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

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OPERABLE UNIT NO. ONE - MINE TUNNEL DISCHARGE TREATMENT (RECORD OF DECISION SIGNED IN SEPTEMBER, 1987) OPERABLE UNIT NO. TWO - TAILINGS AND WASTE ROCK REMEDIATION OPERABLE UNIT NO. THREE - BLOWOUT/DISCHARGE CONTROL. ADDITION, THE STATE OF COLORADO HAS SUBMITTED AN APPLICATION TO EPA FOR MONIES TO FUND AN INVESTIGATION TO IDENTIFY OTHER AREAS WITHIN THE MINING DISTRICT WHICH MAY BE SIGNIFICANTLY IMPACTING NORTH CLEAR CREEK AND CLEAR CREEK. THE STATE WILL ALSO INVESTIGATE THE QUALITY OF THE GROUNDWATER IN THE AREA. DEPENDING UPON THE RESULTS OF THE STATE STUDY, EPA MAY CONSIDER ADDITIONAL OPERABLE UNITS. #CSS SITE CHARACTERISTICS A PUBLIC HEALTH EVALUATION WAS CONDUCTED TO IDENTIFY COMPOUNDS WHICH COULD POSE A SIGNIFICANT THREAT TO HUMAN HEALTH AND THE ENVIRONMENT. BASED ON SAMPLING OF ENVIRONMENTAL MEDIA AND CONSIDERATION OF TOXICITY, TWELVE CONTAMINANTS OF CONCERN WERE IDENTIFIED AND POTENTIAL EXPOSURE PATHWAYS WERE ANALYZED. IMPACTS ON HUMAN HEALTH AND THE ENVIRONMENT WERE ASSESSED FOR EXPOSURES DUE TO INHALATION AND INGESTION OF MATERIAL FROM THE PILES AND DUE TO RUNOFF FROM THE PILES AND CATASTROPHIC SLOPE FAILURE OF THE PILES INTO THE STREAMS. AS STATED, TWELVE CONTAMINANTS WERE IDENTIFIED DURING THE PUBLIC HEALTH EVALUATION AS CONTAMINANTS OF CONCERN IN THE CLEAR CREEK/CENTRAL CITY STUDY AREA. CONTAMINANTS OF CONCERN WERE CHOSEN SEPARATELY FOR HUMAN RECEPTORS AND AQUATIC ORGANISMS. ARSENIC, CHROMIUM (VI), AND NICKEL ARE PRESENT IN RELATIVELY HIGH CONCENTRATIONS IN THE TAILINGS AND WASTE ROCK AND HAVE BEEN RATED BY EPA AS GROUP A HUMAN CARCINOGENS BY THE INHALATION PATHWAY. CADMIUM IS A GROUP B1 CARCINOGEN BY INHALATION AND IS A POTENT KIDNEY TOXIN WHEN INGESTED. LEAD AND SILVER ARE TOXIC NONCARCINOGENS AND ARE PRESENT IN RELATIVELY HIGH CONCENTRATIONS IN THE TAILINGS AND WASTE ROCK. CONTAMINANTS OF CONCERN FOR AQUATIC LIFE WERE CHOSEN BASED ON THEIR CONCENTRATION IN WATER, K LISHED CRITERIA VALUES (E.G., AMBIENT WATER QUALITY CRITERIA (AWQC)), AND SUPPLEMENTAL DATA CHEMICALS THAT LACKED CRITERIA. CONTAMINANTS INCLUDE ALUMINUM, ARSENIC, CADMIUM, CHROMIUM, COPPER, FLUORIDE, LEAD, MANGANESE, NICKEL, SILVER, AND ZINC. EXPOSURE TO METALS IN TAILINGS OR WASTE ROCK CAN POTENTIALLY OCCUR THROUGH INHALATION OF DUST BY PEOPLE AT OR NEAR THE SITES. TWO MECHANISMS FOR DUST GENERATION WERE CONSIDERED IN THE EVALUATION: (1) DUST RESULTING FROM WIND ENTRAINMENT OF TAILINGS OR SOIL PARTICLES; AND (2) DUST GENERATED FROM HUMAN ACTIVITIES (IN PARTICULAR, RIDING OF DIRT BIKES ON THE TAILINGS PILES). THE GREGORY TAILINGS PILE IS READILY ACCESSIBLE AND IN SOME AREAS IS QUITE COMPACTED OR HAS A SURFACE CRUST. DIRT-BIKE RIDING IS KNOWN TO OCCUR AT THE GREGORY TAILINGS PILE. THE ARGO TAILINGS ARE ALSO READILY ACCESSIBLE AND ARE LESS COMPACTED AND MORE FRIABLE THAN THE GREGORY TAILINGS. THE ARGO TAILINGS ARE NOT USED EXTENSIVELY BY DIRT-BIKE RIDERS DUE TO THEIR STEEPNESS. CURRENTLY, HOWEVER, WASTE ROCK AT ARGO IS BEING REMOVED FOR USE IN CONSTRUCTING ROADS. THIS ACTIVITY, WHICH INVOLVES OPERATION OF DUMP TRUCKS AND FRONT-END LOADERS, INCREASES DUST EMISSIONS FROM THIS AREA. IN ADDITION TO INHALATION, EXPOSURE TO METALS IN SOIL OR TAILINGS CAN ALSO OCCUR BY INCIDENTAL INGESTION. TOURISTS VISITING THE MINES MAY CONTACT THE TAILINGS, ALTHOUGH THE POTENTIAL FOR SIGNIFICANT EXPOSURE IS LOW. OLDER CHILDREN LIVING IN THE AREA, PARTICULARLY THOSE FROM AGES 6 TO 16 WHO HAVE LESS PARENTAL SUPERVISION THAN YOUNGER CHILDREN, MAY PLAY OR RIDE DIRT BIKES AT THE TAILINGS PILES ESPECIALLY DURING THE SUMMER MONTHS WHEN SCHOOL IS OUT. FUTURE USE OF THE SITES MAY INCLUDE RESIDENTIAL DEVELOPMENT. UNDER THIS SCENARIO, POTENTIAL EXPOSURE PATHWAYS WOULD INCLUDE INCIDENTAL INGESTION OF CONTAMINATED MATERIAL BY THE RESIDENTS OVER THEIR LIFE TIME. THIS POTENTIAL FUTURE USE RESIDENTIAL EXPOSURE SCENARIO WAS ALSO EVALUATED. 0 SUMMARY, THE MAJOR POTENTIAL IMPACTS AT THE SITE DUE TO TAILINGS AND WASTE ROCK ARE: DEGRADATION OF SURFACE WATER QUALITY CAUSED BY RUNOFF FROM THE PILES; DEGRADATION OF SURFACE WATER QUALITY CAUSED BY COLLAPSE OF THE PILES INTO THE CREEKS; AND,