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Cresson Project – AM-11 Adequacy Review <br />Page 14 <br />May 03, 2016 (Revised May 31, 2016) <br /> <br />11.” However, this statement only holds true as long as rocks in the saturated zone <br />remain saturated, meaning that mining activities are restricted to rocks above the <br />saturated zone and/or the water table does not lower. As pointed out above, you state <br />in this section that the proposed underground mining activities may penetrate the <br />saturated zone. Please explain this discrepancy. <br /> <br /> Page 4-5: The text states “Deleterious change in saturated groundwater or surface <br />water chemistry is not expected as a result of AM-11 activities.” Does this also apply <br />to shallow groundwater in the region? Have you considered adding a shallow <br />groundwater monitoring well(s) in Poverty Gulch? If not, how will you know <br />whether a deleterious change to shallow groundwater chemistry has occurred <br />due to increased mining activities near Poverty Gulch? <br />4.6 – Hydrology <br />4.6.1 Surface Water <br /> Page 4-8 - Grassy Valley: The text states that the proposed increase to the final crest <br />elevation of ECOSA to 10,960 feet is not expected to impact surface water quality of <br />Grassy Valley nor will it impact the locations of current monitoring stations in th e <br />drainage. However, in Volume II, you discuss the toe seepage occurring from <br />ECOSA (on the portion located outside of the diatreme) during high infiltration <br />events. Do you anticipate an increase in seepage intensity with a greater load <br />being placed on ECOSA with AM-11? How will you work to minimize impact to <br />the Grassy Valley drainage? <br />4.6.2 Groundwater <br /> Page 4-10 - Poverty Gulch: The text states “The underground workings that will be <br />accessed by the Chicago Tunnel portal lie within the diatreme and have been <br />dewatered by the historic drainage tunnels”, and that “no impacts are anticipated to <br />the groundwater quality in Poverty Gulch as a result of AM-11”. However, under <br />Section 4.5 Geochemistry, page 4-5, you mention that the underground exploration <br />may penetrate the zone of saturation in the northern portion of the diatreme. Please <br />explain this discrepancy. <br />4.6.3 Summary <br /> Page 4-12: The text states “the presence of historic mine features in many of the <br />drainages appears to have some influence on the current surface water quality”. <br />Please describe in particular what impact(s) you are referring to. Furthermore, <br />how do you differentiate impact from historic mine features from impact from <br />mining activities occurring under this permit? <br />If you have any questions, please contact me by telephone at (303) 866-3567, extension 8129, or <br />by email at amy.eschberger@state.co.us. <br /> <br />Sincerely, <br /> <br /> <br />Amy Eschberger <br />Environmental Protection Specialist