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~. <br />rd <br />contaminants that might be of greatest threat to a drinking water supply; locals can use this <br />information to adopt protective measures for their source waters and contingency plans in the <br />event of a mishap. The approach used in my work was an ultraconservative groundwater <br />velocity calculation which is technically consistent with and applied based on the recommended <br />methods for WPHA/SWAA delineation within the State's programs. The resulting value of time <br />of travel was presented for comparison versus the existing State policy of 5 yeazs to show <br />whether or not the facility in question would be located within the WHPA/SWAA that would be <br />delineated based on ground-water flow time of travel determinations. <br />The calculation of time of travel from the southwestem mine permit boundary to the <br />town's nearest drinking water-supply well was performed using values for aquifer parameters of <br />the Alamosa Formation within which the town's drinking water-supply wells are co;npleted. <br />This hydrogeological assessment was made even though it is not the Alamosa Formation but the <br />Santa Fe Formation, a low permeability unit, that underlies the southwest permit boundary area <br />and extends out into the basin. It is between the area occupied by the Santa Fe Formation and the <br />town that the Alamosa Formation actually becomes a part of the ground-water pathway of <br />concern. Nevertheless, by using the Alamosa Formation in the analysis, the approach becomes <br />ultraconservative and consistent with the State's drinking water protection programs for <br />development of the WHPA/S WAA for the town's wells. Based on this approach, the estimated <br />time of travel of ] 5 yeazs from the southwestem extreme of the mine permit boundary to the <br />nearest we]] exceeds the State policy value for drinking water protection by a factor ~f 2. <br />Therefore, this facility would not fall within the WHPA/SWAA based on the ground-water flow <br />pathway alone under the State's policy and ultraconservative approaches to delineation. <br />If you should have any questions, please feel free to contact me at 303-312-6595. <br />Sincerely, <br />2N.'4 M ,.~~ <br />Rich Muza, Hydrologist <br />Ecosystems Protection Program <br />Office of Ecosystems Protection and Re~mediation <br />cc. Juanita Bernal, SLWSD <br />Mike McGowan, CCCD <br />Jim Dillie, CDNR-DMG <br />Cazol Russell, 8EPR-EP <br />