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., ..... 1-- W I- NPDE$ Permit No. CO-0042161 Salinity Control Study Twentymile Coal Company In this qonceptual evaluation it is assumed that the treatment process and deep injection well are loca,ted at a treatment facility located near the existing sedimentation pond. The RO treatment unit would be caPable of treating flow up to 1 cfg, and the deep injection well would be capatile of injecting a flow of 112 gpm. It is impprtant to recognize that this does not result in total elimination of salt discharge.' The RO trea$lent options cannot remove all salt from the process discharge, and the primary outlet woulddjscharge flows without RO treatment when dewatering from the fish Creek Borehole exceeded the treatment system capacity of 1 cfs and the available storage capacity of the pond. In this cpnceptual design. the existing sedimentation pond would remain in place to facilitate removal lof particulates. 3.3 Option 3: - Minimization or Salt Discharge Using Deep Well Injection In this Conceptual option, the discharge up to 0.5 cfs from point 001 is injected in a deep disposal' well. Occasional discharge from the sedimentation pond would' occur when dewateri~g exceeded the injection well capacity of 0.5 cfs (224 gpm) arid the pond storage capacity .' It is asSUmed that the Dakota Sandstone would be used for deep well injection although it is possible ~at isolated sand units, could be found at shallower depths within the Mancos shale which might accept the anticipated quantity of discharge. The well is assumed to be 10ca,ted near the ~ump station adjacent to the existing sedimentation pond. The existing sedimentation pond wojlld remain in place to facilitate removal of particulates, and to Provide surge storage. The deep injection well should be capable of injecting a flow of 224 gpm, twice the average discharg~ measured during the 1990 - 94 record, If the injection well capacity was not as much as :224 gpm, it would still likely be higher than the average dewatering flow, and, so leave frei storage capacity in the surge pond. ' ~ .~! ;t ~{ '~ ;J .~ J , - -~ AHA Fdeoamc: 14SAlCNl.DOC Page 16 2:52 PM 09/29/95 ,-J :7 .