2013-07-19_PERMIT FILE - C2010089A (3)

Home Browse Search

Irrigation The NHN Permit area has (since about 1910) and is currently serviced by an extensive man-made irrigation system. The water, primarily used for flood irrigation, is diverted from the San Miguel River approximately 15 miles east of the New Horizon North Mine by the Colorado Cooperative Ditch Company. The irrigation ditches transect drainage basins and commonly run along the basin divides (see Map 2.04.7 -1 for the location of the main irrigation ditch at NHN permit area.). The main irrigation ditches have a network of feeder ditches running from them for irrigating more distant fields. These ditches are a source of ground water recharge, causing ground water mounding in the shallow ground water bedrock system. The effects of seasonal water mounding near the NHN permit area are apparent from monitor well water levels and hydrographs (see Appendix 2.04.7 -1 of Section 2.04.7). Perennial flow occurs in Tuttle Draw and Coal Creek Canyon tributaries as a result of ground water discharge and return flow from the irrigation of the upland area. Site inspections confirm that water used for irrigation is obtained from the San Miguel River and no flood irrigation water is obtained from Tuttle Draw or Meehan Draw. In regard to the agricultural water quality standards, the San Miguel River water delivered by the irrigation ditches is more suitable for irrigation purposes than the waters in the Tuttle Draw or Coal Creek Canyon tributaries. The agricultural suitability (National Academy of Sciences. 1972. Water Quality Criteria 1972:National Academy of Engineering, Washington, D.C.. p. 335) of surface water in the permit area falls within the category of water that can only be used for salt tolerant plants on permeable soils with careful management practices (TDS from 2,000 to 5,000 mg/1). Using the same classification system, water supplied by the 2 Park Lateral irrigation ditch with a TDS of 500 mg/1 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 Section 2.05.6(3) Page 10 November 2011