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EFCI Southfield Mine - 2009 Annual Hydrology Report <br />March 10, 2010 <br />3.0 GROUNDWATER AND SURFACE WATER MONITORING RESULTS <br />3.1 Groundwater Monitoring Results <br />Mine Area <br />In the Mine Area, groundwater occurs in surficial alluvial/colluvial deposits and as water table <br />conditions in the sequence of sedimentary rocks corresponding to the Vermejo, Raton, and Poison <br />Creek formations. Due to semi-arid conditions and the limited extent and continuity of the <br />alluvial/colluvial deposits, these units do not store or transmit appreciable quantities of groundwater <br />in the general mine area. There is limited lateral or regional continuity of potential water-bearing <br />units due to variable lithology and significant cross-bedding and inter-bedding within the bedrock <br />units. As a result, there are no known aquifers in the mine area, and bedrock groundwater <br />occurrences are limited to isolated units and zones that have sufficient local recharge and <br />characteristics that allow it to store and transmit water. Therefore, only isolated shallow perched <br />groundwater zones may develop. Additional "minor" groundwater storage may occur in abandoned <br />and flooded mine workings, which serve as small collection and storage reservoirs as well as for <br />origination of fracture flows (refer to Section 2.04.7 of the Southfield permit application for more <br />details). <br />In the mine area, the approved groundwater monitoring program includes the following monitoring <br />wells, located as shown on Figure 1, Mine Monitoring Stations: <br />Well Location Depth/Completion Zone Geologic Completion Zone <br />MW-16 E'/ZNW'/4, Sec 30 136/ 106'-136' Jack O'Lantern Coal Seam <br />MW-23 E'/zSW'/4, Sec 19 179'/ 149'-179' Red Arrow Coal Seam <br />MW-65 W'/zSW'/4, Sec 24 1448/ 968'-988' Jack O'Lantern Coal Seam <br />MW-NW W'/zSW'/4, Sec 19 380'/ 360'-380' Red Arrow Coal Seam (mine void) <br />Monitoring wells MW-7A, MW-713, MW-8, MW-10, and MW-22 were previously included in the <br />monitoring program, but have since been mined-through and eliminated from ongoing monitoring. <br />Wells MW-7A, MW-7B, MW-22 were mined-through by Dorchester Coal Co. prior to 1985. EFCI <br />later collapsed wells MW-8 and MW-10 as a result of ongoing mining operations. <br />A former mine dewatering well known as the North Well was originally used to dewater abandoned <br />mine workings in the Red Arrow Coal Seam north of the main mine entries. EFCI discontinued its <br />use as a dewatering well in 1994, later removing the pump and associated equipment. In 2003, it <br />was converted to and approved for use as a monitoring well named MW-NW. <br />In Technical Revision 35 (TR-35), the approved groundwater monitoring schedule was reduced <br />from quarterly to semi-annually and is typically conducted in June and December at the four <br />monitoring wells. Field measurements and laboratory data for active monitoring wells are <br />summarized in the following discussions. Field and laboratory data for 2009 are provided in <br />Appendix A. Measured water levels for all wells are summarized in Table 3, Monitor Well Water <br />Levels, for years 2000-2009. Previous well water level data for all monitoring wells are <br />2009 AHR.doc WP Page 4