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

20120723-4002 FERC PDF (Unofficial) 07/23/2012
aquatic habitat degradation, as discussed in section 3.3.1.2, Geologic and Soils
Resources. It is uncertain whether there currently exist alternative release points that
could be used to minimize potential effects when project flow conduits need to be
drained. If there are, some release points may be better than others. Therefore,
consistent with Forest Service condition no. 32, we recommend that PCWA develop a
plan for Commission approval that evaluates penstock and other drainage structure
release points to document whether or not options for dewatering release points are
available for each project flow conduit and, if so, which option would minimize adverse
effects. The plan should include provisions for assessing site-specific conditions
associated with each option so that a proactive protocol of prioritizing release points can
be developed that would minimize the potential for increased slope instability or
adverse effects on aquatic habitat. The benefits of such a plan would be worth the
estimated levelized annual cost of $800.
Woody Debris Management Plan
Currently, PCWA conducts LWD management on an as-needed basis at all
project impoundments except French Meadows reservoir. Forest Service condition no.
29 specifies that PCWA file an LWD management plan that describes existing location
of LWD collection by project facilities, describes potential options for moving LWD
below project facilities and keeping it in the river corridor, and identifies suitable
locations where PCWA can place LWD within the active channel for mobilization by
high flow events. With the implementation of our recommended small diversion dam
screening systems, PCWA would pass woody debris downstream of these three
diversion dams and there would be no need for LWD management. Woody debris that
accumulates in Middle Fork interbay and Ralston afterbay is currently flushed through
the spillway gates, typically every 5 years. Thus LWD is already made available to the
reaches downstream of these two dams and there would be no need for woody debris
management at these two developments.
Currently, PCWA removes LWD from Hell Hole reservoir and typically burns it
on site. Identifying alternatives to this practice that would restore the supply of LWD to
the Rubicon River downstream of the dam could reduce air emissions associated with
burning and provide a slight enhancement to channel morphology and associated habitat
(as discussed in section 3.3.1.2, Geologic and Soils Resources). The Forest Service
condition does not focus on any specific project development and therefore the specified
plan could include all project facilities. However, our analysis indicates that there is no
need to assess LWD transport downstream of other project impoundments. Therefore,
we recommend that PCWA develop an LWD management plan for Commission
approval that focuses on identifying viable options for removing LWD from Hell Hole
reservoir and placing it in the active channel of the Rubicon River. Given the expected
limited scope of this plan, the modest estimated levelized annual cost of $1,400 would
be worth the expected environmental benefits.
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