Laserfiche WebLink
Monitor well M-1 iR samples a portion of the alluvial aquifer, as do other alluvial monitor wells <br />installed during the TR-15 Response Plan (BMRI, 1999, Fig. 3-1; MW- and M- series wells). As <br />shown in Table 6-1, the water quality differs at the various monitor wells. In part this is related <br />to the position of the well with respect to the flow of groundwater from the pit to the alluvial <br />aquifer. <br />While groundwater quality, evaluated at any given time, generally improves down-gradient from <br />the `window," the changes in water quality aze not uniform across the whole of the alluvial <br />aquifer because the local concentrations aze controlled by five principal factors: <br />• The flux ofhigh-solute water out of the pit <br />• The flux oflow-solute water from sources other than the pit <br />• The extent of mixing that occurs as the co-mingled waters move through the <br />heterogeneous flow system of the alluvial aquifer <br />• • Reactions between groundwater and the local mineral-solids as groundwater flows <br />through the aquifer <br />• The time period over which the mixing process has occurred along the flow path to a <br />given location. <br />Given these complexities of the transport system, one cannot assert that a given monitor well <br />represents the "water quality of the alluvial aquifer" any better than any other location. <br />6.4.1 Performance-Monitoring Concept <br />The Statement of Basis for the Colorado groundwater quality regulations (20 CCR8, 8-97, <br />41.14A) recognizes that the heterogeneities that exist in groundwater systems and the <br />contingencies of site-specific discharge conditions often indicate that it may be well to defer <br />identification of formal points-of-compliance until a strong, site-specific understanding exists. <br />• <br />Bau(e Maunmin Resources, /ne. <br />p:11002671reporlslmarchrplllr26wlrmng(mareh.dot 70 March 21. /999 <br />