[Federal Register Volume 71, Number 80 (Wednesday, April 26, 2006)]
[Proposed Rules]
[Pages 24627-24633]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 06-3899]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 300

[EPA-HQ-SFUND-1987-0002; FRL-8161-6]


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

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of intent for partial deletion of the Rocky Mountain 
Arsenal National Priorities List Site from the National Priorities 
List.

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SUMMARY: The Environmental Protection Agency (EPA) Region 8 announces 
its intent to delete the Internal Parcel, encompassing 7,399 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 Internal Parcel 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 media (soil, surface 
water, sediment) and structures within the Internal Parcel of the On-
Post OU of the RMA/NPL Site as well as the groundwater below the 
Internal Parcel that is east of E Street, with the exception of a small 
area of contaminated groundwater located 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 Off-Post OU will remain on the NPL 
and response activities will continue at those OUs.

DATES: Comments must be received on or before on or before May 26, 
2006.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
SFUND-1987-0002, by one of the following methods:
     http://www.regulations.gov: Follow the on-line instruction 
for submitting comments.
     E-mail: [email protected].
     Fax: 303-312-6961
     Mail: Ms. Jennifer Chergo, Community Involvement 
Coordinator (8OC), U.S. EPA, Region 8, 999 18th Street, Suite 300, 
Denver, Colorado, 80202-2466.
     Hand Delivery: 999 18th Street, Suite 300, Denver, 
Colorado, 80202-2466. 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 the EPA's Region 8 
Superfund Records

[[Page 24628]]

Center, 999 18th Street, Denver, Colorado 80202-2466 and the Joint 
Administrative Records Document Facility, Rocky Mountain Arsenal, 
Building 129, Room 2024, Commerce City, Colorado 80022-1748. The Region 
8 Docket Facility is open from 8 a.m. to 4 p.m. by appointment, Monday 
through Friday, excluding legal holidays. The EPA Docket telephone 
number is 303-312-6473. The RMA's Docket Facility is open from 12 p.m. 
to 4 p.m., Monday through Friday, excluding legal holidays, or by 
appointment. The RMA Docket telephone number is 303-289-0362.

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 (303) 312-6601; fax number: 303-
312-6961; e-mail address: [email protected].

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 Internal Parcel 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 
Internal Parcel 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 
40 CFR 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;
    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 of 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 Internal Parcel from the RMA/NPL Site:
    (1) The Army has requested 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 May 26, 2006, 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 
repositories 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 Internal Parcel 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 repositories 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 Internal Parcel of the RMA/NPL Site from the NPL and EPA's finding 
that the proposed final deletion satisfies 40 CFR 300.425(e) 
requirements. Additional detail is provided in the ``Technical 
Memorandum in Support of Partial Deletion of the Internal Parcel 
Deletion Area'' that consolidates all information for the 11.5 square 
mile area within the On-Post Operable Unit of the RMA/NPL Site.

[[Page 24629]]

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--the ``Federal Facility 
Agreement for the Rocky Mountain Arsenal'' (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 for the On-Post Operable Unit'' (ROD). 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 original On-Post OU of the RMA/NPL Site (see map, RMA Internal 
Parcel) encompassed 27 square miles (17,000 acres) in southern Adams 
County, Colorado, approximately 8 miles northeast of downtown Denver. 
On January 21, 2003, 940 acres known as the Western Tier Parcel were 
partially deleted from the NPL. This was followed by the partial 
deletion of 5,053 acres in perimeter areas of RMA on January 15, 2004, 
which led to the establishment of the Rocky Mountain Arsenal National 
Wildlife Refuge on April 2, 2004. As a result of these prior partial 
deletions, the On-Post OU of the RMA/NPL Site currently encompasses 
17.2 square miles (11,007 acres).

Internal Parcel of the On-Post OU

    The Internal Parcel is an area of approximately 7,399 acres (11.5 
square miles) in the interior of RMA. The proposed deletion includes 
all or portions of Sections 1, 2, 3, 4, 6, 10, 19, 20, 22, 23, 24, 25, 
26, 27, 28, 29, 30, 31, 32, 34, and 35, but excludes areas where the 
remedy is incomplete such as the former central processing areas, 
munitions demolition areas, sanitary sewers, select structures, haul 
roads, and designed drainage areas for future covers (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 
twelve separate soil cleanup projects within the Internal Parcel. These 
include:
    (1) The Burial Trenches Soil Remediation project which included two 
remedy sites in Sections 30 and 32 considered to potentially contain 
ordnance or explosives, unexploded ordnance, and munitions debris as 
well as general construction-related debris and trash, and soils that 
exceeded acceptable contaminant levels for protection of human health 
(HHE) that was contaminated with chromium and lead;
    (2) The CAMU (Corrective Action Management Unit) Soil Remediation 
project in Sections 23, 24, 25, and 26 including Borrow Area 5 and 
other areas within the CAMU that contained soils presenting an 
unacceptable risk to biota (biota-risk) primarily due to pesticides 
(aldrin and dieldrin);
    (3) The Existing (Sanitary) Landfills which included seven remedy 
sites in Sections 1, 4, 30, and 36 that contained construction debris, 
metal fragments, asphalt, trash, and asbestos-containing material;
    (4) The Lake Sediments Soil Remediation project which included two 
remedy sites within Section 1 that contained HHE and biota-risk soils 
contaminated with chlordane, chromium, aldrin, and dieldrin as well as 
some mercury;
    (5) The Miscellaneous Northern Tier Soil Remediation project which 
included three remedy sites in Sections 24, 25, and 29 that contained 
HHE and biota-risk soils contaminated with aldrin and dieldrin, 
chloroacetic acid, and lead;
    (6) The Miscellaneous Southern Tier Soil Remediation project which 
included eight remedy sites in Sections 1, 2, 3, 4, and 12 that 
contained HHE and biota-risk soils contaminated with aldrin, dieldrin, 
and heavy metals;
    (7) The Munitions Testing Soil Remediation project which included 
seven remedy sites in Sections 19, 20, 25, 29, and 30 considered to 
potentially contain slag, munitions debris, and unexploded ordnance;
    (8) The North Plants Structures Demolition and Removal project 
which included one remedy site with HHE and biota-risk soils within 
Section 25 and structures where the nerve agent GB, also called Sarin, 
was manufactured;
    (9) The Sanitary and Chemical Sewer Plugging project which included 
two remedy sites in Sections 1, 2, 3, 4, 24, 25, 26, 34, 35, and 36 
that contained sewer lines which potentially served as conduits for the 
migration of groundwater contamination;
    (10) The Section 35 Soil Remediation project which included eight 
remedy sites within Section 35 that contained HHE and biota-risk soils 
contaminated primarily with aldrin and dieldrin;
    (11) The Toxic Storage Yards Soil Remediation project which 
included three remedy sites within Sections 5, 6, and 31 that contained 
HHE and biota-risk soils considered to potentially contain chemical 
warfare agent based on use histories and detections of agent breakdown 
products; and
    (12) The Residual Ecological Risk (RER) Soil project which included 
80 remedy sites throughout the RMA/NPL Site that were identified 
through a ROD (On-Post Record of Decision)--directed process to address 
soils that present a health risk to biota primarily due to aldrin and 
dieldrin.
    A structures survey identified 798 structures within the RMA/NPL 
site. Forty-eight of these structures had no

[[Page 24630]]

history of contamination and were designated to be retained for future 
use. The contaminants identified within the other 750 structures 
include asbestos, pesticides, polychlorinated biphenyls (PCBs), 
herbicides and heavy metals.
    Fifteen individual contaminant groundwater plumes were identified 
below the western portion of the original RMA site (west of E Street) 
and consolidated into five plume groups. Treatment of the groundwater 
plumes is ongoing through operation of groundwater treatment systems 
and will continue until contaminant concentrations are below remedial 
action levels. Therefore, the groundwater media below the Internal 
Parcel west of E Street is not included in this partial deletion and 
will remain on the RMA/NPL Site. With the exception of a small area of 
groundwater located in the northwest corner of Section 6, no 
contaminant plumes were identified in the eastern portion of the 
Internal Parcel; therefore, most of the groundwater media below the 
Internal Parcel east of E Street is included in this partial deletion.
    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 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 munitions 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 to be 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 ROD 
also required continued use restrictions for the property.
    The remedy for structures included the demolition of the 750 ``no 
future use'' structures identified in the structures survey. The 
selected groundwater remedy consisted of continued operation of the On-
Post groundwater treatment systems, including three boundary systems 
and four internal systems. The On-Post ROD also required the 
``monitoring and assessment of NDMA (n-nitrosodimethylamine) 
contamination * * * in support of design refinement/design 
characterization to achieve remediation goals specified for the 
boundary groundwater treatment systems.'' This resulted in the addition 
of an ultraviolet-oxidation system to the NBCS for the treatment of 
NDMA. Also, water levels in the South Lakes were to be maintained to 
support aquatic ecosystems, prevent plume migration into the lakes, and 
cover human health exceedance soils in Lower Derby Lake sediments. 
Additionally, wells that had the potential to provide a cross-
contamination pathway from the contaminated, upper groundwater aquifer 
to the deeper, confined aquifer were to be closed.

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 on 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 Internal Parcel 
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, UV-Oxidation System and each of the soil projects were 
generally provided to the public for a thirty calendar day review and 
comment period at both the 30 percent and 95 percent design completion 
stages (21 separate public comment periods). Each design was also 
presented for discussion at the regular meetings of the RMA Restoration 
Advisory Board which is composed of community stakeholders, regulatory 
agencies, the Army, Shell Oil Company, and the USFWS. No written 
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 Burial Trenches Soil Remediation (Parts I and II) project was 
completed in 2004. A total of 87,790 bank cubic yards (bcy) of HHE 
soil, munitions debris and related soil, red ash from mustard 
demilitarization, and asbestos-containing material was excavated from 
thirty-one remedy sites within the Internal Parcel and disposed in the 
on-site hazardous waste landfill. Another 2,119 bcy of material with 
lesser degrees of contamination, e.g., biota-risk soils, asphalt 
pavement, general construction debris and trash, were disposed in the 
Basin A consolidation area. In addition, 520 pounds of ordnance and 
explosives debris, and general debris--mostly packing materials, were 
removed from two ``Dense Munitions Debris'' areas and disposed in the 
hazardous waste landfill.
    The CAMU Soil Remediation project was completed in 1998. A total of 
278,532 bcy of biota-risk soils were excavated from one remedy site 
within the Internal Parcel to a depth of one foot and disposed in Basin 
A.
    The Existing (Sanitary) Landfills Remediation (Sections 1 and 30) 
project was completed in 2005. A total of 148,487 bcy of HHE soil, 
munitions debris, polychlorinated biphenyl (PCB)-contaminated 
equipment, and asbestos-containing material was excavated from two 
remedy sites within the Internal Parcel and disposed in the hazardous 
waste landfill. Another 1,875 bcy of biota-risk soil were used as cover 
for the asbestos-containing material in the landfill. Approximately 
14,826 bcy of biota risk soils and trash and debris were excavated and 
disposed in Basin A.
    The Lake Sediments Soil Remediation project was completed in 2000. 
A total of 30,690 bcy of HHE soil, miscellaneous debris and mercury-
contaminated biota-risk soils was

[[Page 24631]]

excavated from two remedy sites within the Internal Parcel and disposed 
in the hazardous waste landfill. Another 2,372 bcy of biota risk soil 
were disposed in Basin A.
    The Miscellaneous Northern Tier Soil Remediation project was 
completed in 2000. A total of 19,400 bcy of HHE soil, debris from one 
structure with a contamination use history, and asbestos-containing 
material was excavated from three remedy sites within the Internal 
Parcel and disposed in the hazardous waste landfill. Another 35,365 bcy 
of biota-risk soil, demolition debris, sanitary sewer lines and grout-
filled manholes, and debris from six structures with no contamination 
history were disposed in Basin A.
    The Miscellaneous Southern Tier Soil Remediation project was 
completed in 2000. A total of 17,676 bcy of HHE soil, asbestos, and 
lower concentrations of lead was excavated from four remedy sites 
within the Internal Parcel and disposed in the hazardous waste 
landfill. Another 20,008 bcy of biota-risk soil, demolition debris, and 
structural debris from three buildings and railroad tracks including 
ballast and ties were taken from the Internal Parcel and disposed in 
Basin A. In addition, a total of 5,919 bcy of biota-risk soil was 
excavated and used to backfill an HHE soil excavation and covered with 
two feet of clean soil.
    The Munitions Testing Soil Remediation (Part I) project was 
completed in 2002. A total of 10,100 bcy of munitions debris was 
excavated from two remedy sites within the Internal Parcel and disposed 
in the hazardous waste landfill. No soil/debris was excavated for 
disposal in Basin A.
    The North Plants Structures Demolition and Removal project was 
completed in 2004. Approximately 800 feet of an 18-inch concrete sewer 
pipe from one remedy site within the Internal Parcel were excavated and 
disposed in the hazardous waste landfill. No soil/debris was excavated 
for disposal in Basin A.
    The Sanitary and Chemical Sewer Plugging (Phase I) project was 
completed in 1998. This project required plugging eighteen sanitary 
sewer manholes within Section 35 of the Internal Parcel with grout. The 
sanitary sewer manholes located in Section 24 were plugged, and the 
entire sewer subsequently excavated to facilitate excavation of clean 
soils from Borrow Area 5. The excavated sanitary sewer was disposed in 
Basin A.
    The Section 35 Soil Remediation project was completed in 2003. A 
total of 4,375 bcy of HHE soil, chemical sewers, and associated debris 
as well as 1,300 linear feet of pipe was excavated from seven remedy 
sites within the Internal Parcel and disposed in the hazardous waste 
landfill. Another 121,374 bcy of biota risk soil and miscellaneous 
debris were disposed in Basin A.
    The Toxic Storage Yards Soil Remediation project was completed in 
2000. A total of 3,404 bcy of HHE soil, munitions debris and non-
routine odorous soils was excavated from two remedy sites within the 
Internal Parcel and disposed in the hazardous waste landfill. 
Structural debris from the demolition of nine ``Other Contamination 
History'' buildings was disposed in Basin A.
    The RER (Part 1) project was completed in 2006. A total of 804,348 
bcy of RER soil was removed from five borrow areas that are located at 
least in part within the Internal Parcel. The RER soil from the borrow 
areas was used as gradefill at depths at least two feet below final 
grade in areas that will remain in Army control. Twenty-three 
additional sites located outside of borrow areas and at least partially 
within the Internal Parcel also required remediation of biota-risk 
soils. An additional 35,591 bcy of soil was excavated from five of the 
sites and placed at least two feet below final grade in Army controlled 
areas; twelve sites (including a portion of one that also required 
excavation) required tilling with sampling verification that soil 
concentrations had been adequately reduced; and seven sites (including 
a portion of one that also required tilling) were determined to be of 
acceptable risk based on sampling alone. In addition, one of the sites 
was eliminated based on existing data and another site, where 
excavation also occurred, was identified for biomonitoring. The 
biomonitoring data indicated that no further remedy action is required.
    Demolition and removal of 97 of the 183 structures slated for 
removal within the Internal Parcel was completed as part of the 
Miscellaneous RMA Structure Demolition and Removal--Phase I (completed 
in 2002) and Phase II (completed in 2006) project. This project 
consisted of the demolition of the structures and foundations; removal 
and on-site 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 remaining 86 structures, eighteen were demolished as part of the 
Miscellaneous Northern Tier Soil, Miscellaneous Southern Tier Soil, and 
Toxic Storage Yards Soil projects; 47 had been demolished prior to 
remedial action; and 21 structures--currently in use as groundwater 
treatment facilities and supporting groundwater wells and electrical 
substations--were incorporated as components of their respective 
groundwater remedy projects and retained for continued operations until 
each groundwater remedy component is completed and the structure then 
demolished as part of that project.
    The North and Northwest Boundary Containment Systems continue to 
treat groundwater and minimize migration of groundwater plumes offsite. 
The ICS extraction wells met the ROD shut-off criteria and 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 in 2001 to more directly treat the contaminated 
groundwater associated with the Rail Yard. The Motor Pool extraction 
wells met shut-down criteria in 1998 and their operation was 
discontinued. The Basin A Neck Containment System (BANCS) treats 
groundwater migrating from the Basin A area toward the northwest 
boundary. Until shut-down of the North of Basin F extraction well in 
2000, the groundwater from the Basin F area was treated at the BANCS. 
Monitoring of groundwater, including that previously extracted/treated 
at the ICS, Motor Pool, and North of Basin F, is conducted as part of a 
site-wide monitoring program, as required by the ROD.
    In 1997, an ultraviolet-oxidation treatment system was put into 
operation at the North Boundary Containment System to treat NDMA. The 
ultraviolet-oxidation treatment is a ``polishing'' step performed after 
treatment through the carbon filters, and has effectively decreased 
NDMA concentrations in groundwater to below detectable levels.
    Lake Level maintenance requirements are addressed through adherence 
with the ``Management Plan for Protection and Monitoring of Lake 
Ladora, Lake Mary and Lower Derby Lake During RMA Remediation'' and the 
``Interim Rocky Mountain Arsenal Institutional Control Plan.'' An 
Explanation of Significant Differences was signed on March 31, 2006, to 
eliminate maintenance of lake levels to prevent plume migration. This 
change to the On-Post ROD is based upon groundwater monitoring data 
that indicate lake level maintenance does not affect plume migration.
    The Confined Flow System Well Closure project was completed in 
2000. A total of fifty-one wells, twenty-seven in the Internal Parcel, 
which extended

[[Page 24632]]

into the deeper, confined flow aquifer were closed. Closure was 
accomplished by overdrilling the well casing and installing a grout 
plug.
    Use of the groundwater below the Internal Parcel 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 
Internal Parcel is transferred to the U.S. Department of Interior. 
Additional prohibitions imposed by the FFA, Public Law 102-402, and the 
ROD include the use of the Internal Parcel 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 Internal Parcel. The conduct of 
long-term groundwater monitoring required by the ROD is delineated in 
the ``Long-Term Monitoring Plan for Groundwater'' with continued, long-
term access to groundwater wells delineated in the Interim Rocky 
Mountain Arsenal Institutional Control Plan.

Post-ROD Investigations

    Since the signing of the ROD on June 11, 1996, five main studies 
have been conducted that are relevant to the deletion of the Internal 
Parcel. 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 ten 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 Internal Parcel) and concluded that the future 
discovery of additional sites with ordnance/explosives or recovered 
chemical warfare materiel hazards is highly unlikely.
    This evaluation also resulted in the identification of five areas 
with dense amounts of subsurface metal and debris, three within the 
Internal Parcel. A surface sweep and removal of the munitions debris 
was performed in each of the three areas. Approximately 520 pounds of 
munitions debris was disposed in the hazardous waste landfill.
    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 Internal Parcel, 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. In addition, an Aquatic Residual 
Risk Assessment was completed in 2003. The Assessment presented an 
evaluation of risks to the great blue heron, shorebird and waterbird 
and the conclusion that there are no significant risks to aquatic birds 
in the South Lakes beyond those already identified for remediation in 
the ROD.
    Based on the extensive investigations and risk assessment performed 
for the Internal Parcel of the RMA/NPL Site, there are no further 
response actions planned or scheduled for this area. Currently, no 
hazardous substances remain at the Internal Parcel 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 Internal Parcel is subject to these restrictions on land 
and water use, it will be included in the RMA-wide five-year reviews. 
Operation and maintenance of the On-Post boundary and internal 
groundwater treatment facilities will continue until contaminant 
concentrations are below remedial action levels, as well as continued 
maintenance of groundwater wells for long-term groundwater monitoring. 
As a result, all completion requirements for the Internal Parcel 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 Internal Parcel 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 Internal 
Parcel of the On-Post OU of the RMA/NPL Site from the NPL.

BILLING CODE 6560-50-P

[[Page 24633]]

[GRAPHIC] [TIFF OMITTED] TP26AP06.008


    Dated: April 17, 2006.
Robert E. Roberts,
Regional Administrator, Region 8.
[FR Doc. 06-3899 Filed 4-25-06; 8:45 am]
BILLING CODE 6560-50-C