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• <br />DRAFT <br />QUESTIONS AND ANSWERS <br />What does time travel 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, 1n rhis case, <br />the time of travel estimates look at how long it would take for any possible contaminants <br />in the ground water under tiatiir~ 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, t>f other attenuation mechanisms within the system. a.~-~ ~ krL2 - <br />Why are the values detctmined for this project different? <br />The time of travel 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 subsurfacc azea most likely to be contributing water io a well <br />from that point outwazd. The approach makes ultraconservative assumptions to <br />maximize public health protection. <br />In tl»s case, the hydrogeologic properties for the Alamosa Formation, the unit ix which <br />the town's drinking water supply wells aze completed, were used in the calculatian. 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 but utilized the <br />approach taken when evaluating potential contaminant sources (ie., looking from the <br />potential source of contaminants outwazds). In this case the hydrogeologic properties for <br />the Santa Fe Formation, the unit underlying this azea of the facility, were used in the <br />calculation as this was an evaluation of migration from the potential contaminant source <br />~...~ , ~w<.~., si... <br />to the receptor, Thus, the resulting 190 yeah is a wnservatrve 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 hydro@eologic <br />mapping and modeling is necessary in order to complete a definitive deteaninatio~z of <br />contaminant fate and transport from this potrntial source of contaminants to this 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 />~yjUV4 <br />O <br />