2016-10-28_PERMIT FILE - C2010089A (27)

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ditch with a TDS of 500 mg/l and lower (although a slightly higher pH of 8.0 and higher) has no detrimental effects on plants as witnessed by the success of irrigation in the area. Since the early part of this century, it has been a regional practice to obtain water for irrigation from the San Miguel River. Because of the incised nature of the drainage channels, it is difficult to flood irrigate from them. From field reconnaissance investigations, no cases of water being pumped from these draws for irrigation purposes, has been discovered. Sub -irrigation A small amount of sub -irrigation does occur along the drainage channels. Much of the ground water along these draws is a result of seepage through the weathered zone of the bedrock from the irrigation ditches. In areas where the sub -irrigation occurs, the vegetation and soil quickly dry up when the ditch is turned off from October to April. The sub -irrigation along the drainage bottoms of the NHN permit area is not considered extensive enough to support agricultural development. Conclusion DRMS concluded in its Decision and Findings of Compliance Document (1983) for Peabody's New Horizon Mine that no alluvial valley floors exist in either the New Horizon permit area or the potentially affected area (Tuttle Draw) associated with the New Horizon Mine. The tributaries of Tuttle Draw and Coal Creek Canyon are developed on and have incised a dip slope. The water in the drainages runs on top of weathered bedrock strata. The incised channels, with perennial flow, make it infeasible to construct a gravity flow flood irrigation system. NHN therefore concludes that no alluvial valley floors exist along the potentially affected area of Tuttle Draw and Coal Creek Canyon and their tributaries. This conclusion is substantiated by the results of an EPA alluvial valley floor study (EPA 1977) which addresses most coal mining areas of the west and the fact that flood irrigation from drainages is not being practiced. Hydrology Monitoring Plan NHN has developed a baseline hydrological monitoring program for the NHN Permit area with the advice and consent of DRMS. This monitoring program will continue for the foreseeable future and is proposed to be used with possible minor modifications during the mining and reclamation operations. The monitoring program is described in Appendix 2.05.6(3)-3 of this Section 2.05.6(3). B) PROBABLE HYDROLOGIC CONSEQUENCES Previous mining by NHN at the New Horizon Mine and Peabody's experience while mining at the old Nucla mine have provided the experience upon which the determinations of "Probable Hydrologic Consequences" are founded. This experience is documented in the New Horizon 1 and New Horizon 2 permit documents and the "Annual Hydrology" reports. The knowledge provided by the long term hydrologic monitoring in relation to the earlier baseline data allows more accurate prediction of consequences than would otherwise occur. Peabody Coal Company performed extensive and detailed computer modeling to determine probable hydrologic Section 2.05.6(3) Page 10 April 2016 (PR -01)