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• <br />TABLE 4. Nonmandatory standards and goals for total dissolved solids (from Hem, 1992, <br />p. 212. <br />USPHS 500 mg/L <br />AWWA <200 mg/L <br />Thus, TDS values at the Bedrock station, while averaging near the US Public Health <br />Service value, exceed levels recommended by the American Water Well Association. <br />TDS values above and below the proposed Line Camp Pit bracket the AWWA <br />recommended value and fall below the USPHS recommended value. <br />Overall, the absence of evidence that alluvial wells in the River valley pose water quality <br />problems, and the lack of mention of existing water quality problems in the vicinity of the <br />proposed gravel operation together suggest that surface water quality is not locally an <br />issue. Elevated salinity, in the downstream river water, indicates a relatively high salinity <br />source upstream. Changes in average TDS between the Twin Spruce and Tam-Koenig <br />pits, which bracket the proposed Line Camp pit, provide permissive evidence of increased <br />halite dissolution with distance of river travel. <br />Although there are sources of high metals loads below some previous metal mining <br />operations, there is no indication of elevated metals near the proposed Line Camp <br />operations (US Bureau of Reclamation, ca. 1993). Low pH and high metals concentrations <br />near former mining operations in the upstream are apparently diluted and appear to be <br />within metal standards for all uses near the Line Camp area. There are no geological <br />indications that the proposed operation would intersect source rock that could release high <br />metal concentrations. <br />OBJECTIONS <br />The following objections are addressed. <br />A. Mining will release (a) toxins, (b) carcinogens, and (c) heavy metals from the site to <br />(d) groundwater, (e) the Dolores River, and (~ McPhee Reservoir. <br />Response: Objectors correctly noted that some of the elements deemed to harbor <br />potential adverse effects are considered toxins or carcinogens and some are commonly <br />considered heavy metals. These objections do not note the levels above which toxicity <br />effects are noted, which is the most important consideration. Evidence on the metal <br />concentrations that could develop due to mining was not provided. No evidence <br />showing how any of the named elements or compounds or any other compound or <br />s <br />