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water from Sneffels Creek. This is a good result since the purpose of the wells is to measure the groundwater and <br />not the water from Sneffels Creek. The data used in this analysis along with the corresponding relative percent <br />difference calculations can be found in Appendix C. <br />Well Water and Seep Water Data <br />An analysis was conducted to determine whether the water sampled in the seep after the mine water pond was <br />drained represented groundwater. Although there was a significant change in the water composition after the <br />mine water pond was drained, comparison of seep data and groundwater results from the well samples indicates <br />that the seep does not entirely consist of groundwater, or the groundwater that is being measured is of poor <br />quality. The relative percent difference between each well sample and an average value of concentrations in the <br />seep water after the mine water pond was calculated. For the June sample date, this percent difference ranged <br />from 49% to 65 %. In the July sample date, the percent difference ranged from 47% to 74 %. These large percent <br />differences indicate that the seep water does not represent the previous condition when mine water was being <br />delivered to the Revenue Pond and exiting to Sneffels Creek through the seep. It can also be assumed that the <br />source of the seep water has another natural source such as runoff. The data used in this analysis along with the <br />corresponding relative percent difference calculations can be found in Appendix 0. <br />Chapter 6 - Groundwater Representation <br />Explanation of Methodology <br />A representative value for the baseline groundwater for each parameter tested was determined by comparing the <br />well sample results. Because the shallow well samples tended to be worse in quality than the deep samples, the <br />shallow well results were used to determine the representative value. When an average of the three shallow well <br />values was taken for each parameter, one of the wells was almost always out of compliance with the <br />representative groundwater level. Thus, the maximum level for each parameter was used to set the representative <br />groundwater value. The calculations justifying this methodology along with the complete ICP lab results for the <br />groundwater well samples can be found in Appendix E. As allowed by DRMS, 25 percent was added to this value <br />to determine the final representative groundwater standard value. This value represents the highest amount <br />encountered in the baseline data and is more or less a worst case scenario, as the interaction between the shallow <br />and deep wells cannot be fully estimated. <br />5 <br />