2012-03-12_REPORT - C1982056 (2)

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Since mid -1987, hydrologic monitoring and reporting has primarily been conducted by TC personnel. In May of 1995, a private firm (Miller Water Monitoring Service) was contracted to assist with hydrologic monitoring at the TC sites, and continues to assist in monitoring to date. Prior to June 1986, water quality analyses were performed by the on -site CYCC laboratory. From 1987 to 2000, water quality analyses were primarily performed by ACZ Laboratories (formerly Bookcliffs) of Steamboat Springs, Colorado. From 2001 through 2005, water quality analysis was primarily been performed by SGS North America laboratory of Denver, Colorado. Since mid - 2005, analyses are again primarily performed by ACZ Laboratory of Steamboat Springs, Colorado. Whole Effluent Toxicity (WET) testing was historically conducted by SGS, but has been conducted by Aqua -Tox of Wheatridge Colorado, since the summer of 2009. Note that in 2003, DRMS approved TR03 -42 (See Permit Exhibits 14 -5, 14 -6, and 14 -10), and PR 03 -06 (See Permit Exhibits 14 -7 through 14 -9), which eliminated several surface, alluvial, and bedrock well monitoring sites, and reduced the monitoring frequency of other sites, while adding additional monitoring requirements to existing surface site 305. Data from terminated sites can be found in previous AHRs. Three former US Geologic Survey (USGS) surface water sites (USGS 09243700, USGS 09243800 and USGS 09243900) were monitored for flow by the USGS through the 2001 water year. Prior to the 1989 Water Year, the USGS had collected and analyzed water quality samples from these sites. From the 1989 water year to date, TC has collected water quality samples from these sites for laboratory analysis. Beginning with the 2002 water year, TC took over monitoring of these three sites (referred to as sites 700, 800, and 900, respectively) from the USGS. In 2003, TR03 -42 eliminated site 700 on Middle Creek. 3.0 2011 HYDROLOGIC MONITORING PROGRAM Specific monitoring site locations and their elevations are shown on Figure 2 (Map pouch at back of report). Required monitoring frequencies are listed in Permit No. C -82 -056, under Exhibit 14. 2011 data tables and figures for each site are referenced in the following discussions. Statistical summaries of the historical data base are provided after presentation of the 2011 data. 3.1 Bedrock Groundwater Monitoring Hydrogeology: TC's underground mining operations are currently located roughly 1700 feet beneath the surface of Twentymile Park Basin. This is an enclosed synclinal ground water basin, rimmed by outcrops of major lithologic units. Ground water in the Twentymile Park Basin exists primarily under confined conditions within the bedrock units. All ground water aquifers in the general area, except the alluvial aquifers, are recharged by infiltration in outcrop areas, located primarily in the southern and western margins of the Twentymile Park Basin. Recharge is limited, due to low average annual precipitation and the loss of moisture through evapotranspiration and sublimation in this semi -arid climatic zone. Ground water occurrence and movement within the bedrock aquifer system is controlled by geologic structure and lithology. Ground water movement tends to follow the structural dip of the lithologic units toward the basin axis. The general trend of movement in the permit area is to the north and northwest. This results in confined aquifer conditions down gradient from the outcrop area. A 3