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

20120723-4002 FERC PDF (Unofficial) 07/23/2012
small diversion pools, so any positive effect of the proposed project on habitat
downstream of the diversion dams would be small. As part of the Sediment Management
Plan, post-construction effectiveness monitoring would be conducted at the small
diversions to document the ability of structures to pass LWD. If the proposed diversion
dam modifications are not effective in passing woody debris downstream, other options
identified in an LWD management plan could be considered.
Our analysis indicates that the only facility where LWD management may be
warranted is at Hell Hole reservoir and dam. Identifying alternatives to the practice of
burning LWD removed from the reservoir onsite would have the benefit of reducing air
emissions associated with burning and could result in a minor enhancement of aquatic
habitat. However, there is no evidence that lack of LWD is limiting the quality of aquatic
habitat in the Rubicon River downstream of Hell Hole dam. The LWD management plan
specified by the Forest Service would enable options for moving LWD downstream of
Hell Hole dam to be identified and potential locations where LWD could be placed in the
active river channel. This information would provide a basis for determining if
placement of LWD in the active Rubicon River channel is warranted and feasible given
the amount of LWD that is already present in the reach immediately downstream of the
dam. Developing the specified Forest Service plan would enable specific protocols for
disposing of LWD to be established and implemented upon Commission approval. As
such, developing an LWD management plan focused on the Hell Hole development may
reduce atmospheric emissions if onsite burning of LWD is reduced or eliminated.
The Forest Service specifies that the LWD management plan describe the location
of LWD collection by project facilities. PCWA describes the existing locations of LWD
collection by project facilities in its geomorphology technical study report (PCWA,
2009). Transferring this information into an LWD management plan would provide
background information and support the rationale for any potential changes to woody
debris management.
Monitoring the Response of Project-Affected Stream Reaches to Altered
Flows and Sediment Management
PCWA proposes to implement its Geomorphology and Riparian Monitoring Plan
to enable documentation of the effects of its proposed sediment management and altered
flow regimes in project-affected reaches on channel and shoreline habitat. The objectives
of this plan are to monitor channel and sediment conditions and riparian vegetation
communities at 10 sites in the bypassed and peaking reaches. Monitoring would include
photo documentation, survey of channel cross sections, measurements of residual fine
sediment in pools, and riparian vegetation mapping. Data from the monitoring would be
used to evaluate the effectiveness of sediment augmentation and pulse flow measures and
identify the need for potential adjustments to both. Forest Service 4(e) condition no. 28
includes the Geomorphology and Riparian Monitoring Plan among the plans that still
need to be finalized. The Forest Service did not indicate if and what issues remained to
be resolved to finalize the Geomorphology and Riparian Monitoring Plan. Therefore, for
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