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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 similarly when compared to the well water data. Although there was a <br />significant change in the water composition after the mine water pond was drained, comparison of seep data and <br />groundwater results from the well samples indicates that the seep does not entirely consist of groundwater, or <br />the groundwater that is being measured is of variable quality. The relative percent difference between each well <br />sample and an average value of concentrations in the seep water after the mine water pond was calculated. For <br />the June sample date, this percent difference ranged from 49% to 65 %. In the July sample date, the percent <br />difference ranged from 47% to 74 %. These large percent differences indicate that the seep water does not <br />represent the previous condition when mine water was being delivered to the Revenue Pond and exiting to <br />Sneffels Creek through the seep. It can also be assumed that the seep water may in part have another natural <br />source such as runoff. Another possible explanation is that the seep water travels through different materials <br />before appearing at the surface. For instance, if the water were to travel through historic mine material (waste <br />rock, tailings, etc.) the water quality could be altered. When compared to the ground water sampled in the wells, <br />which doesn't travel through such a path, the quality would be variable. The data used in this analysis along with <br />the corresponding relative percent difference calculations can be found in Appendix D. <br />Because the seep data does not directly relate to the groundwater wells it would not be appropriate to apply to <br />the development of standards for such water. However, despite the fact that it has been determined that the <br />water in the seep is of differing quality than the water sampled in the wells, it should be noted that the data <br />collected at the seep is still of significant value. More specifically, it provides a larger picture of groundwater <br />interacting with various historic mine workings. It also provides additional quarters of sampling to accommodate <br />for groundwater characterization. Due to the large amount of historical data present for the seep, it is suggested <br />that the standard five quarters of data collection at the wells may not be necessary to fully characterize the <br />baseline water quality. <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. When an average of the well values was taken for each parameter, one of the wells was <br />always out of compliance with the representative groundwater level. Thus, the maximum level for each parameter <br />was used to set the representative groundwater value. The complete ICP lab results for the groundwater well <br />samples can be found in Appendix E. As allowed by DRMS, 25 percent was added to this value to determine the <br />final representative groundwater standard value. This value represents the highest amount encountered in the <br />baseline data and is more or less a worst case scenario, as the interaction between the shallow and deep wells <br />cannot be fully estimated. <br />