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2.04.7 <br />documentation existsforthemorerecentlydrilledholes. Many of the deeper <br />holes were drilled with mud, such that the static water level recorded should <br />be considered dubious at best. Any holes drilled with bentonite based mud <br />can greatly inhibit the hydrologic properties due to mud cake within the drill <br />hole. When air and foam are used as a drilling medium, the hydrologic <br />conditions of the in-situ rock are virtually unaffected, and observation of <br />subtle inflow or lost circulation zones are greatly enhanced. The progress of <br />these holes was monitored in the field and recorded by competent personnel. <br />Drill holes 13, 15, 16, 25, 346, 38, 39, 42, 49, 52, 54, and 55 were completed <br />as monitoring wells in the bedrock following exploration. Refer to section <br />2.05.6 for further discussion of the deep bedrock groundwater monitoring <br />program. <br />Lower Perched Water Zone and Rollins Sandstone <br />A sufficient number of data points were obtained from the drill holes to plot <br />the potentiometric surfaces on the maps. As seen on Maps 10 and 11, the <br />• potentiometric contours fit the geohydrological setting of the permit area in <br />that the saturated horizons (or potentiometric surface) gently dip northward, <br />following the structural attitude of the bedrock horizons. <br />The Rollins Sandstone in the permit and adjacent area is characterized as <br />dry along the outcrop and develops piezometric head as the formation dips <br />to the north. Monitoring well DH-346, NM4-98-29 and TC-03-01(R) are <br />completed in the Rollins Sandstone. The water level in all three wells is <br />under artesian conditions ranging from 200 to 475 feet. Monitoring well <br />NM4-98-29 was located underground in the Bowie No. 2 Mine, D-Seam north <br />mains. Oxbow has two wells completed in the Rollins Sandstone (SC-1 & <br />SC-2) and they are also reported to be under artesian conditions (SMC <br />permit section 2.04.7). Mountain Coal Company has one well completed in <br />the Rollins Sandstone (SOM-128-H) which is also under artesian conditions <br />(MCC 1994 AHR). The quality of the water in the Rollins Sandstone is poor <br />with the Bowie No. 2 Mine wells exhibiting betterqualitythan adjacent mines. <br />The following table presents typical values for selected chemical parameters <br />from the water in the Rollins Sandstone from the three mines referenced <br />above: <br />• <br />PR-09 <br />~~p/zovE~ <br />I a~~-~o5 <br />2.04 - 26 - <br />09/05 <br />