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PROBABLE HYDROLOGIC CONSEQUENCES <br />CHIMNEY ROCK MINE <br />.•~...,.~zzs's::::x's::<+:s:::a:-x;:~:x~~ ;;~.ss.~;axti ~.N.c:;:;r.'~;:a:•.~:.: ~a~;>;'w:.rs?~sxsxw; -:::::z.:::y„r e::c~:::::~:m:a~:;ss:.::x'.z^:~:rx;;.m<uz:;:cr:;ra'xa~~ ::~ x:•~z.:r:e~;- exc~ ::~:a;w ~x::: a'^: <br />INTRODUCTION <br />Rule 2.04.6(3)(b)(iii) and Rule 2.05.6(3)(b)(iii) require probable hydrologic consequences for <br />mining operations to be determined. This rule further defines that these consequences must be <br />defined for both the permit and adjacent area, for quantity and quality of waters, and for surface <br />and groundwater. Baseline conditions must be established and possible impacts from the activities <br />determined. <br />The Chimney Rock Mine is located approximately 5 miles south of the junction of Highway 160 <br />and Highway 151 in Archuleta County, Colorado. The approximate elevation of the area is 6500 <br />feet above sea level. Stollsteimer Creek, a perennial stream, is encompassed by the mine area and <br />four ephemeral drainages also exist in the mine plan area. Figure 1 is a section of a United States <br />Geologic Survey (USGS) topographic map depicting the site location. <br />SURFACE WATER CONDITIONS <br />One perennial stream, Stollsteimer Creek, exists in the permit area. This stream trends from east <br />to west through the permit area and eventually enters the Piedra River. Baseline studies conducted <br />in 1980 indicate that flows measured from October 1980 to January 1981 range from 1.3 to 1.79 <br />cubic feet per second (cfs) at station S-1 and from 1.5 to 3.11 cfs at station S-2, respectively. The <br />surface water may be classified as a mixed calcium magnesium-sulfate/bicarbonate type water. <br />Measurements from the monitoring period 1984-1990 indicate that the flows varied more widely <br />than indicated in the baseline period. Flows ranged from a low of 0 cfs to 195 cfs at station S-1. <br />Maximum recorded flow was 300 cfs during April 1986. <br />GROUND WATER CONDITIONS <br />Groundwater in the area occurs in three different zones. The first zone is associated with the <br />alluvium of Stollsteimer Creek. The second occurs in the coal of the Fruitland Formation. The <br />third zone is associated with the Pictured Cliffs Sandstone. The Kirtland Shale, not considered <br />a water bearing unit, overlies the coal sections of the Fruitland Formation. The Fruitland <br />Formation is composed of shale, sandstone, and coal. Three economically viable seams were <br />mined, the "A", "B", and "C" seams. Below the lowest seam, a layer of sandstone and shale <br />exists between the seam and the Pictured Cliffs Sandstone. This layer is generally considered <br />relatively impermeable. Baseline aquifer analyses were performed in September 1982. These <br />smdies determined the approximate transmissivity of the alluvium associated with Stollsteimer <br />Revised hydrologic-05)\OS-22-0(126PM) 1 <br />