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Lazamie formation. TDS of leachate migrating through these units will be diluted to within 25% of uncontaminated ground water after five dilution cycles. SAR will be less than 10 after two dilution cycles. If one dilution cycle occurs over a migration distance of 100 feet, then a significant plume would not extend more than 500 feet downgradient from the pit. It will take a time period on the order of 500 years for a plume to extend 500 ft. from the pit (using the 1 ft/yr flow velocity calculated in Table 1). The plume would spread out (attenuate) vertically and laterally along its flow path in the alluvium and sand. This attenuation would further reduce the concentration of the plume. Compliance with the Interim Narrative Standard for Ground Water, Section 41.5(C)(6)(a)(i) of Colorado Water Quality Control Commission's Basic Standards for Ground Water. Ennis Draw alluvium -The limited extent of the leachate plume described above indicates the Keenesburg Mine does not have the potential to negatively impact ground water in the Ennis Draw alluvium. Absence of potential for negative impact indicates it is not necessary to establish a ground water point of compliance for the Ennis Draw alluvium at the mine. Although a ground water point of compliance is not necessary for the alluvium, alluvial well DH-96 indicates the mine is in compliance with the Basic Standards for ground water. The Division would informally classify ground water in the Ennis Draw alluvium as "Potentially Useable Quality" in a specified azea comprised of Ennis Draw. Compliance with Section B of the Interim Narrative Standard would indicate compliance with the Basic Standards. The water quality standard applicable under Section B is "background TDS times 1.25". "Background" is defined in Regulation 41.3.1 of the Basic Standards. TDS refers to total dissolved solids. Table 4, below, shows that the TDS concentration in ground water in the Ennis Draw alluvium in well DH-96 is no more than its background TDS value multiplied by 1.25; therefore the mine in is in compliance with the Basic Standards for Ground Water. Table 4 - Premining/postmining comparison of total dissolved solids in Ennis Draw Alluvial monitoring well DH-96 TDS concentration (0.7 X specific conductivity) Background postmining value times 1.25 (1999 -2003) 1982-1984 1750 mg/1 1399 mg/1 Laramie sandstone and coal. The limited extent of the leachate plume described above indicates the Keenesburg Mine does not have the potential to negatively impact ground water in the sandstone and coal beds of the Laramie formation. Absence of