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Mr.Alex Alarcon January 21,2019 Page 3 Information collected during groundwater sampling activities was recorded onto Groundwater Sampling Record fonds,which are provided in Attachment D. Water Qualit)f Anal}uses Field measurement and laboratory analytical results are summarized in Table 1,and full laboratory reports and chain of custody forms are provided in Attachment E. Samples were analyzed for the full suite analysis per TR-06(Table 3, Colorado Agricultural Standards, CDPHE 2016)plus total dissolved solids, with some exceptions. During January, there was not adequate sample volume from MW-6 to analyze in the laboratory for pH,TDS, Fluoride and Nitrite. For the December analyses,TDS was not able to be reported for either MW-6 or MW-7 due to a lab error.The lab accidentally filtered all unpreservod volume that was remaining after the lab ran the anions for dissolved metals.This did not leave any remaining volume for the TDS analysis(Attachment E). Discussion of Results As shown in Table 1,the only analytical result elevated with respect to Colorado Agricultural Use Standards is manganese. As stated in the basis and purpose for Regulation 41 (CDPHE, WQCC 2016),the original agricultural manganese standard was derived from EPA's 1972 Water Quality Criteria ("Blue Book"),and addressed crop toxicity in acidic soils. In order to remain consistent u ith the 1972 criteria,as well as with Regulation No. 31,the Commission elected to add a footnote to specify that the agricultural manganese standard is only appropriate where irrigation water is applied to soils with pH values lower than 6.0. Manganese,along with iron, are often elevated in shallow water wells naturally, and there is no conceptual rationale why the quarry would result in elevated concentrations of this parameter. Exposure of the fault zone could result in some oxygen infiltration to the subsurface that could result in reductions in manganese and iron through the formation of oxides and hydroxide minerals. Results of several analyses,including iron and manganese,were higher in initial samples and then decreased in subsequent samples. This could be due to the fresh oxygenation and/or residuals from initial well development. Comparing MW-6 and MW-7 water quality results in Table 1.it is notable that field parameters for the wells are very similar. The pH for both wells is circumneutral. Differences between the two wells are noted mostly in iron and manganese, with iron higher in MW-7 and manganese higher in MW-6. The data suggest that the groundwater at these two closely spaced locations are of the same general origin,but b�cause of the low hydraulic conductivity(i.e., lack of fracturing)at MW-6,there are some differences. Given the distinctly different groundwater yields produced by closely spaced wells installed in the same stratigraphic interval. it is apparent that groundwater flow is dominated by fracturing and groundwater yield from the unfractured Fort Hays Limestone is relatively low even when adjacent to a productive facture system (possibly associated with the mapped fault). This suggests higher water yielding zones are not oriented sub-horizontally with bedding,but more vertically along the orientation of the fracturing. This finding downplays the importance of monitoring the Codell Sandstone,as it appears that the sub-vertical fault is the primary sourer;of groundwater flowing across the site downgradient of the quarry panel. The fault is likely producing groundwater that is a composite of The units it t ansects(i.e..the Fort Hays and Codell). Close Consulting Group LLC