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Page 20 of 27 <br /> umhos/cm respectively. Overall,the trends in water levels and the water quality indicate mining has not <br /> adversely impacted the Middle Sandstone aquifer outside the permit boundary. <br /> Twentymile Sandstone <br /> Water level monitoring data reported through the 2022 annual hydrology report had shown no substantial <br /> change in the piezometric levels in the Twentymile Sandstone that could be attributable to mining <br /> activities. The water quality data for the two Twentymile Sandstone wells,No. 9 Mine Well and Well <br /> 259, showed no adverse impact has likely occurred, although conductivity in the 49 Well appears to have <br /> risen since 2011 and is currently trending down.,while the trend is upward in well 259. <br /> Williams Fork Alluvium <br /> Ground water levels in the alluvium have remained fairly regular,with normal seasonal fluctuations <br /> apparently related to changes in river levels. Ground water levels in the alluvium are plotted in Figure 22 <br /> in Section 2.04.7 of the permit application package. Annual hydrology reports through 2022 indicate no <br /> depletion has occurred and suggest that mining appears to not have affected Williams Fork River alluvial <br /> water quality. <br /> Compliance with the Basic Standards for Ground Water <br /> (Regulation 41 of the Colorado Water Quality Control Commission) <br /> Section 4.05.13(1) of the Regulations requires the establishment of one or more ground water points of <br /> compliance (wells) for an operation which has the potential to negatively impact the quality of ground <br /> water. The mine monitors the Middle Sandstone in well TR-7a and the Williams Fork alluvium in well <br /> AVF-5. The TR-7a well is within the expected bedrock flowpath of mine leachate, should the mine <br /> discharge leachate to bedrock units. The AVF-5 well is within the expected alluvial flowpath of leachate, <br /> should the mine discharge leachate to Williams Fork River alluvium. AVF-5 is also within the expected <br /> flow path of pumped mine water, should mine water adversely impact the alluvial water. Both wells meet <br /> the qualifications of a compliance point, as those qualifications are listed in Section 4.05.13(1)(b). <br /> Monitoring data from both wells indicate the mine has not caused an exceedance of the Basic Standards <br /> for Ground Water with the exception of Manganese levels in AVF-5 which is often above the Basic <br /> Standards for Groundwater drinking limit. However, according to section 2.04.7 of the permit, dissolved <br /> solids, iron, lead,manganese and sulfate often exceed the drinking water standards naturally. <br /> Observed Surface Water Impacts <br /> Discharges from the 5 and 6 Mines have not caused measurable depletion of stream flows in the mine <br /> vicinity. Monitoring data in the annual hydrology reports from 1981 through 2022 indicate the Williams <br /> Fork Mines have not significantly impacted the water quality of the Williams Fork River. <br /> F. Stream Buffer Zones -Rule 4.05.18 <br /> The Williams Fork Mines included several structures located within 100 feet of the perennial Williams <br /> Fork River. Locations of these structures are shown on Permit Map 26. <br /> Williams Fork Mines Prepared by: R ReiRey M.S. GISP <br /> C1981044 December 2023 <br />