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Mr. Ben Moline <br />Coors Energy Company <br />June 6, 2016 <br />Page 2 of 3 <br />Item #2: A reply to this item is pending as stated in the Response. <br />Item #3: The Response included the locations of groundwater sampling wells DH -96 and DH -122. Please assure all <br />monitoring locations are identified in future groundwater monitoring reports. <br />Item #4: Limited field notes were copied and submitted in response to this item. These limited notes are unclear <br />as to whether enough groundwater was purged to assure the collection of formation water. The Facility should <br />note that standard industry practice includes collection of this type of information for groundwater monitoring <br />(reference ASTM D6452-99 (reapproved 2005)). The purpose of this standard information in part is to assure <br />formation water is collected by the sampler to minimize false -positive errors. <br />The Facility's response indicates that in accordance with the Plan that this information is maintained "in the <br />operating record". Based on the submittal attached to the Response the Division is concerned that the sampler <br />cannot assure that three well volumes have been collected, or alternatively that groundwater being purged has <br />stabilized, providing evidence that formation water is being collected for analysis. <br />Item #5: This item clarifies that groundwater monitoring well SMW-2 is completed in the Facility's mine spoils. The <br />Response then provides a treatise on the definition of a mine spoil and other information that includes the <br />following: <br />a) The Facility attests that the mine spoil is comprised of claystone and sandstone. <br />b) The formerly open pit was dewatered creating a groundwater depression. <br />c) The average hydraulic conductivity is approximately 3.3 x 10"5 cm/sec (34.14 feet/year) for in place <br />geologic materials. <br />d) The groundwater is being impacted by the mining spoils. Manganese concentration increases are <br />associated with leaching from these in place spoils as the groundwater depression re -saturates. <br />Based on this response the Division has two follow-up questions: <br />i) What is the predicted time to refill the depression? <br />ii) What month and year did the dewatering activity cease at this mining pit? <br />Item #6: The response to this item indicates that the term "outlier" is being used to address statistical increase <br />verifications. The Response references what is termed by the Plan as a "one -of -two verification resampling <br />scheme". <br />The Plan also identifies a notification concern that is in apparent conflict with current Regulation. Note that the <br />Facility is required to notify the Division and the local governing body having jurisdiction within 14 -days of a <br />statistically significant increase pursuant to Appendix B, section B4(C). While the Division agrees with verification <br />sampling the Regulations do not specify that any allowed verification processes preclude the notification pursuant <br />to Appendix B, section 64(C). The Plan states that this notification is only required after an additional sampling <br />event to be completed after 7 -days of a statistical increase verification made by a second verification resampling <br />event. <br />The Response further concludes that manganese concentrations in groundwater are present and that these <br />concentrations are likely the result of the Facility's operations. <br />Item #7: Please include copies of the statistical reports discussed by the Response in future annual groundwater <br />monitoring reports for review by the Division. <br />Item #8: The Response confirms the discrepancy between the language in the Plan. <br />