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CHAPTERFOUR Environmental conseuuences <br />talus slopes could result in some destabilization of slope materials. However, the final detailed <br />pipeline routing would avoid azeas that have the greatest potential for creating unstable slopes <br />wherever possible. <br />Parachute Site <br />There would be no effect to geologic resources from the development of the processing facilities. <br />Accelerated Development Alternative <br />The direct and indirect impacts would be similar to the Proposed Action. <br />No Action Alternative <br />Under this alternative, mining activities at the test mine facility would likely cease. No further <br />extraction of nahcolite would occur. No subsidence would be likely to occur from the test mine <br />cavities. <br />4.1.3 Mitigation and Monitoring <br />In addition to the mitigation and monitoring discussed in Chapter 2.0, the BLM would require <br />that a monitoring well be installed in each mining panel and a suite of downholc~ geophysical <br />logs be run annually to assess subsidence. The monitoring well approach would be necessary <br />only if the Time Domain Reflectometry (TDR) method proposed by American Soda is not <br />acceptable for monitoring subsidence. <br />Several cavities distributed across the first mining panel should be monitored for subsurface <br />subsidence. Information gained from the program would be used to verify the thermomechanical <br />modeling and to determine whether monitoring of additional cavities is warranted. <br />4.1.4 Unavoidable Adverse Impacts <br />Under the three alternatives, no unavoidable adverse impacts aze foreseen. <br />4.2 SOILS <br />4.2.1 Introduction <br />Impacts to soils from construction of project facilities and from mining activities would include <br />changes in physical, chemical and biological properties. Impacts to fragile soils, especially <br />accelerated erosion of topsoil and loss of soil productivity to the extent that reveg:etation and <br />reclamation success would be impaired, aze the key issues for analysis of impacts to the soils <br />resource. <br />Such adverse impacts would result from the clearing of vegetation, excavation, st~lvage, <br />stockpiling and redistribution of soils during construction, mining and reclamation activities. <br />Blading or excavation to achieve desired grades could result in slope steepening of exposed soils <br />in cut and fill azeas, mixing of topsoil and subsoil materials and the breakdown of soil aggregates <br />4-4 Geology <br />