sediment removal may occur to ensure proper functioning of the existing water supply intake serving the upper Carmel Valley Village area. Water in the reservoir may need to be lowered to reduce loading behind the Dam (depending on sediment levels). Inflowing streams would be diverted around the work area and the plunge pool at the base of the Dam would be dewatered during the Dam thickening. This proposed action also includes replacing the existing ladder with a new fish ladder compliant with existing National Marine Fisheries Service (NMFS) and California Department of Fish and Game (CDFG) criteria to provide fish passage. A tower crane would be staged at the base of the Dam to move construction materials from the batch plant to the Dam face and fish ladder. Access to the Dam would be improved by building a new road along the east side of the Carmel River, between the Old Carmel River Dam and the base of San Clemente Dam. The Dam thickening project would take an estimated four years to complete.

3. Reasonable Alternatives: In accordance with the requirements of Section 15124 of the State CEQA Guidelines and 40 CFR 1502.14, reasonable alternatives to the proposed action will be evaluated in the Draft EIR/EIS as listed below:

a. Dam Notching Alternative. This alternative would meet the need to reduce seismic safety risks by notching the Dam. The action would reduce the mass sufficiently to avoid catastrophic failure of the Dam during a MCE event. Notching would also be of sufficient size to prevent overtopping of the Dam during the PMF. The gates, piers and walkway at the top of the Dam would be removed and the Dam would be notched to an elevation of about 505 feet in the area of the present spillway bays. Sediment in the reservoir would to be removed down to the level of the notch. A new intake structure would be constructed to allow the Dam to continue serving the upper Carmel Valley Village area. A new access road would be constructed to connect Carmel Valley Road to the Carmel Valley Filter Plant, to bypass the Sleepy Hollow community and to improve safety for large construction equipment. In addition, road access from the filter plant to the Dam would be improved. The existing primitive road from the Old Carmel River Dam to the base of San Clemente Dam would be rebuilt to an elevation above winter flood levels. Both the Carmel River and San Clemente Creek would be diverted around the reservoir and Dam site and the reservoir would be dewatered each year during construction. Accumulated sediment would be removed from behind the Dam over two seasons by excavation with heavy equipment and transported from the reservoir by truck or via a conveyor belt system to a disposal area near the Carmel Valley Filter Plant. The existing fish ladder would be rebuilt compliant with existing NMFS and CDFG criteria to accommodate the lowered Dam elevation. The Carmel River channel in the inundation zone would be restored. The Dam notching project would take an estimated six years to complete, depending on the effects of annual precipitation upon the construction schedule.

b. Dam Removal Alternative. This alternative would eliminate seismic safety and flooding risks through the removal of the Dam and the accumulated sediment behind the Dam. A new access road would be constructed to connect Carmel Valley Road to the Carmel Valley Filter Plant, to bypass the Sleepy Hollow community and to improve safety for large construction equipment. In addition, road access from the filter plant to the Dam would be improved. The existing primitive road from the Old Carmel River Dam to the base of San Clemente Dam would be rebuilt to an elevation above winter flood levels. Both the Carmel River and San Clemente Creek would be diverted around the reservoir and Dam site and the reservoir would be dewatered each year during construction. Accumulated sediment would be removed from behind the Dam over three seasons by excavation with heavy equipment and transport from the reservoir by truck or via a conveyor belt system to a disposal area near the Carmel Valley Filter Plant. The existing Dam and fish ladder would be demolished and removed from the site. A new intake structure would be constructed to allow CAW to continue serving the upper Carmel Valley Village area. The river channel would be restored through the historic inundation zone. If the Dam and sediment were removed in stages, a trap and truck facility would need to be built and operated at the Old Carmel River Dam for at least three years. The Dam removal project would take an estimated seven years to complete, depending on the effects of annual precipitation upon the construction schedule.

c. No Action Alternative. Under this alternative, no changes to the existing Dam would be made. The Dam would be left in place with all its existing facilities, although the fish ladder would be replaced with a new ladder compliant with existing NMFS and CDFG criteria to provide fish passage. Most of the sediment would be left in place behind the Dam. The reservoir would continue to accumulate sediment at an average rate of about 15 acre-feet per year. Minor sediment removal may occur to maintain the existing water supply intake serving the upper Carmel Valley Village acre. The existing draw down ports in the Dam and the existing fish bypass facility would both likely remain operational until the reservoir fills with sediment. The existing road between the Carmel Valley Filter Plant and the Dam would be improved to provide access to the Dam site for fish ladder construction equipment and supplies.

4. Scoping Process: Pursuant to NEPA, the USACE must include a scoping process for the Draft EIS/EIR. Scoping preliminarily involves determining the scope of the issues to be addresses in the Draft EIR/EIS and identifying the anticipated significant issues for in-depth analysis. The scoping process includes public participation to integrate public needs and concerns regarding the proposed action.

a. Public Involvement Program: Venues for public comment on the proposed action will include: Scoping meetings to be held on November 4, 2004 in Carmel Valley; preparation of a Draft EIR/EIS; and receipt of public comment in response to the Draft EIR/EIS.

b. Significant Issues to be Analyzed in Depth in the Draft EIR/EIS include: Impacts to the aquatic environments; impacts to endangered species, including but not limited to the California red-legged frog and the California Central Coast steelhead; water quality; cultural resources; traffic, fish and wildlife resources; public safety, including downstream flooding; and other issues identified through the public involvement process and interagency coordination.

c. Environmental Review/Consultation Requirements: NEPA; Section 404 of the Clean Water Act; Section 401 of the Clean Water Act; Endangered Species Act; Magnusun-Stevens Act Provision—Essential Fish Habitat; Clean Air Act; National Historic Preservation Act.

d. Scoping Meeting/Availability of Draft EIR/EIS: The USACE will hold a public scoping meeting to provide information on the project and receive oral or written comments on the scope of the document. This scoping meeting for the project will be held at 6:30 p.m. to Thursday, November 4, 2004, at the Rancho Canada Gold Club, 4860 Carmel Valley Road, Carmel Valley, California. The Draft EIR/EIS is expected to be available for public review in winter of 2006.