2013-04-29_REPORT - C1981014 - Laserfiche WebLink

Home Browse Search

EFCI Southfield Mine — 2012 Annual Hydrology Report April 18, 2013 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, then continued declining levels through the period of this report. Water levels for Well MW- 65, shown on Figure 3, have generally remained stable, with minor fluctuations of less than 5 feet from an average level of 281 feet, from 1987 through 2012. Well MW -NW has been reported as dry since monitoring was initiated in early 2003. Figure 4 illustrates the dry well condition with a "water level" line synonymous with the total original well depth to the floor of the mine opening, approximately 375 feet. The well depth that can be monitored changed in 2012 due to a failure in the last 20 feet of casing (see Section 2.3). Figure 4 is modified accordingly to show the current total depth of the well of 354 feet, reported as dry. 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 2012, and the minimum, maximum and average values calculated using all historical monitoring data. Only wells MW -23 and MW -65 produced water and thus provided water sample data for the reporting period. A review of the 2012 quality data for MW -65 indicates an increase in the amount of Nitrogen ammonia for both samples as compared to the average value for data obtained since 1984, but below the maximum value sampled in 2003. The data suggests an increasing quantity of this parameter beginning in 1996. Quality data for MW -23 indicates elevated values of dissolved Calcium, Chloride, and Magnesium as compared to the average values for quality data obtained since 1979. According to these data, Chloride and Calcium values have been slowly increasing since 2006, whereas Magnesium values have gradually increased since 2008. EFCI will continue to monitor trends by further sampling of the wells 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 condition of monitor wells is checked at the time each well is monitored. Typically the wells have been found in good condition, although EFCI did replace several well caps in 2001/2002 to 2012 AHR text doc Page 6