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JD-8 Mine—Drainage Design Plan <br /> • 1. INTRODUCTION <br /> 1.1 Purpose <br /> This report presents the design analysis for the storm water drainage facilities at the JD-8 Mine, located in <br /> Montrose County, Colorado. The report addresses aspects of storm water collection, conveyance, and <br /> retention design necessary to comply with the Colorado Division of Reclamation Mining and Safety <br /> (DRMS)drainage criteria. <br /> The JD-8 Mine is currently not actively mined. However, the JD-8 Mine is expected to be operational in <br /> the future, and the existing waste rock pile will be expanded as the underground workings are further <br /> developed. This drainage design plan is intended to address both the current and expected final drainage <br /> conditions. The design criteria and methodology are described in Section 2. <br /> 1.2 Background - Lower Runoff Areas and Routing <br /> Storm water runoff at the JD-8 Mine occurs from both disturbed and undisturbed areas. Runoff from <br /> undisturbed areas is considered "non-contact" storm water because it has not had exposure to potential <br /> industrial pollutants (roof runoff, access roads, employee parking areas, waste rock piles, etc.). The fuel <br /> storage area is bermed and lined, and does not contribute storm water to any catchment onsite. As shown <br /> in Figure 1 and Table 1, drainage areas have been divided into four contributing sub-basins and two <br /> receiving sub-basins. <br /> Table 1. Sub-Basin Areas at the JD-8 Mine under Current Conditions <br /> 4110 Sub- Area Area <br /> Basin (ft2) (acres) Type <br /> 1 50,280 1.15 Contributing non-contact area(undisturbed) <br /> 2 49760 1.14 Contributing disturbed area <br /> 3 24,660 0.57 Receiving area(near soil stockpile) <br /> 4 73,550 1.69 Contributing non-contact area(undisturbed) <br /> 5 137,600 3.16 Contributing disturbed area <br /> 6 8,050 0.18 Receiving area(Constructed Catchment) <br /> Drainage at the site is controlled by ditches, berms,culverts, and topography. Sub-basins located above the <br /> Lower Mine Permit Area that would contribute run-on to the site during extreme storm events under <br /> current site conditions are shown in Figure 1 and Table 1. <br /> Surface flow from undisturbed contributing Sub-Basin 1 and disturbed contributing Sub-Basin 2 is routed <br /> to retention Pond 1 in Sub-Basin 3, near the topsoil stockpile. In addition, a portion of the western waste <br /> rock pile area(on which the mine facilities have been constructed) slopes westward toward receiving Sub- <br /> Basin 3 (Figure 1). <br /> Similarly, runoff from undisturbed areas above the mine(Sub-Basin 4) and disturbed areas associated with <br /> the access road, ore storage area, and a portion of the eastern waste rock pile (Sub-Basin 5) are routed to <br /> the constructed retention Pond 2 in Sub-Basin 6. The eastern portion of the waste rock pile is sloped <br /> gradually westward while the berm along the crest of the waste rock pile diverts flow westward and <br /> prevents runoff from eroding the face of the pile(Photo 2). Runoff from the waste rock is intercepted by a <br /> constructed notch in the berm,where water is routed down the face of the waste rock pile to the constructed <br /> catchment (Pond 2). Photo 3 shows a former rivulet that developed into a small gully on the face of the <br /> pile, and was then mitigated by repairing the berm along the crest of the waste rock pile. <br /> 4122A.120702 Whetstone Associates• <br />