Mokelumne Aqueducts Resiliency Project

Mokelumne Aqueducts Resiliency Project

The Project includes construction across the Delta of an approximately 16.5 mile long, 15-foot diameter tunnel, containing a 120-inch steel carrier pipeline with a capacity of 325 mgd that would replace the vulnerable section of the Mokelumne Aqueducts. The Tunnel would be located in stable soil deposits at an approximate depth of 90 to 130 feet below mean sea level, below weak, compressible soils comprised of surficial floodplain soil deposits. The Tunnel would be excavated by an electric-powered Tunnel Boring Machine (TBM) and supported using approximately 5-foot-long watertight precast concrete segmental rings that will be installed as the TBM advances. Excavated soil from the Tunnel would be stockpiled temporarily at the launch shaft sites and dried out prior to transporting the soils to a permanent disposal site using large trucks and/or using the railroad. After the tunneling has been completed, the 120-inch steel carrier pipeline will be installed and welded together within the Tunnel. Low-density cellular concrete would be pumped into the annular space outside the carrier pipeline to encase the pipeline and cement mortar lining would be applied to the inside of the carrier pipeline to protect the steel from corrosion. The Tunnel would be constructed in two to three tunnel drives, each from a concrete launch shaft approximately 70 feet in diameter to a concrete reception shaft approximately 35 feet in diameter. Depending on the number of Tunnel drives, up to four Tunnel shafts would be constructed, including one reception shaft to be located at the east end of the Tunnel alignment in the City of Stockton, one reception shaft at the west end at EBMUD’s Bixler Maintenance Yard in unincorporated Contra Costa County, and two intermediate shafts including a launch shaft located at Holt and combination launch and reception shaft near Bacon Island Road. The Tunnel access shafts would remain after construction for long-term maintenance access to the carrier pipeline installed inside the Tunnel. The access shafts at Holt and near Bacon Island Road are in the Delta and therefore would extend approximately 30-feet above the ground surface to provide access to the Tunnel in the event of Delta flooding. Additional property adjacent to EBMUD’s existing ROW would be obtained for the purpose of constructing Tunnel access shafts that would be used during construction and operation of the Tunnel. Access routes, including bridges, may require improvements to accommodate large vehicles transporting heavy equipment and materials to and from the launch shafts. Mokelumne Aqueduct No. 3 would remain in service to provide operational flexibility and support future planned and unplanned outages of the Tunnel. The above ground section of existing Mokelumne Aqueduct No. 3 would be retrofitted to help mitigate seismic and flooding risks. After the Tunnel is constructed and placed in service, existing Mokelumne Aqueducts Nos. 1 and 2 would be decommissioned for approximately 16.5 miles, with aboveground sections removed and underground sections abandoned in place and filled with cellular concrete to prevent a potential collapse hazard.

Stockton

Contra Costa, San Joaquin

Citywide, Countywide, Northern California

California Air Resources Board (ARB), California Department of Conservation (DOC), California Department of Fish and Wildlife, Bay Delta Region 3 (CDFW), California Department of Fish and Wildlife, Habitat Conservation Planning (CDFW), California Department of Fish and Wildlife, North Central Region 2 (CDFW), California Department of Forestry and Fire Protection (CAL FIRE), California Department of Parks and Recreation, California Department of Transportation, District 10 (DOT), California Department of Transportation, District 4 (DOT), California Governor's Office of Emergency Services (OES), California Highway Patrol (CHP), California Natural Resources Agency, California Public Utilities Commission (CPUC), California San Joaquin River Conservancy (SJRC), California State Lands Commission (SLC), Central Valley Flood Protection Board, Delta Protection Commission, Delta Stewardship Council, Office of Historic Preservation, State Water Resources Control Board, Division of Drinking Water, State Water Resources Control Board, Division of Water Quality, State Water Resources Control Board, Divison of Financial Assistance, California Department of Toxic Substances Control (DTSC), California Native American Heritage Commission (NAHC), California Regional Water Quality Control Board, Central Valley Sacramento Region 5 (RWQCB), California Department of Water Resources (DWR), State Water Resources Control Board, Division of Water Rights

California Department of Toxic Substances Control (DTSC), California Native American Heritage Commission (NAHC), California Regional Water Quality Control Board, Central Valley Sacramento Region 5 (RWQCB), California Department of Water Resources (DWR), State Water Resources Control Board, Division of Water Rights

Water Facilities (Water Facilities)(Type Aqueduct, MGD 325)

Water Transmission Upgrade

Aesthetics, Agriculture and Forestry Resources, Air Quality, Biological Resources, Cumulative Effects, Flood Plain/Flooding, Geology/Soils, Land Use/Planning, Mineral Resources, Noise, Population/Housing, Public Services, Recreation, Schools/Universities, Solid Waste, Transportation, Utilities/Service Systems, Vegetation, Wetland/Riparian, Wildfire