06-6572. National Oil and Hazardous Substances Pollution Contingency Plan; National Priorities List

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Notice of partial deletion of the Rocky Mountain Arsenal National Priorities List Site from the National Priorities List.

SUMMARY:

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 RMA/NPL Site had occurred.

DATES:

This partial deletion of the Internal Parcel is effective on July 31, 2006.

FOR FURTHER INFORMATION CONTACT:

Ms. Jennifer Chergo, Community Involvement Coordinator (8OC), U.S. Environmental Protection Agency, Region 8, 999 18th Street, Suite 300, Denver, Colorado 80202-2466; telephone number: 1-800-227-8917 or [phone]; fax number: 303-312-6961; e-mail address: [e-mail].

SUPPLEMENTARY INFORMATION:

The Rocky Mountain Arsenal National Priorities List (RMA/NPL) Site is located in southern Adams County, Colorado and is comprised of two operable units (OU), the On-Post and Off-Post. The On-Post OU of the RMA/NPL Site encompasses 17.2 square miles (11,007 acres) approximately eight miles northeast of downtown Denver, Colorado. The Off-Post OU addresses contamination north and northwest of the RMA proper boundaries. The Internal Parcel consists of approximately 11.5 square miles (7,396 acres) of the On-Post OU of RMA in Commerce City, Colorado.

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 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, and the Off-Post OU will remain on the NPL.

On April 26, 2006, EPA published a Notice of Intent for Partial Deletion (NOIDp) in the Federal Register (71 FR 24627) and local newspapers which proposed to delete the Internal Parcel from the RMA/NPL Site. EPA received comment letters from ninety-four organizations/entities and individuals. Authors of six letters were opposed to the proposed partial deletion of the Internal Parcel. One of these letters requested postponement of the deletion stating that the 60-day review time was insufficient to review and resolve questions regarding characterization of the eastern portion of the Internal Parcel and their perception of unnecessary risk posed by deletion of the western portion of the Internal Parcel. Several commenters also questioned the “piece-meal” approach to the Internal Parcel deletion.

In our Responsiveness Summary, EPA described the CERCLA investigation process and how various areas of the Internal Parcel, including the eastern portion which includes the groundwater aquifer below a demolition range, were characterized. This process included file searches, “desktop” information (e.g., aerial photographs) searches, site reconnaissance, and collection of both soil and groundwater samples during the Remedial Investigation (RI). Soil samples were collected from burn pits and ordnance disposal areas, specific areas of concern to the commenters, during the RI. Explosive residue and Toxicity Characteristic Leaching Procedure (TCLP)-metals were addressed during pre-design studies for the Burial Trenches and Munitions (Testing) Soil Remediation Project. These studies showed that explosive residue and TCLP-metal concentrations were below risk-based regulatory levels. Considering these studies, the geology of the area, as well as the history of the disposal areas, there is no evidence of explosive or TCLP-metal soil contamination that could act as a source of groundwater contamination. The discovery of limited additional contamination at one area subsequent to the original excavation being completed demonstrates the multiple, sometimes overlapping, elements of the selected remedy that protect human health and the environment. These elements include excavation of known contaminated soil, further evaluation of ecological risks, and collection of confirmatory samples.

EPA ensures that human health is protected from on-going remedial activities on the remaining NPL areas through effective control of project emissions, restricting visitor access, and implementation of the Site-Wide Air Quality Monitoring Program Plan, including monitoring of air emissions. There are two major project areas that involve disturbance of contaminated soil remaining in the NPL area. Visitors to the Refuge are restricted to areas located approximately one mile from the Lime Basin slurry wall project and approximately two miles from the Basin F projects. Air emissions are measured at the current fenceline and near the Visitor Center to verify that potential risks to visitors and the nearby communities are minimized. These requirements to protect human health will remain in place irrespective of the deletion of the Internal Parcel.

EPA's responsiveness summary further explained how only areas which met the criteria of “Responsible parties or other persons have implemented all appropriate response actions required” (40 CFR 300.425(e)(1)(i)) were considered for deletion. EPA's Partial Deletions Rule, published November 1, 1995, was intended to allow portions of a site or an OU that have been cleaned up to be available for productive use, especially where total site cleanup may take many years. This description accurately reflects the ongoing cleanup at the RMA/NPL Site, which is over 50 percent complete, i.e., ten years of the fifteen-year schedule have passed and 16 of the 31 remedy projects have been completed. Partial deletion of the Internal Parcel communicates to the public the successful implementation of the remedy and progress toward final cleanup. In addition, it helps the Army achieve its goal of transferring property and furthers the purposes of the RMA National Wildlife Refuge Act (1992). The Internal Parcel deletion, though described as “piece-meal” by the commenters, is consistent with other partial deletions that leave islands of an NPL site surrounded or abutted by deleted lands, e.g., Cecil Field, (68 FR 27746).

The remaining eighty-eight letters supported proceeding with the Internal Parcel deletion based upon their confidence in the thoroughness of the cleanup activities conducted by the Department of the Army (Army) and Shell Oil Company (Shell). EPA agrees that completion of the remedy requirements as well as recent, site-wide studies adequately demonstrate that the Internal Parcel does not present a threat to the environment or human health and deletion of the Internal Parcel from the RMA/NPL Site is appropriate.

EPA identifies sites that appear to present a significant risk to public health, welfare, or the environment and maintains the NPL as the list of those sites. Any site deleted from the NPL remains eligible for Fund-financed actions in the unlikely event that conditions at the site warrant such action. Section 300.425(e)(3) of the NCP states that Fund-financed actions may be taken at sites deleted from the NPL. Deletion of a site from the NPL does not affect responsible party liability or impede Agency efforts to recover costs associated with response efforts.

List of Subjects in 40 CFR Part 300

• Environmental protection
• Air pollution control
• Chemicals
• Hazardous substances
• Hazardous waste
• Intergovernmental relations
• Penalties
• Reporting and recordkeeping requirements
• Superfund
• Water pollution control
• Water supply

Dated: July 24, 2006.

Robert E. Roberts,

Regional Administrator, Region 8.