Transmission Line Clearance Mitigation Moderate and Low Risk Project Various

The SFPUC owns and operates the Hetch Hetchy Power System which includes three hydroelectric powerhouses. Hydroelectricity generated at these facilities is delivered using SFPUC-Hetch Hetchy-owned transmission lines within its 168-mile rights-of-way to a PG&E substation in the city of Newark where the power is passed through to San Francisco. The SFPUC’s transmission facilities consist of 11 transmission lines and are located within Tuolumne, Mariposa, Stanislaus, San Joaquin, and Alameda counties. To ensure sufficient clearance between the conductors and the ground, SFPUC would conduct one of the following at over 100 locations (locations may have multiple towers) along the transmission lines: • Limited Grading/Site Clearing: Limited grading beneath the conductors (power lines) to increase the clearance distance between the ground and power lines. • Increase Tension: Increasing tension on existing power lines to raise conductors to meet requirements on sections between dead-end towers. • Insulator Replacement (Floating Dead-ends): Replacing existing insulators on the arms of the tower from a vertical suspension to a horizontal orientation. • Insulated Crossarms: Replacing the tower arms with a high-strength insulator assembly that allows forthe power lines to be raised up just underneath the arms • Tower Raises: Increasingthe height ofthe tower and thus the transmission lines • Tower Replacement: Replace the existing tower with a taller tower • New Midspan Tower: Constructing a new mid-span tower in-line with the existing transmission alignment to raise up the existing power line(s) • Reconductor: Replacing the power lines with new High-Temperature Low-Sag power lines (reconductor) • Hybrid Solutions: Implementing a combination of one or more ofthe above solutions. The overall work area would be up to an approximate 50-foot perimeter outside the base of each tower. Staging areas would likely be accommodated within the existing SFPUC rights-of-way and would center around the various tower locations. The staging areas would be used for storage of materials, construction vehicles, equipment, worker facilities, and dumpsters to temporarily store discarded materials. The project construction is anticipated to start in early 2027. Construction ofthe entire project would require a total of approximately 36 months. The work duration at each individual tower location will vary depending on the type of mitigation strategy pursued and could range from a few days for grading to six weeks for tower replacement or installation of a mid-span structure.