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

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VERIFIED WITH DATA, CDH SUGGESTED QUALIFYING IT. EPA'S RESPONSE: THE STATEMENT WAS BASED ON DATA COLLECTED BEFORE THE RI WAS INITIATED. NO STUDIES WERE PERFORMED AS PART OF THE RI. EPA WILL MAKE THAT CLEAR IN THE FS REPORT. OITIONAL STUDIES ARE PLANNED TO BE COMPLETED. COMMENT: CDH COMMENTED THAT THE DISCUSSION OF TUNNEL DISCHARGE FLOW PATHS (FS REPORT, PAGE 1-35) SHOULD BE CHECKED FOR ACCURACY. BY EXAMPLE, CDH STATES THAT DISCHARGES FROM THE ARGO TUNNEL AND THE NATIONAL TUNNEL TRAVEL SOME DISTANCE BEFORE FLOWING INTO THE CREEK, AND THAT MOVEMENT THROUGH THE DISCHARGE CHANNEL MAY AFFECT THE SUSPECTED CONTRIBUTION TO GROUND WATER CONTAMINATION. EPA'S RESPONSE: CURRENTLY, IT IS BELIEVED THAT IRON HYDROXIDE PRECIPITATES CREATE A "SEAL" IN THE DISCHARGE CHANNELS, THUS MINIMIZING INFILTRATION. THIS IS VERIFIED AT THE ARGO TUNNEL IN THAT NO SEEPS ARE OBSERVED ON THE BANK BELOW THE DISCHARGE CHANNEL AND NO GENERAL GROUND WATER MOUND IS OBSERVED. THAT IS, NO GENERAL GROUND WATER RISE IS OBSERVED AROUND THE DISCHARGE AREA. COMMENT: CDH COMMENTED THAT EPA MUST PROVIDE FURTHER JUSTIFICATION FOR ITS USE OF THE MINE WASTE MATERIAL UNDERLYING THE TAILINGS AND WASTE ROCK PILES TO DETERMINE THE BASELINE ELEMENTAL ANALYSES OR "BACKGROUND," DUE TO THE POSSIBILITY THAT THIS MATERIAL IS CONTAMINATED BOTH BY MINE WASTES ABOVE THE MATERIAL AND BY GROUND WATER BELOW IT. EPA'S RESPONSE: ALL AVAILABLE DATA WERE EXAMINED TO DETERMINE BACKGROUND CONCENTRATIONS. SOME MATERIAL BELOW THE TAILINGS CONTAINED ELEVATED CONCENTRATIONS OF METALS. EPA DETERMINED THAT THESE SAMPLES WERE NOT REPRESENTATIVE OF BACKGROUND CONDITIONS, AND THEY WERE ELIMINATED FROM THE BACKGROUND SAMPLES. TO VERIFY THAT THE BACKGROUND CONCENTRATIONS WERE REASONABLE, THE VALUES WERE COMPARED TO PUBLISHED DATA FOR WESTERN SOILS. IN ADDITION, EPA RECENTLY TOOK ADDITIONAL SAMPLES BOTH ABOVE AND BELOW THE BIG FIVE TAILINGS ON THE SOUTH SIDE OF CLEAR CREEK. BASED ON ANALYSIS OF THESE SAMPLES AMD COMPARISONS OF ALL GATHERED DATA, EPA HAS CONCLUDED THAT THE IDENTIFIED BACKGROUND CONCENTRATIONS ARE REASONABLE. WENT: WITH REGARD TO SLOPE STABILIZATION (FS REPORT, PAGE 2-41), CDH COMMENTED THAT: 1) A DISCUSSION OF THE PROPOSED NO ACTION ALTERNATIVE AT THE ARGO, NATIONAL, AND QUARTZ HILL TUNNELS SHOULD BE INCLUDED; AND 2) STABILIZATION OF THE UNDERCUT PORTIONS OF THE ARGO PILE SHOULD BE INCLUDED IN THE PREFERRED ALTERNATIVE BECAUSE A SLOPE FAILURE COULD IMPACT PEOPLE INSIDE THE STRUCTURES ON THE SLOPE, NOT JUST THE STRUCTURES. EPA'S RESPONSE: THE NO ACTION ALTERNATIVE WAS DISCUSSED FOR EACH PROPERTY IN THE ROD. THE OWNER OF THE ARGO PILE HAS RECENTLY PERFORMED SOME SLOPE STABILIZATION. THE SUPERFUND PROGRAM IS AUTHORIZED TO ADDRESS HUMAN HEALTH AND ENVIRONMENTAL PROBLEMS ONLY AS THEY ARE CREATED BY HAZARDOUS SUBSTANCES, POLLUTANTS, OR CONTAMINANTS. SAFETY CONCERNS, SUCH AS THOSE AT THE ARGO WASTE ROCK PILE, ARE MORE APPROPRIATELY ADDRESSED BY OTHER PROGRAMS, SUCH AS THE COLORADO MINED LAND RECLAMATION BOARD, OR BY OWNERS OF THE AFFECTED PROPERTY. COMMENT: WITH REGARD TO COMMENTS MADE AT THE NOVEMBER 24, 1987 MEETING ABOUT THE GREGORY TAILINGS RETAINING WALL, CDH RECOMMENDS THAT EFFORTS AT THAT PROPERTY BE DIRECTED TOWARD A NEGOTIATED SETTLEMENT WITH THE LANDOWNER TO REPROCESS THE PILE WITHIN A REASONABLE TIME FRAME, MAINTAIN THE GABION WALL UNTIL COMPLETION OF THE PROJECT, AND CONSTRUCT A FINAL SLOPE THAT DOES NOT REQUIRE A PERMANENT RETAINING WALL. IF SETTLEMENT IS NOT POSSIBLE, THE STATE RECOMMENDS THAT REMEDIATION PLANS UTILIZE RATHER THAN REMOVE THE GABION WALL AS PART OF THE FINAL PLAN. EPA'S RESPONSE: USE OF THE CURRENT GABION WALL AS PART OF A MORE PERMANENT WALL HAS BEEN EVALUATED AND DETERMINED NOT TO BE COST EFFECTIVE. THAT IS, THE GABION WALL CANNOT BE MADE MORE PERMANENT WITHOUT MAJOR COSTS. EPA IS RECOMMENDING THAT THE CURRENT GABION WALL BE MAINTAINED AND MONITORED, AND REPLACED ONLY WHEN NECESSARY. EPA WILL CONTINUE DISCUSSIONS WITH THE LANDOWNER ABOUT REPROCESSING. AULMMENT: THE STATE COMMENTED THAT ACTIVE EROSION AT THE QUARTZ HILL PARKING LOT IS NOT DRESSED IN THE FS REPORT, NOTING THAT THIS ISSUE SHOULD BE CONSIDERED. PROBLEMS ASSOCIATED WITH THIS EROSION INCLUDE ENVIRONMENTAL AND HEALTH CONCERNS ABOUT THE SEDIMENT, AND THE POSSIBLE SAFETY HAZARD POSED BY CARS PARKED ON THE EDGES OF THE LOT. THE DEPARTMENT RECOMMENDS REGRADING OF THE LOTS TO PROVIDE MORE STABLE SIDE SLOPES; CONSTRUCTION OF BERMS AROUND THE PARKING SURFACE PERIMETER TO CONTROL RUNON TO THE SIDE SLOPES; ROUTING OF RUNOFF TO STABILIZED CHANNELS; AND