2012-05-03_REPORT - C1981014 (2)

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EFCI Southfield Mine — 2011 Annual Hydrology Report April 25, 2012 Water levels for well MW -16, shown on Figure 1, indicate significant cyclic /seasonal fluctuations prior to 2001. It was essentially dry beginning in December 2001 until June 2004, possibly associated with drought conditions. The well has silted -up to approximately 110 feet below ground surface leaving 4 feet of perforated casing above the current depth. Water levels for 2004 and 2005 were between 97 and 106 feet but the well has been dry from 2006 through the reporting period. Well MW -23 has demonstrated steadily declining water levels since July of 1984, shown on Figure 2. A slight increase in water level was observed at this well for both measurements taken during 2011. Water levels for Well MW -65, shown on Figure 3, have generally remained stable with minor fluctuations of less than 10 feet through the reporting period. MW -NW has been dry since monitoring was initiated in early 2003, shown on Figure 4 (the water level line represents the well depth). Water quality data for monitoring wells MW -16, MW -23, MW -65 and MW -NW are included on Tables 4, 5, 6, and 7, respectively. These tables provide any analytical results obtained during 2011, and the minimum, maximum and average values calculated using all historical monitoring data. Only wells MW -23 and MW -65 provided water sample data for the reporting period. A review of the 2011 quality data for MW -65 indicates that sample parameters were close to historic values, suggesting no significant changes to groundwater quality are occurring at this site. Quality data for MW -23 indicates elevated values of dissolved Calcium and Magnesium relative to historic values. This trend is similar to that noted for the previous (2010) monitoring period. EFCI will monitor this potential trend by further sampling of the well in accordance with the monitoring plan. Loadout Area In the Loadout Area, groundwater occurs primarily in alluvial /colluvial deposits in and adjacent to the Oak Creek flood plain. Due to limited surface and groundwater flows and recharge and the character of the alluvial /colluvial deposits, these deposits do not appear to store or transmit significant quantities of water, as indicated by the lack of sub - irrigation. A 2003 evaluation at the site, performed by the Fremont County Soil Conservation Service, concluded that no AVF areas exist within the Loadout permit boundary. Because the alluvial / colluvial deposits associated with Oak Creek do not represent a significant groundwater source or aquifer, no groundwater monitoring was ever required at the Loadout site or immediate vicinity. 3.2 Monitoring Well Inspections The depth and general condition of monitoring wells are checked each time the wells are monitored. EFCI replaced several well caps in 2001/2002 to assure ongoing access control and prevent any surface - source contamination. Based on most recent inspections, Southfield's four monitoring wells are in good condition and are performing as designed for obtaining representative water samples. 2011 AHR text doe Page 6