The Phoenix Hydroelectric Project (Project) is located along the South Fork Stanislaus River in Tuolumne County, California approximately 10 miles northeast of the town of Sonora. The Project provides water to the Tuolumne Utilities District (TUD), generates power, and is required to meet streamflow requirements for the South Fork Stanislaus River.
The major components of the Project include: Lyons Dam and Reservoir; a cushion dam about 80 feet downstream of Lyons Dam; the Main Tuolumne Canal (MTC); Phoenix Header Box (forebay to the powerhouse); a penstock; and the Phoenix Powerhouse. Water enters the Project from the South Fork Stanislaus River and is released from Lyons Dam (the uppermost Project component), either through the low-level outlet or radial gates, from which water flows into a regulating reservoir impounded by a cushion dam approximately 80 feet downstream of Lyons Dam. The water behind the cushion dam is diverted into the MTC or discharged to the South Fork Stanislaus River to meet instream flow requirements. The South Fork Stanislaus River downstream of the cushion dam flows from an elevation of about 4,200 feet above mean sea level (msl) to approximately 1,110 feet above msl at New Melones Reservoir. Some of the water diverted into the MTC is delivered to TUD at multiple locations along the MTC. Water that is not delivered to TUD along the MTC ultimately reaches the Phoenix Powerhouse penstock and thereby the Phoenix Powerhouse. From the Phoenix Powerhouse, water is discharged to Powerhouse Creek and ultimately to TUD’s Phoenix Reservoir for consumptive use. Public recreational opportunities in the Project boundary include day use areas with fishing opportunities at Lyons Reservoir and the MTC section 4 ditch as well as various hiking trails.
Phoenix Powerhouse is located at the upper end of the Tuolumne Water System, a domestic water supply system owned by TUD. Phoenix Powerhouse has an installed generation capacity of 1.6 megawatts. PG&E is not proposing new developments; however, PG&E is proposing to modify the existing Project boundary to encompass all facilities necessary for operation and maintenance of the Project.