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

20120723-4002 FERC PDF (Unofficial) 07/23/2012
Central Valley Steelhead (Draft Recovery Plan), also includes a conceptual scenario for
reintroducing steelhead to the North Fork American River, Middle Fork American River,
and South Fork American River (NMFS, 2009b).
On July 29, 2011, NMFS submitted comments, preliminary prescriptions under
section 18 of the FPA, and recommendations for terms and conditions under sections
10(j) and 10(a) of the FPA on the final license application for the Middle Fork American
River Hydroelectric Project pertaining to this potential future condition (NMFS, 2011).
Because passage above Nimbus and Folsom dams would bring steelhead into contact
with the project-affected reaches and facilities of the Middle Fork Project, NMFS
requests that additional measures be incorporated as conditions of the new license. Once
steelhead are introduced to waters upstream of the dams, NMFS will request an opening
of the project license, in accordance with their authority under the FPA, to prescribe
fishways and make recommendations for additional terms and conditions for the
protection of listed anadromous fish and their habitat.
3.3.2.2 Environmental Effects
Protecting Water Quality during Sediment Management
Sediment management is performed at the project’s three small diversion pools
(Duncan Creek, North Fork Long Canyon, and South Fork Long Canyon) and two
medium-sized reservoirs (Middle Fork interbay and Ralston afterbay) to maintain and
protect system reliability and is discussed in more detail in section 3.3.1.2, Geologic and
Soils Resources. Under existing conditions, sediment has routinely been excavated on an
as-needed basis (generally after episodic high-flow events) from the three small diversion
pools. PCWA proposes to modify the infrastructures at the three small diversion pools to
allow bedload and suspended load to be naturally transported past the diversion facilities
during high-flow events. This would reduce and potentially eliminate sediment removal
activities at the small diversion pools. Interim and contingency sediment management
activities may be conducted at the small diversion pools prior to and following
completion of the diversion dam modifications. During modification of the infrastructure
at the diversion dams, erosion and sedimentation could temporarily increase turbidity
levels in the adjacent water bodies. In addition, the accidental release of hazardous
materials from heavy equipment used during these activities could degrade water quality.
The proposed action also includes new sediment augmentation activities
downstream of Middle Fork interbay and Ralston afterbay. At these locations, it is
infeasible to modify the infrastructure to allow bedload material to pass downstream, so
active sediment removal by heavy equipment would be periodically necessary to
maintain safe and reliable project operations. During sediment removal activities at these
two medium reservoirs, a portion of the removed material (preferentially selected within
the preferred spawning particle size requirements of aquatic resources) would be placed
in the new sediment augmentation areas below Middle Fork interbay. At high flows, the
material would be mobilized and transported downstream to enhance aquatic resources.
97