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0209%00 WED 1J:59 FAE IdJ00~ <br />• • <br />DRAFT <br />QUESTIONS AND ANSWERS <br />What does timed of travel mean? <br />Time of travel is the amount of time it takes for water, and anything in the water, to move <br />from one point to another. For Source Water Protection, time of travel is calculated using <br />information about how water moves through the ground to reach the well. In this case, <br />the time of travel estimates look at how long it would take for any possible r;ontaminants <br />in the ground water under natural conditions to flow from the mine permit boundary to <br />the drinking water supply wells for the town. There is no consideration of dilution, <br />dispersion, or other attenuation mechanisms within the system. <br />Why are the values determined for this project different? <br />The time of navel was determined by EPA using a simple analytical method consistent <br />with those used by CDPHE for delineating wellhead protection areas in their Wellhead <br />Protection and Source Water Assessment and Protection programs. Such a delineation <br />determines the surface and subsurface azea most likely to be contributing water to a well <br />from that point outwazdb The approach makes ultraconservative assumptions t <br />maximize public health pro ection. <br />In this case, the hydrogeologic properties for the Alamosa Formation, the unit in which <br />the town's drinking water supply wells are completed, were used in the calculation. This <br />is consistent with the State's procedure for a drinking water source protection evaluation. <br />Thus, the resulting 15 years is an ultraconservative, worst-case scenario time of travel <br />value. <br />The CDNR-DMG determination employed the same analytical technique buy. utilized the <br />approach taken when evaluating potential contaminant sources (ie., looking iiom the <br />potential source of contaminants outwazds). In this case the hydrogeologic properties for <br />the Santa Fe Formation, the unit underlying this area of the acil' we •e ed ' e ~;" <br />calculation as this was an evaluation of migration from the nat~Esattree <br />to the receptor. Thus, the resulting 190 yeazs iservative contaminant transport <br />value. { <br />Neither value is intended to be a definitive determination of the likelihood of <br />contamination reaching this specific drinking water well. More extensive h}~drogeologic <br />mapping and modeling is necessary in order to complete a definitive determination of <br />contaminant fate and transport from this potential source of contaminants to Phis receptor. <br />What is a wellhead protection area and how is it determined? <br />A wellhead protection area (WHPA) is the surface and subsurface area surrounding a <br />O QJ <br />