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

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THE THIRD AND FOURTH EXPOSURE PATHWAYS OF CONCERN ARE INGESTION AND DUST INHALATION. AS PREVIOUSLY DISCUSSED, ACCEPTABLE RISKS ARE PRESENT FOR TOURISTS AND THE OCCASIONAL SITE VISITORS (EPISODIC EXPOSURE), THEREFORE, NO REMEDIAL ACTIONS ARE CURRENTLY RECOMMENDED TO ALLEVIATE INGESTION AND DUST INHALATION. HOWEVER, THE PUBLIC HEALTH EVALUATION FOR THE SITE INDICATED T, FOR A RESIDENTIAL SCENARIO, RISKS RESULTING FROM THE INHALATION AND INGESTION EXPOSURE HWAYS ARE OF SOME CONCERN. THEREFORE, EPA WILL EVALUATE THIS NO ACTION DECISION WHEN THE FINAL REMEDY IS SELECTED FOR THE SITE. EPA, IN COORDINATION WITH THE STATE OF COLORADO AND LOCAL OFFICIALS, WILL EVALUATE THE USE OF INSTITUTIONAL MEASURES WHICH WOULD CONTROL ANY HUMAN HEALTH OR ENVIRONMENTAL THREAT THAT COULD BE CREATED BY FUTURE DEVELOPMENT UPON THESE TAILINGS AND WASTE ROCK PILES AND ANY OTHER PILES WHICH THE STATE IDENTIFIES IN ITS STUDY. IN ADDITION, PURSUANT TO SARA SECTION 121 (C), EPA WILL REVIEW NO LESS THAN EVERY FIVE YEARS ALL PROPERTIES WHERE HAZARDOUS SUBSTANCES CONTINUE TO REMAIN ONSITE AND, IF NECESSARY, WILL RECONSIDER THIS NO ACTION DECISION. DOCUMENTATION OF SIGNIFICANT CHANGES EPA IDENTIFIED THE SLOPE STABILIZATION AND RUNON CONTROL ALTERNATIVE AS THE PREFERRED ALTERNATIVE IN THE PROPOSED PLAN WHICH WAS RELEASED TO THE PUBLIC ON NOVEMBER 9, 1987. THE KEY ELEMENTS OF THIS ALTERNATIVE AS STATED IN THE PROPOSED PLAN WERE RUNON CONTROL ON ALL FIVE TAILINGS AND WASTE ROCK PILES AND SLOPE STABILIZATION OF THE BIG FIVE AND THE GREGORY INCLINE. AT THE TIME OF THE RELEASE OF THE PROPOSED PLAN, EPA WAS PROPOSING TO REMOVE THE GABION-BASKET WALL AT THE GREGORY INCLINE AND REPLACE IT WITH A CRIB WALL. EPA INTENDED TO TAKE THE PROPERTY OWNER'S DESIRE TO REPROCESS TAILINGS AT THE GREGORY INCLINE INTO ACCOUNT WHEN REPLACING THE GABION-BASKET WALL. SINCE THAT TIME, EPA HAS RECEIVED EXTENSIVE COMMENT ON THIS PORTION OF THE PROPOSED PLAN AND HAS MODIFIED THE SELECTED REMEDY TO ADDRESS THESE CONCERNS. THE PRIMARY DIFFERENCE BETWEEN THE PREFERRED REMEDY AS PRESENTED IN THE PROPOSED PLAN AND THE SELECTED REMEDY AS PRESENTED IN THIS RECORD OF DECISION IS THAT EPA NO LONGER PLANS TO IMMEDIATELY REPLACE THE GABION-BASKET WALL, BUT WILL INSTEAD MAINTAIN THE WALL UNTIL MONITORING INDICATES THAT THE WALL NEEDS TO BE REPLACED OR UNTIL THE TAILINGS ARE REMOVED FOR REPROCESSING. THE EPA L STILL TAKE THE OWNER'S REPROCESSING CONCERNS INTO ACCOUNT WHILE MONITORING AND MAINTAINING WALL. THE SELECTED REMEDY IS A LOGICAL OUTGROWTH OF THE REMEDY IDENTIFIED IN THE PROPOSED PLAN AND OTHER ALTERNATIVES DEVELOPED AND EVALUATED IN THE OPERABLE UNIT NO. TWO FS. THE COMPONENTS OF THE SELECTED REMEDY WERE CONCEPTUALLY EVALUATED IN THE FS AND THE SELECTED REMEDY IS WELL WITHIN THE RANGE OF ALTERNATIVES THE PUBLIC COULD HAVE REASONABLY ANTICIPATED EPA TO BE CONSIDERING. #OEL STATUTORY DETERMINATIONS PROTECTIVENESS: THE PUBLIC HEALTH EVALUATION FOR THE CLEAR CREEK/CENTRAL CITY SUPERFUND SITE CLEARLY SHOWS THAT CLEAR CREEK AND NORTH CLEAR CREEK ARE BEING IMPACTED BY THE ACID MINE DISCHARGES AND THE TAILINGS AND WASTE ROCK PILES WHICH ARE ASSOCIATED WITH THE SITE. THESE IMPACTS INCLUDE: - DEGRADATION OF DOWNSTREAM SURFACE WATER QUALITY RESULTING FROM DISSOLVED AND SUSPENDED METALS IN THE DISCHARGES AND RESUSPENDED METAL LADEN SEDIMENTS BELOW THE DISCHARGES; - DEGRADATION OF DOWNSTREAM SURFACE WATER QUALITY DUE TO POTENTIAL COLLAPSE OF THE TAILINGS AND WASTE ROCK PILES INTO EITHER CLEAR CREEK OR NORTH CLEAR CREEK; AND - DEGRADATION OF DOWNSTREAM SURFACE WATER QUALITY DUE TO RUNON AND RUNOFF FROM THE TAILINGS AND WASTE ROCK PILES. THESE IMPACTS POSE NO IMMEDIATE DANGER TO PUBLIC HEALTH BECAUSE THE CITIES OF IDAHO SPRINGS, CKHAWK, CENTRAL CITY, AND GOLDEN HAVE MUNICIPAL WATER SUPPLY SYSTEMS THAT MEET MCLS. EVER, THESE IMPACTS RESULT IN SEVERELY DEGRADED WATER QUALITY AFFECTING AQUATIC LIFE AND PRODUCTIVITY AND REDUCED OR DESTROYED AQUATIC HABITAT IN CLEAR CREEK AND NORTH CLEAR CREEK. THE FIRST IMPACT MENTIONED ABOVE IS ASSOCIATED WITH THE ACID MINE DISCHARGES AND WAS ADDRESSED UNDER OPERABLE UNIT NO. ONE. THE OTHER TWO IMPACTS ARE ASSOCIATED WITH THE TAILINGS AND WASTE