Condit Dam Removal Condit Dam Removal - Access Washington

Condit Dam Hydroelectric Project
Final Supplemental EIS
road to the lower part of the dam. However, the seep would continue to generate water. The
new slope between the Powerhouse Road and the access road is likely to regrow wetland
vegetation. Therefore, there may be only a short temporal loss of wetland area and function
at this location.
Altogether, up to 3,055 square feet, or 0.07 acre of wetland would be filled for the access
road construction. About 2,000 square feet of the affected Wetland 12 would be dewatered
by the draining of the lake and would lose a key feature that makes it a wetland.
Dam Breaching and Removal
Lake-fringe Wetlands 2, 3, 7, 9, 11, 17, 18, 19, 20, 23, 24, and 25 would lose their primary
hydrologic source with the drawdown of Northwestern Lake. It is reasonable to assume that
all of Wetlands 7, 9, 11, 17, 18, 19, 20, 23, 24, and 25 would no longer be wetlands.
However, it is also reasonable to assume that part of Wetlands 2 and 3 would remain as
wetlands watered by a seep (Wetland 3) or an ephemeral stream (Wetland 2) or other runoff
and seepage from the slope not previously identified. Therefore, it is reasonable to assume
that Wetland 3 would shrink from a total of 1.3 acres to about 0.8 acre and that Wetland 2
would shrink from 1.6 acres to about 0.6 acre. The total reduction in lake-fringe wetland
would be approximately 2.8 acres.
Tributary riverine Wetlands 5, 8, 10, and 12 would decrease in size and extent below the
point where these streamside wetlands are influenced by the hydrologic patterns of
Northwestern Lake. Over time, the streams would cut down through the deposited delta
sediments and the adjacent wetland areas would no longer have wetland hydrology. A
reasonable assumption is that the wetland area would be reduced by half (0.5 acre total).
This reduction includes the 2,000 square feet of Wetland 12 that would be filled for the
access road. However, the tributaries will continue to be tributaries, and pockets of wetland
may develop along the route between the current lake edge and the restored confluence with
the White Salmon River. It is not unreasonable to expect that among the dozen or so
tributaries, that the collective area of associated new wetland would total 0.5 acre, and
perhaps as much as 2 acres (PacifiCorp 2004).
Slope/lake fringe Wetlands 3, 6A, 6B, and 21 would lose their lake-fringe components.
However, it is reasonable to assume that the seeps would influence additional areas
downslope at each location. This phenomenon has been accounted for regarding Wetland 3.
Wetlands 6A and 6B are located toward the upper end of the reservoir, where the slope
exposed by removal of the reservoir would be less than further downstream. However, the
sediments in the lake are relatively deep in that area, and any residual deposits directly
wetted by the seep or spring from above would likely become wetland. It is therefore
reasonable to conclude that Wetlands 6A and 6B would increase in size to 0.3 and 0.45 acre,
respectively. Wetland 21 is in an area with steeper and higher sidewalls, so it would
probably remain very narrow and increase less than 0.1 acre in size. The net increase in
wetland area at Wetlands 6A, 6B, and 21 would be expected to be 0.25 acre. It is also likely
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