Condit Dam Removal Condit Dam Removal - Access Washington

Condit Dam Hydroelectric Project
Final Supplemental EIS
Based on telephone conversations with local WDFW, National Oceanic and Atmospheric
Administration (NOAA) (formerly NMFS), and USFWS biologists, observed behavior patterns
of dip-in anadromous salmonids indicate that they utilize deep pools throughout the bypass reach
for thermal refuge. The increased flows in the bypass reach and colder water after dam removal
would increase both the quality and quantity of thermal refuge habitat, compensating for any
potential loss of thermal refuge below the bypass reach.
Issue 4: Temporary migration impacts to steelhead associated with the presence of the
cofferdam after the dam is removed could occur.
Resolution: PacifiCorp has committed to remove the cofferdam by May 1 of the year following
dam removal to prevent blocking passage for migrating salmonids. The FSFEIS (FERC 2002)
indicates that the entire year-class of age-0 (juveniles produced during the spring of the year of
dam removal) winter-run steelhead are expected to be lost as a result of turbidity levels in the
river associated with the proposed dam removal. According to PacifiCorp, the cofferdam would
be removed in time for the following summer run to pass unobstructed. PacifiCorp does not
anticipate migration impacts to winter or summer steelhead from the cofferdam.
The FSFEIS acknowledges the loss of most of the fish in the river channel at the time of dam
removal and the loss of a year-class of winter-run steelhead as a result of turbidity levels
associated with dam removal. The cofferdam would be removed in time for summer steelhead,
salmon, and subsequent year-classes of winter-run steelhead passage to upstream habitat. Thus,
unavoidable impacts to fish from dam removal have been recognized. There is enough overlap
in the life history of winter-run steelhead (i.e., a portion of adult winter-steelhead from other
year-classes will return to the White Salmon River during the years that adults from the lost yearclass
would have potentially returned) that the run from that year-class would likely rebuild over
the long term.
Issue 5: There is a potential for erosion and scour impacts to the structural stability of the two
downstream bridges (one highway, one railroad) across the White Salmon River.
Resolution: The supports for the downstream highway and railroad bridges are located in the
slack water pool at the mouth of the river created by Bonneville Dam. These bridge supports
have withstood historical flood flows, including the flow from the 1996 flood estimated at
45,000 cfs. The highest flow anticipated from the dam breach is 10,000 cfs. Because the dam
breach flows are less than one-quarter the flow from the 1996 flood, no significant erosion or
scour impacts are anticipated from the short-term high flows associated with the dam breach.
2.4 SCOPE OF THIS SEIS
The focus of this SEPA SEIS is the “Settlement Agreement with Modifications” alternative,
since it was the FERC staff-recommended alternative in the FSFEIS. The description of that
alternative has been supplemented with additional detail provided by PacifiCorp. The no-action
alternative and its analysis from the FEIS is adopted and not further addressed. In the FSFEIS,
FERC considered an adequate range of alternatives, which are not addressed further here.
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