Canyon Tunnel Project Addendum

Canyon Tunnel Project Addendum

The work would include temporary construction access, laydown, and staging areas; permanent downstream tunnel portal and tie-in to the existing canal; approximately 12,106 lineal feet of new tunnel; permanent upstream tunnel portal and tie-in to the existing Goodwin Reservoir; and permanent access improvements leading to the existing Goodwin Dam right abutment: The Project specifically includes the following components: • Construction of approximately 12,106 feet tunnel; approximately 20-foot diameter with a flat floor; • Use of existing roads paved and dirt roads to be rehabilitated where necessary; • Rehabilitation of an existing boat ramp and new boat landing: o Rehabilitation of the existing boat ramp would be constructed at the same location and with a slightly larger footprint at the south shore of Goodwin Dam Reservoir at the current parking lot location; o Construction of a new boat landing and tunnel inlet access road at the north shore of Goodwin Dam Reservoir; o Protective cofferdams would be used to dewater around the existing boat ramp, boat landing and tunnel inlet during construction; • Improve and re-align existing livestock fences including barbed wire fencing and panel gates; • Tunnel inlet would start on the north side of the reservoir, upstream of the dam, above the existing diversion canal and on the dry side of the forebay and trash rack; • Installation of new control gates at the tunnel inlet; o The tunnel size would be approximately 16 feet in diameter along the majority of its length, with some areas slightly larger to accommodate hydraulics and portal transitions; • Temporary installation of a coffer dam at the existing trash rack for forebay dewatering; • Installation of a concrete cover cap over the existing forebay to provide rockfall protection; • Existing ram pump to be abandoned; • Proposed vertical conduit to be drilled vertically to tunnel for upland property owner (well with steel casing, removable screen and sump at tunnel sidewall, submersible solar power pump); • Existing canal gates at dam to remain for side-spill • Existing canal inlet gates to be abandoned • Tunnel Outlet would be located at the southwest end of the Project area at the downstream portal. • The proposed Canyon Tunnel would bypass the existing canal for approximately 12,250 feet and tie back into the existing canal through a downstream tunnel portal. Construction Phases are as follows and are referenced throughout the document: 1. Excavate Downstream Portal Work Area 2. Shotcrete Portal Face 3. Excavate First 800 LF D + S 4. Tunnel Excavation, Stage 1 Shotcrete 5. Stage 2 Shotcrete 6. Place Concrete Slab D+S and Invert Concrete 7. Tunnel Cleanup 8. Excavate Upstream Portal Work Area 9. Shotcrete Upstream Shoring Walls 10. Construction Concrete Intake Structure 11. Tie-In Canal Facilities

Calaveras, Stanislaus, Tuolumne

Northern California

Calaveras, Stanislaus, Tuolumne