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Record of Decision System (RODS)

ROCKY MOUNTAIN ARSENAL (USARMY)

Abstract

Site Name:  ROCKY MOUNTAIN ARSENAL (USARMY)
Address:  IMMED N STAPLETON INTL ARPT 
City & State:  ADAMS COUNTY  CO  80022
County:  ADAMS
 
EPA ID:  CO5210020769
EPA Region:  08
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R08-90/038
ROD Date:  02/26/1990
Operable Unit(s):  18
 
Media:  SOIL GROUND WATER
 
Contaminant:  VOCS, BENZENE, TCE
 
Abstract:  THE ROCKY MOUNTAIN ARSENAL (RMA) (OPERABLE UNIT 18) SITE COMPRISES PART OF THE 17,000-ACRE RMA SITE, WHICH IS A FORMER US ARMY CHEMICAL WARFARE AND INCENDIARY MUNITIONS MANUFACTURING AND ASSEMBLY PLANT IN ADAMS COUNTY, COLORADO. FROM THE 1950S UNTIL LATE 1969, THE US ARMY USED THE RMA FACILITY TO PRODUCE THE NERVE AGENT GB (ISOPROPYL METHYL- PHOSPHONOFLUORIDATE). IN ADDITION, BETWEEN 1947 AND 1982, PRIVATE INDUSTRIES LEASED MAJOR PORTIONS OF THE PLANT FACILITIES TO MANUFACTURE VARIOUS INSECTICIDES AND HERBICIDES. SINCE 1970, FACILITY OPERATIONS PRIMARILY HAVE INVOLVED THE DESTRUCTION OF CHEMICAL WARFARE MATERIALS. BECAUSE FINAL REMEDIATION OF THE RMA SITE WILL TAKE MANY YEARS TO COMPLETE, THIRTEEN INTERIM RESPONSE ACTIONS (IRAS) WERE DETERMINED NECESSARY PRIOR TO IMPLEMENTING THE FINAL ON-POST RECORD OF DECISION (ROD). OPERABLE UNIT 18 (MOTOR POOL AREA) IS ONE OF SEVERAL AREAS INCLUDED IN THE OTHER CONTAMINATION SOURCES IRA. THE US ARMY ACQUIRED THE MOTOR POOL AREA IN 1942, AND USED IT FOR STORING DIESEL FUEL, GASOLINE, ROAD OIL, AND FLAMMABLE LIQUIDS IN AN ABOVE-GROUND STORAGE TANK FARM. IN ADDITION, DURING THE EARLY 1950S, SEVERAL BUILDINGS WERE USED FOR PESTICIDE AND HERBICIDE STORAGE, AND LATER THESE BUILDINGS HOUSED AN AGRICULTURAL RESEARCH AND BIOASSAY LABORATORY. THE ARMY CONTINUES TO USE THE AREA TO SERVICE EQUIPMENT, VEHICLES, AND RAILROAD CARS. A DIESEL FUEL SPILL AND OTHER SPILLS RELATED TO PIPING FROM UNDERGROUND TANKS HAVE BEEN RECORDED. IN 1985, GROUND WATER MONITORING IDENTIFIED TCE CONTAMINATION NEAR THE MOTOR POOL AREA AND IN DOWNGRADIENT WATER SUPPLY WELLS. RECORDS INDICATE THAT VEHICLE MAINTENANCE OPERATIONS INVOLVED DISCHARGING WATER AND OTHER LIQUIDS, AND RUST RESIDUES THROUGH FLOOR DRAINS AND PIPES INTO UNLINED DITCHES. THIS ROD ADDRESSES INTERIM REMEDIATION OF SOURCE AREAS AND MANAGEMENT OF MIGRATION. THE PRIMARY CONTAMINANTS OF CONCERN AFFECTING THE SOIL AND GROUND WATER ARE VOCS, INCLUDING BENZENE AND TCE.

THE SELECTED INTERIM REMEDIAL ACTION FOR THIS SITE INCLUDES CONDUCTING A VAPOR EXTRACTION PILOT TEST; INSTALLING AND OPERATING AN IN-SITU VAPOR EXTRACTION SYSTEM, FOLLOWED BY GRANULAR ACTIVATED CARBON TREATMENT OF CONDENSED WATER VAPOR WITH OFFSITE THERMAL CARBON REACTIVATION; CAPPING THE SITE WITH A LAYER OF ASPHALT TO IMPROVE THE EFFICIENCY OF THE VAPOR EXTRACTION SYSTEM; CONDUCTING AIR MONITORING, FOLLOWED BY POSSIBLE STACK TREATMENT BY A VAPOR PHASE CARBON FILTER OR CATALYTIC OXIDIZER; AND GROUND WATER PUMPING, TREATMENT, AND REINJECTION IN CONJUNCTION WITH THE RAIL CLASSIFICATION YARD IRA. NO COSTS WERE PROVIDED FOR THIS REMEDIAL ACTION.

PERFORMANCE STANDARDS OR GOALS; NO CHEMICAL-SPECIFIC GOALS WERE IDENTIFIED FOR SOIL CONTAMINANTS. CHEMICAL-SPECIFIC GOALS FOR GROUND WATER TREATMENT, WHICH APPLY AT THE POINT OF INJECTION, ARE CONTAINED IN THE ROD FOR THE RAIL CLASSIFICATION YARD IRA AND INCLUDE BENZENE 5 UG/L (MCL). INSTITUTIONAL CONTROLS; NOT APPLICABLE.
 
Remedy:  THE SELECTED INTERIM REMEDIAL ACTION FOR THIS SITE INCLUDES CONDUCTING A VAPOR EXTRACTION PILOT TEST; INSTALLING AND OPERATING AN IN-SITU VAPOR EXTRACTION SYSTEM, FOLLOWED BY GRANULAR ACTIVATED CARBON TREATMENT OF CONDENSED WATER VAPOR WITH OFFSITE THERMAL CARBON REACTIVATION; CAPPING THE SITE WITH A LAYER OF ASPHALT TO IMPROVE THE EFFICIENCY OF THE VAPOR EXTRACTION SYSTEM; CONDUCTING AIR MONITORING, FOLLOWED BY POSSIBLE STACK TREATMENT BY A VAPOR PHASE CARBON FILTER OR CATALYTIC OXIDIZER; AND GROUND WATER PUMPING, TREATMENT, AND REINJECTION IN CONJUNCTION WITH THE RAIL CLASSIFICATION YARD IRA. NO COSTS WERE PROVIDED FOR THIS REMEDIAL ACTION.
 
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