2012-02-29_REVISION - M1981021 (3)

Home Browse Search

Page 6 of 10 believes that potential groundwater recharge to the Dakota Aquifer is nil. The ore deposit is located over 2,000 feet to the south of the affected area. The host stratum of the ore body is the Salt Wash sandstone member of the Morrison Formation, which, where saturated, is the Saltwash Aquifer. Given the southerly dip of the sandstone stratum and its depth where the ore occurs, the groundwater occurs only in the more remote sections of the underground mine. The Saltwash member is older and deeper than the Dakota, and upward and upgradient groundwater migration does not occur. The Division believes that it is unlikely for the mine to contaminate the Dakota Aquifer because the Saltwash sandstone is bounded above and below by layers of shale, isolating the Saltwash Aquifer, and limiting the inflow of other groundwater. Furthermore, groundwater recharge appears possible mainly where non - ore - bearing Dakota sandstone crops out, in this case, the groundwater will not be contaminated. Additionally, regional faulting appears to have further isolated the ore - bearing area. There is no evidence of a hydrologic connection between the ore - bearing sandstone and the other areas where aquifer occurs or is used. 6. Objection: The Division should require the Operator to demonstrate how collection of storm water in waste rock areas will affect leachate and demonstrate the best management practices that will be used to minimize percolation of storm water into the waste rock. The Division should also address waste rock berms that direct storm water towards Big Gypsum Creek. August 2009 Letter, 3. The Division's Response: The mine is subject to an existing CDPHE stormwater management permit and plan, which require regular monitoring and maintenance. Stormwater control structures are designed to meet the 100 -year, 24 -hour precipitation event. There is little to no runoff from the site due to the arid climate, and unless there is a significant precipitation event, runoff will not reach Big Gypsum Creek. Big Gypsum Creek is an intermittent stream, tributary to the Dolores River. The creek is over one -half mile from the closest portion of the site, and is nearly always dry. The Dolores River is approximately five miles from the site. Further, the setting for the permitted area is arid, with potential evaporation far exceeding actual precipitation amounts. The site contains maintained stormwater control structures that were installed before this EPP Amendment in accordance with WQCD and BLM requirements. Given the coarse - textured development rock (sandstone waste rock), the normally low amount of precipitation typically evaporates before it can percolate or run off, which reduces adverse impacts to ground and surface water. 7. Objection: The Operator has stated that it will monitor down - gradient wells and will take additional actions if the ambient water quality is degraded. The Division should require Operator to develop such a plan now. August 2009 Letter, 4. The Division's Response: At the time this issue was raised by Objectors, the EPP required two monitoring wells. It now requires a groundwater monitoring plan, which includes six wells, which the operator will construct and sample throughout the life of the permit. The groundwater monitoring plan is thoroughly described above. The BLM was actively involved in the designation of well locations in the monitoring program. The EPP meets the requirements of the Act and Rules, further contingency plans are unnecessary and inappropriate at this time. Coordination of EPP Review with Other Agencies (Interagency Memoranda of Understanding) 8. Objection: The Division should review the Amendment in coordination with EPA (regarding air quality issues) and the Water Quality Control Division ( "WQCD "). September 2011 Letter, 2.