Draft EIS_072312.pdf - Middle Fork American River Project ...

20120723-4002 FERC PDF (Unofficial) 07/23/2012
2.1.3 Existing Project Boundary
The existing project boundary includes a total of 4,554 acres of land; 3,268 acres
are lands of the United States managed by the Forest Service, and 1,286 acres are owned
by PCWA. The project boundary delineates buffer zones around project reservoirs that
are approximately as follows: Duncan Creek, 120 to 500 feet; French Meadow, 250 to
2,000 feet; Hell Hole, 200 to 2,000 feet; North Fork Long Canyon Creek, 0 to 250 feet;
South Fork Long Canyon Creek, 150 to 200 feet; Middle Fork interbay, 200 feet; and
Ralston afterbay, 100 to 650 feet. All project dams, powerhouses, and flow conduits are
within the existing project boundary, as are most of the project recreation sites and flow
gages. However, some project recreation sites, ancillary facilities, access roads, and trails
to project facilities are either partially or completely outside of the existing project
boundary.
2.1.4 Existing Project Operation
Typical annual operation of the project results in capture of runoff, diverted to
increase storage in French Meadows and Hell Hole reservoirs in the winter and spring
(filling period) and release reservoir storage during the summer, fall and early winter
(release period). Operation of the project varies from year-to-year based on the timing
and magnitude of spring runoff, which is influenced by the amount of winter snow pack,
ambient temperature conditions, and precipitation.
During the filling period, flows through the project powerhouses are highly
dependent on projected and actual runoff conditions. These flows are used to manage the
runoff to maximize water storage while minimizing spills. In drier years, releases are
minimized during the filling period to increase the volume of water in storage to meet
upcoming summer consumptive use and peak power demands. In wetter years, releases
during the filling period are increased to minimize spills from the reservoirs. In years
when storage levels are expected to be adequate to meet consumptive demands and the
chance of spilling is low, releases are adjusted through the filling season based on the
volume of water in storage, projected runoff, and current and projected power demands.
Because the water available from runoff varies significantly from one year to the next,
the amount of water held in storage at the end of the filling period (July 1) also may vary
significantly.
During the release period, after the reservoirs have reached their maximum
capacity, monthly releases for generation are largely predictable for the remainder of the
year. However, daily and hourly releases for generation, which respond to demand for
electricity and electrical grid reliability, remain highly variable. During the release
period, flows are managed to: (1) meet storage and flow license requirements; (2) meet
consumptive water supply requirements; (3) optimize power generation to meet peak
electrical demand; and (4) achieve end-of-year carryover target storage levels.
Decisions on the extent of the drawdown and the carryover target storage level are
based on balancing competing needs including: (1) providing sufficient reservoir storage
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