Document ID: EPA-HQ-SFUND-1987-0002-0144
Agency: epa
Document Type: Proposed Rule
Title: National Oil and Hazardous Substances Pollution Contingency Plan; National Priorities List: Partial Deletion of the Rocky Mountain Arsenal Federal Facility
Posted Date: 2010-06-17T04:00Z

[Federal Register: June 17, 2010 (Volume 75, Number 116)]
[Proposed Rules]               
[Page 34405-34415]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr17jn10-31]                         

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 300

[EPA-HQ-SFUND-1987-0002; FRL-9163-4]

 
National Oil and Hazardous Substances Pollution Contingency Plan; 
National Priorities List: Partial Deletion of the Rocky Mountain 
Arsenal Federal Facility

AGENCY: Environmental Protection Agency.

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) Region 8 is issuing 
a Notice of Intent to Delete portions of the On-Post Operable Unit 
(OU3), specifically the Central and Eastern Surface Areas including 
surface media and structures (CES), and the surface media of the entire 
Off-Post Operable Unit (OU4) (OPS) of the Rocky Mountain Arsenal 
Federal Facility (RMA) from the National Priorities List (NPL) and 
requests public comment on this proposed action. The NPL, promulgated 
pursuant to section 105 of the Comprehensive Environmental Response, 
Compensation, and Liability Act (CERCLA) of 1980, as amended, is an 
appendix of the National Oil and Hazardous Substances Pollution 
Contingency Plan (NCP). The EPA and the State of Colorado, through the 
Colorado Department of Public Health and Environment (CDPHE), have 
determined that all appropriate response actions at these identified 
parcels under CERCLA, other than operation, maintenance, and five-year 
reviews, have been completed. However this deletion does not preclude 
future actions under Superfund.
    This partial deletion pertains to the surface media (soil, surface 
water, sediment) and structures (both former structures that have been 
demolished and structures retained for future use) within the CES and 
the surface media of the entire OPS. The rest of the On-Post OU (Figure 
1), including groundwater below RMA that is west of E Street, and the 
groundwater that comprises the Off-Post OU (see Section IV and Figure 
1) will remain on the NPL and response activities will continue at 
those OUs. The groundwater media east of E Street (with the exception 
of a small area below the northwest corner of Section 6) was previously 
deleted from the NPL as part of the Internal Parcel Partial Deletion in 
2006 (71 FR 43071).

DATES: Comments must be received by July 19, 2010.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-

[[Page 34406]]

SFUND-1987-0002, by one of the following methods:
     http://www.regulations.gov: Follow the on-line 
instructions for submitting comments.
     E-mail: chergo.jennifer@epa.gov.
     Fax: 303-312-7110.
     Mail: Ms. Jennifer Chergo, Community Involvement 
Coordinator (8OC), U.S. EPA, Region 8, 1595 Wynkoop Street, Denver, 
Colorado, 80202-1129.
     Hand Delivery: 1595 Wynkoop Street, Denver, Colorado, 
80202-1129. Such deliveries are only accepted during the Docket's 
normal hours of operation, and special arrangements should be made for 
deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-SFUND-
1987-0002. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
http://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through http://
www.regulations.gov or e-mail. The http://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through http://www.regulations.gov, your e-mail address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses.
    Docket: All documents in the docket are listed in the http://
www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at:

--EPA's Region 8 Superfund Records Center, 1595 Wynkoop Street, Denver, 
Colorado, 80202-2466. Hours: 8 a.m. to 4 p.m. by appointment (call 303-
312-6473), Monday through Friday, excluding legal holidays; and the
--Joint Administrative Records Document Facility, Rocky Mountain 
Arsenal, 5650 Havana Street, Building 129, Commerce City, Colorado 
80022-1748. Hours: 12 p.m. to 4 p.m., Monday through Friday, excluding 
legal holidays, or by appointment (call 303-289-0983).

FOR FURTHER INFORMATION CONTACT: Ms. Jennifer Chergo, Community 
Involvement Coordinator (8OC), U.S. Environmental Protection Agency, 
Region 8, 1595 Wynkoop Street, Denver, Colorado, 80202-1129; telephone 
number: 1-800-227-8917 or 303-312-6601; fax number: 303-312-7110; e-
mail address: chergo.jennifer@epa.gov.

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 CES and OPS of the RMA Site, Commerce City, 
Colorado, from the NPL and requests comment on this proposed action. 
The NPL constitutes Appendix B of 40 CFR part 300 which is the 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) of 1980, as amended. 
EPA maintains the NPL as those sites that appear to present a 
significant risk to public health, welfare, or the environment. Sites 
on the NPL may be the subject of remedial actions financed by the 
Hazardous Substance Superfund (Fund). This partial deletion of the RMA 
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), a portion of a site deleted from the NPL remains 
eligible for further remedial actions if warranted by future 
conditions.
    EPA will accept comments on the proposal to partially delete this 
site for thirty (30) days after publication of this document in the 
Federal Register.
    Section II of this document explains the criteria for deleting 
sites from the NPL. Section III discusses procedures that EPA is using 
for this action. Section IV discusses the CES and OPS of the RMA Site 
and demonstrates how they meet 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. In making such a 
determination pursuant to 40 CFR 300.425(e), EPA will consider, in 
consultation with the State, whether any of the following criteria have 
been met:
    i. Responsible parties or other persons have implemented all 
appropriate response actions required;
    ii. All appropriate Fund-financed response under CERCLA has been 
implemented, and no further response action by responsible parties is 
appropriate; or
    iii. The remedial investigation has shown that the release poses no 
significant threat to public health or the environment and, therefore, 
taking of remedial measures is not appropriate.
    Pursuant to CERCLA section 121(c) and the NCP, EPA conducts five-
year reviews to ensure the continued protectiveness of remedial actions 
where hazardous substances, pollutants, or contaminants remain at a 
site above levels that allow for unlimited use and unrestricted 
exposure. EPA conducts such five-year reviews even if a site is deleted 
from the NPL. EPA may initiate further action to ensure continued 
protectiveness at a deleted site if new information becomes available 
that indicates it is appropriate. Whenever there is a significant 
release from a site deleted from the NPL, the deleted site may be 
restored to the NPL without application of the hazard ranking system.

III. Deletion Procedures

    The following procedures apply to the deletion of the CES and OPS 
of the RMA Site:
    (1) EPA consulted with the State before developing this Notice of 
Intent for Partial Deletion.
    (2) EPA has provided the State 30 working days for review of this 
notice prior to publication of it today.
    (3) In accordance with the criteria discussed above, EPA has 
determined that no further response is appropriate.
    (4) The State of Colorado, through the CDPHE, has concurred with 
the deletion

[[Page 34407]]

of the CES and OPS of the RMA Federal Facility Site, from the NPL.
    (5) Concurrently, with the publication of this Notice of Intent for 
Partial Deletion in the Federal Register, a notice is being published 
in a major local newspaper, the Denver Post. The newspaper announces 
the 30-day public comment period concerning the Notice of Intent for 
Partial Deletion of the Site from the NPL.
    (6) The EPA placed copies of documents supporting the proposed 
partial deletion in the deletion docket and made these items available 
for public inspection and copying at the Site information repositories 
identified above.
    If comments are received within the 30-day comment period on this 
document, EPA will evaluate and respond accordingly to the comments 
before making a final decision to delete the CES and OPS. If necessary, 
EPA will prepare a Responsiveness Summary to address any significant 
public comments received. After the public comment period, if EPA 
determines it is still appropriate to delete the CES and OPS of the RMA 
Site, the Regional Administrator will publish a final Notice of Partial 
Deletion in the Federal Register. Public notices, public submissions 
and copies of the Responsiveness Summary, if prepared, will be made 
available to interested parties and included in the site information 
repositories listed above.
    Deletion of a portion of a site from the NPL does not itself 
create, alter, or revoke any individual's rights or obligations. 
Deletion of a portion of a site from the NPL does not in any way alter 
EPA's right to take enforcement actions, as appropriate. The NPL is 
designed primarily for informational purposes and to assist EPA 
management. Section 300.425(e)(3) of the NCP states that the deletion 
of a site from the NPL does not preclude eligibility for future 
response actions, should future conditions warrant such actions.

IV. Basis for Intended Partial Deletion

    The following information provides EPA's rationale for deleting the 
CES and OPS of the RMA Federal Facility from the NPL.

Site Background and History

    The Rocky Mountain Arsenal Federal Facility (RMA), EPA ID No. 
CO5210020769, is located in Commerce City--approximately eight miles 
northeast of downtown Denver--in Adams County, Colorado. RMA was 
established in 1942 by the U.S. Army to manufacture chemical warfare 
agents and incendiary munitions for use in World War II. Following the 
war and through the early 1980s, the facilities continued to be used by 
the U.S. Army. Beginning in 1946, some facilities were leased to 
private companies to manufacture industrial and agricultural chemicals. 
Shell Oil Company, the principal lessee, manufactured pesticides at the 
site from 1952 to 1982. Common industrial and waste disposal practices 
resulted in contamination of structures, soil, surface water, and 
groundwater. As a result of this contamination, RMA was proposed to the 
NPL, excluding the Basin F surface impoundment, on October 15, 1984, 
(49 FR 40320). On July 22, 1987, RMA was finalized on the NPL and 
expanded to include Basin F (52 FR 27620 and 52 FR 27643).
    RMA is located at the western edge of the Colorado Plains, 
consisting of a rolling terrain characterized by grasslands, 
shrublands, wetlands, aquatic habitats, and extensive weedy areas. 
Regional surface drainage is northwest into the South Platte River 
which eventually joins the North Platte River in Nebraska. The RMA Site 
consists of 30 OUs (numbers 0 through 29) including 24 Interim Response 
Actions (IRA) conducted between October 1985 and June 1996 as part of 
the On-Post (OU 3) remediation and 4 IRAs completed in 1993 for 
remediation of the Off-Post (OU 4). The IRAs were conducted to prevent 
or minimize further migration of groundwater contaminants and eliminate 
potential releases from source areas through isolation or destruction 
of the contaminants. Each of the OUs is described below.

OU 00: South Adams County--Installation of temporary granular activated 
carbon filters (GAC) at the South Adams County plant to address 
trichloroethene in the potable water supply (1986).
OU 01: Klein Water Treatment Plant--Groundwater treatment plant 
constructed on RMA property (Section 33) to treat off-post contaminant 
plumes along the western boundary of RMA (1989).
OU 02: Chemical Sales--Remedial investigation of off-post groundwater 
plumes which resulted in identification of the Chemical Sales Company 
Superfund Site located upgradient (south) of RMA (1990).
OU 03: On-Post--Addresses soil and groundwater contamination within the 
fenced 27 square miles of RMA proper (ongoing). OUs 6 through 29 
contributed to remediation of the On-Post OU and were completed prior 
to or integrated into the On-Post OU as part of the 1996 On-Post ROD.
OU 04: Off-Post--Addresses contamination north and northwest of the RMA 
proper site. OUs 00 through 02 and OU 5 contributed to remediation of 
the Off-Post OU and were completed prior to or integrated into the Off-
Post OU as part of the 1995 ROD.
OU 05: Off-Post Groundwater Intercept and Treatment System IRA--
Treatment plant constructed to address contaminant plumes that had 
migrated off post prior to installation of the boundary treatment 
systems (1993).
OU 06: North Boundary Groundwater Treatment System IRA--Recharge 
trenches were added along the entire length of the North Boundary 
Treatment System slurry wall and operational improvements were made to 
the existing system (1993).
OU 07: Basin F Groundwater Treatment System IRA--Extraction of 
contaminated groundwater migrating from the Basin F area for treatment 
at the Basin A Neck Treatment System (1990).
OU 08: Abandoned Well Closure IRA--Old or deteriorating farm wells and 
unused on-post wells were grouted closed (1990).
OU 09: Basin A Neck Groundwater Treatment System IRA--Groundwater 
treatment plant constructed to treat contaminant plumes migrating 
through paleochannels from the Basin A area (1990).
OU 10: Basin F Liquids & Sludges IRA--Containment of 600,000 cubic 
yards of Basin F sludges/soil in a lined, 16-acre storage area with a 
leachate collection system (1989).
OU 11: Building 1727 Sump IRA--Treatment of liquid in the Building 1727 
Sump with activated alumina and GAC to remove contaminants (1989).
OU 12: Hydrazine IRA--The hydrazine facility was demolished and the 
debris disposed at an off-site hazardous waste landfill. The area was 
regraded and revegetated (1992).
OU 13: Fugitive Dust Suppression IRA--Reapplication of a dust 
suppressant was applied to Basin A (1991).
OU 14: Sanitary Sewer IRA--Sanitary sewer manholes were plugged to 
eliminate potential transport of contaminated groundwater that may have 
entered the sewer system

[[Page 34408]]

through cracks or loose connections (1992).
OU 15: Asbestos IRA--Continuation of the Army's survey and removal of 
friable asbestos from on-post structures (1996).
OU 16: M-1 Settling Basins IRA--The objective was to treat the M-1 
Settling Basins sludge using in situ vitrification (ISV). However, due 
to technology complications with the ISV, implementation of the IRA was 
suspended (1991).
OU 17: CERCLA Wastewater Treatment Plant IRA--Facility constructed to 
treat wastewater generated by investigative activities and 
implementation of response actions (1992).
OU 18: Motorpool IRA--An extraction well system was constructed to 
remove a trichlorethene plume emanating from the Motorpool area for 
treatment at the Irondale Containment System (1990). A soil vapor 
extraction system was operated in 1991 to remove volatile contaminants 
from the soil.
OU 19: Rail Classification Yard IRA--An extraction well system was 
constructed to remove a dibromochloropropane plume emanating from the 
Rail Yard area for treatment at the Irondale Containment System (1991).
OU 20: Lime Settling Basins IRA--A soil cover was constructed over the 
Lime Settling Basins to minimize infiltration of precipitation through 
the basin waste (1993).
OU 21: South Tank Farm Plume IRA--Continued monitoring of groundwater 
plumes to assess if additional action was necessary (1994).
OU 22: Army Trenches IRA--Continued monitoring of groundwater plumes to 
assess if additional action was necessary (1994).
OU 23: Shell Trenches IRA--A slurry wall was constructed to isolate the 
trenches from surrounding groundwater and a soil cover placed over the 
trenches to minimize infiltration of precipitation through the trench 
waste (1994).
OU 24: Northwest Boundary Containment System IRA--Additional 
extraction, reinjection, and monitoring wells were installed to 
increase treatment capacity (1993).
OU 25: Basin F Liquid (SQI) IRA--Incineration of 11 million gallons of 
basin liquids and decontamination waters (1995).
OU 26: Chemical Process-Related Activities IRA--Decontamination and 
disposal of process related equipment and piping for both agent and 
non-agent manufacturing processes in the North Plants and South Plant 
facilities (1996).
OU 27: Underground Storage Tank IRA--Content characterization, 
deactivation, excavation, decontamination, and removal of underground 
storage tanks (1995).
OU 28: Waste Management IRA--Temporary management of hazardous waste in 
storage at RMA or generated by the response actions, and not addressed 
by another IRA (1996).
OU 29: Polychlorinated Biphenyls (PCB) IRA--Inventory and remediate 
PCB-contaminated structures and soil (1996).

    The original On-Post Operable Unit (OU 3) encompassed 27 square 
miles (16,990 acres) and was bounded by 56th Avenue and the former 
Stapleton International Airport on the south, Buckley Road and Denver 
International Airport on the east, Quebec Parkway and Commerce City on 
the west, Colorado Highway 2 and the Off-Post OU on the northwest, and 
96th Avenue and the Off-Post OU on the north (Figure 1). In the 1980s, 
it was observed that over 300 species of wildlife, including bald 
eagles, utilize much of the natural environment that remains at RMA. In 
recognition of these unique urban wildlife resources at RMA, President 
George H.W. Bush signed the 1992 Rocky Mountain Arsenal National 
Wildlife Refuge Act (Public Law 102-402). Most of the RMA On-Post OU, 
including the CES, is designated to become part of a National Wildlife 
Refuge upon completion of the site-wide remedy.
    Between 2003 and 2006, EPA conducted four partial deletions from 
the On-Post OU consisting of 13,406 acres of surface media so that 
property transfer could be expedited. Of the property deleted to date, 
917 acres were sold to Commerce City for commercial development, 12 
acres were transferred to South Adams County Water and Sanitation 
District for the Klein Treatment Facility, 126 acres were transferred 
to local governments for road-widening, and 12,188 acres have been 
transferred to the National Wildlife Refuge. Another 163 acres were 
retained by the Army, primarily for water treatment systems. While EPA 
has not conducted any partial deletions for the Off-Post OU, EPA did 
issue a Ready for Reuse (RfR) Determination in September 2009 for a 
portion of the Shell Oil Company property (approximately 294 acres) 
that is within or adjacent to the Off-Post OU. EPA's determination 
indicated that the Shell RfR Property ``is ready for use for any 
purpose allowed under local land use and zoning laws.'' While there has 
been no redevelopment/reuse of the Shell RfR Property thus far, the 
area around the Shell RfR Property and Off-Post OU has undergone 
primarily residential development in recent years.
    The proposed partial deletion for the OPS includes the entire 
surface media of the Off-Post OU (OU 4) without exclusions. Of the 
3,584 acres (5.6 square miles) of the On-Post OU (OU 3) that remain on 
the NPL, the proposed partial deletion for the CES includes 2,500 acres 
(3.9 square miles) of surface media (soil, surface water, and 
sediment), as shown in Figure 1, and structures (both former structures 
that have been demolished and structures retained for future use) 
within the On-Post OU. The entire CES proposed for partial deletion 
will be transferred from the Army to the U.S. Fish and Wildlife Service 
(USFWS) for expansion of the RMA National Wildlife Refuge. The portions 
of the On-Post OU not proposed for deletion, also shown in Figure 1, 
include the following:
     Cover areas (Hazardous Waste Landfill (HWL), Enhanced 
Hazardous Waste Landfill (ELF), Basin F, and Integrated Cover System 
(ICS)) including drainages;
     Three areas of groundwater treatment (Railyard Extraction 
and Treatment System, Lime Basins Mass Removal System, and the South 
Tank Farm Mass Removal System);
     Three laydown areas (areas used to stage equipment and 
construction materials or conduct support activities during remedy 
implementation); and
     Two structures: The CERCLA Wastewater Treatment Facility 
and the Landfill Wastewater Treatment System (LWTS).
    The following information provides EPA's rationale for deletion of 
the CES and OPS of the RMA Site from the NPL:

Remedial Investigation/Feasibility Study (RI/FS) and Selected Remedy

    On-Post OU (OU 3). Prior to the selection of remedial alternatives 
for the On-Post OU, an RI/FS was conducted 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 
RI, completed in January 1992, studied five environmental media at the 
RMA Site, including soils, water, structures, air, and biota. The RI 
identified approximately 3,000 acres of contaminated soil, 15 
groundwater plumes, and 798 structures. The FS was

[[Page 34409]]

finalized in October 1995 for the On-Post OU.
    On June 11, 1996, the Army, EPA, and the State of Colorado signed 
the ``Record of Decision for the On-Post Operable Unit'' (On-Post ROD). 
The On-Post ROD formally established the cleanup approach to be taken 
and specified individual remedial actions to be implemented for soil, 
structures, and groundwater. In general, the remedial action objectives 
were to prevent or limit potential exposure of humans and biota and any 
further contamination of the surface water, groundwater, or air due to 
releases from the soils, sediments, and structures at the On-Post OU. 
The overall remedy for the On-Post OU includes extraction and treatment 
of the contaminated groundwater plumes, demolition of 750 structures 
with no designated future use, excavation and disposal of soil and 
demolition debris with a cumulative contamination concentration 
presenting an excess cancer risk to human health of greater than 
1x10-\4\ or a Hazard Index greater than 1.0 for non-cancer 
risks (collectively referred to as human health exceedance (HHE) 
soils), as well as munitions debris, in two state-of-the-art hazardous 
waste landfills to be built within the On-Post OU; and excavation and 
consolidation of debris and soil presenting a risk to biota (biota 
soil) in the Basin A, South Plants, and Basin F project areas. The 
excavated HHE soil areas were backfilled with on-post borrow material 
and revegetated. The On-Post ROD also requires continued use 
restrictions for the CES that restrict ``current and future land use, 
specifies that the U.S. government shall retain ownership of RMA, and 
prohibits certain activities such as agriculture, use of on-post 
groundwater as a drinking source, and consumption of fish and game 
taken at RMA.''
    Multiple changes to the On-Post ROD have been made during 
implementation of the remedy over the past 14 years through 
Explanations of Significant Differences (ESD) and two ROD Amendments. 
With regard to the CES, there are 13 ESDs which document changes in the 
project boundaries, volumes of soil excavated, and associated costs for 
each of the implementation projects. These changes have included 
significant increases in excavated HHE soils at the Section 35 Soil 
project and excavated biota soils at the Munitions (Testing) Soil 
project. Of note, any contaminated soils to be contained under soil 
covers at the North Plants, Secondary Basins, and South Plants Balance 
of Areas projects were excavated based on additional sampling efforts 
and the 1- and 2-foot soil cover requirements were eliminated. These 
boundary, volume, and cover changes have resulted in an estimated 
increase of $123.5 million for the combined individual projects while 
the overall On-Post RMA remedy cost has remained unchanged at $2.2 
billion.
    Off-Post OU (OU 4). The Off-Post OU followed the same investigative 
process and an RI for the Off-Post study area that evaluated 
groundwater, soil, surface water, sediment, air and biota was completed 
in 1988 with an addendum issued in 1992. The RI identified two plume 
groups encompassing 590 acres in the Off-Post area and wind-deposited 
contamination in surface soils immediately north of the On-Post 
boundary in the southeast portion of Section 14 and the southwest 
portion of Section 13. The Off-Post Endangerment Assessment/Feasibility 
Study (EA/FS) was issued in 1992 and the Off-Post ROD was signed by the 
Army, EPA, and the State of Colorado on December 19, 1995. The Off-Post 
remedy includes extraction and treatment of the contaminated 
groundwater plumes, and closure of poorly constructed wells that could 
be acting as migration pathways. For settlement purposes, though the 
health risks present in the soils were within EPA's acceptable cancer 
risk range (less than 1 x 10-\4\) for residential use, Shell 
agreed to revegetate approximately 160 acres of soil to enhance the 
degradation of low-level pesticide residues. The Off-Post ROD also 
required institutional controls to prevent the use of groundwater 
exceeding remediation goals. There have been no remedy modifications 
related to the OPS.

Post-RODs Investigations

    On-Post OU (OU 3). Since the signing of the On-Post ROD on June 11, 
1996, three main studies have been conducted that are relevant to the 
deletion of the On-Post CES. These include the ``Summary and Evaluation 
of Potential Ordnance/Explosives and Recovered Chemical Warfare 
Materiel Hazards at the Rocky Mountain Arsenal'' completed in 2002 
(Summary Team), the ``EPA Denver Front Range Dioxin Study'' completed 
in 2001, and a two-part Residual Ecological Risk (RER) Assessment that 
was completed in 2003. Each of these on-post investigations is 
described below:
    Summary and Evaluation of Potential Ordnance/Explosives and 
Recovered Chemical Warfare Materiel Hazards at the Rocky Mountain 
Arsenal (2002). This effort was conducted in response to the unexpected 
discovery of ten M139 bomblets as part of the Miscellaneous Structures 
Demolition and Removal Project--Phase I in the Section 36 Boneyard 
(central portion of the RMA 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, all in the CES, 
and concluded that the future discovery of additional sites with 
ordnance/explosives or recovered chemical warfare materiel hazards is 
highly unlikely. Remediation of four of the Summary Team sites (BT29-1, 
BT29-2, BT30-01, and BT32-11) was completed in 2004 and is documented 
in the Construction Completion Report (CCR) for the Burial Trenches 
Soil Remediation Project, Part II. Remediation of the fifth Summary 
Team site (ESA-4a) was completed in 2008 and is documented in the CCR 
for the Munitions (Testing) Soil Remediation Project, Part II. 
Remediation of the sixth Summary Team site (CSA-2c) was completed in 
2008 and is documented in the Munitions (Testing) Soil Remediation 
Project, Part III.
    Dioxin Study. In 2001, EPA conducted a four-part Denver Front Range 
Dioxin Study which determined that the concentration of dioxins at most 
of the RMA Site, including the CES, was 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.
    RER Assessment. As required by the ROD, a RER assessment was 
completed in 2003 addressing both terrestrial and aquatic health risks. 
The 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. The Aquatic Residual Risk Assessment was completed in 2003. 
The Assessment presented an evaluation of risks to the great blue 
heron, shorebirds and waterbirds and concluded that there are no 
significant risks to aquatic birds in the South Lakes beyond those 
already identified for remediation in the ROD.
    Off-Post OU (OU 4) Indoor Air Evaluation. Since the signing of the 
Off-Post ROD in 1995, one study has been conducted for the Off-Post OU. 
Based on EPA guidance issued in 2002 and 2003,

[[Page 34410]]

EPA conducted an indoor air evaluation of volatile organic compounds 
for the entire Off-Post OU using the Johnson and Ettinger Model (GW-
SCREEN) as implemented by EPA. Estimated indoor air concentrations and 
potential cancer and non-cancer risks were calculated for theoretical 
inhalation exposure to vapors emanating from groundwater at a depth 
that varies from less than 5 feet to 27.5 feet. Where the depth to 
groundwater was less than 11 feet, slab on grade foundations were 
assumed; otherwise, the future residential scenario assumed the 
residences would be constructed with basements. The result of the 
assessment indicated that modeled concentrations were below human 
health risk criteria, that no further evaluation of the vapor intrusion 
pathway was warranted, and that there was no need to implement 
intrusion controls in buildings overlying the groundwater plumes in the 
Off-Post OU.

Response Actions

Remedial Action for the CES of the On-Post (OU 3)
    Surface media: The surface media of the CES consists of soil, 
sediment, and surface water within approximately 3.9 square miles 
(2,500 acres) in the central and eastern portions of the RMA On-Post 
OU. Areas with similar contamination were combined into individual 
projects based upon evidence gathered during the RI. This resulted in 
18 separate soil/sediment cleanup projects within the CES including 
portions of Sections 1, 2, 3, 4, 6, 10, 19, 20, 23, 24, 25, 26, 29, 30, 
31, 32, 34, 35, and 36. Completion of these 18 remediation projects is 
documented in individual project CCRs. The following is a brief summary 
of these projects and the soil contamination that was remediated within 
the CES.
     The Basin F/Basin F Exterior Soil Remediation Project 
included the excavation of soil from three pesticide-contaminated sites 
within Section 26 of the CES (NCSA-4a, 4b, and 5c). HHE soil was 
excavated from all three sites and disposed in the HWL. Biota risk soil 
was excavated from two of these sites (NCSA-4a and NCSA-4b) and 
consolidated in Basins A and F. This work, completed in 2008, is 
documented in two CCRs: Basin F/Basin F Exterior Remediation Project--
Part 1 and Basin F/Basin F Exterior Remediation Project--Part 1, Phase 
2.
     The Burial Trenches Soil Remediation Project included the 
excavation of soil from six chromium- and lead-contaminated soil sites 
within Sections 29, 30, 31, and 32 of the CES (BT29-1, BT29-2, BT30-1, 
BT32-10, BT32-11, ESA-2c). All six sites contained ordnance and 
explosives, munitions debris and related soil, as well as asbestos-
containing material, general construction-related debris and trash that 
was excavated and disposed in the HWL. This work, completed in 2004, is 
documented in the CCRs for the Burial Trenches Soil Remediation 
Project--Part I and Part II.
     A portion of the Complex (Army) Disposal Trenches Subgrade 
Construction Project is located within Section 36 of the CES. This 
project consisted of surface grading to provide permanent stormwater 
drainage off of the adjacent RCRA-Equivalent Cover. No contaminated 
soils were identified in Section 36 for excavation as part of the 
Complex Trenches Subgrade Project. The grading, completed in 2008, is 
documented in the CCR for the Complex (Army) Disposal Trenches 
Remediation Project, Subgrade Construction.
     The Corrective Action Management Unit (CAMU) Soil 
Remediation Project included the excavation of soil from one site (site 
``CAMU'') within Sections 23, 24, 25, and 26 in the CES. This site 
consisted of pesticide-contaminated, biota risk soils and miscellaneous 
debris that was excavated and consolidated in Basin A. This work, 
completed in 2000, is documented in CCRs for the CAMU Soils Remediation 
Project, and the CAMU Soils Remediation Completion and Support Project.
     The Existing (Sanitary) Landfills (ESL) Remediation 
Project included the excavation of contaminated soil from four sites 
within the CES: one site in Section 1 (P1 soil site adjacent to SSA-4) 
and three sites in Section 36 (CSA-1d, CSA-2d, and P1 soil site 
adjacent to CSA-1d). As documented in the CCR for the Section 1 
Existing (Sanitary) Landfills Remediation Project, completed in 2006, 
biota risk soil was excavated from the P1 soil site adjacent to SSA-4 
and consolidated in Basin A. As documented in the CCR for the Section 
36 ESL Project, completed in 2004, HHE soil, biota risk soil, and trash 
and debris were excavated from site CSA-1d and disposed in the HWL; 
munitions debris was excavated from site CSA-2d and disposed in the 
HWL; and additional biota risk soil was excavated from the P1 soil site 
adjacent to CSA-1d and consolidated in Basin A.
     The Miscellaneous Northern Tier Soil Remediation Project 
included the excavation of one site in Section 25 of the CES (NPSA-4) 
that contained HHE soil contaminated with chloroacetic acid. As 
documented in the CCR for the Miscellaneous Northern Tier Soil 
Remediation Project, completed in 2006, HHE soil was excavated and 
disposed in the HWL and biota risk soil was excavated and consolidated 
in Basin A.
     The Miscellaneous RMA Structures Demolition and Removal 
Project included the excavation of two sites in Section 25 of the CES 
(BA9A Parcel 3 and 25CC-3). As documented in the CCR for the 
Miscellaneous RMA Structures Demolition and Removal Project--Phase III, 
completed in 2009, ACM-contaminated soil, trash, debris, and munitions 
debris was excavated from the two sites and disposed in the Enhanced 
Hazardous Waste Landfill (ELF). Some of the ACM-contaminated soil was 
also disposed off-site at a permitted, CERCLA off-site rule approved 
landfill.
     The Miscellaneous Southern Tier Soil Remediation Project 
included excavation of three sites within the CES (SSA-2a, SSA-2b, and 
a P1 soil site adjacent to SSA-2a) where former process water and 
wastewater ditches in Sections 1 and 2 contained HHE and biota risk 
soils contaminated with aldrin, dieldrin, and heavy metals. This work, 
completed in 2006, is documented in the CCR for the Miscellaneous 
Southern Tier Soil Remediation Project. A subsequent project, the Sand 
Creek Lateral Project, involved excavation of additional contaminated 
soil from two of the Miscellaneous Southern Tier Soil Remediation sites 
including site SSA-2b located in Section 1 and site SSA-2a located in 
Section 2. As documented in the CCR for the Sand Creek Lateral Project, 
completed in 2008, additional HHE soil was excavated from these two 
sites and disposed in the HWL and ELF, and biota risk soil was 
excavated and consolidated in Basin A.
     The Munitions (Testing) Soil Remediation Project included 
11 sites within Sections 19, 20, 25, 29, 30, 31, and 32 of the CES 
(BT32-10, CSA-2c, ESA-1b, ESA-1c, ESA-1d, ESA-4a, ESA-4b, MT29-1, MT-
DREZ, BA 9A Parcel 2, and BA10 Burn Area). As documented in the CCRs 
for the Munitions (Testing) Soil Remediation Project, Parts I, II, III, 
and IV, completed in 2009, munitions debris and related soil, asbestos-
containing material, mercury-contaminated biota risk soil, and 
miscellaneous debris were excavated from all these sites and disposed 
in the HWL and the ELF. Biota risk soil and miscellaneous debris was 
excavated and consolidated in Basin A.
     The North Plants Structures Demolition and Removal Project 
included seven soil remediation sites in Section 25 of the CES (NPSA-1, 
NPSA-3, NPSA-5, NPSA-6, NPSA-8c, NPSA-9f, and a P1 soil site associated 
with NPSA-1). HHE soil, biota risk soil, a

[[Page 34411]]

chemical sewer system, and a sanitary sewer system were present in the 
North Plants area where the nerve agent GB, also called Sarin, was 
manufactured. As documented in the CCR for the North Plants Structure 
Demolition and Removal Project, completed in 2004, HHE soil and 
chemical sewers were excavated from three remedy sites within the CES 
(NPSA-1, 5 and 6) and disposed in the HWL. Over 6,000 linear feet of 
sanitary sewer line was removed from the North Plants manufacturing 
area and also disposed in the HWL. In addition, biota risk soil and 
miscellaneous debris was excavated from six remedy sites within the CES 
(NPSA-3, 5, 6, 8c, 9f and the P1 soil site associated with NPSA-1) and 
consolidated in Basin A.
     The Residual Ecological Risk Soil Project included 
excavation or tilling with sampling of biota risk soil from 18 remedy 
sites within Sections 1, 2, 24, 26, 35, and 36 (1CN-2, 1WC-1, 2NW-4, 
6NW-3, 24SW-1, 26NW-5, 26SE-6, 26SW-1, 26WC-2, 35NC-7, 35SW-2, 35SW-3, 
35WC-4, 36EC-1, 36NE-3, 36NW-4, Ditch 2d backfill, Basin F Area 1) and 
8 Borrow Areas within Sections 1, 6, 23, 24, 25, 26, 30, 31, 35, and 36 
(Borrow Areas 3, 4, 5, 6, 7, 8, 9 and 11) of the CES. These soils were 
contaminated with low levels of pesticides, primarily aldrin and 
dieldrin, which presented a residual health risk to biota. As 
documented in the CCRs for the Residual Ecological Risk Soil 
Remediation Project--Part 1 and Part 2, completed in 2009, soil at the 
18 RER sites was either excavated and consolidated in Basin A, Basin F, 
or in South Plants, or tilled to an 18 inch depth with follow-up 
sampling. Biota risk soil was removed from the eight borrow areas and 
used as daily cover in the HWL, ELF, and Basin A consolidation area, as 
well as gradefill at depths at least two feet below final grade in 
areas that will remain in Army control.
     The Sanitary and Chemical Sewer Plugging Project consists 
of two project phases that were conducted independently of each other. 
Phase I included plugging manholes associated with sanitary sewer lines 
in Sections 2, 24, 25, 26, and 35 of the CES. These sewer lines 
potentially served as conduits for the transport of contaminated 
groundwater and, therefore, the ROD required that the manholes be 
plugged with grout. As documented in the CCR for this project, 
completed in 1998, 62 sanitary sewer manholes in the CES were plugged. 
Subsequent to this plugging project, 37 of the plugged manholes were 
excavated as part of implementation of soil remediation projects.
     The Sanitary Sewer Manhole Plugging Project--Phase II 
included plugging additional manholes in Sections 3, 4 and 35 of the 
CES. As documented in the CCR for this project, completed in 2009, 21 
sanitary sewer manholes in the CES were plugged with grout. There are 
three manholes in Section 35 which will remain open to support an 
existing future use structure.
     The Secondary Basins Soil Remediation Project included the 
excavation of soil from six pesticide-contaminated sites within Section 
26 of the CES including two former liquid disposal basins (NCSA-2a and 
-2b), one ditch (NCSA-2d) between the two basins, and adjacent surface 
soil areas (NCSA-4b, Surface Soil site, P1 Soil Area). As documented in 
the CCR for the Secondary Basins Soil Remediation Project, completed in 
2004, HHE soil was excavated from four of these sites NCSA-2a, -2b, -
2d, and the Surface Soil site and disposed in the HWL. Biota risk soil 
and miscellaneous debris were excavated from all six sites and 
consolidated in Basin A. In 2009, additional HHE soil was excavated 
from the ditch (NCSA-2d) and disposed in the ELF. This additional 
excavation is documented in the CCR for the Secondary Basins Soil 
Remediation Project, NCSA-2d (Basin F Drainage Ditch) Contingent Soil 
Volume (CSV) (NCSA-2d CSV Project).
     The Section 26 Human Health Exceedance and Biota 
Exceedance Soil Removal Project included the excavation of soil from 
one pesticide-contaminated site (NCSA-4b) within Section 26 of the CES. 
As documented in the CCR for the Section 26 Human Health Exceedance and 
Biota Exceedance Soils Removal Project, completed in 2000, HHE soil was 
excavated from this site and disposed in the HWL, and the biota risk 
soil was excavated and either consolidated in Basin A or used as daily 
cover in the HWL. In 2003, additional contaminated soil was excavated 
at this site where low level biota risk soil was identified. The 
additional excavation is documented in an Addendum to the Section 26 
Human Health Exceedance and Biota Exceedance Soils Removal Project CCR.
     The Section 35 Soil Remediation Project included 
excavation of soil from nine sites within the CES that were 
contaminated by liquid waste from a former retention/detention basin 
including a basin located in Section 35 (NCSA-5b), former process water 
and wastewater ditches in Sections 2 and 35 (NCSA-1c, NCSA-5a, NCSA-5c, 
NCSA-5d, NCSA-6a), and areas surrounding the ditches (Surficial Biota, 
Surficial P1, Additional Surficial P1). As documented in the CCR for 
the Section 35 Soil Remediation Project, completed in 2004, HHE soil, 
chemical sewers, and associated debris were excavated and disposed in 
the HWL, and biota risk soil was excavated and consolidated in Basin A. 
A subsequent project, the Sand Creek Lateral Project, included 
additional work at three sites within Section 35 of the CES including 
two of the Section 35 Soil Remediation sites (NCSA-5b and -5c) and a 
section of sanitary sewer (NCSA-8a). As documented in the CCR for the 
Sand Creek Lateral Project, completed in 2008, HHE soil was excavated 
from NCSA-5b and -5c and disposed in the HWL and the ELF, and biota 
risk soil was excavated and consolidated in Basin A. The sanitary sewer 
(NCSA-8a) was removed and consolidated in Basin A.
     The Section 36 Balance of Areas Soil Remediation Project 
included the excavation of soil from six sites within Section 36 of the 
CES (CSA-1d, -2b, -3, -4, P1 East, and P1 North). As documented in CCRs 
for the Section 36 Balance of Areas Soil Remediation Project (Parts 1 
and 2), completed in 2009, HHE soil, munitions debris, chemical sewers 
and associated debris from two sites (CSA-3 and -4) were excavated and 
disposed in the HWL. Biota risk soil and miscellaneous debris from four 
sites (CSA-1d and -2b, P1 East and P1 North) were excavated and 
disposed in Basin A. Part 2 of the project also included grading in 
Sections 31 and 36 to construct permanent stormwater drainages off of 
the adjacent Complex (Army) Trenches RCRA-Equivalent Cover and the 
Shell Disposal Trenches 2-Foot Cover.
     The South Plants Balance of Areas and Central Processing 
Area Soil Remediation Project included 16 remedy sites located in 
Sections 1 and 2 of the CES (SPSA-2b, -2e, -4a, -4b, -5b, -6, -7a, -7b, 
-7c, -8a, -8b, -8c, -9a, -9b, -10, and a P1 soil area outside of Borrow 
Area 11) which contained chemical sewers, HHE and biota risk soils 
contaminated with pesticides, chloroacetic acid, volatile organic 
compounds, metals, and mercury, as well as the potential for chemical 
warfare agents, munitions debris and unexploded ordnance. As documented 
in the CCRs for the South Plants Balance of Areas and Central 
Processing Area Soil Remediation Project--Phase 1 and Phase 2, 
completed in 2009, HHE soil, chemical sewers, and associated debris, 
and munitions debris from 12 of the sites (SPSA-2b, -2e, -4a, -4b, -5b, 
-6, -7c, -8a, -8b, -9a, -9b, -10) were

[[Page 34412]]

excavated and disposed in the HWL. Biota risk soil was excavated from 
all of the sites excluding SPSA-10 and consolidated under the South 
Plants Covers or in Basin A. Structural debris from foundation 
demolition was consolidated within the South Plants soil cover areas.
    Structures: All but one of the 750 ROD-identified ``no future use'' 
structures within the On-Post OU have been demolished. The remaining 
ROD structure is the CERCLA Wastewater Treatment Facility in Section 
36, which was constructed to treat remedy-generated wastewater. The 
CERCLA facility currently treats groundwater from the Groundwater Mass 
Removal Project and is excluded from this proposed partial deletion. 
One other structure, the LWTS facility, built as part of the remedy to 
treat wastewater from the on-post landfills, is being decommissioned 
and is also excluded from this proposed partial deletion.
    Demolition and removal of structures within the CES was 
accomplished by several projects. The remedial action for structures 
included demolition of the structures and foundations; removal and 
disposal of debris, substations, 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. The demolition of most structures is documented 
in the following project CCRs.
    (1) South Plants Structure Demolition and Removal Project Phase 1 
and Phase 2 (2002);
    (2) South Plants Balance of Areas and the Central Processing Area 
Soil Remediation Project Phase 2 (2009);
    (3) North Plant Structure Demolition and Removal Project (2004); 
and
    (4) Miscellaneous RMA Structure Demolition and Removal Projects--
Phases I, II and III (2009).
    Groundwater: The proposed partial deletion of the CES does not 
include groundwater; however, the following groundwater remedy projects 
are or were located within the CES footprint of the RMA Site. The 
Section 36 Bedrock Ridge Groundwater Plume Extraction System, 
constructed in 2008, is an ongoing project which extracts contaminated 
groundwater flowing from the Basin A and South Plants areas for 
treatment at the Basin A Neck Groundwater Treatment System. The North 
of Basin F IRA intercept system was permanently shut down in 2004 due 
to declining flows, biofouling, declining well capacity, and decreasing 
contaminant concentrations. The Confined Flow System Well Closure 
project, completed in 2000, included the closure of 15 wells in the CES 
which extended into the deeper, confined-low aquifer.
    In addition, the portion of the On-Post OU that currently remains 
on the NPL includes several groundwater remedy components that are not 
within the proposed CES deletion area and will remain part of the NPL 
site. These include:
     The Rail Yard Treatment System, located in Section 3, is 
an ongoing project which treats contaminated groundwater associated 
with the Rail Yard.
     The Lime Basins and South Tank Farm Groundwater Mass 
Removal extraction systems, located in Section 36 and Section 1 
respectively, are part of an ongoing project that extracts contaminated 
groundwater for treatment at the CERCLA Wastewater Treatment Facility.
     The CERCLA Wastewater Treatment Facility, located in 
Section 35, is an ongoing project which treats contaminated groundwater 
from the Lime Basins and South Tank Farm areas as part of the 
Groundwater Mass Removal Project.
    Use of the groundwater and surface water for potable purposes from 
the entire original On-Post OU, including the CES, is prohibited by the 
FFA and On-Post ROD. The FFA and On-Post ROD also prohibit residential 
development, agricultural activities, and hunting and fishing for 
consumptive purposes throughout the original On-Post OU. These 
restrictions will continue to be prohibited even after the CES is 
transferred to the U.S. Department of Interior and are enforced by the 
Army through an ``Interim Rocky Mountain Arsenal Institutional Control 
Plan'' approved in 2003 and revised in 2006 and 2008.
Remedial Action for the OPS of the Off-Post (OU 4)
    Soil: The Off-Post OU of the RMA Site is located directly north and 
northwest of the On-Post OU. To date, none of the Off-Post OU has been 
deleted. As agreed in the Off-Post ROD, though the health risks present 
in the soils were within EPA's acceptable cancer risk range for 
residential use (less than 1 x 10-\4\), Shell completed 
tilling and seeding of approximately 160 acres in Sections 13 and 14 of 
the OPS for settlement purposes to enhance the degradation of low-level 
pesticide residues. This activity is documented in the ``Final 
Inspection/Implementation Report for the Off-Post Tillage Task'' 
completed in 1997.
    Groundwater: The proposed partial deletion of the OPS does not 
include groundwater; however, the following groundwater remedy 
components are or were within the OPS footprint of the RMA Site. The 
Off-Post Groundwater Intercept and Treatment System (OGITS), 
constructed in 1993, is an ongoing project that treats contaminated 
groundwater plumes that flow off-post to the north and northwest of 
RMA. The Off-Post Well Abandonment project, completed in 1999, included 
the closure of 7 wells in the Off-Post OU that extended into the 
deeper, confined flow aquifer. Institutional controls to prevent the 
use of groundwater exceeding remediation goals as well as deed 
restrictions on the Shell Property have been in place since 1996.

Cleanup Goals

    Cleanup goals for the On-Post OU were established based upon a 
scenario for potential contaminant exposure incurred by a biological 
worker, e.g., a wildlife biologist working in the field, in 
consideration of the anticipated future land use of the On-Post OU as a 
National Wildlife Refuge. Soils and structures with a cumulative 
contamination concentration presenting an excess cancer risk to human 
health of greater than 1 x 10-\4\ or a Hazard Index greater 
than 1.0 for non-cancer risks were identified for excavation/demolition 
and on-site disposal. To confirm that the ROD-delineated soil 
contamination areas and depths met remedial action objectives, the On-
Post ROD provided for excavation of an additional 150,000 cy of soil 
beyond that estimated in the selected remedy. For the entire On-Post 
OU, this volume was identified using 1,014 confirmatory samples as well 
as visual observations (e.g., for staining, debris, and odors). For the 
CES, more than 100 samples were collected and roughly 22,000 cy of 
additional soil was excavated.
Operation and Maintenance (O&M)
    No O&M is required for any of the proposed CES and OPS partial 
deletion areas. However, the Army is responsible for O&M of the On-Post 
internal groundwater treatment facilities, and Off-Post OGITS until 
contaminant concentrations are below remedial action levels, as well as 
continued maintenance of groundwater wells for long-term groundwater 
monitoring. Long-term access to groundwater wells within the On-Post OU 
is delineated in Public Law 102-402 and the ``Interim Rocky Mountain 
Arsenal Institutional Control Plan.'' Long-term access to the 
groundwater wells in the Off-Post OU is

[[Page 34413]]

provided through a license agreement between the Army and Shell.

Five-Year Review

    Pursuant to CERCLA Section 121(c) and Sec.  300.430(f)(4)(ii) of 
the NCP, the next five-year review will be completed in 2011 to ensure 
the continued protectiveness of remedial actions where hazardous 
substances, pollutants, or contaminants remain at a site above levels 
that allow for unlimited use and unrestricted exposure. Because the CES 
and OPS are subject to restrictions on land and water use, they will be 
included in future, RMA-wide five-year reviews.
    Two site-wide, five-year reviews have been conducted to date 
including the Five-Year Review Report completed in January 2001 and the 
Five-Year Review Report completed in December 2007. The 2005 Five-Year 
Review identified 13 issues requiring followup actions, none of which 
affected the protection of human health or the environment for the Off-
Post or On-Post OUs. Seven of these actions were related to improving 
reporting and coordination, and clarification of remedy requirements. 
Other issues concerned the incomplete capture of groundwater at the 
Bedrock Ridge Extraction System, operating problems of the primary sump 
system in Cell 2 of the Basin F Wastepile, modification of the OGITS 
extraction system, the discovery of fuel contamination in the 
groundwater below the North Plants area, and updating portions of the 
groundwater treatment systems including site-specific treatment 
criteria known as Practical Quantitation Limits (PQLs), and updating 
monitoring well networks. None of the issues impacted the CES or OPS, 
though actions regarding the groundwater monitoring networks may 
indirectly affect small portions of the CES and OPS.
    All but three of the followup actions have been completed. 
Modification of the OGITS extraction system has been completed and the 
start-up data is being reviewed. A pilot study for assessing the North 
Plants Fuel Release has been approved and is ongoing. The PQL study was 
initiated in 2009 and submittals from laboratories are under review.
    A fourth extraction well was installed at the Bedrock Ridge 
Extraction System and, in 2008, was determined to be adequately 
capturing the groundwater plume. The Basin F Wastepile Remediation 
Project, completed in 2009, included the excavation of the Wastepile 
and the liner system, and disposed the waste in the ELF, thereby 
eliminating any continuing concerns regarding the sump system.

Community Involvement

    Public participation activities have been satisfied as required in 
CERCLA Section 113(k), 42 U.S.C. 9613(k) and CERCLA Section 117, 42 
U.S.C. 9617. 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. Upon 
completion of the 30 calendar day public comment period for this 
proposed partial deletion of the RMA Site, 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.
    CES of the On-Post (OU 3): Following the release and distribution 
of the draft Detailed Analysis of Alternatives report for the On-Post 
OU (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 On-Post RMA Site. The Proposed Plan 
for the On-Post OU was issued for public review from October 16, 1995, 
through January 19, 1996. A public meeting was held on November 18, 
1995, attended by approximately 50 members of the public, to obtain 
public comment on the Proposed Plan. Minimal comments were received on 
the alternatives presented for the projects in the Central Area of the 
On-Post OU. Specifically, the comments requested that the health and 
safety of nearby communities be protected from air emissions during 
excavation and demolition activities and that potential dioxin 
contamination of the entire RMA Site be evaluated.
    The designs for the each of the 29 remediation projects within the 
CES (18 soil remediation projects and 11 structure demolition 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 (45 separate public comment periods). Most designs were also 
presented for discussion at the RMA Restoration Advisory Board which is 
composed of community stakeholders, regulatory agencies, the Army, 
Shell Oil Company, and USFWS. No written comments regarding the 
excavation/demolition approach or the proposed health and safety 
controls for each project were received.
    OPS of the Off-Post (OU 4): An expanded Community Relations 
outreach was implemented to ensure community members had the 
opportunity to comment on the Proposed Plan for the Off-Post OU. In 
January 1993, all documents supporting an expected Proposed Plan were 
made available for public review in local libraries. A direct mailing 
to more than 1200 local citizens was made. The RI, RI Addendum, EA/FS, 
and Proposed Plan for the Off-Post OU were issued for public review on 
March 21, 1993, and was extended until June 21, 1993. On April 28, 
1993, a public meeting was held to obtain public comment of the 
Proposed Plan. Comments received focused on requests for expanded 
groundwater treatment, incorporation of a surface soil remedy, and 
concerns over the selection of a DIMP cleanup standard.
    The Draft Final ROD (1993) was revised in consideration of comments 
received from the city and county governments, environmental action 
groups and private citizens. Settlement discussions involving 
municipalities, local health departments, special districts, and 
citizen groups were held from late 1994 until April 1, 1995, to discuss 
the final remedies for both the On-Post and Off-Post OUs.

Determination That the Criteria for Deletion Have Been Met

    EPA, with concurrence from the State of Colorado, dated March 22, 
2010, has determined that all appropriate CERCLA response actions have 
been completed for the CES and OPS of the RMA Site to protect public 
health and the environment and that no further response action by 
responsible parties is required. Based on the extensive investigations 
and risk assessment performed for the CES and the OPS of the RMA Site, 
there are no further response actions planned or scheduled for these 
areas.
    There are no known hazardous substances remaining in the CES above 
health-based levels with respect to anticipated uses of and access to 
the site which are identified in the FFA, On-Post ROD, and Public Law 
102-402. Similarly, no known hazardous substances remain in the OPS 
above health-based levels with respect to anticipated uses of and 
access to the site which are limited through deed restrictions. As a 
result, all completion requirements for the CES and OPS have been 
achieved as outlined in OSWER

[[Page 34414]]

Directive 9320.2-09A-P and the NCP. Therefore, EPA proposes to delete 
the CES and OPS portions of the RMA Site from the NPL.

List of Subjects in 40 CFR Part 300

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

    Authority: 33 U.S.C. 1321(c)(2); 42 U.S.C. 9601-9657; E.O. 
12777, 56 FR 54757, 3 CFR, 1991 Comp., p.351; E.O. 12580, 52 FR 
2923, 3 CFR, 1987 Comp., p.193.

    Dated: June 10, 2010.
Carol Rushin,
Deputy Regional Administrator, Region 8.
BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TP17JN10.000

[[Page 34415]]

[FR Doc. 2010-14524 Filed 6-16-10; 8:45 am]
BILLING CODE 6560-50-C