Condit Dam Removal Condit Dam Removal - Access Washington

Condit Dam Hydroelectric Project
Final Supplemental EIS
1.6 IMPACTS AND MITIGATION MEASURES
1.6.1 Beneficial Effects of Dam Removal
Since a major impetus for removing the Condit Dam is to provide benefits to fish, it is
appropriate to summarize the beneficial effects that are expected. This will allow a direct
comparison of the adverse effects in order to understand the tradeoffs of the proposed action.
The most notable beneficial effects would accrue to the fish and aquatic organisms that would
use the free-flowing stream. Potentially, 32 miles of new steelhead habitat and 15 miles of new
salmon habitat may be accessed by anadromous salmonids after dam removal, increasing the run
size of anadromous salmonids in the White Salmon River and increasing the availability of
salmon and steelhead angling opportunities in the White Salmon river basin. New thermal
refuge habitat for migrating Columbia River anadromous salmonids from other sub-basins also
will be accessible after the removal of Condit Dam. Additional stream habitat for resident fish
will be created in the lakebed of the former reservoir. Additionally, the small increase in water
temperature below Condit Dam from the discharge of warmed reservoir surface water will be
eliminated, improving the quality of thermal refuge, and the recruitment of gravel and large
woody debris from sources above the dam site will be reestablished. Foraging, wintering, and
refuge habitat, and possibly spawning habitat, will be created for Columbia River bull trout.
Juvenile anadromous salmonids will provide forage for bull trout, and salmon carcasses in the
watershed above the site of Condit Dam will provide an additional source of marine-derived
nutrients to the watershed. There will be more suitable substrate for stream-dwelling aquatic
macroinvertebrates after the stream substrate has stabilized.
In addition to benefits to aquatic organisms, there will be other changes that will benefit some
users and adversely affect others. For example, while there would no longer be reservoir-based
recreation opportunities, there would be river-based recreation opportunities, such as kayaking
and stream fishing.
1.6.2 Direct Impacts and Mitigation Measures
The impacts and mitigation measures for the proposed action alternative (dam removal) are
summarized by element of the environment in Table 1-1 at the end of this chapter.
1.6.3 Significant Unavoidable Adverse Impacts
Geology, Soils and Sediments
Downstream from the dam, movement of sediment through the channel and floodplain
redevelopment and formation are unavoidable adverse impacts. Therefore, much more sediment
will be deposited in the Bonneville pool of the Columbia River than with the Condit Dam in
place, especially at and near the in-lieu site at the mouth of the White Salmon River. The natural
sediment flux in the lower White Salmon River will then deposit into the Bonneville pool rather
than a free-flowing Columbia River. The sediment deposition will be a result of the Bonneville
dam.
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