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deep fracture-flow system, but the pH values measured at this bog may be less than in the <br /> ground-water system due to the precipitation of iron hydroxides. <br /> A pH of 6.0 was measured at a small spring near the head of the South Fork of Cement Creek <br /> on August 2, 1991 by HSI staff. This spring may originate from a shallow flow system from <br /> nearby snowmelt. <br /> Langston (1978, p. 129-133) es imated that the pH of the water in the Sunnyside vein system <br /> was between 3.5 and 5.0 durin ore deposition. This estimate was based on the presence or <br /> absence of certain mineral species, combined with the measured concentration of dissolved <br /> species measured by Casadevall and Ohmoto (1977). Flow conditions were different <br /> immediately prior to mining than during ore deposition, but the ores are considered to have been <br /> deposited under a relatively local meteoric ground-water flow system (Casadevall and Ohmoto, <br /> 1977). The metals which were deposited in the vein systems of the Sunnyside Mine had <br /> previously been leached by meteoric water from disseminated minerals in the bedrock located <br /> upgradient. <br /> In summary, prior to mining, ground water which had traversed the length of the bedrock flow <br /> system appears to have had a pH of less than 5.0 and a dissolved load of metals greater than in <br /> unmineralized areas. Ground water near the recharge area had a more neutral pH, yet had a <br /> relatively high concentration of lead and manganese. <br /> sanjuan\sunny\110361\oct9 LRpt 26 <br /> eOR� simon mem <br />