2009-09-25_PERMIT FILE - M2009076 (42)

Home Browse Search

COLORADO; THE U.S. ECOLOGY DISPOSAL SITE NEAR BEATTY, NEVADA; AND THE USPCI DISPOSAL SITE AT GRASSY MOUNTAIN, UTAH. CONSTRUCTION OF THE BFI SITE HAS NOT YET BEGUN, BUT WILL PROBABLY COMMENCE WITHIN THE NEXT YEAR. THE BFI SITE IS SCHEDULED TO PROVIDE CELLS OF APPROXIMATELY 158,000 CUBIC YARD CAPACITY. SEVERAL OF THESE CELLS COULD BE DEDICATED TO DISPOSAL OF THE CLEAR &EK MINING WASTE. THE U.S. ECOLOGY AND USPCI SITES ARE PRESENTLY IN OPERATION. THE OFF-SITE DISPOSAL ANALYSIS INDICATED THAT OFF-SITE DISPOSAL IS A TECHNICALLY FEASIBLE ALTERNATIVE THAT IS EFFECTIVE AND CAN BE IMPLEMENTED. THEREFORE, THIS ALTERNATIVE WAS CONSIDERED FURTHER IN THE DETAILED ANALYSIS OF REMEDIAL ACTION ALTERNATIVES. CHEMICAL FIXATION ALTERNATIVES MODIFYING THE CHEMICAL ENVIRONMENT WITHIN THE CLEAR CREEK/CENTRAL CITY TAILINGS AND WASTE ROCK PILES IS A MEANS OF REDUCING THE MOBILITY OF METALS IN THE PILES. BY CHANGING THE CHEMICAL ENVIRONMENT OF THE TAILINGS THROUGH THE ADDITION OF NEUTRALIZING MATERIALS, THE GENERATION OF ACID AND THE SUBSEQUENT DISSOLUTION OF METALS CAN BE ELIMINATED. SUCH CHANGES ALSO WOULD LIMIT DUST GENERATION AND COULD POTENTIALLY REDUCE THE IMPACT OF DIRECT INGESTION. SEVERAL METHODS EXIST FOR THE MODIFICATION OF THE CHEMICAL ENVIRONMENT IN THE PILES. THE EFFECTS ON THE METAL-SPECIFIC SPECIES PRESENT WILL VARY ACCORDING TO THE TECHNIQUE CHOSEN FOR MODIFICATION. THE ADDITION OF MATERIALS WITH LARGE NEUTRALIZATION (BASIC) CAPACITY, SUCH AS KILN DUST, IS A COMMON METHOD AVAILABLE FOR RAISING THE PH OF AN ACIDIC MATERIAL WITH THE ACCOMPANYING "FIXATION" OF METALS AS METALLIC HYDROXIDES. THIS IS A COST-EFFECTIVE OPTION BUT ITS TOTAL EFFECTIVENESS IS LIMITED BY THE FACT THAT SOME METALS MAY REMAIN SLIGHTLY LEACHABLE BY THIS METHOD. ANOTHER APPROACH IS FIXATION OF CONTAMINANT METALS BY CHEMICAL BINDING WITH AN ACCOMPANYING PHYSICAL ENCAPSULATION. THIS IS ACCOMPLISHED BY THE ADDITION OF FIXATION AND SOLIDIFICATION ENTS THAT MAKE THE CONTAMINANTS UNAVAILABLE TO OXIDATION AND LEACHING. METALS THAT CANNOT BE ED BY SIMPLE PH ADJUSTMENT RESPOND TO THIS TECHNIQUE. POZZOLANS AND CEMENTS CONSTITUTE THE MAJOR PORTION OF THESE FIXATION AGENTS. THEIR ADDITION TO AN ACIDIC MATERIAL ALSO CAUSES AN INCREASE IN PH. APPROXIMATELY THIRTY DIFFERENT FIXATION AGENTS WERE EVALUATED DURING THE SCREENING PROCESS. THESE MATERIALS WERE SCREENED FOR EFFECTIVENESS AS SHOWN BY ACTUAL LEACH RESULTS, IMPLEMENTABILITY AND COST PER UNIT NEUTRALIZATION CAPACITY. THE DETAILS OF THIS EVALUATION ARE PROVIDED IN SECTION 2 OF THE FEASIBILITY STUDY. BASED ON THE SCREENING EVALUATION, FIXATION APPEARS TO BE A TECHNICALLY FEASIBLE CONTAINMENT OPTION AND WAS, THEREFORE, FURTHER INVESTIGATED IN THE DETAILED ANALYSIS OF REMEDIAL ACTION ALTERNATIVES. IN PARTICULAR, THE FOLLOWING TECHNIQUES/FIXATION AGENTS WERE CONSIDERED: - KILN DUST - THREE PROPRIETARY FIXATION AGENTS. EACH OF THESE FIXATION AGENTS WERE SUBJECT TO BENCH SCALE TESTS. THE RESULTING FIXED MATERIALS WERE ALSO TESTED FOR EFFECTIVENESS BY USING LEACHING TESTS. THE RESULTS OF THESE TESTS ARE SUMMARIZED IN THE DETAILED ANALYSIS SECTION. REPROCESSING ALTERNATIVES THERE ARE MANY PROCESSES THAT HAVE BEEN DEVELOPED TO REMOVE METALS FROM ORES AND THESE PROCESSES COULD POTENTIALLY BE APPLIED TO REMOVE TOXIC METALS FROM THE FIVE WASTE PILES. THE PROCESSES FALL INTO TWO CATEGORIES: PYROMETALLURGICAL - PROCESSES USING HEAT; AND HYDROMETALLURGICAL - PROCESSES USING WATER SOLUTIONS. FACILITIES USING THESE PROCESSES EXIST IN SEVERAL PARTS OF THE UNTRY AND COULD POTENTIALLY REPROCESS MATERIALS FROM THE CLEAR CREEK/CENTRAL CITY SITE. THESE CESSES COULD ALSO POTENTIALLY BE USED AT A FACILITY CONSTRUCTED IN THE CLEAR CREEK/CENTRAL CITY SITE AREA. THE SCREENING OF TECHNOLOGIES FOR REPROCESSING OF TAILINGS AND WASTE ROCK PILES INDICATED THAT FLOTATION AS A REPROCESSING ALTERNATIVE IS TECHNICALLY FEASIBLE AND CAN BE IMPLEMENTED. IN