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the highest of the three areas for which whole rock chemistry data were available. Zinc in Poverty Gulch <br /> groundwater is two orders of magnitude higher than in the other two drainages, yet the whole rock zinc is <br /> the same order of magnitude in all three drainages. <br /> The drill holes from which the whole rock data were obtained were all drilled within the diatreme, with the <br /> exception of one hole in Poverty Gulch (CCV-SEC-00007). The results from the one hole in outside the <br /> diatreme in Poverty Gulch show a geometric mean concentration of 61 mg/L for manganese and 248 <br /> mg/L for zinc. The data in Table 6 do not appear to shed any light on the source of the elevated <br /> constituents in Poverty Gulch, Arequa Gulch, or Vindicator Valley. <br /> The six drainages are discussed in detail in the following sections. <br /> 6.1 Squaw Gulch <br /> The source of the elevated sulfate, manganese, and zinc in Squaw Gulch may be anthropogenic, <br /> resulting from the rather substantial historic mining that took place in Squaw Gulch. Figure 22 is a portion <br /> of Plate 1 from Lindgren and Ransome (1906). In addition to the numerous mines up-gradient of the <br /> Squaw Gulch monitoring wells, three rail lines used to pass through the area. The significant mines near <br /> and up-gradient of the monitoring wells include the Anaconda, Blue Bell, Morning Glory, Doctor-Jackpot, <br /> and Mary McKinney. These mines produced ores that were sulfidic to partly oxidized (Lindgren and <br /> Ransome, 1906), and ore from the Blue Bell mine assayed up to 18% zinc (Cross and Penrose, 1895). <br /> However, these mines were largely within the limits of the diatreme, so it is probable that most of the <br /> soluble species leached from the waste rock dumps associated with the historic mines infiltrated into the <br /> diatreme. After construction of the various drainage tunnels, groundwater would have traveled down the <br /> Squaw Gulch drainage only in local perched, relatively shallow aquifers. <br /> During recent mining (from the 1970s on), waste rock began to be placed in the head of Squaw Gulch <br /> around 1997. In 2000 the footprint of the waste rock pile began to be expanded, reaching its maximum in <br /> 2006, when the toe of the dump was approximately 2800 feet from the Precambrian-diatreme contact. In <br /> 2012 additional waste rock was placed near the head of Squaw Gulch for construction of the new <br /> processing plant, with the toe of this material approximately 1300 feet from the Precambrian-diatreme <br /> contact. Figure 22 shows the extent of waste rock in Squaw Gulch in 2006, 1997, and 1991, the <br /> Precambrian-diatreme contact, and the Squaw Gulch compliance monitoring point, in comparison with the <br /> 1951 USGS 1:24000 topography. <br />