2012-04-18_REVISION - M1984014 (13)

Home Browse Search

Response to DRMS Adequacy Review — Cotter JD -8 Mine Reclamation Plan Amendment RESPONSE TO TIM CAZIER MEMORANDUM The Division of Reclamation, Mining and Safety (DRMS) engineering staff has reviewed the June 1, 2011 Attachment A Drainage Design Plan for the JD -8 Mine EPP Stornwater Management Plan prepared by Whetstone Associates, Inc. The following comments are posed to ensure adequate engineering analyses and design practices are implemented to eliminate or reduce to the extent practical the disturbance to the hydrologic balance expected by the mining operation with respect to water quality and quantity in accordance with Rules 3.1.6(1) and 6.4.21 (10). Cotter response: The Drainage Design Plan has been revised in response to DRMS comments, and is provided as Attachment 4 (see Revised Supporting Documentation for Exhibit U). 1. Page 1 and Figure 1 - Existing Drainage. Run off from non - contributing drainage area N -A appears to report to the west side of area N -B where runoff from both areas would report to the low spot in the access road (approximate elevation 6, 760), with the only outlet being to discharge across the road and report to the low spot (approximate elevation 6,720) on the road below (forming the boundary of area N -C). Runoff reporting there would presumably report to yet another low spot (approximate elevation 6,580) on the road forming the boundary of area N -E. There does not appear to be another road borrow ditch downgradient of the area N -E boundary to divert runoff away from the permit area. Please provide discussion on available storage at the aforementioned low spots and the capacity to store the required 10-year, 24 -hour storm runoff (pursuant to the DRMS 2008 inspection report, included in the reference section) or provide further detail as to how this non - contact runoff is diverted away from the affected area. Cotter response: The Drainage Design Plan provided in Attachment 4 (see Revised Supporting Documentation for Exhibit U) has been revised to provide clarifications and further details regarding water routing and capacity for conveyance of non - contact stormwater. Specifically, additional information is provided in Section 3.2, Table 4, and Figure 2 of the revised Drainage Design Plan. Multiple site inspections were conducted to refine the information presented in the Drainage Design Plan. In the June 1, 2011 Plan, the figures showed county road locations above the mine site that were derived from USGS DEM files and U.S. Census Bureau Tiger files. As a result, the roads and topography were approximated within the upland runoff areas. The site inspection confirmed a continuous grade direction that routes the remainder of upland flows to the southeast of the mine site. A culvert on county road DD19 that captures and directs non - contributing drainage flows to the northwest of the mine site has been added to the site map, and Figure 1 of Attachment 4 has been updated to show a more accurate representation of county road DD19 and the associated flow paths. Flows below DD19 (catchment N -F) are captured by the water tank access road (and ditch) that similarly does not contain any low spots along the road profile. Page 16