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,0:~ 0900 R7:D 1J:58 FA~C f~00-t <br />• <br />u <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. In this case, <br />the time of travel estimates look at how long it would take for any possible contaminants ~, C ~,s „-~ <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 3ilution, <br />dispersion, or other attenuation mechanisms within the system. rr, , s u ~ ui r, ~ o ~ , s <br />Why are the values determined for this project different? <br />The time of travel was determined by EPA using a simple analytical method consistent <br />with those used by CDPI-IE for delineating wellhead protection areas in their Wellhead <br />Protection and Source Water Assessment and Protection programs. Such a delincation <br />determines the surface and subsurface azea most likely to be contributing water to a well <br />from that point outwazd. The approach makes ultraconservative assumptions to <br />maximize public health protection. <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 yeazs is an ultraconservative, worst-case scenario time of travel <br />value. <br />The CDNR-DMG determination employed the same analytical technique but utili2ed the <br />approach taken when evaluating potential contaminant sources (ie., looking from the <br />potential source of contaminants outwazds). In this case the hydrogeologic oroperties for <br />the Santa Fe Formation, the unit underlying this area of the facility, were used in the <br />calculation as this was an evaluation of mit?ration from the~otential contaminant source <br />to the receptor. Thus, the resulting 190 yeazs is a conservative 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. Moro extensive hydrogeologic <br />mapping and modeling is necessary in order to complete a definitive determination of <br />contaminant fate and transport from, this potential source of contaminannts to this re1ceptor. <br />-1~;•,.~v.~'f ~t nn l.~5 ~,~,~~8~-d xsf~ ir~ pil .~..n1ly~.~ Xil e.. ~1 'J-We.E.- <br />What is`a`wellhead Prot tt n area andlrow is it determined? ) <br />A wellhead protection area (WHPA) is the surface and subsurface azea surrounding a <br />o QJ <br />