Condit Dam Removal Condit Dam Removal - Access Washington

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Condit Dam Hydroelectric Project Final Supplemental EIS • Condit Hydroelectric Project Sediment Behavior Effects on Beneficial Uses Report, G&G Associates, dated May 2004 Since the SEPA DSEIS, the following additional documents have been produced and were used to complete this Final SEIS: • Letter to Jim Hemstreet, Senior Engineer, at PacifiCorp re: Condit Dam and Northwestern Lake Hydrographic Surveys, Finley Engineering Company, dated August 8, 2006 • Biological Opinion and Magnuson-Stevens Fishery Conservation and Management Act Consultation. NMFS Northwest Region, Hydropower Division. NMFS Log Number 2002/00977, dated October 12, 2006 2.3.1 Issues Resolved Some of the potential impacts and unresolved issues initially identified by Ecology have since been determined not to be significant or have been resolved. These issues and impacts and the manner in which they have been resolved are discussed below and not further addressed in this SEPA Final SEIS. Issue 1: The natural gas pipeline crossing the upper end of the reservoir could be impacted by erosion and scour following removal of the dam. Resolution: Available information and drawings regarding the gas pipeline indicate that it is buried in a trench through bedrock. It is therefore not expected to be affected by scour. Issue 2: Critical aquifer recharge areas adjacent to the reservoir could be affected by removal of the dam and reservoir. Resolution: No adjacent area around the reservoir has been designated a critical aquifer recharge area by either Skamania or Klickitat Counties. Consequently, there would be no impact to critical aquifer recharge areas. Issue 3: Thermal refuge for fish at the mouth of the White Salmon River could be lost. Resolution: According to information provided by PacifiCorp, thermal refuge in the White Salmon River would not be lost, but would change in location. The bypass reach between the dam and the powerhouse is not a depositional area and contains deep pools that would provide thermal refuge for dip-in fish. Also, cold water from the White Salmon River after dam removal would provide thermal refuge near the mouth of the White Salmon River. Thermal refuge also would be available upstream of river mile 5 after dam removal. Finally, according to PacifiCorp’s analysis, after dam removal, water in the lower reach of the White Salmon River is expected to become colder even in those areas that become shallower, because the removal of the reservoir would eliminate a source of warming. 2-4
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. 2-5
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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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Contents Public Meetings Response P
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Contents Individuals Individuals A-
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