2013-10-31_REVISION - M1977284 (3)

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Mineral Joe Mine — Drainage Design Plan 1 1. INTRODUCTION 1.1 Purpose This Drainage Design Plan presents the design analysis for the stormwater drainage facilities at the Mineral Joe Mine, which is located in Montrose County, Colorado and owned by Cotter Corporation (N.S.L.) (Cotter). The plan addresses aspects of stormwater collection, conveyance, and retention design necessary to comply with the Colorado Division of Reclamation Mining and Safety (DRMS) drainage criteria. 1.2 Overview - Runoff Areas and Routing The Mineral Joe Mine is located below the north- facing escarpment of Monogram Mesa. The permitted mine area (3.64 acres) lies within Sections 21 and 22, T46N, R17W, NMPM, and on the Mineral Joe Claims (MJ -2, MJ -12, MJ -14, MJ -17, MJ -18, and MJ -19, which total 118 acres). Mining activities that have the potential to affect stormwater discharge at the Mineral Joe Mine include the following: • The waste rock storage pile (2.73 acres) • Temporary ore stockpile area (0.08 acres) • Fuel and oil storage area • Equipment fueling area • Access road In addition to the facilities listed above, the Mineral Joe Mine facilities include a vent hole in Area C and an emergency egress portal (at the Mineral Joe 2 Adit) in Area A. The vent hole and associated access road are located off County Road EE19. The area surrounding the vent hole has been minimally graded to direct water away from the vent hole, and vegetation is well established. The area surrounding the emergency egress portal is similarly revegetated. The vent hole and the emergency egress portal (Mineral Joe 2 Adit) would have minimal or no effect on stormwater quality. These facilities occur in two main sub - basins, which are identified as B 1 and B2 on Plate 1. Sub -basin B 1 occupies 1,205.7 acres and is drained by an unnamed intermittent stream that flows west and northwest into the Paradox Basin (Plate 1). Sub -basin B2 occupies 296.1 acres and is drained by an unnamed intermittent stream that flows north into the Paradox Basin (Plate 1) and is tributary to East Paradox Creek. The stream is intermittent in its upper reaches and ephemeral on the floor of the Paradox Valley. Sub -basin B2 contains the mine facilities which are the area of primary focus for this Drainage Design Plan. Stormwater is managed to reduce the potential for runoff from upslope to contact disturbed ground in the mine facilities area, as described in detail in the following sections. Runoff from undisturbed surfaces, areas of minor disturbance, and areas not containing designated chemicals or potentially toxic or acid forming materials is considered "non- contact" stormwater because it has not had potential exposure to pollutants. Table 1. Major Sub -Basin Areas at the Mineral Joe Mine Sub -Basin Area Area Description (ft2) (acres) B 1 52,519,930 1,205.7 Main sub -basin for underground workings B2 12,899,050 296.1 Main sub -basin containing waste rock pile, adit, mine facilities area 1.3 Adjacent and Ancillary Facilities The adjacent JD -6 Mine waste rock pile and JD -6 lease tract are owned/leased by Cotter and are permitted under a separate mining permit (No. M- 1977 -310) and stormwater permit (COR 040024). The separate claims for the Mineral Joe and JD -6 Mines share a common portal and surface facilities, except for separate 4148B.131029 Whetstone Associates 6