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

20120723-4002 FERC PDF (Unofficial) 07/23/2012
During placement of the material at the sediment augmentation areas, 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 Sediment Management Plan contains specific Forest Service BMPs
and avoidance and protection measures to protect water quality during sediment
management activities, including:
• Restricting sediment management activities to the dry season when rain and
runoff are unlikely to occur, to minimize erosion
• Restrictions on the use of equipment to avoid soil compaction and excessive
rutting and to avoid wetted areas to minimize erosion
• Construction of drainage facilities or other erosion and sedimentation control
measures in conjunction with earthwork
• Erosion control measures including planting stabilizing vegetation and
mechanical measures (straw waddles, riprap, silt fencing, etc.)
• Creation of a Spill Prevention, Contamination, and Counter Measures Plan to
guide response to spills and discovery of hazardous materials
• Implementation of measures to prevent pollutants from being discharged into
rivers, streams, or other impoundments
• Controlling in-channel excavation to minimize the in-channel disturbances and
associated sediment production
• Carefully planning the diversion of stream flows around construction sites to
minimize downstream fine sediment delivery and to restore channels to their
natural grade, condition, and alignment as soon as possible.
In addition, PCWA proposes the following water quality protection measures for
sediment augmentation downstream of Middle Fork interbay:
• Prior to placing sediment in the augmentation areas, the instream flow release
from Middle Fork interbay would be temporary diverted into a bypass pipe that
extends to a location downstream of the augmentation areas. The intent is to
reduce initial mobilization of fine sediment during placement of the material.
• A silt screen would be placed downstream of the sediment augmentation areas
to capture fine sediment. Fish present in the area between the dam and silt
screen would be removed and placed downstream prior to implementation of
these activities.
The proposed Sediment Management Plan also includes several types of
monitoring, including turbidity monitoring at the three small diversions and two medium
reservoirs, methylmercury monitoring in the sediment and water column at and
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