FERC Project No. 2079 - PCWA Middle Fork American River Project ...

Application for New License Middle Fork American River Project (FERC Project No. 2079)
• Middle Fork Powerhouse and Upper and Lower Switchyards
The Middle Fork Powerhouse (also known as the L. J. Stephenson Powerhouse)
contains two Pelton-type waterwheels, each connected to a 61.2 MW electrical
generator with an installed generating capacity of 122.4 MW. The minimum
estimated hydraulic capacity of the Middle Fork Powerhouse is 50 cfs and the
maximum estimated hydraulic capacity is 940 cfs. The above-grade portion of
the powerhouse includes an approximately 62-foot by 154-foot concrete slab, two
circular 18-foot-high generator housings, a small rectangular entry building, and
main transformers. A moveable metal gantry crane stands over the powerhouse.
Water to the powerhouse is delivered from Hell Hole Reservoir via the Hell Hole
– Middle Fork Tunnel and Penstock. Water from the powerhouse is discharged
to Middle Fork Interbay.
Electricity generated at the powerhouse is increased to 60 kV at the powerhouse
main transformer bank. Two switchyards are adjacent to the Middle Fork
Powerhouse—the Upper and Lower switchyards. The switchyards provide
interconnection to PG&E’s 60 kV and 230 kV Transmission System. The
switchyards include metal towers and electrical switching gear. The powerhouse
and switchyards are contained within an approximately 250-foot by 360-foot
fenced area that is graded.
• Ralston Powerhouse and Switchyard
The Ralston Powerhouse contains a single Pelton-type waterwheel and electrical
generator with an installed generating capacity of 79.2 MW. The minimum
estimated hydraulic capacity of the Ralston Powerhouse is 75 cfs and the
maximum estimated hydraulic capacity is 924 cfs. Water to the powerhouse is
delivered from Middle Fork Interbay via the Middle Fork – Ralston Tunnel and
Penstock. The above-grade portion of the powerhouse includes an
approximately 82-foot by 90-foot concrete slab, a circular 22-foot-high generator
housing, and small rectangular entry building. A moveable metal gantry crane
stands over the powerhouse. Water from the powerhouse is discharged to
Ralston Afterbay.
Electricity generated at the powerhouse is increased to 230 kV at the
powerhouse main transformer bank. The Ralston Powerhouse is interconnected
to PG&E’s 60 kV and 230 kV Transmission System through the switchyard
located adjacent to the powerhouse. The switchyard includes metal towers and
electrical switching gear. The powerhouse and switchyard are enclosed in an
approximately 80-foot by 295-foot fenced area that is graded.
• Oxbow Powerhouse and Switchyard
The Oxbow Powerhouse contains a single Francis-type turbine and electrical
generator with an installed generating capacity of 6.1 MW. The minimum
estimated hydraulic capacity of the Oxbow Powerhouse is 200 cfs and the
February 2011 4-9