2012-05-04_GENERAL DOCUMENTS - C2010089

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there is separation of the three zones (underburden, coal, and overburden). Groundwater flow direction in each zone is generally to the southwest towards topographic lows. Discharge is down dip to the outcrops and old Peabody high-wall (see Map 2.04.5-1 of the permit document). Previous aquifer testing of the Dakota Formation coal strata in the NHN area indicates that the overburden, coal, and under-burden zone transmissivity and hydraulic conductivity values in the NHN area are low to very low; see Tables 7-5 and 7-6 in Appendix 2.04.7-1 of the permit document. The aquifer characteristics (production potential) of the three stratigraphic zones indicate that they are marginal at best for domestic use and totally inadequate as a source for irrigation water. Water level monitoring and the piezometric maps show that each monitoring zone is directly affected by surface irrigation. The water levels decline in the fall and winter, after the irrigation nd water is shut off in the “2 Park Lateral,” and rapidly recover in the spring when the irrigation flow resumes. WFC concludes that the predominant source of recharge to the shallow saturated nd zones at the NHN permit area is direct leakage from the 2 Park Lateral irrigation ditch where it crosses the outcrop of each of the respective zones, over-burden; coal; and under-burden (OB, Coal, UB), and infiltration of excess flood irrigation waters into the weathered overburden. Minor recharge also results from infiltration of precipitation. Groundwater migrates through the OB, coal and UB zones downdip to the southwest toward the bedrock outcrop. Given the calculated hydraulic conductivity values, gradients, and cross-sectional areas, WFC estimates that the total migration of groundwater from NHN through these shallow bedrock zones at the rate of only 3.3 gpm would account for the entire amount of water available for infiltration. Groundwater data collected from the nine monitoring wells constructed in the three isolated saturated zones of the Dakota Formation were compared to WQCC Regulation No. 41 Drinking Water and Agricultural Standards. This comparison shows that the OB, Coal, and UB zones in the NHN permit area are unsuitable for domestic drinking water and crop irrigation. The overburden and under-burden zones in most cases, however, would be marginal for livestock; the coal zone would not. Low permeability, cyclic water levels, and resulting low well yields greatly reduce any potential use of water from the three strata OB, Coal, and UB. The water quality data from the 9 new monitoring holes supplements the water quality data reported in the New Horizon 1 permit documents. Ground water monitoring holes GW-N8 and GW-N9, installed by Peabody for the old Nucla Mine, are within the NHN permit area. Several other monitoring holes, GW-N3, GW-N4 and GW-N4R, are in close proximity to the NHN permit area and provide additional water quality information. NHN permit area is isolated from any potential impacts from the nearby New Horizon (NH2) Mine as a result of stream incision of the three stratigraphic zones (OB, Coal, and UB) by Tuttle Draw. Additionally, the old Peabody Nucla Mine is down dip and down drainage from NHN which essentially eliminates impacts to the NHN permit area from the old mine. During the review process for the NHN new permit application and given the information we now have as provided on geologic cross-sections, piezometric level maps, and the proposed disturbance boundary the Division believes that one additional group of nested wells is warranted. The reason for this is that the full extent of the disturbed area is not being monitored in the downgradient direction (i.e., the southwest end of the southernmost mineable block). This 9