Condit Dam Removal Condit Dam Removal - Access Washington

Condit Dam Hydroelectric Project
Final Supplemental EIS
4.2 WATER RESOURCES
The water resources discussed in this section include surface water features such as rivers,
streams, and lakes, as well as groundwater that might be affected by activities associated with
removal of Condit Dam, the resulting actions during removal, or the absence of the reservoir.
Adjacent areas that might affect the water also are discussed.
4.2.1 Affected Environment
The affected environment for water resources includes Northwestern Lake, the White Salmon
River downstream from Condit Dam, and the portion of the Columbia River downstream at the
confluence with the White Salmon River (Figure 4.2-1). Upland areas where work would occur
that could affect water resources include the area immediately surrounding Condit Dam, access
roads to work areas and staging areas, the tailrace from the power plant, the corridor occupied by
the wood stave pipe and power line, and spillway from the surge tank to the White Salmon
River.
Surface Water
The White Salmon River basin is approximately 386 square miles in area. The drainage basin is
typically rugged, and the river has eroded canyons into the basalt bedrock. The river is generally
narrow (30 to 60 feet in width), except at Northwestern Lake and near the mouth of the river at
its outlet into the Columbia River. Basin stream gradients are relatively steep, falling
approximately 6,800 feet from the headwaters to the Columbia River, although the gradient
decreases significantly in the last river mile. At river mile (RM) 0.5, the river emerges from the
narrow canyon and widens in an area referred to at the ‘Riffles’ prior to flowing into the
Columbia River.
The headwaters of the basin derive their water from snowmelt and glacial melt from the White
Salmon and Avalanche glaciers on Mount Adams at an elevation of approximately 7,500 feet
above sea level. Major tributaries to the river include Spring Creek, Cascade Creek, Trout Lake
Creek, and Rattlesnake Creek. Stream discharge is monitored at USGS gauging station
#14123500 at Underwood, approximately one river mile downstream of Condit Dam. Condit
Dam currently alters natural streamflow, and discharges vary based on inflow rates, seasonal
recreational use, and electrical power demand. Normal observed flows at the gauging station
average 900 cfs, with monthly averages ranging from approximately 550 cfs in October to 1,600
cfs in April (FERC 1996).
The White Salmon River is classified as a Class A (excellent) water body by Ecology. Several
studies of the White Salmon River have indicated that values for most water quality indices are
generally consistent with Ecology standards. In addition to hydroelectric power generation,
surface water in the project area is used for municipal and domestic supply and limited irrigation
(FERC 1996).
In addition to the White Salmon River, Northwestern Lake is fed by several smaller tributaries
that discharge directly into the lake. These tributaries include Buck Creek, Spring Creek, Little
Buck Creek, and Mill Creek to the west, as well as several small unnamed drainages on the east
4.2-1