2014-11-06_REVISION - C1981014 - Laserfiche WebLink

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capacity of the impoundments which includes the capacity to handle 24 hour, 10 year storm events and 24 hour, 25 year events. Another factor for non - discharges is the revegetation success that has stabilized the drainage areas to the ponds reducing the amount of runoff and sedimentation in the respective pond's drainage areas. With the approval of Technical Revision No.35 (TR -35) during 2003 and during the onset of the reclamation activities at Southfield, water monitoring activities were reduced from quarterly monitoring intervals to semi - annual monitoring periods. The schedule for water monitoring is provided in Exhibit 25, Water Monitoring Program located in the permit document. TR -35 (2003) also approved conversion of the north dewatering well to a groundwater monitoring well. The conversion designated the monitoring well as the "MW -NW" monitoring well. Hydrology Monitoring Results and Probable Hydrologic Consequences: The DRMS provided EFCI with a copy of an extensive hydrogeologic review of Southfield submitted as an Interoffice Memorandum from Mike Boulay, DRMS' hydrologist, to Dan Hernandez of the DRMS, dated June 3, 2013. A copy of the review is included with this submittal (Attachment B). In summary, the DRMS hydrogeologic findings concur with the determinations described in the Southfield approved permit document concerning the Probable Hydrologic Consequences for the Southfield operations (page 12 of the Memorandum). The Review also concludes that there is no reason to expect further disturbance at the site or further degradation of water quality in the Red Arrow or Jack O' Lantern coal seams or workings. With regard to considering additional monitoring wells, the Review concludes that additional monitoring of the coal zone is not warranted (page 13 of the Memorandum). Probable hydrologic consequences identified in Section 2.05.6 of the Permit are listed below. Groundwater Consequences 1. Minor reductions in down - gradient groundwater flows 2. Possible dewatering of abandoned mines in the Vento seam 3. Localized reductions in the piezometric surface 4. Localized alteration of groundwater flow patterns 5. Possible increases in recharge as a result of mine dewatering 6. Potential increases in the levels of TDS and concentrations of specific chemical constituents Probable groundwater consequences appear to be consistent with the findings made by Boulay and the DRMS (refer to above referenced Memorandum) and are supported by the groundwater data provided in the Annual Hydrology Reports. Historical surface water and groundwater data is included with this submittal in Attachment C. EFCI concurs that there are possible minor reductions in down - gradient groundwater flows due to groundwater inflows to the mine void. There is, however, no evidence of adverse impacts to down - gradient water users (refer to Water Rights Consequences, below). Partial dewatering of abandoned mines in the overlying Vento seam may have occurred due to their close proximity to the Southfield Mine, though there is no monitoring data to support the extent of the dewatering. Further, these mines are likely to be refilling with groundwater given the low vertical permeability of the interburden between the upper seams and the Red Arrow and Jack O' Lantern seams. Localized reductions in the piezometric surface, or more accurately, potentiometric head levels, have occurred according to water level data from the three current monitoring wells (MW -16, MW -23, and MW- 65). Review of data provided in the Annual Hydrology Reports show that MW -16 went dry in late 2001 until 2004, recharged briefly, then again went dry from 2006 to present. MW -23 exhibited a rapid water level rise in level between 1979 and 1984, then a steady decline from 1984 to 2003, followed by steady levels 2 TR -43 Revised: 10/2014