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RULE 2 PERMITS <br />The analytical data from the Colowyo boreholes includes: pH, conductivity, saturation percentage, <br />percent sand, silt, and clay, sodium absorption ratio, exchangeable sodium percentage, cation exchange <br />capacity, boron, molybdenum, selenium, nitrate -nitrogen, calcium carbonate equivalent, sulfur forms, <br />non -sulfate sulfur and total sulfur. The AGP and the ANP:AGP ratio for samples collected in 1997 were <br />calculated based on pyritic -sulfur percent. The AGP and the ANP:AGP ratio for samples collected in <br />1999 and 2000 were calculated based on total -sulfur percent. For samples collect in 2000 if the ABP was <br />negative based on an AGP calculated using total -sulfur then, nonsulfate-sulfur was determined and used <br />to calculate the AGP, ABP, and ANP:AGP ratio for that sample. <br />The criteria shown on Page 2.05-8 of Volume 1 of the current permit will be used to measure reclaimed <br />overburden suitability. These criteria are based on negotiations with the DRMS and in part on the <br />Wyoming Department of Environmental Quality, Land Quality Division (WDEQ-LQD), Guideline No. 1, <br />Topsoil and Overburden, Table 1-4 (August, 1994). The WDEQ-LQD guidelines were used since <br />Colorado has no published standards as of the date this permit was revised. The overburden suitability <br />criteria used by WDEQ-LQD are shown in Table 2.04.6-2. A summary of borehole overburden and <br />interburden results compared to the WDEQ criteria is provided in Table 2.04.6-3, and a summary of the <br />percentage of each borehole that is less than "suitable" for each selected WDEQ criterion is shown on <br />Table 2.04.6-4. These comparisons are for informational purposes only, since the criteria on Page 2.05-8 <br />of Volume 1 will determine regraded overburden success in the South Taylor/Lower Wilson mining <br />areas. <br />Selenium was found to exceed the WDEQ "suitable" criterion of 0.3 ppm in 1.74% of the borehole <br />intervals across South Taylor and Lower Wilson (Table 2.04.6-4). The Colowyo Mine regraded <br />overburden sampling performed since 1983 and reported by Colowyo in the 2005 Annual Reclamation <br />Report shows mean selenium concentration of 0.03 ppm, with a maximum value of 0.47 ppm and <br />exceedances of the WDEQ "suitable" criterion in only two of the 279 samples. Similarly, boron was <br />found to average 0.34 ppm in 279 samples, with only one sample exceeding the WDEQ boron "suitable" <br />criterion of 5 ppm in the regraded overburden. Only one borehole (83-133-14) exceeded the boron <br />criterion in one interval with only 0.47% of all borehole samples in South Taylor and Lower Wilson <br />exceeding the WDEQ boron criterion. Lead did not exceed the existing permit "suspect level" of 20 ppm <br />in any borehole sample, and only one regraded spoil sample out of 279 exceeded this value at 20.9 ppm. <br />Molybdenum exceeded the WDEQ "suitable" criterion of 1 ppm only in boreholes from the Lower <br />Wilson area, and none of the boreholes from South Taylor. Similarly, all seven regraded overburden <br />samples obtained by Colowyo that were analyzed for molybdenum contained 0.4 ppm molybdenum. This <br />information indicates that selenium, boron, lead, and molybdenum are not issues in the regraded <br />overburden in the mined formations using current mining practices. The regraded overburden analyte <br />monitoring shown on page 2.05-8 of the existing permit has been modified with this submittal to reflect <br />this information. <br />A small percentage of the overburden samples are acidic or have a potential to generate acid. Only four <br />samples representing 21 feet or 1.23% of the overburden sampled contained ABP less than —5 tons <br />CaCO3 equivalent/1000 tons material. Thirty-seven samples representing 85.3 feet or 1.8% of the <br />overburden sampled had a saturated paste pH less than 5.5. Three samples representing 10.8 feet or <br />0.23% of the overburden and interburden sampled had a pH greater than the WDEQ "suitable" criterion <br />of 8.5. Of 308 regraded spoil pile samples reported in the 2005 Annual Reclamation Report, none <br />exceeded any pH criteria, with 8.4 the maximum pH, 6.3 the minimum measured pH, and 7.5 being the <br />mean overburden pH. This indicates that homogenization of the overburden during mining results in <br />overburden that has an ideal paste pH. <br />One hundred and thirty samples representing 805.9 feet or 17.04% of the borehole overburden and <br />interburden sampled in the South Taylor/ Lower Wilson areas had a SAR greater than "suitable" criterion <br />South Taylor/Lower Wilson — Rule 2, Page 17 Revision Date: 11 / 18/16 <br />Revision No.: MR -163 <br />