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to the San Miguel River located approximately two miles downstream from this site. Water level <br />responses to precipitation events are not discernible as the effects of recharge from the <br />irrigationditches mask any water level fluctuations that may result from ground water recharge by <br />precipitation. Monitoring of this well was discontinued after New Horizon 2 Mine became <br />operational. In May 1993, it was replaced by two wells (GW-N39 and GW N40) along the Calamity <br />draw. The upstream well (GW-N39) is located in the flood plain near Lincoln Street in the south- <br />east corner of the mine while the downstream well (GW-N40) is located down gradient of the mine <br />but up gradient of the Nucla waste lagoons in Calamity Draw. <br />Overburden Water Levels. Eight monitor wells (GW-N15, GW-N18, GW-N18P1, GW-N21, GW- <br />N31, GW-N32, GW-N41 and GW-N44) were installed to monitor water levels in the overburden <br />aquifer system at the New Horizon 2 mining area. Maps 2.04.7-1A and 2.04.7-2 show the <br />overburden monitor well locations and the potentiometric surface, respectively. Monthly water level <br />data including hydrographs for New Horizon 2 Mine are contained in Appendix D of Attachment <br />2.04.7-5 Hydrological Monitoring Plan. In May 1993, an additional well, GW-N36, was drilled in the <br />north-east corner of the permit area. <br />Water in the overburden is unconfined or only slightly confining with a downward head pressure. <br />Saturated thicknesses penetrated by the overburden monitor wells range from 13.5 feet at Well <br />GW-N31 to 70.7 feet at GW-N18. The mean saturated thickness is approximately 24 feet. <br />Perusal of overburden water level data contained in Appendix D of Attachment 2.04.7-5 indicates <br />that the overburden water level fluctuations are a direct result of the operation of the ditch irrigation <br />system. During the 1987 water year, water level fluctuations in monitor wells GW N18, GW-N 18P1, <br />GW-N21 and GW-N15 varied 18.4, 20.6, 23.3 and 11.4 feet, respectively. Water level shallowing <br />generally occurs from April to September when all the irrigation ditches are flowing and flood <br />irrigation is occurring. Water level responses to precipitation events are indistinguishable, as the <br />effects of recharge from the ditch irrigation system have masked any evidence of recharge that <br />could be attributable to precipitation. Mining at the New Horizon 1 area has had no discernible <br />affects on the water levels of the overburden monitor wells. <br />Dakota Coal Water Levels. Ten monitor wells were installed to monitor water levels in the Dakota <br />coal aquifer. Two of the monitor wells (GW-N4 and GW-N4R) were located at New Horizon 1 and <br />2.04.7-9