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' Bluestone and Section 16 Wildlife Issues Report <br />Weslcrn Aggregates, Inc. <br />' PJAI will identify the groundwater table by visual observation during gravel extraction. <br />V~Jhen groundwater is encountered, the excavation will back off 1 to 2 feet above the <br />' level of the seasonally high water table and 2 to 3 feet during the seasonally low <br />water table. This procedure will be followed at any time of year that gravel <br />' extraction is occurring. <br />Review of well hydrographs for the Rocky Flats alluvium in this area indicates a <br />' mlaximum seasonal fluctuation of 2 to 3 feet in the elevation of the water table. It <br />is conceivable that WAI could excavate the gravel pit floor during the dry season to <br />an elevation 2 to 3 feet below the seasonal high water table. In this event, <br />' groundwater could flow into the pit during wet periods and pond on the pit floor, <br />allowing evaporative losses. <br />' Empirical evidence from WAI's existing gravel pit indicates that this does not happen. <br />As a operating practice, WAI stops excavating when the sand and gravel becomes <br />' moist to wet. Even if evaporative losses did occur, the amount would be relatively <br />insignificant with respect to down gradient wetlands, seeps, and mesic vegetation. <br />' WAI introduces water to its gravel sites for washing the pit run sand and gravel. This <br />water that is brought to the site is stored in unlined ponds on-site in a series of <br />sediment ponds and raw water storage ponds. Seepage losses from these ponds into <br />th.e groundwater provides supplemental water available to down gradient hydrologic <br />outcrops and the associated vegetative communities. In addition, WAI plans to <br />cclnstruct a raw water storage reservoir on the east side of Section 16, at the head of <br />a side drainage to Woman Creek. Controlled and uncontrolled seepage from this <br />reservoir would make additional water available to the groundwater system. <br />' Tl`te water that WAI introduces to its gravel sites more than compensates for any <br />' evaporative losses of seasonally exposed groundwater. <br />2. Smart Ditch is a small, historic irrigation canal seasonally used for down-gradient <br />' af;ricultural purposes. An alternative ditch is now available to meet existing needs. <br />However, to maintain hydrologic contributions to Woman Creek and PJM habitat, <br />WAI proposes to relocate this ditch around the proposed mining area (i.e., south <br />' from the reservoir outlet, then east along the south boundary of Section 16, then <br />nclrth to where the ditch presently enters Section 15). All herbaceous wetlands <br />' vegetation and soils now present along sections of Smart Ditch would be live-handled <br />arld deposited along the relocated ditch to facilitate wetlands reestablishment. <br />' 3. What little snowmelt and rainfall might normally run off site, would be contained <br />within mine pits. Some of this precipitation would contribute to the groundwater <br />' regime, either directly through immediate infiltration, or diversion to sediment ponds. <br />Sediment ponds would also reduce the introduction of solids into areas below mining. <br /> <br />Walern Ecosystems, Inc. <br />12 <br />December, 1994 <br />