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• underburden monitor well site locations and the potenti ometric surface, respectively. <br />Monthly water level data including hydrographs for each site may be found in Appendix 7-1. <br />Cround water in the underburden aquifer is under artesian conditions. Mean artesian heads <br />in the underburden aquifer range from 9.7 feet at Monitor Well GW-N11 to 66,7 feet at <br />Monitor Well GW-N33. The average artesian head for the underburden aquifer is 40.0 feet. <br />A downward vertical head is generally observed in the underburden but an upward <br />(recharging) vertical head is exhibited at Monitor Well GW-N 16. All of the underburden <br />monitor rrells at Nucla and Nucla East display seasonal variability to some degree. The <br />seasonal water level fluctuations at the Nucla and Nucla East mining area range from only <br />a fen tenths of a foot at Monitor Wells GW-N3 and GW-N11 to nearly 11.0 feet at monitor <br />well GW-N13. All of the underburden monitor wells exhibit steady-state water levels over <br />time with the exception of Monitor Wells CW-N1, GW-N1P1 and GW -N6. These wells have <br />displayed a slight shallowing trend with time. There are no distinguishable effects from <br />the mining operation at Nucla Mine or recharge from precipitation events on the <br />underburden aquifer system. <br />• Spoil Water Levels. Four monitor wells (GW-N10, GW-N26, GW-N27 and GW-N28) have been <br />installed to monitor water levels in the spoil aquifer at the Nucla Mine. Exhibit 7-1 <br />sh ors the spoil monitor well locations. Monthly water level data ilncl udi ng hydrographs <br />are contained in Appendix 7-1. <br />The spoils aquifer is dry or nearly dry except for the area in the vi eini ty of GW-N27. At <br />this location the spoil aquifer has approximately 6.4 feet of saturation. This well was <br />installed in August of 1987 and will require further monitoring to determine annual water <br />level fluctuations and long term trends. <br />Multiple Completion Well Water Levels. Five wells with multiple seam completions have <br />been installed at the Nucla Mine (Exhibit 7-1 ). Monitor Wells GW-N8 and GW-N9 were <br />installed in the overburden and the Dakota coal aquifers northwest of the Nucla Mine. <br />Monitor Wells GW-N23, CW-N 24 and GW-N 25 are located in what has been referred to as the <br />scraper area in the southeastern portion of the permit area. Those monitor wells were <br />completed in early June, 1986 in the overburden, Dakota coal and underburden aquifers. <br /> Water level information indicates that the scraper area monitor wells are dry. Water <br />• level information has been gathered for Monitor Wells GW-NB and GW-N9 on a monthly basis <br />7-9 Revised 04/11/88 <br />