2008-02-22_APPLICATION CORRESPONDENCE - C2008086 (39)

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CHAPTERFOUR Environmental Consequences and Mitigation Access Road The proposed construction of the access road (CR X) will traverse approximately 2.4 miles and also impact the following soil map units: • Killpack-Persayo complex; 3 to 25 percent slopes • Killpack-Badlands-Persayo complex; 3 to 12 percent slopes; saline • Leebenchtyarm-Avalon complex; 3 to 12 percent slopes The impacts, risks, and hazards associated with these soils are the same as the proposed rail spur. Temporary Impacts Construction activities can have serious detrimental effects on the soils on construction sites. Topsoil removal, grading, and filling drastically reduce soil quality on these sites, resulting in long-term adverse impacts on plant growth and runoff. Another construction practice is allowing heavy equipment and even smaller construction vehicles to drive or park on the site. The vehicles compact the soil and compaction lowers the rate or water infiltration and reduces the available water-holding capacity (MRCS 2004). Unimproved roads with soils derived from Mancos shale may be impassable when wet due to the sticky and slippery nature of these soils. Erosion from construction sites has offsite environmental and economic impacts. Erosion creates two major water quality problems in surface waters and drainageways, excess nutrients and sediment. Both impacts create unwanted biological growth and turbidity that degrades the habitat for fish and other aquatic organisms. Sediment can accumulate in stream channels, lowering the flow capacity and causing more frequent flooding in areas that were never flooded or were only rarely flooded in the past (MRCS 2004). This total area of temporary disturbance would be reduced through successful reclamation as described in the Mitigation Measures section. Permanent Impacts Permanent impacts would result from soil-disturbing activities related to construction of the mine, facilities, and associated linear features. Impacts resulting from construction of the mine site and associated facilities could include removal of vegetation, exposure of the soil, mixing of soil horizons, soil compaction, loss of topsoil productivity, and increased susceptibility of the soil to wind and water erosion. The project would permanently impact approximately 452 acres of soil. Mitigation Measures Reclamation and Revegetation Soils suitable to support plant growth would be salvaged for use in reclamation. Soil stockpiles would be protected from disturbance and erosional influences. Soil material that is not suitable to support plant growth would not be salvaged. Soil or overburden materials containing potentially harmful chemical constituents would need to be specially handled. After soil is replaced on reclaimed surfaces, revegetation would reduce erosion. The mine would construct sediment control structures as needed to trap eroded soil. 4-79 DBMS 634