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LORENCITO CANYON MINE <br />ANNUAL HYDROLOGIC MONITORING REPORT - 2001 <br />SECTION 1 -INTRODUCTION <br />To fulfill the requirements of the Regulations of the Colorado Mined Land Reclamation Board, <br />the following report has been assembled incompliance with Rule 2.04.7. Since the beginning of <br />1996, substantial work has been performed at the Lorencito Canyon Mine site to interpret the <br />hydrology of the area. Specific methodologies employed for this work are described below. Field <br />work accomplished during the baseline period has included the installation and testing of 10 <br />alluvial wells, 16 consolidated aquifer wells, along with the monitoring of 11 surface water sites, <br />11 springs and seeps, and 19 pond sites in the area. From the field data collected, insight has been <br />gained into the recharge and discharge characteristics of aquifers, hydraulic properties, <br />potentiometric and water table surfaces, and water quality for each of the hydrologic units. The <br />program was reduced following issuance of the permit in August 1997, resulting in a reduction <br />of monitoring stations, frequency of monitoring, and water quality parameter analyses. A revision <br />to the program was also approved in early 1999 to reduce the frequency of monitoring during [he <br />premine period until disturbance activities begin. <br />In early 2001, a Permit Revision was submitted for approval of mining operations in the surface <br />mining area. As a result, the monitoring program was adjusted to use only those stations that <br />would detect potential impacts of these operations. These stations and water quality parameters <br />are listed on Tables 1-1 and 1-2. This revision eliminated all deep aquifer wells from the <br />monitoring program. This report presents the results of monitoring for the end of the baseline <br />period early in the year and the start of operations in the fourth quarter of 2001. <br />SEGTION 2 -METHODOLOGY <br />Groundwater <br />To determine the presence of alluvial aquifers, wells were installed in the alluvium of major <br />canyons within the permit area. Four wells were installed in Lorencito Canyon, and two wells <br />in Cow Canyon, with the other canyons having one well installed near the canyon mouth. A total <br />of ten wells were installed. Most wells were installed with ten feet of screen and generally do not <br />exceed thirty feet in depth. Alluvial wells were assigned names based upon location. Each well <br />was designated with an MW prefix, followed by a two or three letter code for the canyon the well <br />was located in, and a number to designate the location with the numbers increasing up the canyon. <br />The location of monitoring wells is depicted on Map 2.04.7-1. <br />AHR-Op.695\Apnl ]6, 2002 <br />