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CHAPTERTHREE Eml~ronmema~ Consequences <br />Since most of the environmental impacts for the Agency Preferred Alternative are the same as <br />the Proposed Action, this analysis is tiered to the discussion of the Proposed Action presented in <br />the Draft EIS. Only changes in the impact analysis brought about by the inclusion of the <br />additional mitigation/monitoring plans or other changes specific to the Agency Preferred <br />Alternative are discussed in the environmental consequences analysis. <br />3.1 GEOLOGY <br />3.1.1 Direct and Indirect Impacts <br />Impacts to geologic resources from implementing the Agency Preferred Altemative would be <br />similaz to those described under the Proposed Action. However, the likelihood of long-term, <br />adverse impacts occurring would be reduced through implementation of the monitoring and <br />mitigation plans discussed below. <br />Piceance Site <br />Impacts to geologic resources under the Agency Preferred Alternative would be similar to those <br />described for the Proposed Action. However, monitoring and mitigation described in the <br />Subsidence Monitoring Plan requires American Soda to monitor for potential surface subsidence <br />at 27 stations within the 0-5 yeaz mine panel and future mining panels. Additionally, Time <br />Domain Reflectometry (TDR) and downhole geophysical logging aze required to assess <br />subsurface movement. If subsurface movement is greater than thresholds presented in the plan, <br />American Soda would implement mitigation measures. These measures (e.g., potential <br />modifications to mining methods) would help minimize adverse impacts to the overlying oil- <br />shale-rich beds in the Mahogany Zone from subsidence. Under the plan, American Soda is also <br />required to evaluate technologies for assessing solution cavity shape and to select a method by <br />June 2000. This method would be used to map cavity development in order to ensure maximum <br />nahcolite recovery while maintaining subsurface stability. <br />Pipeline Corridor <br />Impacts would be the same as those described for the Proposed Action. <br />Parachute Site <br />Impacts would be the same as those described for the Proposed Action. <br />3.1.2 Unavoidable Adverse Impacts <br />No unavoidable adverse impacts aze expected, similaz to the Proposed Action. <br /> <br />Geology 3-1 <br />