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TO: JANET BINNS <br />FROM: ROB ZUBER <br />SUBJECT: COLOWYO SL -05, HYDROLOGY TEXT FOR FINDINGS <br />DATE: 7/9/2012 <br />Evaluation of Hydrologic Impacts Required by Section 3.03.2(2) <br />Rule 3.03.2(2) requires the Division to evaluate hydrologic impacts prior to releasing <br />reclamation liability. This evaluation must consider whether pollution of surface or subsurface <br />water is occurring and the probability of future occurrence of such pollution. The Division's <br />evaluation is summarized below. <br />Ground Water Impacts <br />INTEROFFICE MEMORANDUM <br />The North Good Spring Well (sometimes called the New Good Spring Well) is an alluvial well <br />down gradient of the SL -05 parcels in the East Pit area. Observations of the data from this well <br />indicate that over time TDS and conductivity have increased somewhat. Also, TDS is higher in <br />this well than in the wells above the East Pit area (A6 and A7). However no concentrations of <br />analytes, including TDS, have increased to levels that are cause for concern. TDS values have <br />only rarely risen above 2,000 mg/1 and have generally only been slightly above (less than 120 <br />percent of) values measured prior to the 1990s. Small increases in TDS are in agreement with <br />the expected probable hydrologic consequences of mining listed in the PAP. <br />In the West Pit area there are no alluvial wells in the vicinity of the former pit and SL -05 <br />reclamation area. Per initial Colowyo hydrology reports (e.g., the PAP includes a 1979 report by <br />Leonard Rice Consulting Water Engineers), there was never a significant possibility of <br />groundwater contamination from mining in this area, and there is no reason to believe that <br />groundwater contamination has occurred. <br />Any ground water in alluvial deposits in the bond release area meets the classification of Limited <br />Use and Quality because the alluvial water is of such small volume and is unlikely to be used in <br />the future. The Basic Standards for Ground Water have no water quality standards for the <br />Limited Use and Quality classification. <br />The PHC section of the Colowyo permit states that there will be a slight decrease in the water <br />elevation. Data for NGS Well closely follows this predicted trend. <br />