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Cresson Project – AM-11 Adequacy Review <br />Page 11 <br />May 03, 2016 (Revised May 31, 2016) <br /> <br />4.6.3.3 Discussion <br /> Page 30: The text states “Flow rates (when reported for the same day) increase into a <br />downstream direction from GV-01 to GV-02, but often decrease from GV-02 to GV- <br />03.” Do you suspect this has anything to do with GV-03 being located within the <br />diatreme? <br />4.6.3.4 AM-11 Impacts to Surface Waters <br /> Page 31: The text states “any infiltration from the ECOSA will be captured by the <br />Diatreme drainage system”. However, as noted previously, water infiltrating the <br />ECOSA during high precipitation events has been seeping from its toe. Because the <br />northern portion of the ECOSA is located outside of the diatreme, and the ECOSA <br />underdrains do not appear to be functioning properly, there is potential for impacted <br />waters to enter the Grassy Valley stream system. How do you intend to minimize <br />impact to Grassy Valley from ECOSA seepage? Will the proposed AM-11 raise <br />for the ECOSA intensify the seepage? <br />4.6.4.1 Monitoring Program <br /> Page 31: The text states that there are 4 groundwater monitoring wells in Grassy <br />Valley. However, the wells are not named in this section. Please list the names of the <br />wells here as you have in this section for previous drainages. There appears to be <br />only two groundwater monitoring sites labeled on Figure 2-1, GVMW-8A and <br />GVMW-8B. Please revise Figure 2-1 to show locations of all monitoring wells <br />discussed in this section. <br /> <br /> Page 31: The text states “the monitor program for Grassy Valley since 2012 has <br />focused on water level measurements in 9 monitor wells and compliance monitoring <br />(water quality parameters) in 4 wells.” Please list the names of all of the wells <br />mentioned in this section. Please show locations of all monitoring wells discussed <br />in this section on Figure 2-1. <br />4.6.4.4 AM-11 Impacts to Ground Waters <br /> Page 33: The text states “any infiltration from the ECOSA will be captured by the <br />Diatreme drainage system.” However, the northern portion of the ECOSA is located <br />outside of the diatreme, and the underdrain system does not appear to be functioning <br />properly. Therefore, how will you work to minimize impact to Grassy Valley <br />from any ECOSA infiltrated water that does not drain to the diatreme? <br />5 – Summary and Conclusions <br /> Page 34: The text states “the dewatering by the drainage tunnels has created <br />widespread dry conditions in at least the upper 750 feet of the diatreme and the <br />adjacent granites in portions of Grassy Valley.” However, it was mentioned <br />previously in the evaluation that the diatreme water table is located approximately <br />1,000-3,000 feet below the ground surface throughout most of the diatreme. In which <br />portion(s) of the diatreme is the water table at 750 feet below surface? <br />Table 2-1 Water Quality Monitoring Parameters