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<br /> <br />n <br />U <br />RESPONSE. The Bureau of Reclamation study (ca. 1993) indicates that Hg <br />probably derives from tributaries to the West Dolores. Informal speculation <br />suggest that mercury may have derived from mining practices. No available <br />information indicates that the proposed gravel mine is a mercury source. <br />M. The atnutlative effects on water quality of mining multiple pits in close proximity has <br />not been evaluated. <br />RESPONSE: The objectors comment is accurate. Anecdotal evidence indicates <br />that cumulative effects on water quality are not evidently adverse. <br />CONCLUSIONS <br />1. At specific gravel operations where local conditions or substantive objections <br />warranted groundwater monitoring or other more detailed geochemica] investigation, <br />the Mined Land Reclamation Board has required monitoring, data collection, or <br />studies as conditions of mining. Local conditions at the proposed operation do not <br />support the need for such information. <br />2. Disaggregation and crushing increases the amount of exposed mineral surfaces. <br />3. Disaggregation of unsaturated alluvium due to mining may increase dissolved solids <br />concentrations in the short term if previously unexposed salts are exposed to water. <br />4. Disaggregation of any rock increases concentrations of settlable and suspended solids <br />over the original, intact material mass. <br />5. Disaggregation and the accompanying increase in surface area may enhance <br />weathering rates and increase TDS in the local area if materials are allowed to <br />weather on site prior to shipment. <br />6. The materials to be mined are dominantly volcanic rocks from the San Juan volcanic <br />field. These materials have been mined without incidents of pollution in various <br />places in the state, including the Dolores river valley. <br />7. The proposed dewatering, excavation, and trucking system of mining is a mining <br />practice typical in the industry. These methods are not known to inherently release or <br />concentrate pollutants. <br />8. Definitive studies showing the degree to which TDS may increase due to excavation <br />or material crushing are not known to this reviewer. Anecdotal information and <br />gravel mining history indicate that substantive changes in ground and surface water <br />quality do not occur as a result of these practices. <br />I3 <br />