2010-05-07_PERMIT FILE - C2009087 (6)

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Nitrate - Nitrogen - Nitrate - nitrogen content of floor and roof samples were below the laboratory detection limit of one mg/kg except for one sample that had a result of one mk/kg. According to the • WDEQ guidelines, the aquifer restoration suitability ceiling is 50 mg/kg. Selenium — The average selenium concentration was 0.0937 mg/kg with a range of 0.0399 to 0.195 mg/kg. The average concentration is considered suitable for reclamation with three of the 10 samples slightly over the marginal concentration. No aquifer restoration concerns are anticipated given the low hydraulic conductivities of overburden and underburden materials and the relatively low concentrations. Textural Analysis - The average particle size of all 10 samples analyzed was 63 percent sand, 24 percent silt, and 13 percent clay, which yielded an average texture of sandy loam. The textural analysis has minor relevancy for aquifer restoration purposes. For reclamation purposes the material would be marginal, however, there is little likelihood that texture would significantly impact reclamation and revegetation success. Saturation Percentage - The average saturation percentage of all nine samples was 27 percent, with a range of 23 to 32 percent. According to WDEQ Guideline No. 1, overburden with saturation percentages of 25 to 80 is considered to have a good to fair reclamation suitability. No relevancy is present for aquifer restoration. Sodium Adsorption Ratio - The average sodium adsorption ratio of the 10 samples analyzed was 17.5, with a range of 7.7 to 36. At face value, these analyses results appear to indicate the potential for development of sodic refuse and gob materials; however, it is important to also consider that the • salinity hazard, as predicted by the electrical conductivity test, is very low. Due to this observed inconsistency between salinity potential, as measured by the sodium adsorption ratio, and salinity hazard, as measured by electrical conductivity, Dr. Sterling Olsen, a soils scientist with the USDA Agricultural Research Service at Colorado State University, was consulted. Dr. Olsen's further review of the analyses data determined that the indicated sodium hazard potential results from inappropriate application of sampling and analysis techniques developed for surface agricultural soils to unweathered overburden. According to Dr. Olsen, the calcium values obtained from the analyses are much lower than would be expected for surficial materials. The average (soluble) calcium concentration was found to be 3.87 milliequivalents per liter (meq/L), and, according to Dr. Olsen, the solubility of calcium is correlated with the amount of carbon dioxide present in the atmosphere. The concentration of calcium when it is in equilibrium with air, at a pH of 7, should equal 7 meq/L. From a practical standpoint, Dr. Olsen indicated that once the roof and floor materials are exposed to the atmosphere (both in the mine, and if brought to the surface as refuse), the soluble calcium concentration will increase, and the sodium hazard potential will decrease due to the competition of these two cations for the same exchange sites. The increase in soluable calcium to a minimal concentration of 7 meq/L will result in a relative decrease in the effective average sodium adsorption ratio from an average of 17.5 to a value of around seven. Soluble calcium in excess of 7 meq/L will result in even lower sodium adsorption ratio values. Evidence to support this explanation of chemical process is provided by sodium adsorption ratios from analysis of Wadge Coal Seam overburden is samples collected in this same area as previously discussed in the CYCC Permit Application No. 79- 177. PSCM Permit App. 2.04 -31 6/15/09