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• GW-N33 and GW-N34). Measurements for static water levels began at these wells immediately <br />after they were completed and developed. All of the water level data are presented in <br />tabular and graphic form in Appendix 7-1. <br />Alluvial Water Levels. One alluvial monitor well (GW-N22) was installed at Nucla East to <br />monitor the unconfined alluvial aquifer system along Calamity Draw. Static water level <br />measurements have been taken at this site since July, 1986 (Appendix 7-1). There is <br />approximately 23 feet of unconsolidated material (alluvium) with an average saturated <br />thickness of 15.24 feet at this site. During the 1987 water year the maximum seasonal <br />water level fluctuation for this monitor well was about 3.6 feet, ranging from 5.62 to <br />9.22 feet below ground surface. Shalloni ng occurs at this well from April through <br />September when the irrigation ditches are flowing and irrigation of the local fields is <br />occurring. Water level fluctuations in this well are controlled by the perennial flow <br />patterns of the adjacent drainage (Calamity Draw) which returns much of the excess West <br />Lateral irrigation water to the San Miguel River located approximately two miles <br />downstream from this site. Water level responses to precipitation events are not <br />discernible as the effects of recharge from the irrigation ditches mask any water level <br />• fluctuations that may result from ground water recharge by precipitation. <br />Overburden Water Levels. Six monitor wells (CW-N15, GW-N18, GW-N1 BPi, GW-N21, GW-N31 and <br />GW-N32) have been installed to monitor water levels in the overburden aquifer system at <br />the Nucla East mining area. There are no overburden monitor wells located at the Nucla <br />Mine. Exhibits 7-1 and 7-2 shorv the overburden monitor well locations and the <br />potentiometric surface, respectively. Monthly water level data including hydrographs are <br />contained in Appendix 7-1. <br />Water in the overburden is unconfined or only slightly confining with a downward head <br />C <br />pressure. Saturated thicknesses penetrated by the overburden monitor wells range from <br />13.5 feet at Well GW-N31 to 70.7 feet at GW-N18. The mean saturated thickness is <br />approximately 24 feet. <br />Perusal of overburden water level data contained in Appendix 7-1 indicates that the <br />overburden water level fluctuations are a direct result of the operation of the ditch <br />irrigation system. During the 1987 water year, water level fluctuations in monitor wells <br />CW-N18, CW-N18P1, CW-N21 and GW-N 15 varied 18.4, 20.6, 23.3 and 11.4 feet, respectively. <br />• Water level sh allowi ng generally occurs from April to September when all the irrigation <br />7-7 Revised 04/11/88 <br />