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<br /> <br />the alluvial aquifer, the quantity and quality of the water available For sub- <br />irrigation would be affected. <br />As discussed in our summary of the applicant's statement of probable <br />hydrologic effects, these effects would be short termed. With reclamation and <br />removal of the sediment control system, these effects would be mitigated. Most <br />of the mining that would occur in the Bolton Draw watershed has already occurred <br />under the previously permited operations. Reclamation activities would be com- <br />pleted by the end of 1982. At that time the effects that have already occurred would <br />be reduced. <br />3. Surface coal mining and reclamation operations would be conducted to <br />oreserve, throughout the mining and reclamation process, the essential hydrologic <br />functions of the alluvial valley floor. <br />Mining operations would not physically disturb the alluvial valley floor. <br />With successful reclamation and removal of the sediment control system the surface <br />water flow to the draw would be restored and water chemistry would return to <br />natural conditions. <br />The applicant has suggested that the release of sediment deficient waters <br />from the sediment ponds would cause downstream erosion (780-124). Should this <br />occur, the erosion would begin immediately downstream from the sediment ponds <br />on unnamed tributaries to Bolton Draw. Civen the infrequent nature of streamflow <br />in this area, erosion would be observed and could be mitigated before it could <br />spread to Bolton Draw, and cause channel incision in the Alluvial Valley Floor. <br />Alluvial Valley Floors - Sudduth Draw - Findings <br />1. The proposed surface coal mining operations would not interrupt, discontinue, <br />or preclude farming on an alluvial valley floor. <br />None of the proposed mining operations would be located within the alluvial <br />valley floor. The final mining activities in pit three would be located immediately <br />adjacent to the alluvial valley floor. A buffer would be left along Sudduth Draw, <br />according to Map lSa no mining activities would encroach upon the AVF. <br />2. The proposed operations would not materially damage the quantity and quality <br />of water in surface and underground water systems that supply those alluvial <br />valley floors or portions of alluvial valley floors. <br />Mining in the Sudduth Draw watershed would affect the quantity and quality <br />of surface water supplied to the alluvial valley floor as described in the <br />applicant's statement of probable hydrologic consequences (p. 780-123 to 780-126jjjjj). <br />Mining would reduce surface flow in Sudduth Draw by approximately 3e of the annual <br />yield. The ion balance of the surface water would be altered, and salt Loading <br />on the stream would be increased by 2.7 Kg/yr. These changes do not represent a <br />significant change in surface water quantity or quality. As discussed in the <br />sulmnary of probable hydrologic consequences, the effects are temporary and would <br />be mitigated by reclamation. <br />3. Surface coal minin_q and reclamation operations would be conducted to <br />preserve throughout the mining and reclamation process, the essential hydrologic <br />functions of the alluvial valley floor. <br />hfining operations c/ould not physically disturb the alluvial valley floor. <br />Minor changes in surface water supplied to the alluvial valley floor (discussed <br />above) would occur during the mining ohase of the operation. With successful <br />_17_ <br />