Condit Dam Removal Condit Dam Removal - Access Washington

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Condit Dam Hydroelectric Project Final Supplemental EIS and west sides of the lake. The streams entering the lake on the western side typically have headwaters located along peaks and ridgelines at elevations of 2,500 to 3,000 feet in the Gifford Pinchot National Forest. Where the drainages enter the lake, small deltas have been deposited. Groundwater Groundwater in the project vicinity occurs in both unconsolidated sediments overlying the basalt bedrock and within the bedrock, typically within interflow zones (Ecology 1979). Groundwater discharges as springs where the basalt bedrock is exposed along the valley walls and contributes a significant amount of baseflow to the White Salmon River in the project vicinity (Ecology 1979). Specific groundwater flow direction information was not readily available, but based on the project vicinity geology and topography, groundwater flow is expected to be to the westsouthwest toward the White Salmon and Columbia Rivers on the eastern side of the river and lake, where the majority of activities (road construction, staging areas, demolition, etc.) will take place. A review of well logs in the project vicinity indicated that the majority of wells in the area appear to be completed to depths from 150 to 600 feet (Ecology 2005). The wells typically utilize groundwater occurring within the basalt, as surficial deposits tend to be fine-grained and thin in nature and do not represent a productive aquifer. Groundwater in the basalt aquifer is typically confined, and depths to groundwater within these wells ranged from 0 to over 200 feet below ground surface (bgs) (Ecology 2005). With the exception the City of White Salmon well, wells in the site vicinity are relatively small and are used for domestic purposes. The City of White Salmon Production Well #2 is located within the project area (Figure 3-4). This well is located adjacent to the east edge of Staging Area SA-3, which is proposed for use as concrete debris storage and/or disposal. The well was drilled to a total depth of 1,242 feet bgs and cased and sealed to 804 feet bgs, with open hole to the total depth. According to the driller’s log (Ecology 2005), silt to silty clay was encountered between ground surface and a depth of 91 feet bgs. Basalt bedrock was encountered at 91 feet bgs, and the boring encountered multiple basalt flows between 91 feet and the total depth of the well. A copy of the well log is included as Appendix B. The aquifer at the city well location is confined in nature, and the static water level in the well was at ground surface at the time of the well’s construction. The well was pump-tested at 1,380 gpm. Water quality information for the well was not readily available. 4.2.2 Impacts The individual activities that may affect water resources are described in more detail in the following subsections. Surface and groundwater features for this project are presented on Figure 4.2-1. Pre-Dam Removal Activities Pre-dam removal activities that may affect surface water and/or groundwater include: • Reinforcement of the Northwestern Lake Bridge 4.2-2
Condit Dam Hydroelectric Project Final Supplemental EIS Figure 4.2-1 Surface Water and Groundwater Features Color. Takes 2 pages, Starts on an odd numbered page. 4.2-3
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Condit Dam Removal Final SEPA Suppl
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March 23, 2007 Dear interested part
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Condit Dam Hydroelectric Project Fi
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Appendix A Memorandum of Agreement
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Appendix C Supplemental Aquatic Res
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Agency and Organization Letters and
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Agency and Organization Letters Con
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Contents Public Meetings Response P
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Contents Individuals Individuals A-
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