Condit Dam Removal Condit Dam Removal - Access Washington

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Condit Dam Hydroelectric Project Final Supplemental EIS 4.7.2 Impacts Pre-Dam Removal Activities There are no existing regulated emission sources at the project site, and any temporary or permanent new sources associated with dam removal are not expected to cause significant adverse air quality impacts. Pre-dam removal impacts could result from drilling the tunnel that would be used to drain the reservoir. Assuming liberal use of water during concrete drilling, little or no concrete dust should be made airborne during this activity. PacifiCorp project mitigation documents (dust control, etc.) do not speak to the potential to create dust during tunnel drilling. The final 15 feet of concrete would be blasted; however, the rush of water into the tunnel should negate that impact to the air. Road building would be necessary to gain access to the various areas of demolition. Road construction companies are familiar with regulations to minimize fugitive dust emissions, and use water and chemical binders during dry periods. Since much of the work would be during the wet season, road construction emissions are unlikely to present a problem. Ecology provides a number of pamphlets to assist construction companies to comply with fugitive dust rules, such as Windblown Dust (Publication #04-02-009); Building and Construction Projects (Publication 95-1004); and Outdoor Burning (Publication 92-04). Dam Breaching and Removal Temporary and intermittent dust would be created by the combination of concrete cutting and blasting used in the dam demolition. During blasting operations, blasting compounds sometimes create very localized hazardous and/or toxic emissions. These emissions would be of concern to workers during demolition activities. Blasting emissions are very intermittent and are not regulated by the agencies as a source. Demolition contractors will control safety of blasting operations and report to industrial oversight agencies. Post-Removal Management Post-demolition concerns are probably greatest for the sediments deposited in the reservoir. Some of these sediments would be fine particles capable of becoming airborne during dry weather with high winds. Since winds are channeled up and down the river valley, the potential to impact visibility in the Gorge would be a potential concern. PacifiCorp has scheduled the dam breaching for the typical beginning of the wet season and has taken care to provide dust control plans and characterize the sediments. Stabilization and revegetation is important for a number of reasons, including maintaining good air quality in the vicinity. Toxic chemicals such as pesticides were reported in only one sediment sample in the sediments, so it is assumed that the sediments are not a hazardous or toxic air pollutant concern. Wood debris exposed by draining the reservoir are unlikely to be of a fine enough grain size to become airborne off site, causing public exposure. 4.7.3 Mitigation Measures Mitigation measures are detailed in the dust control and revegetation plans (PacifiCorp 2004). PacifiCorp will implement all of the BMPs for dust control and revegetation of the 4.7-3
Condit Dam Hydroelectric Project Final Supplemental EIS sediments. Air quality in the area attains all standards, and visibility is a highly important natural attribute of the Columbia Gorge, which must be maintained during and after demolition. Some of the measures outlined in the mitigation plans are included below. • Implement the PacifiCorp proposed dust control plan with appropriate BMPs to reduce emissions generated by demolition activities and vehicular traffic. • Implement the PacifiCorp proposed revegetation plan and BMPs for erosion and sedimentation control. When the reservoir is drained, sediments would be exposed to sun and wind. The revegetation plan would require implementation to reduce local dust generation, although the sediments are probably too large to be carried beyond the immediate area, and would have no likelihood of impacting the Gorge areas. 4.7.4 Significant Unavoidable Adverse Impacts If the mitigation measures noted above are implemented fully and in a timely fashion, no significant unavoidable adverse impacts are expected. 4.7-4
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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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