PG&E Ignacio-Alto-Sausalito 60 kV Rebuild Project at San Rafael Creek (Lake or Streambed Alteration Agreement No. EPIMS-MAN-48368-R3)

PG&E Ignacio-Alto-Sausalito 60 kV Rebuild Project at San Rafael Creek (Lake or Streambed Alteration Agreement No. EPIMS-MAN-48368-R3)

The California Department of Fish and Wildlife (CDFW) has executed Lake and Streambed Alteration Agreement number EPIMS-MAN-48368-R3, pursuant to section 1602 of the Fish and Game Code to the project Applicant, Pacific Gas and Electric Company (PG&E). The Project is limited to replacing one existing power line structure (Tower 07/54) on the Ignacio-Alto-Sausalito 60 kV alignment, decommissioning portions of an access boardwalk, building portions of an access boardwalk, placing and removing temporary access and construction matting, and installing and removing temporary cofferdams. Temporary wood or high-density polyethylene access matting will be lowered onto the 1.35 acre temporary work area by a crane or other large equipment such as an excavator or loader. The edges of matting segments interlock; segments will be lowered into place and not require further joining. Four, four-foot diameter steel pipe piles will be driven into the ground approximately 80 feet landward of the existing tower and used as foundations for the replacement tower. Piles will be installed in segments, as there is not sufficient vertical space to erect the entire pile below existing transmission lines. The upper segment of each pile will be spliced into the lower segment after the lower segment is driven to a depth which allows vertical placement of the upper segment. Once driven to depth, each pile will be reinforced internally with rebar cage and concrete. A steel pipe cap will be installed on each pile to connect the pipe piles to the tower leg. Concrete will be transferred by truck to the construction staging areas on the construction mats where it will be pumped into each pile. The new steel lattice tower will be constructed following completion of the new foundations. The tower will be assembled on site and erected with cranes. Once the electric conductors are relocated to the replacement tower and have been fully energized, the existing tower will be removed. The steel lattice will be removed first in segments using mechanical hand tools such as saws and torch cutters in combination with helicopters and cranes to remove pieces of steel for disposal. Following tower removal, footings and associated support piles will be removed to six inches below the mudline. The existing tower has four footings measuring 36 square feet per footing. Mechanical methods such as hoe rams and diamond wire saws will be used to remove tower footings, Untreated plywood cofferdams may be installed around each footing to facilitate access to the footings when water is not present. Existing tower components will be completely removed from the site using trucks, barges, or helicopters and disposed of at an appropriate upland facility. To facilitate construction access and installation of the temporary construction matting, the existing boardwalk access to Tower 07/54, measuring two feet wide by approximately 125 feet long, will be removed. Boardwalk removal will occur with hand tools, beginning with above ground planks and handrails. Support pilings will be cut at ground level or the mud line, and aboveground portions removed. Removed boardwalk materials will then be disposed of at an appropriate off-site facility. After the tower is replaced and construction matting is removed, the boardwalk will be rebuilt. The rebuilt boardwalk will measure three feet wide by approximately 45 feet long. Boardwalk construction will occur using hand tools; no excavation will be required. All materials and tools will be transported by foot with no vehicles or machinery necessary for construction. Four-inch by four-inch wooden support pilings will be installed at approximately 10-foot spacing and driven directly into the mud. A 9-foot-wide work area is required to construct and decommission boardwalk. The project will result in 1.35 acres of temporary impacts to salt marsh habitat hydrologically connected to San Rafael Creek. The Project will result in 185 square feet of permanent impacts associated with building new tower footings and access boardwalk, and 250 square feet of restored salt marsh habitat associated with removing old footings and access boardwalk for a net permanent salt marsh habitat increase of approximately 65 square feet. No in-water work will take place, as cofferdams will be placed and removed at low tide when water is not present where the cofferdam is to be installed. No trees will be removed by the Project.

San Rafael

Marin

San Francisco Bay Area

Marin