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analysis has primarily been performed by SGS North America laboratory of Denver, Colorado. Beginning in <br />mid-2005, some analyses has again been performed by ACZ laboratory of Steamboat Springs, Colorado. <br />Note that in 2003, DRMS approved TR03-42 (See Permit Exhibits 14-5, 14-6, and 14-10), and PR 03-06 (See <br />Permit Exhibits 14-7 through 14-9), which eliminated several surface, alluvial, and bedrock well monitoring sites, <br />and reduced the monitoring frequency of other sites, while adding additional monitoring requirements to existing <br />surface site 305. Data from terminated sites can be found in previous AHRs. <br />Three former US Geologic Survey (USGS) surface water sites (USGS 09243700, USGS 09243800 and USGS <br />09243900) were monitored for flow by the USGS through the 2001 water year. Prior to the 1989 Water Year, the <br />USGS had collected and analyzed water quality samples from these sites. From the 1989 water year to date, TCC <br />has collected water quality samples from these sites for laboratory analysis. Beginning with the 2002 water yeaz, <br />TCC took over monitoring of these three sites (referred to as sites 700, 800, and 900, respectively) from the <br />USGS. In 2003, TR03-42 eliminated site 700 on Middle Creek. <br />3.0 2006 HYDROLOGIC MONITORING PROGRAM <br />Specific monitoring site locations and their elevations are shown on Figure 2 (Map pouch at back of report). <br />Required monitoring frequencies are listed in Permit No. C-82-056, under Exhibit 14. 2006 data tables and <br />Figures for each site aze referenced in the following discussions. Statistical summaries of the historical data base <br />are provided after presentation of the 2006 data. <br />3.1 Bedrock Groundwater Monitoring <br />Hvdroeeoloev: TCC's underground mining operations are located on the southwest flank of the Twentymile <br />Park Basin. This is an enclosed synclinal ground water basin, rimmed by outcrops of major lithologic units. <br />Ground water in the Twentymile Pazk Basin exists primarily under confined conditions within [he bedrock units. <br />All ground water aquifers in the general area, except the alluvial aquifers, are rechazged by infiltration in outcrop <br />areas, located primarily in the southern and western margins of the Twentymile Park Basin. Recharge is limited, <br />due to low average annual precipitation and the loss of moisture through evapotranspiration and sublimation in <br />this semi-arid climatic zone. Ground water occurrence and movement within the bedrock aquifer system is <br />controlled by geologic stmcture and lithology. Ground water movement tends to follow the structural dip of the <br />lithologic units toward the basin axis. The general trend of movement in the permit area is to the north and <br />northeast. This results in confined aquifer condifions down gradient from the outcrop azea. A detailed discussion <br />of [he geology/hydrology for the site is available in the 7wentymile Coal Company, Foidel Creek Mine Permit C- <br />82-056, Volume I, Rules 2.04.6 and 2.04.7. <br />The Twentymile Park Basin is underlain by a large, high quality coal reserve. This reserve, mined by <br />underground operations, is known as the Wadge Seam. The Wadge Seam lies within a sequence of sedimentary <br />rocks characterized by shales, claystones, mudstones, siltstones, sandstones, and minor coal stringers referred to <br />as the Wadge Overburden. The Wadge Overburden is hydrologically isolated from the two major bedrock aquifer <br />units in the Twentymile Pazk Basin, the Twenrymile Sandstone aquifer and the Trout Creek Sandstone aquifer, <br />3 <br />