03-18741. National Oil and Hazardous Substances Pollution Contingency Plan; National Priorities List

AGENCY:

Environmental Protection Agency.

ACTION:

Notice of intent for partial deletion of the Rocky Mountain Arsenal National Priorities List Site from the National Priorities List; request for comments.

SUMMARY:

The Environmental Protection Agency (EPA) Region 8 announces its intent to delete the Selected Perimeter Area (SPA), encompassing 4,930 acres, of the Rocky Mountain Arsenal National Priorities List Site (RMA/NPL Site) On-Post Operable Unit (OU) from the National Priorities List (NPL) and requests public comment on this proposed action. 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).

EPA bases its proposal to delete the SPA of the RMA/NPL Site on the determination by EPA and the State of Colorado, through the Colorado Department of Public Health and Environment (CDPHE), that all appropriate actions under CERCLA have been implemented to protect human health, welfare and the environment and that no further response action by responsible parties is appropriate.

This partial deletion pertains to the surface (soil, surface water, sediment), structures, and groundwater media of the Selected Perimeter Area of the On-Post OU of the RMA/NPL Site. The Surface Deletion Area of the On-Post OU RMA/NPL Site, composed of the surface and structures media only within an additional 123 acres, also is being proposed as a separate partial deletion during the same public comment period. The rest of the On-Post OU and the Off-Post OU will remain on the NPL and response activities will continue at those OUs.

DATES:

Comments concerning this proposed partial deletion may be submitted on or before August 26, 2003.

ADDRESSES:

Comments may be mailed to: Catherine Roberts, Community Involvement Coordinator (8OC), U.S. EPA, Region 8, 999 18th Street, Suite 300, Denver, Colorado, 80202-2466, 1-800-227-8917 or [phone].

Comprehensive information on the RMA/NPL Site, as well as information specific to this proposed partial deletion, is available through EPA's Region 8 Superfund Records Center in Denver, Colorado. Documents are available for viewing by appointment from 8 a.m. to 4 p.m., Monday through Friday excluding holidays, by calling [phone]. The Administrative Record for the RMA/NPL Site and the Deletion Docket for this partial deletion are maintained at the Joint Administrative Records Document Facility, Rocky Mountain Arsenal, Building 129, Room 2024, Commerce City, Colorado 80022-1748, [phone]. Documents are available for viewing from 12 p.m. to 4 p.m., Monday through Friday, or by appointment.

FOR FURTHER INFORMATION CONTACT:

Ms. Laura Williams, Remedial Project Manager (8EPR-F), U.S. EPA, Region 8, 999 18th Street, Suite 300, Denver Colorado, 80202-2466, [phone].

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Introduction

II. NPL Deletion Criteria

III. Deletion Procedures

IV. Basis for Intended Partial Site Deletion

I. Introduction

The Environmental Protection Agency (EPA) Region 8 announces its intent to delete the Selected Perimeter Area (SPA) of the Rocky Mountain Arsenal/National Priorities List (RMA/NPL) Site, Commerce City, Colorado, from the National Priorities List (NPL) and requests comment on this proposed action. The NPL constitutes Appendix B of the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), 40 CFR part 300, which EPA promulgated pursuant to Section 105 of Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), 42 U.S.C. 9605. EPA identifies sites that appear to present a significant risk to public health or the environment and maintains the NPL as the list of those sites. Sites on the NPL may be the subject of remedial actions financed by the Hazardous Substance Superfund (Fund). This partial deletion of the Site is proposed in accordance with 40 CFR 300.425(e) and Notice of Policy Change: Partial Deletion of Sites Listed on the National Priorities List (60 FR 55466 (Nov. 1, 1995)). As described in 40 CFR 300.425(e)(3), portions of a site deleted from the NPL remain eligible for further remedial actions if warranted by future conditions.

EPA will accept comments concerning its intent for partial deletion of the RMA/NPL Site for thirty days after publication of this notice in the Federal Register.

Section II of this document explains the criteria for deleting sites from the NPL. Section III discusses the procedures that EPA is using for this proposed partial deletion. Section IV discusses the Selected Perimeter Area of the RMA/NPL Site and explains how it meets the deletion criteria.

II. NPL Deletion Criteria

The NCP establishes the criteria that EPA uses to delete sites from the NPL. In accordance with 40 CFR 300.425(e), sites may be deleted from the NPL where no further response is appropriate to protect public health or the environment. In making such a determination pursuant to section 300.425(e), EPA will consider, in consultation with the State, whether any of the following criteria have been met:

Section 300.425(e)(1)(i). Responsible parties or other persons have implemented all appropriate response actions required; or

Section 300.425(e)(1)(ii). All appropriate Fund-financed response under CERCLA has been implemented, and no further response action by responsible parties is appropriate; or

Section 300.425(e)(1)(iii). The remedial investigation has shown that the release poses no significant threat to public health or the environment and, therefore, taking remedial measures is not appropriate.

A partial deletion of a site from the NPL does not affect or impede EPA's ability to conduct CERCLA response activities for portions not deleted from the NPL. In addition, deletion of a portion of a site from the NPL does not affect the liability of responsible parties or impede agency efforts to recover costs associated with response efforts. The U.S. Army and Shell Oil Company will be responsible for all future remedial actions required at the area deleted if future site conditions warrant such actions.

III. Deletion Procedures

Upon determination that at least one of the criteria described in Section 300.425(e) of the NCP has been met, EPA may formally begin deletion procedures. The following procedures were used for this proposed deletion of the SPA of the RMA/NPL Site:

(1) EPA has recommended the partial deletion and has prepared the relevant documents.

(2) The State of Colorado, through the CDPHE, has concurred with publication of this notice of intent for partial deletion.

(3) Concurrent with this national Notice of Intent for Partial Deletion, a local notice has been published in a newspaper of record and has been distributed to appropriate federal, State, and local officials, and other interested parties. These notices announce a thirty (30) day public comment period on the deletion package, which ends on August 26, 2003, based upon publication of this notice in the Federal Register and a local newspaper of record.

(4) EPA has made all relevant documents available at the information repositories listed previously for public inspection and copying.

Upon completion of the thirty calendar day public comment period, EPA Region 8 will evaluate each significant comment and any significant new data received before issuing a final decision concerning the proposed partial deletion. EPA will prepare a responsiveness summary for each significant comment and any significant new data received during the public comment period and will address concerns presented in such comments and data. The responsiveness summary will be made available to the public at the EPA Region 8 office and the information repository listed above and will be included in the final deletion package. Members of the public are encouraged to contact EPA Region 8 to obtain a copy of the responsiveness summary. If, after review of all such comments and data, EPA determines that the partial deletion from the NPL is appropriate, EPA will publish a final notice of partial deletion in the Federal Register. Deletion of the Selected Perimeter Area of the RMA/NPL Site does not actually occur until a final notice of partial deletion is published in the Federal Register. A copy of the final partial deletion package will be placed at the EPA Region 8 office and the information repository listed above after a final document has been published in the Federal Register.

IV. Basis for Intended Partial Deletion

The following information provides EPA's rationale for deletion of the SPA of the RMA/NPL Site from the NPL and EPA's finding that the proposed final deletion satisfies 40 CFR 300.425(e) requirements:

RMA/NPL Site Background

The Rocky Mountain Arsenal was established in 1942 by the U.S. Army, and was used to manufacture chemical warfare agents and incendiary munitions for use in World War II. Prior to this, the area was largely undeveloped ranch and farmland. Following the war and through the early 1980s, the facilities continued to be used by the Army. Beginning in 1946, some facilities were leased to private companies to manufacture industrial and agricultural chemicals. Shell Oil Company, the principal lessee, primarily manufactured pesticides from 1952 to 1982. After 1982, the only activities at the Arsenal involved remediation.

Complaints of groundwater pollution north of the RMA/NPL Site began to surface in 1954. Common industrial and waste disposal practices used during these years resulted in contamination of structures, soil, surface water, and groundwater. As a result of this contamination, the RMA was proposed for inclusion on the NPL on October 15, 1984. The listing of RMA on the NPL, excluding Basin F, was finalized on July 22, 1987. Basin F was added to the RMA/NPL Site listing on March 13, 1989. On February 17, 1989, an interagency agreement—referred to as a Federal Facility Agreement (FFA)—formalizing the process framework for selection and implementation of cleanup remedies at the RMA/NPL Site, became effective. The FFA was signed by the Army, Shell Oil Company, EPA, U.S. Department of the Interior, U.S. Department of Justice, and the Agency for Toxic Substances and Disease Registry.

Prior to the selection of remedial alternatives, a remedial investigation/endangerment assessment/feasibility study (RI/EA/FS) was conducted for the On-Post OU to provide information on the type and extent of contamination, human and ecological risks, and feasibility of remedial actions suitable for application at RMA. The remedial investigation (RI) completed in January 1992 studied each of the five environmental media at the RMA/NPL Site, including soils, water, structures, air, and biota. The feasibility study (FS) was finalized in October 1995, and a proposed remedial action plan was prepared and presented to the public in October 1995.

On June 11, 1996, the Army, EPA, and the State of Colorado signed the Record of Decision (ROD) for the On-Post Operable Unit. The ROD, which formally establishes the cleanup approach to be taken for the On-Post OU, specified the remedial actions to be implemented for soil, structures, and groundwater for the On-Post OU of RMA.

The On-Post OU of the RMA/NPL Site (see map, RMA Selected Perimeter Area) encompasses 25.5 square miles in southern Adams County, Colorado, approximately 8 miles northeast of downtown Denver.

Selected Perimeter Area of the On-Post OU

The SPA is an area of approximately 4,930 acres (7.7 square miles) on the perimeter of RMA. The proposed deletion of the SPA includes the surface, structures, and groundwater media of portions of Sections 1, 2, 3, 4, 10, 19, 20, 22, 27, 28, 29, 32, and 33; and all of Sections 5, 7, 8, 11, and 12 (see map).

A remedial investigation (RI) for the On-Post OU completed in January 1992 studied each of the environmental media at the RMA/NPL Site including soil, sediment, structures, water, air, and biota. Based upon evidence gathered during the RI, areas with similar soil contamination were combined into individual projects. This resulted in four separate soil cleanup projects within the SPA. These include the Toxic Storage Yards project located in the southeastern area of the SPA; the Miscellaneous Southern Tier Soil project located in the south-central portion of the SPA near the south lakes; the Existing (Sanitary) Landfill—Section 4 project located in the southwestern portion of the SPA; and the Burial Trenches—Part I project located in the southwestern portion of the SPA and east of the Sanitary Landfill project.

The Toxic Storage Yards project incorporated three contamination areas, one located within the SPA, considered to potentially contain chemical warfare agent based on use histories and detections of agent breakdown products. The Miscellaneous Southern Tier Soil project included eight contamination areas, four located within the SPA, contaminated with pesticides (aldrin and dieldrin), and heavy metals. The Existing (Sanitary) Landfill project incorporated five contamination areas, all within the SPA, which contained trash and debris, asbestos-containing material, and drums with high concentrations of styrene. The Burial Trenches—Part I project included 35 contamination areas, five within the SPA, considered to potentially contain ordnance or explosives, unexploded ordnance, and munition debris as well as general construction-related debris and trash.

A structures survey identified seventeen structures within the SPA. Four of these structures have no history of contamination and were designated to be retained for future use. The contaminants identified within the other thirteen structures include asbestos, polychlorinated biphenyls (PCBs), pesticides, herbicides and heavy metals.

Two groundwater plumes below the western portion of the SPA contain 1,1-dichloroethylene, 1,1,1-trichloroethane, and TCE but are not attributable to the RMA/NPL Site. Because the groundwater does not meet drinking water standards, the Klein Water Treatment Facility—built in 1989, prior to completion of the RI—treats the groundwater contamination that is now known to originate from non-RMA/NPL sources.

The Irondale Containment System (ICS) was constructed during development of the RI/FS as an interim response action (IRA). The ICS was mostly located on the SPA and installed to extract and treat groundwater emanating from the Rail Yard—which is primarily contaminated with dibromochloropropane, and the Motor Pool—which is primarily contaminated with trichloroethylene. Both of these areas in the RMA/NPL Site are in close proximity to the SPA. Two additional groundwater plumes were identified beneath the northwest portion of the SPA along the Colorado Highway 2 border. These plumes originate in the South Plants manufacturing area—which is primarily contaminated with benzene, chloroform, carbon tetrachloride, and trichloroethylene; and the historic basins located in the northwest area of the RMA/NPL Site—which is primarily contaminated with dieldrin, chloroform, and DIMP (a byproduct of nerve agent production).

A feasibility study (FS) was finalized in October 1995, and a proposed plan prepared and presented to the public in October 1995. On June 11, 1996, the On-Post Record of Decision (ROD) was signed by the Army, EPA, and the State of Colorado. The ROD required the excavation and consolidation of soil presenting a risk to human health, as well as munition debris, in a state-of-the-art hazardous waste landfill to be built within the On-Post OU; and excavation of debris and soil presenting a risk to biota and placement of those soils in the Basin A consolidation area which is located in the central portion of the RMA/NPL Site. The excavated human health exceedence areas were backfilled with on-post borrow material and revegetated. Unexploded ordnance was to be transported off-site for detonation or other demilitarization process, unless the unexploded ordnance was unstable and must be detonated on-site.

The remedy for structures included the demolition of thirteen of the seventeen structures identified in the SPA. Four of the seventeen structures had no contamination history and were not identified for demolition by the ROD.

The selected groundwater remedy consisted of continued operation of the groundwater treatment systems, including the ICS to treat the Motor Pool and Rail Yard plumes and the Northwest Boundary Containment System to treat the South Plants plumes. Additionally, wells which had the potential to provide a cross-contamination pathway from the contaminated, upper groundwater aquifer to the deeper, confined aquifer were to be closed. The ROD also required continued use restrictions for the property.

Community Involvement

Since 1988, each of the parties involved with the Arsenal cleanup has made extensive efforts to ensure that the public is kept informed on all aspects of the cleanup program. More than 100 fact sheets about topics ranging from historical information to site remediation have been developed and made available to the public. Following the release and distribution of the draft Detailed Analysis of Alternatives report (a second phase of the FS), the Army held an open house for about 1,000 community members. The open house provided opportunity for individual discussion and understanding of the various technologies being evaluated for cleanup of the RMA/NPL Site.

The Proposed Plan for the On-Post OU was released for public review on October 16, 1995. On November 18, 1995, a public meeting was held, attended by approximately 50 members of the public, to obtain public comment of the Proposed Plan. As a result of requests at this meeting, the period for submitting written comments on the plan was extended one month, concluding on January 19, 1996. Minimal comments were received on the alternatives presented for the projects in the SPA of the On-Post OU. Specifically, the comments requested that excavation of the western tier landfills be “complete,” that the health and safety of nearby communities be protected from air emissions during excavation and demolition activities, that additional treatment capabilities or modification of the existing water treatment systems be considered, and that potential dioxin contamination of the entire RMA/NPL Site be evaluated.

The designs for the Miscellaneous Structures, Confined Flow System Well Closure, and each of the soil projects were provided to the public for a thirty calendar day review and comment period at both the 30 percent and 95 percent design completion stages (twelve separate public comment periods). Each design was also presented at the monthly meeting of the RMA Restoration Advisory Board, composed of community stakeholders, regulatory agencies, the Army, Shell Oil Company, and the USFWS. No comments regarding the excavation/demolition approach or the proposed health and safety controls for each project were received.

Upon completion of the thirty calendar day public comment period for this NOIDp, EPA Region 8 in consultation with the State and the Army, will evaluate each comment and any significant new data received before issuing a final decision concerning the proposed partial deletion.

Current Status

The Toxic Storage Yards Soil project, completed in 2000, consisted of three separate cleanup areas including one in the SPA. A total of 4,400 bank cubic yards (bcy) of soils presenting a risk to human health was removed from this SPA area and disposed in the on-site hazardous waste landfill. Chemical agent screening was conducted during the soil excavation and soil ripping activities and three groundwater monitoring wells were closed. The Miscellaneous Southern Tier Soil project, completed in 2000, remediated eight areas including three in the SPA. A total of 12,649 bcy of soil presenting a risk to human health and 8 bcy of debris were excavated from the three areas within the SPA and disposed in the hazardous waste landfill. Another 3,325 bcy of soil presenting a risk to biota was disposed in Basin A. This project also included the demolition of one structure, Building 863, which was also disposed in Basin A.

The Existing (Sanitary) Landfill—Section 4 project, completed in 2000, consisted of five separate areas which are all in the SPA. A small amount of asbestos containing material and 11,975 bcy of soil presenting a human health risk was disposed in the hazardous waste landfill. A total of 40,260 bcy of trash and debris was disposed in Basin A. Ten intact drums containing high concentrations of styrene were sent to an offsite facility for disposal in accordance with hazardous waste regulatory requirements. The Burial Trenches Soil Remediation project, completed in 2002, remediated thirty-five areas including five in Section 4 of the SPA. All soil presenting a risk to human health, munition debris and related soil, and asbestos containing material was disposed in the on-site hazardous waste landfill. All other material with lesser degrees of contamination, e.g., asphalt pavement, general construction debris and trash, was disposed in the Basin A consolidation area.

Demolition and removal of nine of the thirteen structures slated for removal was completed as part of the Miscellaneous RMA Structure Demolition and Removal—Phase I project completed in 2002. This project consisted of the demolition of the structures and foundations; removal and disposal of structures and foundations, substations, debris piles, roads and parking areas; removal and disposal or recycling of underground storage tanks, structural steel and other metal components; backfilling and grading; and revegetation of the excavated areas. Of the four remaining structures, one was demolished as part of the Miscellaneous Southern Tier Soil project, two had been demolished prior to remedial action, and one structure has been retained for continued operations of the RMA/NPL Site.

The Northwest Boundary Containment System will continue to operate long-term to prevent migration of groundwater plumes offsite. However, monitoring of the groundwater below the SPA indicates that contamination in the groundwater has been below all regulatory standards since 1993. The ICS extraction wells have met the ROD shut-off criteria and were shut down on October 1, 1997. Extraction wells for the Motor Pool IRA also met shut-off criteria in March 1998; therefore, the ICS facility was demolished and removed as part of the Miscellaneous Structures project on May 7, 2002. A treatment system was constructed at the Rail Yard to more directly treat the contaminated groundwater associated with the Rail Yard. The Rail Yard IRA and Treatment System, and Motor Pool IRA are not associated with the SPA. Monitoring of the groundwater aquifer for the Northwest Boundary Containment System and that previously treated through the ICS extraction wells has been incorporated into the sitewide monitoring program, as required by the ROD.

The Confined Flow System Well Closure project was completed in 2000. A total of 51 wells, six in the SPA, which extended into the deeper, confined flow aquifer were closed. Closure was accomplished by overdrilling the well casing and installing a grout plug. An additional 134 monitoring wells within the SPA are part of the long-term, site-wide monitoring plan.

Use of the groundwater below the SPA and surface water for potable drinking purposes is prohibited by the FFA, Public Law 102-402, and the ROD; and will continue to be prohibited even after the SPA is transferred to the U.S. Department of Interior or units of local government. Additional prohibitions imposed by the FFA, Public Law 102-402, and the ROD include the use of the SPA for residential, industrial, and agricultural purposes, and for hunting or fishing for consumptive purposes.

The Army is responsible for ongoing monitoring and maintenance associated with groundwater wells located on land to be transferred to the Department of Interior within the SPA. The conduct of long-term groundwater monitoring required by the ROD is delineated in the Final Interim Rocky Mountain Arsenal Institutional Control Plan.

Post-ROD Investigations

Since the signing of the ROD on June 11, 1996, three studies have been conducted that are relevant to the deletion of the SPA. The Summary and Evaluation of Potential Ordnance/Explosives and Recovered Chemical Warfare Materiel Hazards at the Rocky Mountain Arsenal (2002) was conducted in response to the unexpected discovery of six M139 bomblets as part of the Miscellaneous Structures—Phase I project in the Section 36 Boneyard (central portion of the RMA/NPL Site). Using state-of-the-art computer imaging, mapping technology, and software capability which had not existed previously, a comprehensive RMA-wide evaluation for the potential presence of ordnance and explosives as well as recovered chemical warfare materiel hazards was completed. The evaluation identified six additional areas for remedial action (none in the SPA) and concluded that the future discovery of additional sites with ordnance/explosives or recovered chemical warfare materiel hazards is highly unlikely.

In 2001, EPA conducted a four-part Denver Front Range Dioxin Study which determined that the concentration of dioxins at most of the RMA/NPL Site, including the SPA, is not statistically different from values observed in open space and agricultural areas within the Denver Front Range area. Therefore there is no significant health risk from dioxin in soils to future Refuge workers, volunteers, or visitors.

As required by the ROD, a Terrestrial Residual Ecological Risk Assessment was completed in 2002. This report concluded that no significant excess terrestrial residual risks will remain after the ROD-required cleanup actions for soil, including additional areas of excavation and tilling identified as part of remedial design refinement as required by the ROD, are completed.

Based on the extensive investigations and risk assessment performed for the SPA of the RMA/NPL Site, there are no further response actions planned or scheduled for this area. Currently, no hazardous substances remain at the SPA above health-based levels with respect to anticipated uses of and access to the site, which are limited under the FFA, Public Law 102-402, and the ROD. Because the SPA is subject to these restrictions on land and water use, it will be included in the RMA-wide five-year reviews. There are no operation and maintenance requirements for the remedies implemented at the SPA. All completion requirements for the SPA of the On-Post OU have been achieved as outlined in OSWER Directive 9320.2-09A-P.

EPA, with concurrence from the State of Colorado, has determined that all appropriate CERCLA response actions have been completed within the SPA of the RMA/NPL Site to protect public health and the environment and that no further response action by responsible parties is required. Therefore, EPA proposes to delete the SPA of the On-Post OU of the RMA/NPL Site from the NPL.

Dated: July 16, 2003.

Kerrigan G. Clough,

Acting Regional Administrator, Region 8.