2009-05-14_REPORT - M2007044 - Laserfiche WebLink

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Page 12 May 5, 2009 include Whirlwind Mine Decline seep (WMD), Whirlwind Mine Sump (WMS), the Umetco borehole BM00-1, Packrat Mine (PM), and the Rajah 49 Mine (R49). The main outlier sampling site is that of Dolores River (DR), as sampled by the U.S. BLM in 1994. The Dolores River water is principally of a sodium sulfate water type, which reflects the regional geology of the river basin. Other outliers in relative descending degree include Lumsden Mine No. 2, (L2), monitoring well MW-W1 (MW-W1), Lumsden Canyon Mouth (LCM), Willow Spring (WS), and PR Spring (PRS). These sites each exhibit somewhat unique chemistries. The distinct water types associated with the geologic units is expected considering the general rock types (sandstone and shale). The data in Figure 3 do not indicate that groundwater in the upper strata of Burro Canyon and upper Brushy Basin is necessarily hydraulically connected to groundwater in the lower strata of the lower Brushy Basin. The Willow Spring (WS) and PR Spring (PRS) data fall between the two main data groups, perhaps indicating a groundwater connection or chemical evolution flow path. It is understood that Willow Spring occurs near the base of the Burro Canyon Formation and in the upper Brushy Basin Member of the Morrison Formation. The spring's chemistry may reflect dissolution of minerals in both formations. An in-depth study of the hydraulic connection between Burro Canyon Formation and lower Brushy Basin Member groundwater would require sampling of groundwater within the strata between these geologic horizons. Discharge from Lumsden Mine No. 2 (L2) apparently exhibits water quality from workings in the Salt Wash Member and overlying Brushy Basin Member. This water is similar to that of monitoring well MW-W 1 (MW-W I). Both samples show a higher proportion of sodium plus potassium and chloride than all the other samples plotted in Figure 3. The flow path of DP Spring water from its emanation point has been observed in the field. DP Spring water is the source water of upper Lumsden Canyon. The chemical evolution of DP Spring water involves a slight change from an upgradient calcium-dominant water to a downgradient water slightly more concentrated in magnesium and sodium/potassium. Figure 3 shows that the Lumsden Canyon Mouth site chemistry has a higher proportion of magnesium and sulfate than the upstream sites in upper Lumsden Canyon. This indicates that if the upper Lumsden Canyon sites are hydraulically connected to the Lumsden Canyon Mouth site, water quality evolves toward the magnesium sulfate type though dissolution of minerals in the stream bed and shallow bedrock. Alternatively, other sources of water (seeps) may contribute these elements (by mixing) to Lumsden Canyon between the upper and lower parts of the Canyon. SUMMARY AND RECOMMENDATIONS Interpretations on the Whirlwind Mine area hydrogeology as provided in the September 2008 report remain valid after the December 2008 reconnaissance. Reconnaissance conducted in December 2008 has confirmed and expanded knowledge of the mine area. Information acquired since the June 2008 reconnaissance includes the construction of monitoring well MW-WI, the December 2008 reconnaissance of the mine area and Lumsden Canyon, and additional water quality data. The occurrence of mine water in Whirlwind Mine is associated primarily with a lower sandstone unit in the Brushy Basin Member of the Morrison Formation. This sandstone contributes 2 to 3 gpm to the mine in the decline approximately 1,600 ft from the portal. Currently, this water is collected in a sump and pumped to the surface for treatment and discharge. Water seepage occurs in the new workings beyond the sump at apparent low rates (approximately 1 gpm overall). Seepage is likely associated with drainage of surrounding rock after being recharged from the flooded drift during previous mine closure, and from ambient groundwater. Weans032709.doc