2009-05-19_REVISION - M1977416 (28)

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COR-030000 Stormwater Management Plan e) Existing Vegetation (§I.C.l.e): The Sunday Mines are located in the and Shale Deserts and Sedimentary Basins ecoregion that is sparsely vegetated with mat sagtbrush, bud sagebrush, galleta grass and desert trumpet. Bedrock exposures are common. Floodplains have alkaline soils that support greasewood, alkali sacaton, seepweed, and shadscale (EPA 2007a). The surface areas associated with the mines currently have no vegetation. In areas with preexisting vegetation, estimated densities vary between 30 to 40% ground coverage. There are no identified wetlands disturbed by the project. f) Location of Potential Pollution Sources (§I.C.l.f): The location and description of all potential pollution sources, including ground surface disturbing activities, are described in Section 3.b) of this SWMP. g) Non-stormwater ((§I.C.l.g) and (§I.D.3)): The CDPS General Permit allows the following non-stormwater discharges in combination with stormwater discharges associated with construction sites: • Discharges from fire-fighting activities; • Natural springs; • Landscape irrigation return flow; • Concrete washout water, provided that the washout water is confined in a concrete washout area and does not leave the site as surface runoff or to surface waters, and does not enter groundwater; and • Construction dewatering activities provided that the groundwater or groundwater combined with stormwater does not leave the site as surface runoff or to surface waters. There is no expected potential for these allowable sources of non-stormwater discharges from this site. However, if allowable sources of non-stormwater discharges are encountered during mining activities they will be noted in this SWMP and indicated on the Stormwater Site Maps. h) Receiving Waters (§I.C.l.h): The mine surface working areas are generally flat due to grading for base operations. Dry unnamed ditches are located throughout the area and generally drain to the northeast into the intermittent Big Gypsum Creek in Big Gypsum Valley, which flows to the Dolores River. Surface water runoff for each site location is as follows: Sunday Mine: Surface drainage flows northwest to a series of temporary sediment basins on the north side of the site, into the drainage ditch on the north side of CR 20R, and ?• discharges into an unnamed tributary of Big Gypsum Creek, located approximately lh mile north of the mine workings area. Denison Mines (LISA) Corp. Sunday Mines SWMP 4