Laserfiche WebLink
EFCI South. field Mine -Year 2007 Annual Hydrology Report April 21, 2008 <br />In Technical Revision 35 (TR-35), the groundwater monitoring schedule was reduced from <br />quarterly to semi-annually and is typically conducted in June and December at the four monitoring <br />wells. Field measurements and laboratory data for active monitoring wells aze summarized in the <br />following discussions. Field and laboratory data for the 2007 water year aze provided in Appendix <br />A. Measured water levels for all Mine Area monitoring wells aze summarized in Table 3, Monitor <br />Well Water Levels, for the yeazs 2000-2006. Previous well water level data for all monitoring <br />wells aze documented in Annual Hydrology Reports on file at the Division. All historic water <br />level data aze presented graphically for six monitoring wells (including historical information for <br />Wells MW-8 and MW-10) on Figures 3, 4, 5, 6, 7 and 8. <br />Water levels for well MW-16 have shown some cyclic/seasonal fluctuations. It was essentially <br />dry from December 2001 until June 2004, possibly associated with drought conditions. The well <br />has silted up to approximately 110 feet below ground surface leaving 4 feet of perforated casing <br />above the current depth. Water levels for 2004 and 2005 were between 97 and 106 feet but ;the <br />well was dry during 2006 and 2007. Well MW-23 has demonstrated steadily declining water <br />levels since July of 1984. Water levels for Well MW-65 have generally remained stable with <br />minor fluctuations of less than 10 feet. MW-NW has been dry since monitoring was initiated in <br />eazly 2003. <br />Water quality data for monitoring wells MW-10, MW-16, MW-23, MW-65 and MW-NW ~ aze <br />provided on Tables 4, 5, 6, 7, and 8, respectively. Only wells MW-23 and MW-65 have new data <br />to report. These tables provide any analytical results for 2007 and the minimum, maximum 'and <br />average values calculated using all historical monitoring data. Consistent with the historic <br />monitoring schedule, water quality samples were not obtained for Well MW-8. Review of 2,007 <br />data and historic water quality monitoring data compared to the Colorado Groundwater Standards <br />provided in Regulation no. 41 -Basic Standards for Ground Water indicated the following <br />exceedances. <br />- MW-16: The historic averages for dissolved Iron and Sulfate exceed the Secondary Drinking <br />Water Standazd although no historic sample pazameter averages exceed the Agricultural Standards. <br />- MW-23: The historic average for dissolved Iron exceeds the Secondary Drinking Water <br />Standazd; none of the 2007 sample parameters exceeded either Secondary Drinking Water <br />Standards or Agricultural Standards. <br />- MW-65: Both samples in 2007. and the historical average of dissolved Manganese exceed the <br />Secondary Drinking Water Standazd although no 2007 samples or historic sample parameter <br />averages exceed Agricultural Standards. ' <br />Loadout Area <br />In the Loadout Area, ground water occurs primarily in alluvial/colluvial deposits in and adjacent to <br />the Oak Creek floodplain. Due to limited surface and ground water flows and rechazge and the <br />character of the alluvial/colluvial deposits, these deposits do not appear to store or transmit <br />significant quantities of water, as indicated by the lack of sub-irrigation (refer to Section 2.04'.7 of <br />the Southfield Mining and Reclamation Plan document for more details). ~ , <br />2007 AHR.doc WP Page 7 <br />