National Oil and Hazardous Substances Pollution Contingency Plan; National Priorities List

The Environmental Protection Agency (EPA) Region 8 announces the deletion of the Internal Parcel of the Rocky Mountain Arsenal National Priorities List (RMA/NPL) Site from the National Priorities List (NPL). All areas originally proposed for deletion (71 FR 24627), except for a three-acre area which encompasses the Rail Yard Treatment System, are being deleted (see map). The Rail Yard Treatment System is excluded from the Internal Parcel due to a delay in developing the Interim Construction Completion Report. With the Rail Yard area excluded, the Internal Parcel consists of 7,396 acres (11.5 square miles) of the On-Post Operable Unit of RMA. The NPL constitutes Appendix B of 40 CFR part 300, which is the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), which EPA promulgated pursuant to section 105 of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), as amended. EPA and the State of Colorado, through the Colorado Department of Public Health and Environment (CDPHE), have determined that the Internal Parcel of the RMA/NPL Site poses no significant threat to public health or the environment and, therefore, no further remedial measures pursuant to CERCLA are appropriate. This partial deletion pertains to the surface media (soil, surface water, sediment), structures, and groundwater of the Internal Parcel of the On-Post OU of the RMA/NPL Site. The Internal Parcel includes groundwater that is east of E Street with the exception of a small area in the northwest corner of Section 6. The Rail Yard Treatment System and the rest of the On-Post OU, including groundwater below RMA that is west of E Street and the small area in the northwest corner of Section 6, as well as the Off-Post OU will remain on the NPL. This partial deletion of the Internal Parcel will not change Appendix B of 40 CFR part 300, which was previously amended in January 2003 (68 FR 2699) to reflect that a partial deletion of 1.5 square miles from the RM