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

20120723-4002 FERC PDF (Unofficial) 07/23/2012
to no effect on existing water quality. The proposed sampling methods and sites are
consistent with those in the Commission-approved pre-filing licensing studies, with the
exception of a new coliform sampling station on Duncan Creek downstream of the
proposed new primitive recreation site. The proposed coliform sampling locations are all
near locations where public recreational use is focused, and would document that the
sanitation measures in place are effective or whether changes to the facilities may be
needed.
Elevated levels of iron and manganese in water collected from leakage channels
immediately below French Meadows dam were observed during project relicensing
studies. The source of the iron and manganese is the rock and gravel dam material (local
source material). As water seeps through the dam, iron and manganese become soluble
under anoxic conditions. These conditions are partially related to low oxygen levels in
seepage water, but are otherwise not controllable. Water samples collected 800 feet
downstream showed concentrations that were within range of basin plan water quality
objectives due to oxygenation and dilution by instream flow releases and accretions
downstream from the leakage channels. Under the proposed and Alternative 1 actions,
minimum instream flow releases from French Meadows dam would be increased
(ranging from 8 to 20 cfs), thereby further diluting the water from the leakage channels
(see table 3.3.2-8) as the proposed action. PCWA’s proposed Water Quality Monitoring
Plan would monitor iron and manganese as part of its general water quality sampling.
Sampling results would document whether the expected decrease in downstream iron and
manganese concentrations occurs and provide a basis for assessing whether additional
actions may be necessary.
The Water Quality Monitoring Plan would confirm whether water quality
objectives are being met and proper conditions are being maintained for aquatic biota and
recreational users at the project for the term a new license. The Water Quality
Monitoring Plan includes protocols for modification of the monitoring program in
consultation with the resource agencies based on the monitoring results.
Project Effects on Spawning Habitat
The proposed Sediment Management Plan, discussed in detail in section 3.3.1.2,
Geologic and Soils Resources, includes measures to retrofit existing small diversion
structures on Duncan, South Fork Long Canyon, and North Fork Long Canyon Creeks
with self-cleaning, wedge-wire screen intakes on the upstream side of the diversion weirs
that would facilitate passage of sediment and woody debris over the diversion dams. In
addition, coarse sediment removed from Middle Fork interbay and Ralston afterbay
would be added to the river channel downstream of these two reservoirs at approved
augmentation sites. The Sediment Management Plan includes monitoring of sediment
transport in augmentation areas and monitoring of channel conditions associated with
augmentation activities. Additional monitoring related to fluvial geomorphic conditions
in the reach would also be conducted as part of implementation of the proposed
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