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1 Bluestone and Section 16 Wildlife Issues Report Western Aggrep~tes, Inc <br />1 from occupied habitat, it could be managed for PJM, and portions of the area <br />support native upland grassland communities. <br />With the: above commitments, there should not only be no direct impacts to PJM or its <br />' habitat, but the Habitat Preservation Area would protect some of the most important PJM <br />habitat in the RFP buffer zone. <br />4.1.2 INDIRECT IMPACTS TO PREBLE'S MEADOW JUMPING MOUSE HABITAT <br />' As indic:lted above, PJM in the RFP buffer zone have been captured in mixed shrub-grass <br />communities along mesic drainage bottoms. These mesic habitats, at least locally expressed <br />' as linear strips of riparian and wetland communities, are supported by intermittent streams <br />that flow from winter snowmelt and spring runoff, and by localized seeps and springs. Some <br />habitats used by PJM receive contributions from unlined, man-made irrigation ditches, <br />including Smart Ditch (tributary to Woman Creek) and Upper Church and McKay Ditches <br />(tributaries of Walnut Creek). The South Boulder Diversion Canal (Denver Water Dept.), <br />Francis Smart Reservoir, and local irrigation practices also contribute to groundwater <br />' recharge and surface flow. <br />' Part of the alluvium proposed to be mined at the Bluestone and Section 16 sites functions <br />as a low volume groundwater conduit, generally flowing to the east. This aquifer occurs <br />where relatively impermeable Arapahoe Formation sandstones and claystones subcrop below <br />' the unconsolidated alluvium (EG&G 1991). Where pediments give way to down gradient <br />drainage:i and these impermeable formations are exposed, some of this groundwater surfaces <br />' as seeps and springs, which support the types of vegetative communities inhabited by PJM <br />along drainage bottoms. In some areas, groundwater volumes are seasonally adequate to <br />support mesic vegetation extending from mid-slope areas to similar communities along <br />' drainage bottoms. In some areas, this mesic vegetation is the type of mixed shrub-grass <br />community in which most PJM have been captured along drainage bottoms. In other areas, <br />mesic conditions only support grass stands dominated byJultctcs. PJM has not been captured <br />' in these potentially suitable graminoid habitats located in horizontal bands along mid- to <br />upper drainage slopes, although trapping efforts have concentrated along drainage bottoms. <br />' It is possible that with more trapping, PJM will be located in the more suitable mid-slope, <br />seep-supported habitats, at ]east during theorized seasonal dispersals. Nevertheless, the <br />exposed groundwater not only supports potential PJM habitat, but surface and subsurface <br />' flows provide unquantified, but minor contributions to mesic drainage bottom habitats where <br />PJM have been captured. <br />' Depth to groundwater varies between the Bluestone and Section 16 sites. At the Bluestone <br />site, adjacent to the existing Bluestone Aggregates Mine, gravels are approximately 80 feet <br />thick above the underlying shale bedrock. Groundwater in this permeable alluvium is <br />thought to be concentrated just above the shale subcrop. The groundwater level varies over <br />' Wcstem Ecosystems, Ina tQ December, 1994 <br />