PERMFILE41127 - Laserfiche WebLink

Home Browse Search

• PROBABLE HYDROLOGIC CONSEQUENCES CHIMNEY ROCK MINE .~......~...~........o......,.~.s.,..~.r ................ ...... ~.....~~~~...~....~................., .... , . ~ ...~_ ~....~...._...~...~.~~...~..~.~......._ INTRODUCTION Rule 2.04.6(3)(b)(iii) and Rule 2.05.6(3)(b)(iii) require probable hydrologic consequences for mining operations to be determined. This rule further defines that these consequences must be defined for both the permit and adjacent area, for quantity and quality of waters, and for surface and groundwater. Baseline conditions must be established and possible impacts from the activities determined. The Chimney Rock Mine is located approximately 5 miles south of the junction of Highway 160 and Highway 151 in Archuleta County, Colorado. The approximate elevation of the area is 6500 feet above sea level. Stollsteimer Creek, a perennial stream, is encompassed by the mine area and four ephemeral drainages also exist in the mine plan area. Figure 1 is a section of a United States Geologic Survey (USGS) topographic map depicting the site location. SURFACE WATER CONDITIONS One perennial stream, Stollsteimer Creek, exists in the permit area. This stream trends from • east to west through the permit area and eventually enters the Piedra River. Baseline studies conducted in 1980 indicate that flows measured from October 1980 to January 1981 range from 1.3 to 1.79 cubic feet per second (cfs) at station S-1 and from 1.5 to 3.11 cfs at station S-2, respectively. The surface water may be classified as a mixed calcium/magnesium- sulfate/bicarbonate type water. Measurements from the monitoring period 1984-1990 indicate that the flows varied more widely than indicated in the baseline period. Flows ranged from a low of 0 cfs to 195 cfs at station S-1. Maximum recorded flow was 300 cfs during April, 1986. GROUND WATER CONDITIONS Groundwater in the area occurs in three different zones. The first zone is associated with the alluvium of Stollsteimer Creek. The second occurs in the coal of the Fruitland Formation. The third zone is associated with the Pictured Cliffs Sandstone. The Kirtland Shale, not considered a water bearing unit, overlies the coal sections of the Fruitland Formation. The Fruitland Formation is composed of shale, sandstone, and coal. Three economically viable seams were mined, the "A", "B", and "C" seams. Below the lowest seam, a layer of sandstone and shale exists between the seam and the Pictured Cliffs Sandstone. This layer is generally considered relatively impermeable. Baseline aquifer analyses were performed in September 1982. These studies determined the approximate transmissivity of the alluvium associated with Stollsteimer Creek as 100,000 gallons per day per foot (g/d/ft). Transmissiviry and storativiry of the RL053\7\0128-95(9J9am) 1