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ARCADIS <br />4. Conclusions and Recommendations <br />Based on the information presented in this report, we have concluded the following: <br />• The March 2013 results at well MW -7 appear to be similar to the March 2012 <br />results for manganese, while TDS and sulfate concentrations are higher. The <br />potassium to sodium ratio remains low in this well. <br />• The sodium concentration in monitoring well MW -7 exceeded the DRMS <br />compliance standard by more than 10 percent. No other analytes exceeded the <br />compliance values. <br />• Generally stable or decreasing trends for manganese, TDS and potassium to <br />sodium ratios continue to be observed in wells MW -12 and MW -13, while sulfate <br />concentrations in these wells show a slight increasing trend. <br />• For the downgradient well MWA 3, the concentrations remain below the proposed <br />NPLs for all parameters except sulfate. The sulfate concentration in groundwater <br />from MWA 3 exceeded the NPL by approximately 4.5% which is less than 10% per <br />the DRMS letter dated November 27, 2012. <br />• Groundwater flow is to the south and velocity is 0.3 to 1.9 ft/yr, which is consistent <br />with historical data. In addition, groundwater elevations and interpreted flow <br />direction are similar to previous sample rounds. <br />Although the March 2013 sampling results indicate that sodium in groundwater from <br />MW -7 and sulfate in groundwater from MW -13 exceed the respective NPL, semi- <br />annual monitoring is no longer required per the DRMS letter dated February 24, 2009 <br />for MW -7 and the DRMS letter dated November 27, 2012 for MW -13. <br />Based on March 2013 sampling results that indicate there is no discernible impact from <br />CKD, ARCADIS recommends that annual groundwater monitoring resume unless <br />future results require in increased monitoring frequency. <br />2013 Groundwater <br />Monitoring Report <br />Florence, Colorado <br />11 <br />