Superfund Record of Decision Milan Army Ammunition Plant Operable Units 3 and 4 TN


                                    EPA/ROD/R04-96/241
                                    1996
EPA Super fund
     Record of Decision:
     MILAN ARMY AMMUNITION PLANT
     EPA ID: TN0210020582
     OU 05, 06, 07, 08, 17
     MILAN, TN
     10/02/1995

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                                            Operable Units 3 and 4





                                         MILAN ARMY AMMUNITION PLANT
                                         NORTHERN INDUSTRIAL AREA SOIL
                                               Milan, Tennessee
                                              RECORD  OF DECISION
                                                FINAL DECISION
                                                September 1995

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DECLARATION FOR THE RECORD OF DECISION

SITE NAME AND LOCATION

Milan Army Ammunition Plant (MAAP), Northern Industrial Area soil, Milan, Tennessee.

STATEMENT OF BASIS AND PURPOSE

This decision document presents the selected remedial action for the soil within the
northern industrial area of Milan Army Ammunition Plant, Milan, Tennessee. The selected
remedial action was chosen in accordance with the requirements of the Comprehensive
Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), as amended by the
Superfund Amendments and Reauthorization Act of 1986 (SARA) , and to the extent practicable, the
National Oil and Hazardous Substances Pollution Contingency Plan, (NCP, 40 CFR 300). This
decision document explains the factual basis for selecting the remedy for the Northern
Industrial Area Soil and the rationale for the final decision. This decision is based on the
Administrative Record for this site.

The U.S. Environmental Protection Agency and the State of Tennessee concur with the
selected remedy.

ASSESSMENT OF THE SITE

Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response action selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare, or the environment.

DESCRIPTION OF THE REMEDY

The goal of the cleanup activities at the northern industrial areas of MAAP is to remove
the soil contaminated with explosives compounds above risk-based levels. The excavated soil
will be treated using a bioremediation process to reduce the concentrations of explosives
compounds, the toxicity of the leachate, and the mobility of the remaining organic compounds.
The treated soil will then be placed in an on-site solid waste landfill in compliance with State
of Tennessee regulations. Additionally, in areas where excavation of the explosives-contaminated
soil is infeasible, the soil will be covered with an engineered cap to prevent worker exposure
to the explosives compounds and prevent leaching of these compounds to groundwater.

The northern industrial area consists of all areas north of Route 54 in which industrial
operations have been performed. The industrial areas include the ammunition load, assembly, and
pack (LAP) lines, storage areas, maintenance/fabrication areas, and disposal areas.

STATUTORY DETERMINATIONS

The selected remedy is protective of human health and the environment, complies with
Federal and State requirements that are legally applicable or relevant and appropriate to this
remedial action, and is a cost-effective application of public funds. This remedy utilizes
permanent solutions and alternative treatment (or resource recovery) technologies to the extent
practicable, and satisfies statutory preference for remedies that employ treatment that reduces

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toxicity, mobility, or volume as a principal element.

       If the engineered cap option is exercised during remediation of the site,  then this remedy
will result in hazardous substances remaining on site above risk-based levels.  In this case, a
review will be conducted within five years after commencement of remediation to ensure that the
remedy continues to provide adeguate protection of human health and the environment.
                     
                    Joseph W.  Albright                                 Date
               Lieutenant Colonel, U.S.  Army
       Commanding Officer, Milan Army Ammunition Plant
                     
                      Raymond J. Fatz                                   Date
        Acting Deputy Assistant Secretary of the Army
        (Environment, Safety, and Occupational Health)

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                            John H. Hankinson, Jr.
                            Regional Administrator
       Commissioner Don Dills
         Tennessee Department of Environment and Conservation
       Lieutenant Colonel Joseph W. Albright
         Commanding Officer, Milan Army Ammunition Plant

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STATE OF TENNESSEE
DEPARTMENT OF ENVIRONMENT AND CONSERVATION

DIVISION OF SUPERFUND
4th Floor, L & C Annex
401 Church Street
Nashville, TN 37243-1538
October 3, 1995

Mr. Raymond J. Fatz
Acting Deputy Assistant Secretary of the Army
(Environmental Safety, and Occupational Health)
OSHA-I, LE
Office of the Assistant Secretary
Department of the Army
Washington, DC 20310-0103

RE: 27-505 Milan Army Ammunition Plant
Final Document Record of Decision for OU3 and OU4
Northern Industrial Area Soil

Dear Mr. Fatz:

The Tennessee Department of Environment and Conservation (TDEC) has received the final document
Remedial Action Record of Decision submitted July 12, 1995. The document references the
selected remedy to address the explosives-contaminated soil within both Operable Units 3 and 4
at MAAP. The remedy entails the removal, treatment and containment of soil contaminated above
risk-based levels. The Department concurs with the findings and selected final remedial action
stated in the final document, Record of Decision dated July 1995.

If you should have any guestions regarding the matter, please contact me at (615) 532-0909 or
Ms. Victoria A. Rushing, TDEC Project Manager at (901) 661-6226.

Sincerely,

Clinton W. Wilier
Director
Division of Superfund

CWW/var
TDSF - JFO
TDSF - NCO
EPA IV - Attn:
Peter Dao

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                                               TABIiE  OF CONTENTS

Section                                                                                   Page

DECLARATION FOR THE RECORD OF DECISION 	i

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY CONCURRENCE LETTER 	iii

STATE OF TENNESSEE DEPARTMENT OF ENVIRONMENT AND CONSERVATION
CONCURRENCE LETTER 	iv

1.0    SITE NAME,  LOCATION,  AND DESCRIPTION 	1-1

2.0    SITE HISTORY AND ENFORCEMENT ACTIVITIES 	2-1

3.0    HIGHLIGHTS  OF COMMUNITY PARTICIPATION 	3-1

4 . 0    SCOPE AND ROLE OF OPERABLE UNIT OR RESPONSE ACTION 	4-1

5 . 0    SITE CHARACTERISTICS 	5-1
       5.1   KNOWN OR SUSPECTED SOURCES OF CONTAMINATION 	5-1
              5.1.1 Description of the LAP Line Areas 	5-1
                     5.1.1.1  Line A 	5-1
                     5.1.1.2  Line B 	5-1
                     5.1.1.3  Line C 	5-1
                     5.1.1.4  Line D 	5-2
                     5.1.1.5  Line E 	5-2
                     5.1.1.6  Line F 	5-2
                     5.1.1.7  Line H 	5-2
                     5.1 1.8  Line K 	5-2
                     5.1.1.9  Line 0 	5-2
                     5.1.1.10  Line X 	5-2
                     5.1.1.11  Line Z 	5-3
              5.1.2 Closed Sanitary Landfill 	5-3
              5.1.3 Former Borrow Pit (Construction Debris Pit)  	5-3
              5.1.4 Description of Previous Investigations 	5-3
       5 . 2    DISTRIBUTION OF CONTAMINANTS IN SOIL 	5-4
              5.2.1 Explosives Compounds  Detected in Soil 	5-4
              5.2.2 Distribution of Explosives Compounds with Depth 	5-4
              5.2.3 Estimate  of the Extent of Contamination 	5-5
              5.2.4 Conclusions 	5-5

6. 0    SUMMARY OF  SITE RISKS 	6-1
       6.1    CONTAMINANT IDENTIFICATION  	6-1
              6.1.1 Justification for Use of 2,4,6-TNT, RDX,  and Tetryl as Indicator
                   Compounds 	6-2
       6 . 2    EXPOSURE ASSESSMENT 	6-2
              6.2.1 Potential Exposure Pathways Under Current Land-Use Conditions 	6-4
                     6.2.1.1  Surface Soil 	6-4
                     6.2.1.2  Subsurface Soil 	6-6
                     6.2.1.3  Groundwater  	6-6
                     6.2.1.4  Air 	6-6
                     6.2.1.5  Summary of Pathways  Selected for Evaluation Under Current
                          Land-Use Conditions  	6-6
              6.2.2 Potential Exposure Pathways Under Future Land-Use Conditions 	6-6
                     6.2.2.1  Surface Soil 	6-6
                     6.2.2.2  Subsurface Soil 	6-8
                     6.2.2.3  Groundwater  	6-8
                     6.2.2.4  Air 	6-8

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                                         TABIiE OF CONTENTS (Continued)

Section                                                                                   Page

                     6.2.2.5  Summary of Pathways Selected for Evaluation Under Potential
                          Future Land-Use Conditions  	6-8
              6.2.3 Ecological Exposure Assessment 	6-8
       6 . 3    TOXICITY ASSESSMENT 	6-9
       6.4    RISK CHARACTERIZATION AND DERIVATION OF SOIL REMEDIATION LEVELS 	6-9
              6.4.1 Soil Remediation Goals for Contact with Soil 	6-10
                     6.4.1.1  Overall Soil Remediation Goals for Ingestion and Dermal
                           Absorption of Chemicals 	6-10
                     6.4.1.2  Soil Remediation Levels  for the Protection of Future
                           Groundwater Users  	6-13
              6.4.2  Uncertainty Section 	6-15
                     6.4.2.1  Toxicological Data 	6-15
                     6.4.2.2  Exposure Assessment 	6-16
              6.4.3 Conclusions 	6-17

7.0    DESCRIPTION OF ALTERNATIVES  	7-1
       7.1    ALTERNATIVE A:   NO ACTION 	7-1
       7.2    ALTERNATIVE B:   LIMITED ACTION 	7-1
       7.3    COMMON ELEMENTS OF TREATMENT ALTERNATIVES C AND D 	7-2
              7.3.1 Soil Excavation 	7-2
              7.3.2 Estimated Soil Volume 	7-3
              7.3.3 Optional  Engineered Caps 	7-3
              7.3.4 Other Assumptions Used in the Cost Estimates 	7-3
       7.4    ALTERNATIVE C:   EXCAVATION/STORAGE/INCINERATION/BACKFILL 	7-3
       7.5    ALTERNATIVE D:   EXCAVATION/STORAGE/WINDROW COMPOSTING/ON-SITE LANDFILL 	7-5
              7.5.1  Summary  of Windrow Composting Studies 	7-5
              7.5.2 Conclusions from Previous Studies 	7-10
              7.5.3  Other Elements of Alternative D  	7-10

8 . 0    SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES  	8-1
       8 .1    NINE EVALUATION CRITERIA 	8-1
       8.2    PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT 	8-2
       8.3    COMPLIANCE WITH ARARS 	8-2
       8.4    LONG-TERM EFFECTIVENESS AND PERMANENCE  	8-3
       8.5    REDUCTION OF TOXICITY, MOBILITY, OR VOLUME THROUGH TREATMENT 	8-3
       8.6    SHORT-TERM EFFECTIVENESS 	8-4
       8.7    IMPLEMENTABILITY 	8-4
       8 . 8    COST 	8-5
       8 . 9    STATE ACCEPTANCE 	8-5
       8 .10   COMMUNITY ACCEPTANCE 	8-5
       8 .11   SUMMARY OF DETAILED EVALUATION 	8-5

9.0    SELECTED REMEDY 	9-1
       9.1    SOIL EXCAVATION 	9-1
       9.2    TREATMENT AND DISPOSAL COMPONENTS:  ALTERNATIVE D 	9-1
       9 . 3    OPTIONAL ENGINEERED CAPS 	9-3
       9 . 4    MONITORING 	9-4
       9.5    INSTITUTIONAL CONTROLS 	9-4
       9.6    REMEDIATION GOALS 	9-4
       9. 7    COST OF THE SELECTED REMEDY 	9-5

10 . 0   STATUTORY DETERMINATIONS 	10-1
       10 .1   PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT 	10-1
       10.2   COMPLIANCE WITH APPLICABLE OR RELEVANT  AND APPROPRIATE REQUIREMENTS 	10-1
              10.2.1 Chemical-Specific ARARs 	10-1
              10.2.2 Action-Specific ARARs 	10-1

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                                         TABIiE OF CONTENTS (Continued)

Section                                                                                   Page

              10.2.3 Location-Specific ARARs 	10-2
       10 . 3   COST EFFECTIVENESS 	10-2
       10.4   UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE TREATMENT TECHNOLOGIES
              (OR RESOURCE RECOVERY TECHNOLOGIES) TO THEMAXIMUM EXTENT PRACTICABLE 	10-2
       10 . 5   PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT 	10-3

11.0   DOCUMENTATION OF SIGNIFICANT DIFFERENCES  	11-1

12 . 0   REFERENCES 	12-1

APPENDIX A:  RESPONSIVENESS SUMMARY


                                                LIST OF FICUBES

Figure                                                                                    Page

1-1    Location of MAAP in Western Tennessee	1-2
1-2    Northern Industrial Areas at MAAP 	1-3
7-1    Concentrations of Principal Explosives Compounds and TNT Metabolites in Windrow
       Compost Samples 	7-7
7-2    Concentrations of Principal Explosives Compounds and TNT Metabolites in Windrow
       Compost Leachate 	7-8
7-3    Ames Mutagenicity of Windrow Compost Extract  	7-9
9-1    Diagram of Alternative D 	9-2
                                                LIST OF TABLES

Table                                                                                     Page

6-1    Oral Toxicity Values for Explosives Compounds 	6-3
6-2    Potential Human Exposure Pathways Under Current Land-Use Conditions  	6-5
6-3    Potential Human Exposure Pathways Under Future Land-Use Conditions  	6-7
6-4    Soil Risk-Based Remediation Goals for Residents 	6-11
6-5    Soil Risk-Based Remediation Goals for Excavation and Industrial Workers  	6-12
6-6    Soil Risk-Based Remediation Goals Based on Groundwater Ingestion Exposures  	6-14
6-7    Summary of Soil Risk-Based Remediation Goals 	6-18
8-1    Summary of Estimated Costs for Alternatives B through D 	8-6
9-1    Summary of Costs for the Selected Remedy:  Alternative D,  Excavation/Storage/
       Windrow Composting/On-Site Landfill 	9-6

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1.0 SITE NAME, LOCATION, AND DESCRIPTION

Milan Army Ammunition Plant (MAAT) is located in western Tennessee, one mile east of Milan,
Tennessee, and 28 miles north of Jackson, Tennessee (Figure 1-1). MAAP is a government-owned,
contractor-operated (GOCO) installation with Lockheed Martin Corporation as the operating
contractor. The facility was constructed in 1941 to produce and store fuzes, boosters, and
small- and large-caliber ammunition. At present, the facility comprises 22,436 acres.

The northern portion of the facility (north of route 54) contains eleven ammunition load,
assembly, and pack (LAP) lines (of which eight are active and three are inactive), a
maintenance/fabrication area, two known disposal areas (a closed landfill and borrow pit), and
several storage areas. These areas are shown in Figure 1-2. Although the southern portion of
the facility contains storage areas, a test area, an open burning ground, and an operating
landfill, most industrial operations occur in the northern portion of the facility. In
addition, while a small percentage of the site workers spend time in the southern portion of the
facility, most are employed in the northern industrial areas. Therefore, this remedy has been
developed to addresss the risks associated with the soil in the industrial areas located in the
northern portion of the facility. The southern portion of the facility is being addressed under
a separate study.

MAAP lies within the Coastal Plain Physiographic Province of the Mississippi Embayment,
west of the western valley of the Tennessee River and east of the Mississippi River valley. The
topography of MAAP and surrounding areas is gently rolling to flat. It slopes regionally
westward and contains numerous small streams, creeks, and drainage ditches. The elevation of
the installation varies from a high of approximately 590 feet above mean sea level (ft-msl) on
the south side to a low of approximately 320 ft-msl on the northern boundary of the
installation.

Numerous perennial and ephemeral surface water feature occur within the installation and
flow to the north-northwest. The entire facility, except for its extreme southern portion,
drains via small and medium-sized creeks and ditches to the Rutherford Fork of the Obion River.
The northern portions of MAAP contain several well-developed, ephemeral, natural drainage bodies
that join the Rutherford Fork along the northern boundary of the facility. The two parent
streams, the Forked Deer River and the Obion River, discharge into the Mississippi River about
60 miles west of MAAP.

Groundwater is a primary source of potable and non-potable water in this area of
Tennessee, and therefore, is a resource demanding protection and restoration. The Memphis Sand
formation of the Claiborne Group is the major aguifer at MAAP, and this aguifer is thick,
laterally continuous, and highly transmissive. Groundwater flow in the MAAP area is generally
to the west, in the direction of the regional dip of these sands, and also trends northerly
because of the topographic influence. On a macro scale, there are no abrupt hydrologic
boundaries in the aguifer. Locally, the clay lenses and clay rich zones may alter vertical
groundwater flow, and stratification of the sediments tends to make vertical conductivities
lower than horizontal conductivities. The horizontal hydraulic gradient is small (approximately
0.0015 ft/ft) and consistent throughout the site.

The facility is located in a rural area, with agriculture being a primary land use. There
are scattered residences to the north and east of the facility boundary, while the City of Milan
lies to the west. North of the facility, the nearest residences are located north of the
Rutherford Fork. These residences are approximately 1.5 miles from the northern facility
boundary. On the east and west sides of the facility, residences are located along the facility
property line.

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2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES

The initial construction of the installation was completed in January, 1942, and the plant
has operated continuously since that time. MAAP is a military industrial installation under the
jurisdiction of the Commanding General, Headquarters, United States Army Armament, Munitions and
Chemical Command. Presently, MAAP is operated by Lockheed Martin Corporation. The current
level of employment at MAAP is about 1,350 workers.

In the past, wastewater from various production activities was discharged to open ditches
that drained from sumps or surface impoundments into both intermittent and perennial streams and
rivers. MAAP currently treats all process water from the industrial operations that generate
explosives-contaminated wastewater in six industrial wastewater treatment facilities using
activated carbon adsorption. This wastewater is discharged under the authority of a National
Pollutant Discharge Elimination System (NPDES) permit.

One source of wastewater in the past was the use of a water spray to clean explosives
compounds from equipment and building surfaces in the LAP buildings. In the past, this
wastewater was allowed to flow out of the buildings and onto the ground, or into sumps that led
to open drainage ditches. This technique has been replaced with a dry vacuuming system that
results in the generation of no wastewater.

In 1978, the U.S. Army Environmental Center (USAEC, formerly the U.S. Army Toxic and
Hazardous Materials Agency or USATHAMA) conducted an Installation Assessment of MAAP (USATHAMA,
1978), which consisted of a records search and interviews with employees. This document
reported that wastewater from production areas, contaminated with various explosives compounds,
was commonly discharged to and observed in facility drainage ditches. However, the report
focused on potential migration in surface water, rather than possible infiltration from the
ditches into groundwater. The report concluded that there was the potential for off-post
migration of contaminants at elevated concentrations.

Also in 1978, the U.S. Army Environmental Hygiene Agency's (USAEHA) water well sampling
program (USAEHA, 1978) revealed that three of MAAP's 11 water supply wells were contaminated
with explosives compound. The affected wells are near some of the production areas.

A 1982 USAEC MAAP Contamination Survey report (USAEC, 1982) concluded that contaminated
groundwater was migrating slowly toward the northern facility boundary. Explosives compounds
were detected in groundwater samples collected from northern boundary monitoring wells; however,
none of the detected concentrations were high enough to be considered a threat to human health
and the environment. The facility drainage ditches were noted as a possible source of
groundwater contamination.

In May, 1984, because of the level of contamination in the groundwater, the facility was
proposed for listing on the National Priorities List (NPL). The NPL is the U.S. Environmental
Protection Agency's (USEPA) list of uncontrolled hazardous substance releases in the United
States that are priorities for long-term remedial evaluation and response. Final listing on the
NPL took place in August, 1987.

In 1989, the Army, the USEPA, and the Tennessee Department of Environment and Conservation
(TDEC) entered into a Federal Facility Agreement under the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA) Section 120 and Resource Conservation and
Recovery Act (RCRA) Sections 3008(h), 3004(u), and 3004(v) (USEPA, 1989b). The purpose of this
agreement is to ensure that environmental impacts at the site would be investigated and that
remedial actions would be taken to protect public health, welfare, and the environment.

In 1990-1991, the USAEC conducted a Remedial Investigation (RI) at MAAP (USAEC, 1991a).
The RI was performed to identify the type, concentration, and extent of contamination throughout
the facility. During the RI, soil samples were collected from soil borings drilled downgradient
of all sumps within each of the load lines. Soil samples were also collected from all known and
suspected disposal areas.

In 1991-1993, in-depth studies of Operable Unit 1 (groundwater immediately downgradient of

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the 0-Line Ponds area) and Operable Unit 2 (soil, surface water, and sediment at the 0-Line
Ponds area) were conducted. Remedial alternatives were evaluated for these operable units, and
construction is currently underway for selected actions documented in Records of Decision dated
September 30, 1992 (Operable Unit 1) and September 30, 1993 (Operable Unit 2).

In 1994-1995, studies were conducted which focused on the groundwater at the northern and
western installation boundaries. The goal of this effort is to protect off-site users of
groundwater by preventing the further off-site migration of contaminated groundwater from the
installation. The Record of Decision for the northern boundary was finalized in September,
1994, and the remedial design is currently being developed. The Record of Decision for the
western boundary is currently being finalized.

The environmental data used in the development of this remedial action for the
contaminated soil in the northern industrial areas were collected under the original RI (USAEC,
1991a) and the focused investigation of Line B, which took place in the summer of 1994. These
data were used to develop a conceptual model of the type of contaminants, the manner in which
the contaminants were released into the environment, and the distribution of the explosives
compounds in soil with depth.

In 1995, a Focused Feasibility Study (FS) of the northern industrial area soil was
conducted (USAEC, 1995a). The purpose of the Focused FS was to identify remedial technologies
that are capable, singly or in combination, of mitigating the risks posed by contaminated soil
at the northern industrial areas. Based on the information gathered and presented in the
Focused FS report, the Army has selected a preferred remedy for contaminated soil at the
northern industrial areas. Both EPA and the State of Tennessee concur with the selection of
this remedy. The rationale behind selection of the remedy was presented to the public in a
Proposed Plan (USAEC, 1995b).

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3.0    HIGHLIGHTS OF COMMUNITY PARTICIPATION

       The RI report for MAAP was released to the public in December, 1991, and presented at a
public meeting held during the same month.  The Focused Feasibility Study  (FFS) report and the
Proposed Plan for the northern industrial area soil were released to the public on April 14,
1995.  All of these documents, as well as other information about environmental studies at MAAP,
are available in both the Administrative Record and the information repository maintained at the
Army Industrial Operations Office at MAAP and the Mildred G. Fields Library in Milan, TN.  The
notice of availability of these documents was published in the Milan Mirror-Exchange and the
Jackson Sun newspapers on April 19, 1995.

       A 30-day public comment period was held from April 14,  1995 through May 15, 1995.   In
addition, a public availability session and Restoration Advisory Board meeting were held during
the public comment period on Tuesday, April 25, 1995.  At that meeting, representatives from
MAAP, the USEPA, and TDEC presented a summery of the project and answered guestions about
problems at the site and the remedial alternatives under consideration.  Comments and responses
from the April 25, 1995, public availability session, as well as written comments received
during the public comment period, are included in the Responsiveness Summary  (Appendix A).

       This decision document presents the selected remedial action for explosives-contaminated
soil in the northern industrial areas at Milan Army Ammunition Plant in Milan, TN.  The remedial
action has been chosen in accordance with CERCLA, as amended by SARA, and, to the extent
practicable, the National Contingency Plan.  The decision for this site is based on information
contained in the Administrative Record.

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4.0 SCOPE AND ROLE OF OPERABLE UNIT OR RESPONSE ACTION

Past disposal practices at MAAP have resulted in soil and groundwater contamination at the
facility. The goal of the overall cleanup activities at MAAP and affected off-post areas is to
reduce the levels of contaminants to concentrations that are protective of human health and the
environment, such that no adverse health effects or adverse ecological impacts will result from
future use of the facility and/or any off-post areas that have become contaminated as a result
of operations at MAAP.

This remedy addresses the explosives-contaminated soil within both Operable Unit 3 and
Operable Unit 4 at MAAP. Operable Unit 3 consists of the northeast sector of the facility
(formerly designated as Operable Unit 14), and Operable Unit 4 consists of the northwest sector
of the facility. Further investigation of the groundwater, surface water, and sediment within
these sectors is currently underway. Operable Units 3 and 4 comprise areas with different site
histories and contaminant sources than the other Operable Units in the northern portion of MAAP,
which are Operable Unit 1 (groundwater immediately downgradient of the 0-Line Ponds) and
Operable Unit 2 (soil, surface water, and sediment in the 0-Line Ponds area). Remedies have
already been selected for Operable Units 1 and 2, and construction is presently underway for
both projects. Groundwater at the downgradient installation boundaries (which correspond to the
northern and western boundaries of Operable Units 3 and 4) is being addressed under separate
studies. The groundwater at the northern boundary of OU3 will be remediated as stipulated in
the Record of Decision signed on September 30, 1994. This project is presently in the remedial
design phase. A remedy for the contaminated groundwater on the northern and western boundaries
of OU4 is currently being selected.

The contaminated medium that will be addressed by this Record of Decision is the soil
within the northern industrial areas as listed in Section 5.1. The soil poses a possible threat
to human health because workers are occasionally in contact with the contaminated soil. In
addition, there is the potential for migration of the explosives compounds to the underlying
groundwater, which is a source of drinking water for off-site residents. The purpose of this
response is to prevent current or future exposure to the contaminated soils and to reduce
contaminant migration to groundwater. The cleanup level is driven by the more conservative
exposure pathway, which is the potential contamination of groundwater and ingestion by
hypothetical future residents. This will be the final response action for
explosives-contaminated soil within Operable Units 3 and 4.

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5.0 SITE CHARACTERISTICS

This section provides an overview of the site characteristics of the northern industrial
areas, including the nature and extent of soil contamination. The information presented in this
section has been summarized from the RI Report (USAEC, 1991a) and the FFS Report (USAEC, 1995a).

5.1 KNOWN OR SUSPECTED SOURCES OF CONTAMINATION

The northern industrial areas include the following load lines, storage areas, and
disposal areas:

Load Lines A, B, C, D, E, K, 0, X, and Z;
• Closed Landfill; and
• Former Borrow Pit.

These areas were investigated during the RI in 1990-1991, and the results of the investigation
are presented in the RI Report (USAEC, 1991a) and are summarized below. Other sites within the
northern industrial areas have not yet been investigated but are included in this remedial
action. These areas include Area M (storage), Area N (storage), Area S (storage), Area J
(maintenance/fabrication area), Line F, Line H, and Line V.

5.1.1 Description of the LAP Line Areas

The source of the information presented in this section is a report describing solid waste
management units (SWMUs) performed by A.T. Kearney and Geo/Resource Consultants (USEPA, 1986b);
personal communications with Bill Blaylock, Lockheed Martin Corp.; and a reference manual on
military explosives (U.S. Department of the Army, 1984).

5.1.1.1 Line A. Line A has been in operation since 1941. Past activities have included the
renovation of 60-mm mortar rounds, loading of fuzes, press loading of 40-mm rounds, and rocket
assembly. The explosives handled at this line include Amatol [a mixture of
2,4,6-trinitrotoluene (2,4,6-TNT) and ammonium nitrate], Composition B [a mixture of 2,4,6-TNT
and cyclotrimethylenetrinitramine (RDX)]. and N-methyl-N,2,4,6-tetranitroaniline (tetryl). Past
practices include wastewater discharges to sumps and from the sumps to surface drainages.
Occasional wash down of the entire assembly line with water was also performed. Line wastewater
is presently discharged to an industrial wastewater treatment facility (IWWTF).

5.1.1.2 Line B. Line B has been in operation since 1941. Past activities have included the
renovation of high explosive rocket and artillery rounds; demilitarization of high explosive
37-mm, 40-mm and 75-mm rounds; disassembly of 40-mm shells and 4.5-inch rockets; assembly and
loading of various artillery shells; production of 4.5-inch rockets; and segregation and
handling of cordite. The explosives loaded at this line include Composition A (a mixture of RDX
and a desensitizer, such as beeswax or a synthetic wax) and Composition B. Plastic-bonded
explosives have also been extruded and dried at Line B. These explosives are mixtures of RDX,
polystyrene, and di-N-octyl phthalate. Past practices included wastewater discharges to sumps
and from sumps to surface drainages. Occasional wash down of the entire facility with water was
also performed. Line wastewater is presently discharged to an IWWTF.

5.1.1.3 Line C. Line C operated from 1941 until the 1970s. Past activities have included the
operation of a melt/pour facility, renovation of rockets, the loading of mortar and rockets, and
the disassembly of howitzer shells. Amatol and Composition B were loaded at this line, and it
is possible that Composition A was also used. Past practices included wastewater discharges to
sumps and from sumps to surface drainages. Occasional wash down of the entire facility with
water was also performed. If the line is reactivated, wastewater will be discharged to the
IWWTF. An X-ray facility existed previously at this line.

5.1.1.4 Line D. Line D has been in operation since 1941. Past activities have included the
operation of a melt/pour facility, the renovation of howitzer and mortar shells, and the loading
of howitzer shells. Amatol and Composition B were loaded at this line, and it is possible that
Composition A was also used. Past practices included wastewater discharges to sumps and from
sumps to surface drainages. Occasional wash down of the entire facility with water was also

-------
performed. Currently, wastewater is discharged to an IWWTF. DuPont sheeting TM, a
plastic-bonded explosive, has been cut into sheets at Line D. A former photographic lab and
X-ray facility may have discharged spent solutions to surface drainage ditches.

5.1.1.5 Line E. Line E operated from 1941 until the 1970s. Past activities included the
assembly of fuzes and booster leads, and the blending and pelletizing of tetryl. Prior to the
Vietnam War, the fuzes were made of tetryl. After the Vietnam War, Composition A5, which is a
mixture of RDX and barium stearate, was used. The facility was operated as a dry line, although
past practices may have included discharged to a sump or drainage ditch. The site is presently
on standby status.

5.1.1.6 Line F. Line F operated from 1941 until the 1970s. Past activities included the
assembly of fuzes, pressing of booster pellets and lead charges, and the blending and
pelletizing of tetryl. Prior to the Vietnam War, the fuzes were made of tetryl. After the
Vietnam War, Composition A5 was used. The site is presently on standby status.

5.1.1.7 Line H. Line H has been used for the assembly of delay charges, loading of fuzes,
pressing of small mortar propellants, and pressing of black powder. The explosives handled at
the line include Composition A5, tetryl, and black powder. Line H is presently in use.
Although there are no sumps at Line H, a small drainage channel extends from the load line to
Ditch C.

5.1.1.8 Line K. Line K has been used for both metal parts production and munitions production.
Both activities are currently inactive and the line is now being used as a storage area.
According to Thomas Allen (personal communication, 1991), a retired MAAP employee who previously
supervised the work at Line K, metal plating operations were performed in Building K-50. These
plating operations continued until the late 1970s. Both zinc chromate electrolytic plating and
cadmium electrolytic plating processes were used, and both of these processes were
cyanide-based. In addition, an X-ray facility previously existed at Line K. Prior to 1946,
ammonium nitrate was manufactured by facility personnel at Line K for use in agricultural
fertilizers. In 1946, a large explosion occurred which destroyed a building and resulted in the
release of ammonium nitrate. The production of ammonium nitrate was discontinued following the
accident.

5.1.1.9 Line O. Line 0 has been in operation since 1941. Line 0 is a conventional
demilitarization facility constructed to remove explosives from bombs and projectiles by
injecting a high pressure stream of hot water and steam into the open cavity of the munitions to
melt and wash out the explosives fill. Past practices included wastewater discharges from
concrete sumps to the 0-Line Ponds. Wastewater is presently piped from steel tanks set in
concrete pits to the Line 0 IWWTF.

5.1.1.10 Line X. Line X has been in operation since 1941. Past and present activities include
the loading of mortar rounds, rockets, and fuzes; demilitarization of 20-mm and 37-mm munitions;
renovation of fuzes; and production of mortar and artillery shells. Explosives loaded at this
line include Amatol, Composition A5, Composition B, tetryl, and plastic-bonded explosives. Past
practices included wastewater discharges to sumps and from sumps to surface drainages.
Occasional wash down of the entire facility with water was also performed.

5.1.1.11 Line Z. Line Z was in operation from 1941 to the late 1970s, and production resumed
in 1993. Past production activities included the loading of fuzes. Both tetryl and Composition
A5 have been used at this line. Past practices included wastewater discharges to sumps and from
sumps to surface drainages. Occasional wash down of the entire facility with water was also
performed.

5.1.2 Closed Sanitary Landfill

MAAP operated a landfill located between Line H and Line K, north of Highway 104, from the
late 1960s until 1974. This landfill was reportedly used as a general purpose disposal area for
paper, construction material, and miscellaneous items including RDX-contaminated packing
material. Disposal procedures included the excavation of trenches 8-10 feet deep, 15 feet wide,
and 50-75 feet long. These trenches were then filled with inert material, compacted, then
covered with soil. Natural topographic lows were utilized where possible.

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5.1.3 Former Borrow Pit (Construction Debris Pit)

The former borrow pit is located directly south of Line H and immediately north of Highway
104. The pit is a former borrow area used to excavate sand for construction activities. MAAP
has allowed the disposal of discarded building materials from construction and renovation
activities to occur in this pit. Currently, the former borrow pit contains ponded water.

5.1.4 Description of Previous Investigations

During the RI, all sumps within each of the load lines were investigated by drilling a
borehole on the downgradient side of the sump to a depth of 20 feet. For the few sumps that are
located in areas inaccessible to drilling rigs, a borehole was advanced by hand to a depth of 10
feet. Soil borings were also drilled within each of the other suspected contaminated areas.
From each of these borings, soil samples were collected at the surface and at five-foot
intervals. All samples were analyzed for explosives compounds and select metals (cadmium,
chromium, mercury, and lead). In addition, approximately 10% of the samples were analyzed for
volatile organic compounds (VOCs), semivotatile organic compounds, explosives compounds, and
Target Analyte List (TAL) metals.

In addition, a more in-depth study of Line B was conducted in mid-1994. As part of this
study, more than 300 surface soil samples were collected in suspected contaminated areas
(outside doors in which washout occurred, near sumps, and near ditches). These surface soil
samples were analyzed in the field using immunoassay test kits for 2,4,6-TNT and RDX. Because
near real-time results could be obtained using the test kits, sampling proceeded in each
suspected contaminated area until contaminant contour lines could be established around each
contaminated area, including the non-detect line.

The immunoassay test kit for 2,4,6-TNT actually measures the sum of the concentrations of
2,4,6-TNT, 1,3,5-trinitrobenzene (1,3,5-TNB), 2,4-dinitrotoluene (2,4-DNT), tetryl, and
2-amino-4,6-dinitrotoluene (2-A-4,6-DNT). The method detection limit for this test kit is
approximately 1/Og/g in soil.

The immunoassay test kit for RDX measures the sum of the concentrations of RDX and
cyclotetramethylenetetranitroamine (HMX). The method detection limit for this test kit is also
approximately 1 Og/g in soil.

The distribution of contaminants within Line B is most likely representative of the other
load lines because, at various times, both melt/pour and pressing activities have taken place
within this line. Line B has operated since 1941, and has been one of the most active lines.
Therefore, the general conclusions drawn from data collected at Line B were used in the overall
risk assessment for the northern industrial areas.

5.2 DISTRIBUTION OF CONTAMINANTS IN SOIL

During the RI, approximately 10% of all soil samples were analyzed for Target Compound
List (TCL) VOCs, base/neutral-acid extractable compounds, and TAL metals, as well as the
explosives compounds. For all suspected source areas investigated within the northern
industrial areas, the chemical data indicate that no organic or inorganic analytes other than
explosives compounds have been detected in soil at levels of concern. In addition, other
organic compounds have only been detected in soil samples in which explosives compounds are
present.

During the RI Follow-On for Operable Unit 4 (USAEC, 1995c) thallium and beryllium were
identified as chemicals of concern in soil. However, no evidence exists to suggest that the
occurrence of these analytes is related to site activities. MAAP environmental and engineering
staff have no recollection of the use of thallium or beryllium compounds in any production
activities (telephone conversations with Bill Blaylock and Steve Stephenson, Lockheed Martin
Corp.; and Pat Brew, U.S. Army, 26 June 1995).

5.2.1 Explosive Compounds Detected in Soil

Explosives compounds have been detected at levels up to a maximum of approximately 100,000
Og/g (in a surface soil sample collected at Line B). However, the average total concentration

-------
of explosives compounds is in the range of 10 Og/g to 100 Og/g.

As expected from the history of the facility, the major explosives compounds detected in soil
samples are 2,4,6-TNT and RDX. These two explosives compounds account for approximately 95% of
the total mass of explosives compounds detected in the soil. The following patterns have also
been noted from the data:

• At certain load lines and sumps, only tetryl has been detected in some soil samples.
This has occurred at Line E and specific buildings within Lines A and Z. Due to the
fact that tetryl was loaded into fuzes within these areas

• The breakdown products and/or manufacturing contaminants of 2,4,6-TNT include
1,3,5-TNB, 1,3-dinitrobenzene (1,3-DNB), nitrobenzene, 2,4-DNT, and 2,6-DNT. These
compounds are freguently detected in samples in which 2,4,6-TNT is also detected. In
general, these compounds have not been detected at concentrations exceeding 5% of the
concentration of 2,4,6-TNT detected in the same sample.

• The manufacturing byproduct of RDX detected at MAAP is HMX (which is also an
explosive but has not been handled at MAAP). In general, HMX has not been detected
at a concentration exceeding 5% of the concentration of RDX detected in the same
sample.

5.2.2 Distribution of Explosives Compounds with Depth

Soil has become contaminated with explosives compounds at MAAP by the following
mechanisms:

• Washout of buildings. In the past, buildings in which large amounts of explosives
compounds were handled (e.g., in melt/pour operations) were cleaned by a
high-pressure water spray. This water was allowed to run out the doors and onto the
ground.

• Use of sumps. In the past, industrial wastewater was directed to sumps, where the
bulk of the explosives compounds would settle out and the water was then discharged
to ditches. Presently, all water is directed into an IWWTF prior to discharge. In
cases where the sump leaked or was allowed to overflow during rain events, wastewater
would have been applied to the soil surrounding the sumps.

• Use of unlined drainages for discharge of water. Prior to construction of the IWWTFs
in 1981, wastewater was allowed to flow from the sumps to larger drainage ditches
through unlined drainages.

These mechanisms resulted in the application of contaminated wastewater to surface soil
and subseguent infiltration of the contaminated water through the vadose zone. In each case, it
is expected that contamination would be highest in the near-surface soil and would attenuate
with depth. The chemical data collected during the RI are in agreement with this premise. In
general, the concentration of total explosives compounds decreases at one order of magnitude for
every 5 feet of depth.

5.2.3 Estimate of the Extent of Contamination

The surface soil sampling program for Line B consisted of collecting more than 300 soil
samples from areas that were suspected to have become contaminated. Surface soil samples were
collected from areas outside of all buildings in which explosives were directly handled, around
all sumps and drywells, and in the drainages that run from the sumps to the drainage ditches.
As stated previously, the level and type of contamination at Line B is expected to be
representative of the level of contamination at other load lines because of the similarity of
operations at Line B to those within other load lines.

The soil sampling and analysis program was conducted to establish the extent of
contaminated soil around each suspected source area, which then led to estimation of the total
area within Line B that is contaminated. The results show that the area containing explosives
compounds above the method detection limit (approximately 1 Og/g) is a small fraction

-------
(approximately 0.1%)  of the total area within Line B.

5.2.4  Conclusions

       Based on the results of the overall RI and the representative Line B investigation,  the
type and distribution of contamination throughout the northern industrial areas can be
generalized as follows:

       •     The principal explosives compounds found in soil within the northern industrial areas
            of MAAP are 2,4,6-TNT and RDX.  With the exception of those areas where only tetryl
            was handled, other explosives compounds occur at a concentration egual to or less
            than 5% of principal explosives compounds concentrations.

       •     In general, surface soil contains the highest concentration of explosives compounds
            as compared to subsurface soil samples collected at the same location.  The
            concentration of explosives compounds decreases by approximately one order of
            magnitude per 5 feet of depth.

       •     Approximately 0.1% of the total area within a load line is contaminated.

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6.0 SUMMARY OF SITE RISKS

Risk assessment consists of evaluating the types and levels of contaminants present, the
pathways by which receptors could potentially be exposed to these contaminants, and the toxicity
and/or carcinogenicity of the contaminants. A guantitative estimate of the potential for
adverse health effects to occur in the future can be constructed from these data.

In the case of the explosives-contaminated soil in the northern industrial areas, the
delineation of the exact extent of contaminated areas has not yet been performed. Therefore, a
complete guantitative estimate of the level of risk posed by the explosives-contaminated soil in
the northern industrial areas cannot be developed at this time. However, sufficient data are
available to form a predictive model of the contaminated areas. This model considers the
sources of contamination, the manner in which the contaminants were released to the soil, and
the distribution of the explosives compounds both in depth and in area. This predictive model
was then used to develop soil remediation goals, which are the maximum concentrations of
explosives compounds that could remain in soil while resulting in risks within the USEPA's
acceptable range. Soil which is contaminated with explosives compounds in excess of these soil
remediation goals, therefore, may pose a threat to human health that is higher than these
acceptable risk levels.

In this section, standard risk assessment assumptions and eguations are used to perform
the reverse calculation needed to derive soil remediation goals. The complete development of
soil remediation goals can be found in Section 3.0 of the FFS (USAEC, 1995a).

6.1 CONTAMINANT IDENTIFICATION

During the RI conducted in 1990-1991, surface and subsurface soil samples were collected
immediately of each sump in all of the load lines, as well as within each suspected disposal
area. All soil samples were analyzed for explosives and select metals (Cd, Cr, Pb, Hg), and
approximately 10% of the soil samples were analyzed for TCL VOCs, semivolatile organic
compounds, TAL inorganics, and explosives compounds. The detected inorganic analytes exceeded
background levels infreguently and by relatively small margins. Three polynuclear aromatic
hydrocarbon (PAH) compounds were detected in one subsurface sample at concentrations less than
0.2 Og/g. The source of these PAH compounds may be exhaust from vehicles, the drill rig, or
gasoline-powered generators. Acetone, 1,2-epoxycyclohexene, trichlorofluoromethane, and
2-propanol were detected in approximately 5 samples (out of 115 samples) at levels just above
their respective Certified Reporting Units (CRLs). Several of these organic compounds are
common laboratory or transportation contaminants, and 2-propanol was used in eguipment
decontamination. Although phthalates were used in several of the load lines, these compounds
were not detected in the soil. Therefore, the results of analysis of all of the soil samples
collected to date indicate that the major contaminants of concern are the explosives compounds.

Examination of the risk calculations in the RI Follow-On Report indicates that the
concentrations of thallium and beryllium would not pose a risk to workers under the industrial
land use scenario, which is the current and expected future use of the northern industrial
areas. In addition, beryllium did not pose an unacceptable level of risk to future hypothetical
residents (both adults and children). Adverse health effects are only predicted for the
unlikely future scenario of residential development of the load line sumps and incidental
ingestion of soil by children. This scenario is not considered to represent a reasonable future
use of the land.

Furthermore, because of the known distribution of explosives compounds in soil, it is
possible to use the principal explosives compounds (2,4,6-TNT, RDX, and tetryl) as indicator
compounds in the risk assessment and derivation of soil remediation goals. This is discussed in
more detail in the following section.

6.1.1 Justification for Use of 2,4,6-TNT, RDX, and Tetryl as Indicator Compounds

-------
The information presented in Section 5.0 regarding the principal explosives compounds at
MAAP (2,4,6-TNT and RDX) and the relative concentrations of the breakdown products and/or
manufacturing contaminants indicates that approximately 95% of the total mass of explosives
compounds present in the explosives-contaminated soil at MAAP are the principal explosives
compounds. The secondary explosives compounds, if they are present at all in the
explosives-contaminated soil, have been detected at levels equal to or less than 5% of the
concentration of 2,4,6-TNT and RDX.

The secondary explosives compounds associated with 2,4,6-TNT are 1,3,5-TNB, 2,4-DNT,
2,6-DNT, nitrobenzene, and 1,3-DNB. The secondary explosives compound associated with RDX is
HMX.

The principal explosives compounds (2,4,6-TNT and RDX) are Class C carcinogens and also
have toxic (noncarcinogenic) effects. With the exception of 2,4-DNT and 2,6-DNT, the mixture of
which is a probable carcinogen, the secondary explosives compounds are noncarcinogens. The
Reference Doses (RfD) and Cancer Slope Factors (CSF) for the explosives compounds are listed in
Table 6-1.

The RfD and CSF values in Table 6-1 indicate the following:

• 2,4,6-TNT and RDX have both an RfD and CSF, so both carcinogenic and noncarcinogenic
effects can be estimated for these compounds.
• The secondary explosives compounds associated with 2,4,6-TNT have a wide range in
RfDs and CSFs, with some displaying more severe toxic/carcinogenic effects and some
displaying less toxic/carcinogenic effects.
• HMX is not a carcinogen. Also, HMX is less toxic (noncarcinogenic) than RDX.

As a check on the applicability of the 2,4,6-TNT, RDX, and tetryl RfDs and CSFs to
remediation of the soil within the northern industrial areas at MAAP, calculations were
presented in the FFS Report (USAEC, 1995a) to evaluate the error that could result from focusing
the risk assessment on these compounds. It was concluded that use of 2,4,6-TNT, RDX, and tetryl
as indicator compounds would be appropriate for investigation and confirmatory sampling of soil.
The calculation of risk-based soil remediation goals presented below therefore focuses on the
risks and adverse effects of RDX and 2,4,6-TNT. Tetryl will also be evaluated separately
because it has been used extensively at the fuze load lines.

6.2 EXPOSURE ASSESSMENT

In this section, the potential pathways by which individuals may be exposed to the
explosives compounds of concern in soil are identical. Potential pathways associated with other
media that may be affected by the contamination in the soil (i.e, groundwater) are also
identified. This information will be the basis for calculating soil remediation goals for the
receptors who may be exposed to contaminants of potential concern. Although soil remediation
goals for all selected exposure pathways will be calculated, the most conservative (i.e.,
health-protective) remediation goals in soil will be selected for remediation purposes.

An exposure pathway, which describes the course a chemical takes from the source to the
exposed individual, is defined by four elements:

• A source and mechanism of chemical release to the environment;
• An environmental transport medium (e.g., groundwater, soil) for the released chemical;
• A point of potential contact with the contaminated medium (referred to as the exposure
point); and
• An exposure route (e.g., ingestion) at the contact point.

An exposure pathway is considered complete only if all four elements are present, and only
complete exposure pathways are quantitatively evaluated.

When conducting an exposure assessment, USEPA (1989a, 1991) guidance requires that
plausible exposures under both current and future land-use scenarios be evaluated. The current
land-use scenario assumes conditions as they currently exist, while the future land-use scenario
evaluates conditions that may be associated with probable changes in site use, assuming no
remedial action occurs.

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                                                                                        TABIiE 6-1
                                                                      Oral Toxicity Values for Explosives Compounds
      Chemical
1-3-Dinitrobenzene

Dinitrotoluene
(2,4 and 2,6 isomers)

HMX

Nitrobenzene

RDX

Tetryl

1,3,5-Trinitrobenzene

2,4,6-Trinitrotoluene
                            Chronic
                         Reference Dose
                          (mg/kg-day)
     1x10-4

2x10-3 (2,4)
1x10-3 (2,6)

     5x10-2

     5x10-4

     3x10-3

     1x10-2

     5x10-5

     5x10-4
                   Uncertainty Factor
                          (a)
     3,000

  100 (2,4)
3,000 (2,6)

     1,000

    10,000

       100

    10,000

    10,000

     1,000
                    Target Organ (b)
    Spleen/Weight

      CNS (2,4)
CNS/Blood/Kidney (2,6)

        Liver

     Kidney/Liver

       Prostate

  Liver/Kidney/Spleen

        Spleen

        Liver
                            Reference Dose
                                Source
 IRIS

 IRIS
HEAST

 IRIS

 IRIS

 IRIS

HEAST


 IRIS

 IRIS
                Cancer Slope
                   Factor
                (mg/kg-day)-1
6.8x10-1
 1x10-1
              EPA Weight of
                Evidence
              Cls sification
                   (c)
                   B2


                    D

                    D

                    C
Slope Factor
   Source
   HEAST



    IRIS

    IRIS

    IRIS
                                                                                            3x10-2
                                                                                                                                IRIS
(a)      Safety  factors are the products of uncertainty factors and modifying factors.  Uncertainty factors used to develop reference doses generally consist of multiples of 10, with
        each factor representing a specific area of uncertainty in the data available.  The standard uncertainty factors include the following:
        - a 10-fold factor to account for variation in sensitivity among members of the human population;
        - a 10-fold factor to account for the uncertainty in extrapolating animal data to the case of humans;
        - a 10-fold factor to account for the uncertainty in extrapolating from less than chronic NOAELs to chronic NOAELs; and
        - a 10-fold factor to account for the uncertainty in extrapolating from LOAELs to NOAELs.
        Modifying factors are applied at the discretion of the reviewer to cover other uncertainties in the data.
(b)      A target organ is the organ most sensitive to a chemical's toxic effect.  RfDs are based on toxic effects in the target organ.  If an RfD was based on a study in which a
        target organ was not identified, an organ or system known to be affected by the chemical is listed.
(c)      EPA Weight of Evidence for Carcinogenic Effects:
        [A]  = Human carcinogen based on adeguate evidence from human studies;
        [B2] = Probable human carcinogen based on inadeguate evidence from human studies and adeguate evidence from animal studies;
        [C]  = Possible human carcinogen based on limited evidence from animal studies in the absence of human studies; and
        [D]  = Not classified as to human carcinogenicity.
CNS     = Central Nervous System
IRIS    = Integrated Risk Information Systems
HEAST   = Health Effects Assessment Summary Tables
        = No information available

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6.2.1 Potential Exposure Pathways Under Current Land-Use Conditions

The potential exposure pathways through which human receptors could be exposed to
contamination resulting from past activities are discussed below for current land-use
conditions. Table 6-2 summarizes this analysis, indicating the exposure media, source end
release mechanisms, potential receptors, and exposure routes. This table also indicates whether
the pathway is potentially complete and identifies those pathways for which soil remediation
goals will be calculated.

6.2.1.1 Surface Soil. As noted above, the principal locations of explosives-contaminated soil
are in the vicinity of buildings where the explosives compounds were loaded and packaged, and
around sumps. Thus, under current land-use scenarios, workers who come into contact with the
explosives-contaminated soil may be exposed to the explosives compounds. Although routine
worker activities are likely to be very limited to the buildings in which they work, it is
possible that workers who work inside the buildings as well as maintenance workers who
investigate potential environmental releases could be exposed to surface soil on a routine
basis. Workers who mow and conduct lawn maintenance work around the buildings also could be
exposed to surface soil; however, their exposures would be primarily in grassy areas farther
away from the buildings, and on a less freguent basis. Based on the industrial worker being a
potential receptor in the northern industrial areas, soil remediation goals for a worker's
contact with soil (i.e., incidental ingestion and dermal absorption of chemicals in soil) were
calculated.

Trespassers who enter the site may also be exposed to explosives compounds in the surface
soil. All of the northern industrial areas are fenced, limiting potential access by
trespassers. However, even if trespassers were to come on site, their exposure would be much
less freguent than a worker's exposures (both in the exposure freguency [number of days per year
exposed] as well as the exposure duration [number of years exposed]). Therefore, exposures and
associated soil remediation goals for surface soil by trespassers were not considered in this
assessment because soil remediation goals calculated for workers also would be protective of
trespassers.

6.2.1.2 Subsurface Soil. Subsurface soil is likely to be contacted only if excavation
activities are performed. Excavation or other intrusive activities are not expected in the
northern industrial areas under current land-use conditions; therefore, exposures to subsurface
soil are unlikely to occur under current land-use conditions, and soil remediation goals
associated with an excavation scenario were not calculated.

6.2.1.3 Groundwater. Explosives compounds in the soil may leach into the groundwater below
the northern industrial areas; if receptors drink or dermally contact this groundwater, then
exposures could occur. Groundwater from the contaminated portions of the northern industrial
areas of MAAP is not currently used as a drinking water source or for any other purpose by
either on- or off-site individuals. Rather, personnel working at MAAP obtain their drinking
water from production wells in uncontaminated areas (Areas S and T). As a result, there are no
complete pathways associated with the explosives compounds in groundwater, and soil remediation
goals for the protection of groundwater were not calculated for any groundwater receptors under
current land-use conditions.

6.2.1.4 Air. Inhalation exposures to the explosives compounds could result from the transport
of chemicals on dust particles by wind entrainment and from the volatilization of chemicals from
surface soil or groundwater. Migration of the explosives compounds by wind entrainment of dust
particles is not considered to be a significant transport process in most areas of contamination
in the northern industrial portion of MAAP, as the areas are typically vegetated and/or paved.
Because VOCs are not chemicals of potential concern in soil or groundwater, inhalation of
volatilized chemicals is not a complete pathway in the areas of concern. The explosives
compounds of concern, 2,4,6-TNT, RDX, and tetryl, have very low vapor pressures of 5.5x10-6,
4.03x10-9, and 5.69x10-9 torr at 25° C, respectively, so volatilization will not occur at levels
of concern.

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TABIiE 6-2
Potential Human Exposure Pathways Under Current Land-Use Conditions
Exposure
Medium
Source/Mechanism of
Release
Receptor
Exposure Route
Pathway Potentially
Complete?
Basis
Method of Evaluation
Surface soil
Contaminated
wastewater from washing
down insides of
buildings where
explosives were used.
On-site
industrial
worker
On-site lawn
maintenance
worker
Dermal contact
and/or incidental
ingestion of soil.
Dermal contact
and/or incidental
ingestion of soil.
Yes. Industrial workers
could come into contact
with contaminated soils.
Yes. Lawn maintenance
workers could come into
contact with contaminated
soils.
Remediation goals calculated.
Industrial workers could come into
contact with contaminated soils.
None. surface soil in contaminated
areas around buildings would not be
as frequently contacted by lawn
maintenance workers as by
industrial workers.
Trespassers
Dermal contact
and/or incidental
ingestion of soil.
Yes. Trespassers could
come into contact with
contaminated soils.
None. Surface soil in contaminated
areas around buildings would not be
as frequently contacted by lawn
maintenance workers as by
industrial workers.
Subsurface Contaminated runoff On-site
soil from washing down excavation
buildings and from worker
disposal of liquid wastes
into sumps.
Dermal contact
and/or incidental
ingestion of soil.
No. No ground-intrusive
activities are occurring
under current operations at
the MAAP load lines.
None. Trespassers exposures
would be less frequent than
exposures to industrial workers at MAAP.
None. Pathway is not complete.
Groundwater
Leaching of chemicals
from surface soil and
sumps, primarily around
buildings.
On-site
worker
Ingestion and/or
dermal contact.
No. Groundwater not used
as a drinking water source
or for any other purpose by
individuals at MAAP.
None. Pathway is not complete.
Air
Dust generation from
contaminated soils or
volatilization of VOCs in
soils or shallow
groundwater.
On-site
worker
Inhalation of
wind-generated
dusts or
volatilized VOCs.
No. VOCs are not
chemicals of concern and
area is well vegetated.
None. Pathway is not complete.

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6.2.1.5 Summary of Pathways Selected for Evaluation Under Current Land-Use Conditions. In
summary, based on current activities in the northern industrial areas at MAAP, soil remediation
goals were calculated to be protective of incidental ingestion and dermal absorption of the
explosives compounds in surface soil by an industrial worker.

6.2.2 Potential Exposure Pathways Under Future Land-Use Conditions

The northern industrial areas will most likely remain in their current industrial status
rather than become developed for other uses in the future. This is consistent with the usage of
the industrial areas that have been excessed to date; these areas are now used for the
manufacture of furniture and ammunition containers. Nevertheless, for the purposes of this
evaluation, it was conservatively assumed that a hypothetical resident could reside at the
northern industrial areas at some point in the future. For the purposes of this evaluation, it
was assumed that remediation of soil would not occur at the site.

Table 6-3 summarizes the potential exposure pathway analysis under future land-use
conditions by indicating the exposure media, source and release mechanisms, potential receptors,
exposure route, and whether or not the pathway is potentially complete for explosives compounds
at or originating from the industrial areas of concern. The only exposure pathways that were
evaluated under future land-use conditions are those that are likely to change from the current
land-use conditions.

6.2.2.1 Surface Soil. Although the current industrial nature of the northern industrial areas
will most likely remain the same in the future, It was assumed that residents could build a
house and live in the northern industrial areas. Therefore, soil remediation goals based on a
future resident's potential exposures to surface soil (i.e., via incidental ingestion and dermal
absorption of chemicals in soil) were calculated.

6.2.2.2 Subsurface Soil. Subsurface soil would be accessible for contact by workers performing
excavation activities. Although no excavation activities are currently performed at the site,
ground intrusive activities such as excavation of soil for industrial development could occur.
Excavation workers could be exposed to explosives compounds in subsurface soil via incidental
ingestion and/or dermal absorption. It is unlikely that future residents who could live at the
northern industrial areas would have contact with subsurface soils, so soil remediation goals
associated with their potential exposures to subsurface soils were not calculated. In summary,
only soil remediation goals associated with an excavation worker's exposures to subsurface soils
were calculated.

6.2.2.3 Groundwater. As discussed for the current land use scenario, explosives compounds in
soil may leach into groundwater below the northern industrial areas. Groundwater at MAAP is
potable, so exposure to chemicals in groundwater could occur as a result of installation and use
of wells by future residents who could live at the northern industrial areas. Future residents
could become exposed to the explosives compounds in the groundwater primarily via the ingestion
pathway. As a result, soil remediation goals designed to be protective of groundwater ingestion
by future residents were developed. Ingestion of groundwater was assumed to be the predominant
exposure pathway for future residents, as explosives compounds do not volatilize (thus,
inhalation while showering would not be of concern). Furthermore, exposures and associated
risks via ingestion of RDX, 2,4,6-TNT, and tetryl in groundwater would be much greater than
exposures and associated risks via dermal absorption of these chemicals while bathing. As a
result, groundwater ingestion was the only pathway considered when developing soil remediation
goals protective of groundwater.

In addition to potential future residential uses of groundwater, wells could be installed
at the northern industrial areas to be used for industrial and domestic (e.g., cleaning and
consumption) poses. As a result, workers could be exposed to explosives compounds in
groundwater via ingestion. However, because workers' exposures would most likely be much lower
than those of residents, soil remediation goals only for residents were calculated, since they
also would be protective of potential future workers consuming groundwater.

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                                                                                                                    TABLE 6-3
                                                                              Potential Human Exposure Pathways Under Future  Land-Use  Conditions
Exposure
 Medium
                Source/Mechanism of Release
                                                      Receptor
                                                                               Exposure Route
Pathway Potentially
     Complete?
       Basis
                                                                                                                                                            Method  of Evaluation
               Contaminated wastewater from
               washing down insides of
               buildings where  explosives were
               used.
               Contaminated runoff  from
               washing down buildings and
               from disposal of liguid wastes
               sumps.
                                                                          Dermal contact and/or
                                                                          incidental ingestion of  soil.
                                   None.   It is not  very likely that
                                   residents will dig  this deep.
                                   Further,  exposures  would be less
                                   than via exposures  to surface soil.
               Dust generation from
               contaminated soils  or
               volatilization of VOCs in soil
               or shallow groundwater.
                                                                                                                                                      Remediation goals calculated for
                                                                                                                                                      soil,  to be protective of
                                                                                                                                                      groundwater ingestion.   Inhalation
                                                                                                                                                      and dermal  contact were not
                                                                                                                                                      considered  to  be significant
                                                                                                                                                      pathways of exposure.   See text.

                                                                                                                                                      None.   Pathway is not complete.

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6.2.2.4 Air. As it is unlikely that future conditions at the site would result in greater
generation of dusts at the site, the air pathway was not re-evaluated under future land-use
conditions.

6.2.2.5 Summary of Pathway. Selected for Evaluation Under Potential Future Land-Use
Conditions. As noted above, the evaluation of potential future exposure scenarios focused on
exposure scenarios that may occur in the future, under different land-use conditions.
Remediation goals for soil were calculated to be protective for the following potential exposure
pathways that could occur under future land-use conditions:

• Incidental ingestion and dermal absorption of chemicals in surface soils by future
residents;
• Incidental ingestion and dermal absorption of chemicals in excavated subsurface soil
by an excavation worker; and
• Ingestion of groundwater by a future resident.

6.2.3 Ecological Exposure Assessment

It is highly unlikely that ecological resources would be adversely affected by the
explosives compounds in the northern industrial areas of MAAP. As previously indicated, the
principal areas of explosives compounds in soil are immediately adjacent to the buildings where
explosives were loaded and packaged, and around the sumps. The habitat in these areas is
comprised predominantly of mowed grasses and bare soil areas. Because of the highly disturbed
nature and poor guality of the habitat around the buildings and sumps, very few ecological
receptors are expected to occur and potentially be exposed to chemicals in these areas.
Instead, the majority of wildlife on the northern area of MAAP are expected to occur in the less
disturbed habitats surrounding the industrialized areas. More importantly, however, the total
area of contaminated soil is estimated to be approximately 0.1% of the total industrial area,
and even if ecological resources were to be exposed to explosives compounds in these areas, it
is highly unlikely that adverse effects would occur to ecological receptor
populations/communities.

6.3 TOXICITY ASSESSMENT

For chemicals exhibiting potential carcinogenic effects, USEPA's Carcinogen Assessment
Group has estimated the excess lifetime cancer risks associated with various levels of exposure
to potential human carcinogens by developing Cancer Slope Factors (CSFs) and Unit Risks (URs).
CSFs describe the potential increase in an individual's risk of developing cancer over a 70-year
lifetime per unit of intake or dose, where the unit of exposure is expressed in terms of
reciprocal dose (mg chemical/kg body weight-day)-!. URs are expressed as either a reciprocal
air concentration (Og/m3)-l, or as a drinking water concentration (Og/L)-l. The derivation of
UR values for either inhalation or drinking water exposures reguires the use of specific
(conservative) assumptions about exposure conditions and receptor behavior. Because regulatory
efforts are generally geared to protect public health, including the most sensitive members of
the population, the CSFs and URs are derived using very conservative assumptions.

Health effects criteria for chemicals exhibiting noncarcinogenic effects are generally
developed using verified reference doses (RfDs) and reference concentrations (RfCs). These are
developed by USEPA's RfD/RfC Work Group and are available on IRIS (USEPA 1994a) or through
USEPA's HEAST (USEPA 1994b) . RfDs are expressed in units of dose (mg/kg-day), while RfCs are
expressed in units of concentration (mg/m3). RfDs and RfCs are usually derived either from
human studies involving work-place exposures or from animal studies. Chronic RfDs or RfCs are
estimates (with uncertainty spanning perhaps an order of magnitude) of the daily exposure to a
human population (including sensitive subpopulations) that would not produce an appreciable risk
of deleterious effects during long-term exposures (seven years or longer), RfDs/RfCs are used as
a threshold for evaluating the potential effects of exposures. Usually, exposures (such as
chemical intakes, doses, or inhalation exposure concentrations) that are less than the RfD or
RfC are not likely to be associated with adverse health effects. As the freguency and/or
magnitude or the exposures exceeding the RfD/RfC increase, the probability of adverse effects in
a human population increases.

RfDs and CSFs for the explosives compounds are presented in Table 6-1.

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6.4    RISK CHARACTERIZATION AND DERIVATION OF SOIL REMEDIATION LEVELS

       Based on the rationale provided in Section 6.2.3,  remediation goals were based solely on
protection of human receptors in the northern industrial areas of MAAP; ecological receptors
were not assumed to have significant exposures in these areas.  Remediation goals for soil were
derived by incorporating conservatively-derived USEPA default exposure parameters and USEPA
toxicity criteria into the equations presented below.  As discussed earlier in Section 6.3, the
evaluation of carcinogenic chemicals and noncarcinogenic chemicals is conducted separately, as
the mechanisms of action for these two groups of chemicals are different  (i.e., the no-threshold
effect for carcinogens and a threshold effect for noncarcinogens).  The USEPA has established a
typical acceptable risk range (to evaluate carcinogens) for remedial planning at Superfund
sites.  This target risk range of one in ten thousand  (1x10-4) to one in one million (1x10-6)  is
the chance of developing (not dying of)  cancer as a result of exposure to the carcinogen under
specified exposure conditions.  In this evaluation, risk-based remediation goals were developed
using a target risk level of 1x10-5, which is within the USEPA acceptable risk range of 1x10-6
to 1x10-4.  This target risk level is considered appropriate due to the anticipated limited
industrial uses of the northern industrial areas in the future.

       Potential adverse impacts associated with oral exposures to noncarcinogens are presented
as the hazard quotient.   Hazard quotients that are less than 1.0 should be viewed as indicating
that adverse effects would not be associated with the exposures being evaluated, while hazard
quotients exceeding 1.0 indicate the potential for occurrence of adverse effects.  As a result,
for noncarcinogenic chemicals, risk-based remediation goals were calculated to correspond to a
target hazard quotient of 1.0.  2,4,6-TNT and RDX exhibit both carcinogenic and noncarcinogenic
effects, so two risk-based remediation goals for these chemicals are presented for each pathway
evaluated.  Evidence is inconclusive regarding the possible cancerous effects of tetryl,  and the
USEPA has not made a determination in this regard.  Therefore, only one risk-based remediation
goal for tetryl (based on noncarcinogenic effects) is presented for each pathway.

6.4.1  Soil Remediation Goals for Contact with Soil

       Remediation goals associated with ingestion exposures and direct dermal contact with
explosives compounds in soil for hypothetical future residents were calculated using standard
USEPA equations and exposure parameters.  These remediation goals are presented in Table 6.4.
Since both carcinogenic and noncarcinogenic toxicity criteria exist for both 2,4,6-TNT and RDX,
two remediation goals are presented for these chemicals,  while only one remediation goal is
presented for tetryl.

       Remediation goals associated with ingestion exposures and direct dermal contact with
explosives compounds in soil for industrial and excavation workers were calculated using
standard USEPA equations and exposure parameters and are presented in Table 6-6.  Because
workers within the northern industrial areas would not be in contact with the soil to the same
extent as hypothetical residents, the soil remediation levels are higher for workers than for
residents.

6.4.1.1  Overall Soil Remediation Goals for Ingestion and Dermal Absorption of Chemicals.  In
order to determine remediation goals that would be protective of both ingestion and dermal
exposures simultaneously (as both exposures would likely be occurring at the same time when
workers or residents contact soil), the remediation goals for the individual pathways were
combined, as follows:
                                         1       =      1    +    1
                                        RGsoil        RGing     RGderm

       where:
RGsoil   =   Overall soil remediation goal assuming exposures via both the dermal and
             ingestion pathways;
RGing    =   Ingestion remediation goal; and
Rgderm   =   Dermal absorption remediation goal.

In the above calculation, the lower, more conservative remediation goals from substances with
both carcinogenic and noncarcinogenic data are used in calculating the overall remediation
goals.

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        Along with the  individual ingestion and dermal  remediation goals,  overall soil
remediation goals are presented in Table  6-4 for residents,  while overall  remediation goals  for
both types  of workers are  presented in Table 6-5.  It should be noted that the overall
remediation goals are lower than the individual goals,  since the overall goals are developed to
be protective of simultaneous dermal and  ingestion exposures.
                                                      TABIiE 6-4
                                 Soil Risk-Based Remediation  Goals for Residentsa

    Chemical                                    Residential
                                       Soil  Contact Remediation Goalb
                                                   (Og/g)
                                                                                Overall
                           Carcinogenic       Noncarcinogenic      Remediation Goalc
       RDX                    90    (I)          1,300     (I)               55
                            140     (D)          2,000     (D)
       Tetryl                 --    (I)          4,200     (I)            2,600
                                    (D)          6,600     (D)
       2,4,6-TNT            320    (I)            200     (I)              130
                            620     (D)            400     (D)

(a)  Remediation  goals are in  concentrations of mg/kg, and were rounded to  two significant figures.  The
remediation goal for carcinogens was based on a target risk of 1x10-5,  while the remediation goal for
noncarcinogens was based on a hazard quotient of  1.0.
(b)  Remediation  goals for soil contact  were calculated for both ingestion  and dermal pathways.
      I=remediation goal calculated for  ingestion of chemicals in soil
      D=remediation goal calculated for  dermal absorption of chemicals in soil.
(c)  The overall  remediation goals are based on a  resident simultaneously being exposed to chemicals via the
soil ingestion and dermal pathways.
                                                      TABIiE 6-5
                    Soil Risk-Based Remediation Goals for Excavation and Industrial Workersa
Tetryl

2,4,6-TNT
(a)  Remediation goals are in concentrations of Og/g, and were rounded to two significant figures.  The
remediation goal for carcinogens was based on a target risk of 1x10-5,  while the remediation goal for
noncarcinogens was based on a hazard quotient of 1.0.
(b)  Remediation goals for soil contact were calculated for both ingestion and dermal pathways.
    I=remediation goal calculated for ingestion of chemicals in soil
    D=remediation goal calculated for dermal absorption of chemicals in soil.
(c)  The overall remediation goals are based on a worker simultaneously being exposed to chemicals via the
ingestion and dermal pathways.


6.4.1.2   Soil Remediation Levels for the Protection  of Future Groundwater  Users.  Although
no complete exposure  pathways for groundwater currently  exist, under future land-use conditions
it ispossible that groundwater in the northern industrial  areas could be used as drinking water
by residents.  Thus,  soil remediation goals were developed based on migration of contaminants to
groundwater and subseguent  ingestion by  future residents.

       In  order to estimate  a soil remediation level that  is  protective for potential drinking
water exposures,  the  concentration in groundwater that is  protective of human health must first

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be derived.  The concentration of explosives compounds in groundwater associated with an
acceptable level of risk for ingestion of drinking water by future residents is calculated using
standard USEPA eguations and exposure parameters.

       The groundwater concentrations that were calculated to be protective of hypothetical
residents who ingest the explosives compounds in drinking water are presented in Table 6-6.
Since groundwater concentrations for RDX and 2,4,6-TNT were derived for both carcinogenic and
non-carcinogenic exposures, the more conservative (the more health-protective) groundwater
concentration is presented in bold type (Cgw).   Only one groundwater concentration is presented
for tetryl.  The more conservative groundwater concentrations for each chemical were then used
to derive the maximum soil concentration(i.e.,  soil clean-up goal), as described below.

       The estimation of soil remediation goals for protection of groundwater is based on the
following procedure:

       •     The total mass of each explosives compound in the northern industrial areas is
            estimated to be the product of the average concentration of each explosives compound
            in the soil, the fraction of the area that is contaminated, the depth range over
            which each explosives compound is present in soil, and the total area of the portion
            under consideration.

       •     The total mass of each explosives compound is allowed to partition to percolating
            rainwater at a constant rate over 30 years.  The time assumed is a standard
            assumption used in landfill performance estimates (such as the USEPA's Vertical and
            Horizontal Spread [VHS] model).  It is assumed that the total mass of each explosives
            compound will enter the aguifer over the 30 year time interval.  Given the low
            organic carbon content of the subsurface soil at MAAP, a very small fraction of each
            explosives compound is adsorbed to the soil; therefore, this assumption is
            conservative but reasonable.

       •     The volume of groundwater into which the total mass of each explosives compound would
            mix was then estimated from the hydrologic information gathered during the RI.  It
            was conservatively assumed that each explosives compound would mix in the volume of
            groundwater that consists of the sum of the volume of groundwater immediately under
            the northern industrial areas and the volume of groundwater that flows under the
            industrial area over a period of 30 years.  This procedure used a conservative
            estimate for the average velocity of groundwater at MAAP of 72 feet/year.  Using the
            procedures in the draft USEPA Guidance document "Technical Background Document for
            Soil Screening Guidance" (USEPA, 1994c), a mixing depth in the aguifer of 47 feet was
            derived.
                                                  TABIiE  6-6
                 Soil Risk-Based Remediation Goals Based on Groundwater  Ingestion Exposuresa
       Chemical           Acceptable Groundwater                   Soil Remediation Goal
                              Concentration                               (Og/g)
                                 (Og/L)
                      Carcinogenic    Noncarcinogenic         Carcinogenic    Noncarcinogenic
       RDX                  6               79                     10              150
       Tetryl              —              263                     —              500
       2,4,6-TNT           20               13                     41               25

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       •      The average concentration of each explosives compound in groundwater was then
              calculated using mass balance relations.   These estimated concentrations are due to
              leaching of contaminants from soil only,  and do not include existing groundwater
              contamination or the effects of upgradient sources on groundwater quality.

An equation for the concentration of each explosives compound in groundwater that corresponds to
a remediation level in soil of RGs, was then derived:
                          RGs  =       2 * Cgw * DA(vT + W)
                                   farea * Dexp * W *  (6.2 x 103)
where:
Rgs     =   Remediation level for each explosives compound in the soil  (mg/kg);
Cgw     =   Acceptable groundwater concentration  (Og/L)  (see Table 6-6);
DA      =   Mixing depth within the aquifer  (47 ft);
v       =   Groundwater flow velocity  (72 ft/yr);
T       =   Time in which the individual explosives compound leaches from the soil to the
            groundwater (30 yr);
farea  =    Fraction of the surface area of the industrial area that contains the individual
            explosives compound at levels between the method detection limit  (MDL) and the
            soil remediation level RGs (0.005);
Dexp    =   Depth at which the individual explosives compound exists in soil at a concentration
            above the CRL (5 ft); and
W       =   Width of the industrial area in the direction parallel to groundwater flow (1,000ft)
The soil concentrations associated with acceptable groundwater ingestion risks are presented in
Table 6-6, along with associated acceptable groundwater concentrations.

6.4.2  Uncertainty Section

       There is a large degree of uncertainty associated with many of the factors used in risk
assessments.  Consequently, it should be recognized that many uncertainties also are associated
with the soil remediation goals that were calculated in this evaluation.  For example,
uncertainties are associated with exposure assumptions that were made, the toxicity criteria
that were used, and the groundwater fate and transport modeling.  In general, the primary
sources of uncertainty are the following:

       •    Exposure parameter estimation;
       •    data; and
       •    Fate and transport modeling.

       A complete understanding of the uncertainties associated with the soil remediation goals
is critical to understanding how the values should be used.  Each of the sources of uncertainty
listed above and associated with the soil remediation goals are summarized below.

6.4.2.1  lexicological Data.  One of the largest sources of uncertainty is in health criteria
values.  Health criteria for evaluating long-term exposures such as RfDs or CSFs are based on
concepts and assumptions which bias an evaluation in the direction of over-estimation of health
risk.  As USEPA notes in its Guidelines for Carcinogenic Risk Assessment (USEPA 1986a):

       There are major uncertainties in extrapolating both from animals to humans and from high
       to low doses.   There are important species differences in uptake, metabolism,  and organ
       distribution of carcinogens,  as well as species and strain differences in target site
       susceptibility.  Human populations are variable with respect to genetic constitution,
       diet, occupational and home environment,  activity patterns and other cultural factors.

       These uncertainties are compensated for by using upper-bound 95 percent upper confidence
limits for CSFs for carcinogens, and safety factors for RfDs for noncarcinogens.  At best, the
assumptions used here provide a rough but plausible estimate of the upper limit of risk  (i.e.,
it is not likely that the true risk would be much more than the estimated risk, but it could

-------
very well be considerably lower, even approaching zero). More refined modeling in the area of
dose-response calculation (e.g., using maximum likelihood dose-response values rather than the
95 percent upper confidence limits) would be expected to increase the final soil remediation
goals.

There are varying degrees of confidence in the weight-of-evidence for carcinogenicity of a
given chemical. USEPA's (1986a) weight-of-evidence classification provides information that can
indicate the level of confidence or uncertainty in the data obtained from studies in humans or
experimental animals. For example, several of the explosives compounds that were evaluated are
Class C chemicals, possible human carcinogens, for which there is limited evidence of
carcinogenicity in animals. Although RDX and 2,4,6-TNT are both Class C carcinogens, as opposed
to 2,4-DNT, which is a Group B2 carcinogen, the evidence for their carcinogenicity is considered
to be as strong as that of 2,4-DNT. This factor should be considered when determining soil
remediation goals for these explosives compounds. For RDX, the carcinogenic endpoint was used
in deriving a soil cleanup level, and consideration should be given to the fact that this
chemical has a lower certainty of carcinogenicity. For 2,4,6-TNT, the non-carcinogenic endpoint
was used in deriving a soil cleanup level.

For dermal pathways, there is uncertainty associated with the fact that there are no
toxicity values (RfDs and CSFs) that are specific to the dermal route of exposure. To evaluate
the dermal pathway, therefore, absorbed dermal doses were combined with oral toxicity values.
As described previously (see Section 3.2.3.4), the oral toxicity values, typically expressed in
terms of potential (or administered) doses, should be adjusted when assessing the dermal doses,
expressed as internal (or absorbed) doses. In this assessment, absolute oral absorption
fractions from the literature were used to adjust the oral toxicity criteria. The risk
estimates for the dermal pathways may be over- or under-estimated depending on how closely these
values reflect the difference between effects via the oral and dermal routes.

6.4.2.2 Exposure Assessment. There are several major sources of uncertainty in the exposure
assessment portion of deriving soil remediation goals, including the selection of input
parameters used to estimate chemical intakes and the choice of fate and transport models used.
The uncertainties associated with these various sources are discussed below.

The input parameter values used to describe the extent, freguency, and duration of
exposure to soil and groundwater have some uncertainty associated with them. In order to
compensate for the unknown exposure patterns of potential future receptors in the northern
industrial areas of MAAP, very conservative exposure assumptions were used, to ensure that
potential future exposures would not be underestimated. For example, remediation goals were
calculated to be protective of both workers working at the northern industrial areas of MAAP for
250 days/year for 25 years, as well as residents who live at the northern industrial areas and
contact soil and consume groundwater 350 days/year for 30 years. In addition, the overall
scenario that residents would live at the northern industrial areas is very hypothetical and
unlikely to occur. Additional uncertainty is associated with exposure parameters for certain
individuals within an exposed population that may be higher or lower than those assumed in this
evaluation, depending upon their actual intake rates (e.g., groundwater ingestion rates, soil
ingestion rates), nutritional status, body weights, etc. The exposure assumptions that were
used are conservative, and were designed to produce a reasonable upper-bound estimate of
exposure in accordance with USEPA guidelines regarding Superfund site risk assessments.

The assumptions used in the modeling of leaching of contaminants to groundwater are
generally conservative, including the assumption that 100% of the mass of contaminants in soil
eventually leaches to groundwater. In reality, a certain fraction of the contaminants
biodegrades, attenuates by other natural processes such as photolysis, or becomes bound to the
organic material within the soil.

6.4.3 Conclusions

The human health-based remediation goals for explosives compounds in soil are summarized
in Table 6-7 for direct exposures to soil by industrial and excavation workers and by residents,
as well as for protection of groundwater. As noted earlier, use of the more conservative values
for soil remediation goals is recommended, so that future human health risks will not exceed a
risk of 1x10-5 or a hazard index of 1.0. A comparison between clean-up goals associated with
worker and residential soil exposures and protection of groundwater indicates that the more

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conservative goals are based on the protection of groundwater.  As a result, as shown in Table
6-7, the soil remediation goals selected for the northern industrial areas of MAAP are 10/Og/g
for RDX, 25 Og/g for 2,4,6-TNT, and 500 Og/g for tetryl.

       The soil remediation goals derived for this  project are lower than the concentrations of
explosives compounds in approximately 38,000 tons of soil within the northern industrial areas.
This indicates that actual or threatened releases of hazardous substances from this site, if not
addressed by implementing the response action selected in this ROD, may present a current or
potential threat to public health, welfare, or the environment.
                                                  TABIiE  6-7
                                Summary of  Soil Risk-Based Remediation Goalsa
         Chemical           Soil Contact Remediation Goals       Soil Remediation
                                        (Og/g)                       Goals for
                                                                    Groundwater
                                                                     Exposures

                       Industrial      Excavation      Resident       Resident
                         Worker          Worker

        RDX               220            3,500             55               10
        Tetryl          9,400           12,000          2,600              500
        2,4,6-TNT         470              600            130               25

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7.0    DESCRIPTION OF ALTERNATIVES

       Remedial alternatives for the northern industrial area soil were developed to satisfy the
following remedial action objectives:

       •     Protect human health and the environment;
       •     Attain risk-based soil remediation goals to protect workers and groundwater guality
            in the northern industrial areas of MAAP;
       •     Use permanent solutions and treatment methods to the maximum extent possible; and
       •     Achieve a remedy in a cost-effective manner.

7.1    ALTERNATIVE A:   NO ACTION

       The No Action alternative,  Alternative A,  has been developed to provide a basis for
comparing active treatment alternatives.  The NCP and CERCLA, as amended by SARA, require the
evaluation of this alternative as a baseline for comparison of risk reduction achieved by each
treatment alternative.  Under this alterative, no further action would be taken to address
contamination at the site.  For the No Action alternative, it is assumed that the area may be
used for any purpose,  including residential land use.  Because concentrations of explosives
compounds would be allowed to remain on site without remediation, and because explosives
compounds have been detected at concentrations that exceed the soil remediation levels
calculated in Section 6.0, adverse human health effects may occur under this alternative.

       There is no implementation time or cost associated with the No Action alternative because
no additional remedial activities would be implemented at the site.

7.2    ALTERNATIVE B:   LIMITED ACTION

       The Limited Action alternative,  Alternative B, has been developed to provide minimal
actions which may be taken to limit human exposures to the contaminated soil.  Alternative B
would not reduce the toxicity, mobility, or volume of contaminants, but it would reduce the
probability of physical contact with the contaminated soil.  The Limited Action alternative
would include implementation of the following actions:

       •     Institutional restrictions to limit future land uses to industrial usage;
       •     Maintenance of existing fences to prevent trespassers from being exposed to the
            explosives-contaminated soil;
       •     Public education programs; and
       •     Five-year reviews.

       Institutional controls include continued access restrictions,  deed restrictions,  and land
use restrictions.  Access restrictions include administrative actions to levy fines against
trespassers and long-term maintenance of the fences currently in place around the northern
industrial areas.  Deed and land use restrictions would limit the future uses at the individual
sites and require permits, qualified supervision, and health and safety precautions for any
activities conducted in the vicinity of the northern industrial areas.  Education programs would
be developed to inform workers and local residents of the potential site hazards.

       Five-year reviews are required by the NCP at all sites where hazardous chemicals remain at
the site above levels that allow for unlimited used and unrestricted exposure.  The review would
present the analytical data and include a determination of whether additional remedial actions
are required at the northern industrial areas.

       Although this alternative would not result in the treatment of soil or the reduction of
contaminant concentrations, the alternative would limit potential human exposure to the
explosives compounds,  provide a database of site data, and allow evaluation of changes in site
conditions over time.   The estimated capital costs for Alternative B are $27,000, and annual
operation and maintenance  (O&M) costs are approximately $39,000.  The total present worth of
this alternative is $626,000 based on a 30-year project life and a 5% discount rate.

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7.3 COMMON EIiEMENTS OF TREATMENT ALTERNATIVES C AND D

The remaining soil treatment alternatives contain several common features. Except for the
"No Action" and "Limited Action" alternatives (Alternatives A and B), all of the alternatives
being considered include excavation, on-site treatment, and disposal of soil containing
explosives compounds above the risk-based soil remediation goals. Soil that contains explosives
compounds at concentrations higher than the soil remediation goals derived in Section 6.0 would
be removed from the northern industrial areas using conventional excavation eguipment. The
excavated soil would be placed in a storage building to prevent run-on and run-off from the soil
pile. Additionally, in areas where excavation of the explosives-contaminated soil would pose a
safety hazard to workers (e.g., where the stability of a building foundation would be
compromised by excavation), optional engineered caps would be constructed to prevent human
exposure and prevent the migration of explosives compounds to groundwater.

The treatment technologies introduced and described in this section were selected for
their proven ability to treat explosives-contaminated soil.

7.3.1 Soil Excavation

Conventional earthmoving eguipment would be used for excavation of the
explosives-contaminated soil. Soil excavation would not be performed to a depth greater than 10
feet below ground surface.

The concentration of explosives compounds in the soil would determine the areal extent of
excavation. Field test kits capable of analyzing soil for 2,4,6-TNT and RDX, or other
analytical methods, would be used to determine the concentration of explosives compounds in the
soil removed from the excavated section relative to the risk-based remediation goals of 25 Og/g
for 2,4,6-TNT, 10 Og/g for RDX, and 500 Og/g for tetryl. Also, confirmatory sampling would be
performed after excavation to assess whether the remaining soil exceeds the risk-based
remediation goals.

Soil would be stored in a semi-enclosed steel building to prevent windblown contamination,
precipitation run-on to the soil pile, and run-off from the soil pile. Adeguate space would be
provided to ensure that a buffer volume would be stored in the stockpile area. This stockpile
would allow soil treatment to proceed during inclement weather when excavation would be
difficult.

Activities associated with excavation could produce airborne pollutants and particulates.
The Tennessee Air Pollution Control Regulations establish limits for particulate emissions (Rule
1200-3-7.03), fugitive dust (Rule 1200-3-8.01), and visible emissions (Rule 1200-3-5.01).

If excavation activities within the northern industrial areas disrupt over 5 acres of
land, the substantive reguirements of the Tennessee Water Pollution Control Regulations' general
stormwater permit program for construction activities (Rule 1200-4-10.05) would need to be met.
This permit program reguires that a management plan be developed to control contaminant
migration in stormwater runoff.

7.3.2 Estimated Soil Volume

Insufficient data are presently available to precisely estimate the volume of soil to be
remediated. Based on the results of soil sampling at Line B, it has been estimated that 38,000
tons of soil within the northern industrial areas may reguire remediation.

7.3.3 Optional Engineered Caps

There are certain areas within the northern industrial areas where excavation of the
soil containing explosives compounds above the soil remediation goals is not feasible.
Specifically, in areas where washout of buildings deposited explosives compounds in the soil
next to buildings and where the explosives compounds have infiltrated the soil immediately
adjacent to the building foundations, the excavation of this soil could adversely affect
building stability. In other areas, disposal of explosives-laden water may have occurred in
areas that are now covered by buildings or paved areas. Under this option, select areas of
explosives contaminated soil would be left in place and engineered caps (or existing building or

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paved areas) would be used to prevent the infiltration of rainwater. The use of engineered
caps would reduce direct exposure to the contaminants within the soil and would protect
groundwater quality. The optional engineered cap option would be exercised only for the
contaminated soil immediately adjacent to building foundations or areas already covered by
buildings or paved areas.

The optional engineered caps would be designed and maintained to prevent the infiltration
of water through the contaminated soil. For each area in which the optional engineered cap
option is exercised, the Army will provide a summary report to the USEPA and the State of
Tennessee that describes the conditions of the soil and the reason for use of the cap option.

7.3.4 Other Assumptions Used In the Cost Estimates

Details of the treatment system would be determined in the Remedial Design phase.
Implementation of a treatment alternative would require the construction of a treatment building
and parking/staging area; building heating and lighting; and a five-year review of site
conditions if the engineered cap option is exercised. The cost estimates are based on vendor
information and construction unit costs. These estimates are only preliminary estimates and are
subj ect to change.

7.4 ALTERNATIVE C: EXCAVATION/STORAGE/INCINERATION/BACKFILL

This alternative would consist of the excavation and temporary storage of soil from the
northern industrial areas that contains explosives compounds above the risk-based remediation
goals, followed by treatment of the excavated soil by incineration. This technology has been
used successfully at other sites to treat explosives-contaminated soil and can achieve the
irreversible destruction of greater than 99.99% of the explosives compounds (by mass) in the
excavated soil. The treated soil would then be used as backfill for the areas where
explosives-contaminated soil was excavated or in other areas. Clean topsoil from a borrow area
at MAAP would be used to resurface the backfilled areas, and the areas would be revegetated. In
addition, optional engineered caps would be used to cover explosives-contaminated soil in areas
where excavation is infeasible.

Under Alternative C, an estimated soil mass of 38,000 tons would be excavated and treated.
A small percentage of this soil may be left in place and covered with an engineered cap, if
warranted. It is expected that the incineration process would reduce the concentrations of
explosives compounds in soil to below the soil remediation goals (listed in Table 6-7). This
would result in risk reduction from the present unacceptable levels to 10-5, which is within the
USEPA's acceptable risk range.

To implement this technology, a source of auxiliary fuel would be required to maintain the
temperature within the incinerator. Residuals from this process would include the inert ash and
flue gases. One limitation of this technology is the potential for release of toxic metals into
the atmosphere via the combustion off-gases, a situation which is difficult to control using
conventional air pollution equipment. However, it is expected that the concentrations of metals
in the soil at MAAP are not high enough to pose an air pollution problem.

The ARARs that apply to this alterative include all of the ARARs listed in Section 7.3.1
for excavation. In addition, Federal regulations for hazardous waste incinerators (40 CFR 264
Subpart 0) would be ARARs for this action. Under these regulations, certain exemptions apply to
incinerators which destroy waste that is listed solely for reactivity and contains none of the
constituents listed in 40 CFR 261, Appendix VIII. The RCRA requirements for incinerators
include:

• Waste analysis prior to the startup of incineration and periodically thereafter;
• Treatment of principal organic hazardous constituents (POHCs) to a destruction and
removal efficiency (ORE) of 99.99 percent;
• Specific stack emissions controls for hydrochloric acid, particulates, and carbon
monoxide; and
• Incineration only when operating within design conditions.

To meet the DRE performance requirements, testing of ash from the incinerator is required. The
ash must also be tested to demonstrate that the residue is not a hazardous waste, according to

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RCRA definitions. If the residue is determined to be hazardous, it must be managed in
accordance with the applicable requirements of RCRA found in 40 CFR Parts 262-266.

The Federal Clean Air Act and Tennessee Air Pollution Control Regulations [Rule
1200-3-6.02(3)] would be applicable to stack emissions resulting from incineration. The
requirements are extensive and include providing the best practicable treatment of air
contaminant emissions, complying with specific emission standards, and providing for monitoring
and testing. The Tennessee Air Pollution Control Regulations establish particulate emission
limits based on a percentage of the charging rate to the unit. Particulate emissions limits are
0.2 percent of the charging rate for a charging rate of 2,000 pounds/hour or less to the
incinerator; particulate emissions from incinerators charging over 2,000 pounds/hour are limited
to 0.1 percent of the charging rate.

Incineration activities would have to comply with substantive requirements of the
Tennessee Water Pollution Control Regulations' general stormwater permit program for industrial
activities (Rule 1200-4-10.04). This permit program requires that a management plan be
developed to control contaminant migration in stormwater runoff. Tennessee Water Quality
Standards (Rule 1200-4-3), which require treatment of wastewater to comply with water quality
standards, would also be applicable. This rule would require incinerator scrubber blowdown
water to be treated as necessary prior to discharge. An incinerator would be considered a new
source of industrial wastewater and would thus be required to comply with Tennessee Effluent
Limitations and Standards (Rule 1200-4-5). This requires new sources to meet certain
chemical-specific effluent limitations and to meet standards of performance for new sources.
Siting, permitting (as applicable), operation, closure, and post-closure of an incinerator must
comply with Tennessee Solid Waste Processing and Disposal Regulations (Rule 1200-1-7). Disposal
of treatment residuals generated by incinerators (or any other treatment process) would be
governed by the Tennessee Solid Waste Disposal Act (Title 68, Chapter 31). This law applies to
non-hazardous residuals generated by any treatment process and provides for their safe disposal
to prevent, control, and abate pollution caused by solid waste. Operating and maintenance
requirements are also stipulated by this law.

For treatment residuals that are determined to be a hazardous waste (as defined in 40 CFR
Part 261), the following requirements would apply:

• The hazardous waste recordkeeping and reporting requirements of 40 CFR 262.40;
• The hazardous waste recordkeeping and reporting requirements of Rule 1200-1-11.03-10
(Rules of the Tennessee Department of Environment and Conservation); and
• Disposal of the hazardous waste at a permitted facility in accordance with 40 CFR
Part 264.

The Land Disposal Restrictions established by the USEPA under RCRA are ARARs for the soil
that displays the characteristic of toxicity as defined by 40 CFR 261.24. These restrictions
require that the soil be treated until it no longer displays the characteristic of toxicity
prior to being land-disposed.

Remediation of the explosives-contaminated soil within the northern industrial areas is
expected to take from 27 to 33 months from the design stage through final decommissioning of the
incinerator. The total net present worth of Alternative C is estimated at $24,700,000, which is
calculated over 30 years at a discount rate of 5%. This includes capital costs of $24,100,000
and annual O&M costs of $40,000.

7.5 ALTERNATIVE D: EXCAVATION/STORAGE/WINDROW COMPOSTING/ON-SITE LANDFILL

Soil excavation and storage for this alternative would be similar to that for Alternative
C. Clean soil from a borrow area at MAAP would be used as backfill for the excavated areas.

A method of biological soil treatment known as windrow composting would be used to reduce
the concentrations of explosives compounds in the soil. This method consists of mixing the soil
with sources of organic carbon and bulking agents such as wood chips, straw, and manure. The
mixture would be formed into long piles called windrows. Microorganisms would biotransform and
biodegrade the explosives compounds within the mixture. Treatment with windrow composting would
reduce the toxicity and the concentrations of explosives compounds in the excavated soil. The
concentrations of the principal explosives compounds would be reduced by approximately 90%.

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7.5.1  Summary of Windrow Composting Studies

       Bench- and field-scale studies have been performed at Umatilla Depot Activity (UMDA)  using
windrow composting on explosives-contaminated soil.  Static-pile composting tests have also been
conducted at Louisiana Army Ammunition Plant (LAAP).   The results of these studies indicate that
composting was effective in reducing both explosives concentrations and the toxicity of the
explosives-contaminated soil (USAEC, 1988; USAEC, 1991b).  Large reductions in 2,4,6-TNT,  RDX,
and HMX were observed during studies performed at LAAP under both mesophilic (35°c) and
thermophilic (55°c) conditions.  Total explosives concentrations were reduced from 16,460 Og/g
and 17,870 0/g to 326 0/g and  74 Og/g  for the mesophilic  and  thermophilic  piles,  respectively.
The results of these studies indicated that higher explosives degradation rates occur under
thermophilic conditions (USAEC, 1988).

       In addition, field studies have been performed at UMDA to further evaluate the windrow
composting process (USAEC,  1993).  Aeration studies were performed on windrows with 30 percent
soil by volume to evaluate the effects of aeration on thermophilic composting.   The results of
these studies indicate that windrow composting destroys not only target explosives compounds but
also extractable explosives intermediates under both aerated and unaerated conditions.  The
concentrations of the principal explosives compounds and two of the 2,4,6-TNT metabolites for
the 40-day composting period are graphed in Figure 7-1.  As shown in the graphs,  the
concentrations of intermediates increased during the first 10 days of the studies and then began
to decrease by day 15.  The increase in the concentration of intermediates is due to the
biotransformation of 2,4,6-TNT, and the decrease in the concentration of intermediates is due to
the transformation of the intermediates into other compounds which serve as the ultimate end
products of 2,4,6-TNT biotransformation (USAEC,  1993).

       Tests were also performed on leachate extracted from samples collected over the 40-day
composting studies.  The results of analysis of the leachate indicate that a significant
reduction in the concentrations of explosives compounds and degradation intermediates occurred
in the compost leachate, as shown in Figure 7-2.  As in the compost, the concentration of
intermediates in the leachate increased and then began to decrease due to the transformation of
the intermediates into other compounds.  It should be noted that the leachate samples from the
unaerated windrow contained lower levels of explosives compounds and intermediates than the
aerated windrow  (USAEC, 1993).

       Other results of the composting pilot studies,  as determined from work by Oak Ridge
National Laboratory (ORNL)  (Griest, et al., 1994), are as follows:

       •    Concentrations of aminonitroaromatic intermediates were significantly reduced after
            1540 days of composting.  Most products were not identified; non-degraded explosives
            compounds, amino derivatives,  azo compounds, carbon dioxide, and other identifiable
            species accounted only for a small fraction of the original loading of nitrogen
            compounds.

       •    Solvent extracts of aerated and non-aerated composts showed a reduction in
            mutagenicity (as determined by the Ames Assay) of better than 99 percent after 40
            days of composting  (Figure 7-3).

       •    Weakly acidic extracts showed marked decreases in toxicity  (lethality and
            reproduction effects using Ceriodaphnia dubia); most of the initial leachable
            toxicity was removed after 40 days of composting.

       •    A simulated 1000-year acid rain leaching test  (modified USEPA Synthetic Precipitation
            Leaching Test),  conducted either before or after irradiation of the composted
            material by ultraviolet light, indicated that less than 10 percent of the 2,4,6-TNT
            transformation products were leachable.

       Available data from prior studies strongly suggest that the explosives compounds normally
act as electron acceptors during biodegradation of compost materials by microorganisms, and are
transformed into reduced intermediate species such as amines or azo compounds in the process.
The reaction reguires proper conditions of temperature and moisture content, as well as close
proximity of three components:   a source of energy (electron source) in the form of oxidizable
substances that can be metabolized; a sufficient supply of appropriate organisms; and a

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sufficient supply of the electron acceptor (electron sink) molecules. (The presence of
essential nutrients such as phosphorus and trace metals also is important). Metabolism results
in growth and reproduction of the organisms, formation of metabolic and biotransformation
products, and corresponding depletion of the energy source and the electron acceptor materials.
This reguirement to aggregate three (or four) separate materials accounts for the observations
that thorough mixing is important if composting is to be effective. Mixing may be even more
important for treatment of soil containing low concentrations of explosives compounds, because
depletion could easily occur on a local scale.

Mixing and aeration also may play an important role in the temperature control that is
necessary for optimizing the microbial growth rate. However, optimal conditions for the
nitro-compounds to participate also reguire the absence or depletion of more aggressive
oxidizers (i.e., materials with a higher oxidation-reduction potential) such as free oxygen and
nitrate ions. Moderate to high concentrations of less aggressive oxidizers such as sulfate,
iron(III), and manganese(IV) compounds also may compete unfavorably with the nitro-compounds
during the composting process. Thus, mixing, which results in aeration of the compost, probably
hinders the reduction of nitro-compounds; in fact, reduction probably does not occur until the
available oxygen is locally depleted.

7.5.2 Conclusions from Previous Studies

Several studies have been performed at other Army ammunition plants using windrow
composting to treat explosives-contaminated soil. These studies have found that during the
degradation of the principal explosives compounds, intermediate compounds are formed, some of
which cannot be identified using laboratory analytical technigues and have an unknown level of
toxicity. However, during the bioremediation process, the leachate from the soil undergoing
treatment becomes progressively less mutagenic (as measured using the Ames assay) and less toxic
to aguatic species. The results of these studies also indicate that during composting, the
intermediate compounds become tightly bound to the soil matrix. Therefore, the leachability of
explosives compounds and intermediate compounds from soil treated with windrow composting is
less than that of untreated soil.

7.5.3 Other Elements of Alternative D

Because this alternative would not remove all of the contaminants from the soil, the
treated soil would be placed in a solid waste landfill to ensure that any explosives compounds
remaining in the soil are contained. The design of the landfill would include a liner, and
final closure would incorporate an impermeable cap over the landfill. The liner would extend to
all areas which would be in contact with the treated soil. The cap for the landfill would
provide long-term control of liguid migration through the solid waste landfill. Because the
biodegradation process would continue after the soil has been landfilled, ultimately, the
process will result in complete destruction of the toxic contaminants.

Post-closure care of the landfill and cap would be performed to ensure that the final
contours and drainage of the cap and surrounding area would be maintained. A post-closure
groundwater monitoring program would be implemented to determine if contaminants from the
landfill are entering the groundwater.

In addition, optional engineered caps would be used to cover explosives-contaminated soil
in areas where excavation would pose a safety hazard to workers.

Under Alternative D, an estimated mass of soil of 38,000 tons would be excavated and
treated. A small percentage of this soil may be left in place and covered with an engineered
cap, if warranted. Based on the results from other sites in which windrow composting has been
utilized, it is expected that the bioremediation process is capable of reducing the
concentrations of explosives compounds in soil to less than 20 Og/g for 2,4,6-TNT and less than
20 0/g for RDX during a batch composting time of 40 days. The treated soil would then be
placed in a RCRA Subtitle D solid waste landfill. Because there would then be no potential for
human or ecological exposure to the treated soil, this alternative would result in risk

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reduction from the present unacceptable levels to 10-5, which is within the USEPA's acceptable
risk range.

To implement this technology, a source of organic carbon and bulking agents is needed,
such as cow manure, chicken manure, sawdust, potato waste, straw, wood chips, etc. Because MAAP
is located in a rural area, there are multiple sources available. An adeguate supply of the
appropriate microorganisms must also be available. Microorganisms indigenous to the soil at
MAAP will be used in the process. Both the moisture content and the temperature of the windrow
piles should be controlled at optimal values for the remediation process to occur. Treatability
testing of different sources of organic carbon, moisture content of the windrow piles, and
temperature should be performed prior to full-scale use of this technology in order to select
the most cost-effective combination of parameters.

The only treatment residual from this process is the treated soil. Because the treated
soil may contain unidentifiable intermediate compounds for several years, the treated soil must
be managed to reduce the likelihood that direct contact with the soil or leaching of compounds
from the soil to groundwater will occur. During the treatment process, leachate from the soil
would be managed to prevent the contamination of other areas.

The treated soil would be suitable for placement in a RCRA Subtitle D solid waste landfill
when it contains less than 20 Og/g of 2,4,6-TNT, less than 20 Og/g of RDX, passes the toxicity
characteristic leaching procedure (TCLP) as detailed in 40 CFR 261.24, and passes the Paint
Filter Liguid Test (SW-846, Method 9095).

The ARARs that apply to this alternative include all of the ARARs listed in Section 7.3.1
for excavation. Construction, operation, and closure of the on-site solid waste landfill used
to dispose of treated soil would be performed in compliance with the Tennessee Solid Waste
Processing and Disposal Regulations (Rule 1200-1-7.04) for Class II disposal facilities, which
are applicable to this action. Construction of the optional engineered caps would also be
performed in compliance with the criteria specific to cap construction within these regulations.

The Land Disposal Restrictions established by the USEPA under RCRA are ARARs for the soil
that displays the characteristic of toxicity as defined by 40 CFR 261.24. These restrictions
reguire that the soil be treated until it no longer displays the characteristic of toxicity
prior to being placed in a landfill.

Remediation of the explosives-contaminated soil within the northern industrial areas is
expected to take approximately 75 months from the design stage through installation of the RCRA
Subtitle D solid waste landfill cap. The estimated capital costs for Alternative D are
$15,800,000, and the annual O&M costs are estimated at $44,000. The total present worth of this
scenario is $16,500,000 (30 years at a 5% discount rate).

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8.0    SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES

       This section evaluates and compares each of the alternatives described in Section 7.0 with
respect to the nine criteria used to assess remedial alternatives as outlined in Section 300.430
(e) of the NCP.  Each of the nine criteria are briefly described below.  The alternatives which
include excavation, treatment, and disposal of the explosives-contaminated soil  (Alternatives C
and D) were designed to meet the threshold criteria of protection of human health and the
environment and compliance with ARARs.  To aid in identifying and assessing relative strengths
and weaknesses of the different remedial alternatives, this section provides a comparative
analysis of the alternatives.  As previously discussed, the alternatives are as follows:

       •    Alternative A:  No Action;
       •    Alternative B:  Limited Action;
       •    Alternative C:  Excavation/Storage/Incineration/Backfill; and
       •    Alternative D:  Excavation/Storage/Windrow Composting/On-Site Landfill.

8.1    NINE EVALUATION CRITERIA

       Section 300.430 (e) of the NCP lists nine criteria by which each remedial alternative must
be assessed.  The acceptability or performance of each alternative against the criteria is
evaluated individually so that relative strengths and weaknesses may be identified.

       The detailed criteria are briefly defined as follows:

       •    Overall Protection of Human Health and Environment is used to denote whether a remedy
            provides adeguate protection against harmful effects and describes how human health
            or environmental risks are eliminated, reduced, or controlled through treatment,
            engineering controls, or institutional controls.

       •    Compliance with ARARs addresses whether a remedy will meet all of the applicable or
            relevant and appropriate reguirements of Federal and State environmental statutes or
            if the remedy provides a basis for invoking a waiver.

       •    Long-term Effectiveness and Permanence refers to the magnitude of residual risk and
            the ability of a remedy to maintain reliable protection of human health and the
            environment,  over time, once clean-up goals have been met.

       •    Reduction of Toxicity, Mobility, or Volume through Treatment is the anticipated
            performance of the treatment technologies employed in a remedy.

       •    Short-term Effectiveness refers to the speed with which the remedy achieves
            protection, as well as the potential to create adverse impacts on human health and
            the environment during the construction and implementation period.

       •    Implementability is the technical and administrative feasibility of a remedy,
            including the availability of materials and services needed to implement the chosen
            solution.

       •    Cost includes both capital and O&M costs.

       •    State Acceptance indicates whether, based on its review of the RI/FS Report and
            Proposed Plan, the State concurs with, opposes, or has no comment on the preferred
            alternative.

       •    Community Acceptance is assessed following a review of the public comments received
            on the RI/FS Report and the Proposed Plan.

       The NCP (Section 300.430 (f))  states that the first two criteria,  protection of human
health and the environment and compliance with ARARs, are "threshold criteria" that must be met
by the selected remedial action.  The next five criteria are "primary balancing criteria", and
the trade-offs within this group must be balanced.  The preferred alternative will be that

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alternative which is protective of human health and the environment, is ARAR-compliant, and
provides the best combination of primary balancing attributes. The final two criteria, State
and community acceptance, are "modifying criteria" which are evaluated following comment on the
RI/FS reports and the Proposed Plan.

8.2 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT

The concentrations of explosives compounds that presently exist in the northern industrial
area soil potentially pose the risk of adverse health effects to workers and future hypothetical
residents. Alternative A (No Action) would not meet this criterion because no actions would be
taken to eliminate, reduce or control exposure pathways. Therefore, Alternative A is eliminated
from the comparison of the alternatives.

Alternative B, Limited Action, would provide some additional protection from contaminated
surface soil by implementing and maintaining restrictions such as site security and fencing,
which limits both site access and exposure. Although actions would be taken to prevent access
to areas of contaminated soil, nothing would be done to protect groundwater quality; therefore,
Alternative B would not be protective of human health and the environment. For this reason,
Alternative B is also eliminated from the comparison of the alternatives.

Alternatives C and D would provide additional protection of human health and the
environment by removing soil containing explosives compounds above the risk-based remediation
goals of 25 Og/g for 2,4,6-TNT, 10 Og/g for RDX, and 500 Og/g for tetryl. Alternatives C and D
would remove contaminated surface soil to a maximum depth of 10 feet and treat the soil with
incineration and windrow composting, respectively. Alternatives C and D would provide
protection of human health and the environment by eliminating the surface soil exposure pathway
and providing protection to the groundwater. Long-term maintenance of the landfill cap under
Alternative D would be required.

The optional engineered caps under Alternatives C and D would provide a physical barrier
above the explosives-contaminated soil, which would minimize the leaching of contaminants to
groundwater. Long-term maintenance of the optional engineered caps would be required.

8.3 COMPLIANCE WITH ARARS

Compliance with ARARs is a threshold criterion which must be met by the proposed remedial
action, unless a waiver is justified. There are no promulgated standards governing
concentrations of explosives compounds in soil; therefore, chemical-specific ARARs do not apply
to Alternatives A, B, C, or D.

Because remedial activities would not be implemented under Alternatives A and B,
location-specific and action-specific ARARs also do not apply. Alternatives C and D involve
further actions to eliminate potential exposure to soil containing explosives compounds above
the risk-based remediation goals. Excavation of soil containing explosives compounds could be
performed in compliance with the action- and location-specific ARARs identified in Section
7.3.1. Soil incineration and backfilling the treated soil (Alternative c), or windrow
composting and placing the treated soil in a solid waste landfill (Alternative D) could be
performed in compliance with the action- and location-specific ARARs listed in Sections 7.4 and
7.5.

8.4 LONG-TERM EFFECTIVENESS AND PERMANENCE

Alternatives A and B would not provide long-term effectiveness and permanence. These
alternatives would not reduce the risk posed to workers or provide protection of groundwater.

Alternatives C and D would provide effective and permanent protection in the long term
through the excavation and removal of soil with concentrations of explosives compounds above the
risk-based remediation goals of 25 0/g for 2,4,6-TNT, 10 Og/g for RDX, and 500 0/g for tetryl.
The explosives compounds in the soil would be destroyed by incineration (Alternative c), or the
soil would be treated using windrow composting (Alterative D). Under Alternative D, the
biologically-treated soil would then be isolated in a solid waste landfill. The human and
ecological exposure pathways would be eliminated using these alternatives, and groundwater
quality would be protected.

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Alternative C would incorporate incineration as the treatment method to provide the
greatest degree of long-term effectiveness and permanence. Incineration could achieve the
irreversible destruction of greater than 99.99 percent of the explosives compounds in the
excavated soil. The treated soil would be backfilled, covered with topsoil, and revegetated.

Alternative D would utilize windrow composting as the treatment method to reduce the
concentrations of explosives compounds and the leachable toxicity of the excavated soil. The
treated soil would be disposed in an on-site solid waste landfill in order to contain any
non-biodegraded explosives compounds. Therefore, Alternative D would provide permanent
reduction in risk to workers and future residents, and would protect groundwater guality.

The optional engineered caps proposed under Alternatives C and D would provide long-term
isolation of explosives contaminated soil, and would prevent contaminant leaching to
groundwater. Human exposures to surface soil via direct contact and incidental ingestion would
be eliminated and groundwater guality would be protected.

8.5 REDUCTION OF TOXICITY, MOBILITY, OR VOLUME THROUGH TREATMENT

Alternatives A and B would not provide any reduction of toxicity, mobility, or volume of
the contaminants because removal or treatment of the contaminated soil would not be components
of these alternatives.

Alternative C would involve excavation of the soil containing explosives compounds at
concentrations higher than the risk-based remediation goals of 25 0/g for 2,4,6-TNT, 10 Og/g
for RDX, and 500 Og/g for tetryl. The explosives compounds in the excavated soil from the
northern industrial areas would be destroyed by incineration, thereby reducing the toxicity,
mobility, and volume of contaminants.

Alternative D would involve excavation of the soil containing explosives compounds at
concentrations higher than the risk-based remediation goals of 25 Og/g for 2,4,6-TNT, 10 0/g
for RDX, and 500 0/g for tetryl. The concentration of explosives compounds and the leachable
toxicity of the excavated soil would be reduced using windrow composting. The volume of the
contaminants would be reduced, and the biological treatment would bind the degradation products
into the soil matrix. The treated soil would be disposed in an on-site solid waste landfill,
thus minimizing the mobility of the contaminants and their associated biodegradation byproducts,
while allowing the biological activity to continue toward complete destruction of the explosives
compounds.

The statutory preference for treatment as a remedial method would not be satisfied by the
optional engineered caps proposed for Alternatives C and D. All soil that is presently
contaminated with explosives compounds would remain on site under the optional engineered caps,
with the concentrations of explosives compounds unchanged except for intrinsic biodegradation.

8.6 SHORT-TERM EFFECTIVENESS

Short-term protection of the public, workers, or the environment would be met by
Alternatives A and B because no remedial actions would be implemented at the northern industrial
areas. Alternatives C and D would each provide for short-term protection of the public,
workers, and the environment during implementation. The use of proper dust suppressant measures
would control windblown emissions of contaminated dust to protect the community and on-site
workers. Proper personal protective eguipment would be reguired for site workers. Sediment and
erosion control would be provided to protect the environment.

The length of time which would be reguired to implement the remediation alternatives
follow in increasing order: Alternative B, Alternative C, and Alternative D. Alternative B,
the Limited Action alternative, could be implemented in 1 year. Under Alternative C,
approximately 12 months would be reguired to design and procure materials for excavation and
thermal treatment and approximately 15 to 21 months would be reguired to treat the soil. Under
Alternative D, approximately 12 months would be reguired to design and procure all necessary
eguipment for excavation and windrow composting and approximately 57 months would be reguired to
treat the excavated soil from the northern industrial areas. In addition, approximately 6
months would be reguired to install the impermeable cap on the solid waste landfill.

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Incineration may pose a higher risk to workers and the nearby residents than the
bioremediation alternative because of the potential for release of toxic metals in the flue gas,
a situation which is difficult to control using conventional air pollution equipment. However,
it is expected that the concentrations of metals in the soil at MAAP are not high enough to pose
an air pollution problem.

8. 7 IMPIiEMENTABILITY

Alternatives A and B would be the most easily implemented. Alternative A would require no
change in existing controls, and nearly all components of Alternative B are already in place.

Implementation of Alternatives C and D would consist of excavation, treatment, and
disposal of soil containing explosives compounds above the risk-based soil remediation goals.
The equipment and materials required for the optional engineered caps proposed under
Alternatives C and D are commercially available.

The incineration technology selected for Alternative C has been demonstrated to be easily
implementable for the remediation of explosives-contaminated soil at other sites. The
reliability of the rotary kiln incineration technology is very high; typically, incinerators
treat soil approximately 80 percent of the time with 20 percent downtime for periodic
maintenance.

Alternative D would use windrow composting to reduce the levels of explosives compounds
and the toxicity of the excavated soil. Windrow composting would be easily implementable
because all equipment required for treatment is commercially available, and the technology has
been successfully implemented at other Army ammunition plants to remediate soil contaminated
with explosives compounds.

8.8 COST

The estimated costs for Alternatives A through D are presented in Table 8-1. Total
capital and annual costs and present worth (discount rate of 5 percent) for each alternative are
presented. The progression of total present worth from the least expensive to the most
expensive alternative is: Alternative B, Alternative D, and Alternative C. Although
Alternative B has the lowest estimated costs, it does not meet the threshold criterion of
protection of human health and the environment. Alternative C would be more costly than
Alternative D because it would use rotary kiln incineration to treat the soil instead of windrow
composting.

The cost estimates contain a significant degree of uncertainty in both the capital and O&M
costs. The soil treatment costs for each of the treatment alternatives have the greatest degree
of uncertainty. Final prices for the treatment units may be considerably lower after
competitive bidding and vendor discounts.

8 . 9 STATE ACCEPTANCE

The State of Tennessee concurs with the selection of Alternative D.

8.10 COMMUNITY ACCEPTANCE

Comments from the April 25, 1995, Public Meeting were transcribed and are included in the
Responsiveness Summary (Appendix A). All comments received at the Public Meeting were favorable
toward the selection of Alternative D. One set of written comments was received during the
Public Comment Period; responses to these comments are also included in Appendix A.

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                                                  Table  8-1
                            Summary  of Estimated Costs  for Alternatives B Through D

                                                              Costs In 1994 Dollars
                                                                                 Present Worth
Alternative        Description                                        Annual       (30 years,
                                                    Capital Cost     O&M Cost      5% discount
                                                                                      rate)

    B          Limited Action                            $27,000      $39,000         $626,000
               Excavation/Storage/

    C          Incineration/                         $24,100,000      $40,000      $24,700,000
               Backfill and Cover with Topsoil
               Optional Engineered Caps

               Excavation/Storage/
    D          Windrow Composting/                   $15,800,000      $44,000      $16,500,000
               On-Site Landfill
               Optional Engineered Caps
8.11   SUMMARY OF DETAIIiED EVALUATION

       The following is a brief summary of the evaluated alternatives:

       •    Alternatives A and B would not be protective of human health and the environment.
            Therefore, these alternatives are eliminated from consideration.

       •    Alternatives C and D would remove soil contaminated with explosives compounds above
            the risk-based remediation goals of 25 Og/g for 2,4,6-TNT,  10 Og/g for RDX, and  500
            Og/g for  tetryl from surface soil and subsurface soil  (to a maximum depth of 10  feet)
            through excavation.  The excavated soil would then be treated and disposed in
            compliance with State and Federal laws and regulations.  The optional engineered caps
            would provide long-term isolation of explosives- contaminated surface soil,  and would
            prevent contaminant leaching to groundwater in areas where  excavation would pose a
            safety hazard to workers.

       •    Alternative C would involve the use of incineration, which would permanently destroy
            the explosives compounds to very low levels.

       •    Alternative D would involve the use of a biological treatment method known as windrow
            composting.  The biologically-treated soil would be disposed in an on-site solid
            waste landfill to contain any remaining non-degraded explosives compounds.  Windrow
            composting is a proven and cost-effective method of reducing the levels of explosives
            compounds and the associated toxicity of explosives-contaminated soil.

       •    Alternative D would provide the same level of risk reduction as Alterative C at a
            significantly lower cost.

       Based on the comparative analysis of alternatives as presented in this section, the
selected remedy is Alternative D.

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9.0 SEIiECTED REMEDY

Based upon consideration of the requirements of CERCLA, the detailed analysis of the
alternatives, and public comments, the Army, with the concurrence of the USEPA and TDEC, has
determined that implementation of Alternative D (excavation, windrow composting, and disposal in
an on-site landfill, and the optional engineered caps) is the most appropriate remedy for the
explosives-contaminated soil in the northern industrial areas of Milan Army Ammunition Plant in
Milan, Tennessee.

This remedy includes the design and implementation of a remedial action to protect human
health and the environment. The goal of this remedial action is to prevent worker exposure to
the explosives compounds in the soil and protect groundwater quality through the excavation of
soil containing explosives compounds above risk-based remediation goals.

The implementation time for Alternative D is approximately 75 months. This time estimate
includes the treatment system design and review, and preparation of bid packages, Following the
design phase, the system construction will begin. This includes selection of contractors and
equipment suppliers, installation, and start up. Although this section presents details of the
selected remedy, some changes may be made based on the remedial design and construction
processes.

9.1 SOIL EXCAVATION

The implementation of Alternative D will include the excavation of soil in the northern
industrial areas which contains explosives compounds above the soil remediation goals (25 Og/g
for 2,4,6-TNT, 10 Og/g for RDX, and 500 0/g for tetryl) to a maximum depth of 10 feet below
ground surface. Soil obtained from a clean borrow area at MAAP will be used as backfill for the
excavated areas.

Based on the results of sampling at Line B, the total volume of explosives-contaminated
soil to be excavated has been estimated to be 38,000 tons. The rate of excavation will be
adjusted to ensure that a buffer volume would be stored in the stockpile area. This stockpile
will allow windrow composting to proceed during inclement weather when excavation is difficult.
The stockpile will be located in a semi-enclosed building to prevent windblown contamination,
precipitation run-on to the soil pile, and run-off from the soil pile.

The actual volume of soil to be excavated will be based on analysis of soil samples
collected during excavation. Field test kits capable of analyzing soil for 2,4,6-TNT and RDX
will be used to determine the concentration of explosives compounds in the soil removed from the
excavated section relative to risk-based remediation goals. Also, confirmatory sampling would
ensure that the concentrations of explosive compounds in the remaining soil do not exceed
risk-based remediation goals. Because of the limited data presently available concerning the
vertical and horizontal extent of the explosives-contaminated soil in the northern industrial
area, the locations of the areas requiring excavation have not been determined. These
parameters will be determined during the construction phase.

9.2 TREATMENT AND DISPOSAL COMPONENTS: ALTERNATIVE D

Windrow composting is a static pile method of reducing the levels of explosives compounds
and the leachable toxicity of explosives-contaminated soil. In the composting system,
explosives-contaminated soil will be added to an amendment mixture (sawdust, alfalfa, potato
waste, cow manure, and chicken manure) at 30 percent by volume. Treatability studies will be
conducted using locally-available amendments to evaluate the most cost-effective mixture of
amendments that results in adequate bioremediation of the explosives compounds. In addition,
both the moisture content of the windrow piles and the temperature will be varied to find the
optimal range.

Windrows will be formed in an enclosed building to prevent run-on from precipitation. The
building floor will be sloped to allow leachate to drain into a collection sump. The leachate

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will be tested periodically for explosives compounds and to maintain the proper moisture content
of the windrows. The windrows will be turned over periodically using a windrow turner to mix
the compost. The temperature and moisture content of the soil will be monitored in order to
ensure that optimal treatment conditions are maintained.

The composting medium will be maintained for a period of 40 days. During the winter
months, the microorganisms within the compost may biodegrade the explosives compounds at a
slower rate due to the lower ambient temperatures; therefore, treatment during the winter months
may reguire up to 85 days. After this time period, samples of the compost will be collected and
analyzed for explosives compounds, TCLP, and the Paint Filter Liguid Test. If the compost
contains either 2,4,6-TNT or RDX above 20 Og/g or fails TCLP, it will remain in the windrow for
further treatment. If the soil fails the Paint Filter Liguid Test, it will be solidified
through the addition of amendments.

Treated soil will be placed in a solid waste landfill and compacted. Therefore, the soil
will be isolated from human and ecological receptors and contaminants will not leach to the
groundwater while biological activity continues to occur. Operating eguipment for the landfill
includes excavation, spreading, and compaction eguipment.

The on-site landfill will be designed to comply with all applicable State and Federal
regulations and permitting procedures for solid waste landfills. The design of the landfill
will include a liner, and final closure will include an impermeable cap over the landfill. The
siting, design, construction, operation, and maintenance of the landfill shall be in accordance
with Rule 1200-1-7.04 (Rules of the Tennessee Department of Environment and Conservation) for
Class II landfills.

The impermeable cap will be installed after the excavated soil from the northern
industrial areas has been treated and the final grade of the landfill has been reached. The cap
for the landfill will provide long-term minimization of liguids migration through the solid
waste landfill. The permeability of the cap must be less than or egual to that of the liner
system. Grading of the landfill will be designed to minimize run-on to the landfill, maximize
precipitation drainage off the landfill, and minimize cap erosion.

9.3 OPTIONAL ENGINEERED CAPS

There are certain areas within the northern industrial areas where excavation of the soil
containing explosives compounds above the soil remediation goals is not feasible. Under this
option, select areas of explosives-contaminated soil will be left in place and engineered caps
will be placed over areas in which the soil contains explosives compounds above risk-based
remediation goals. The use of engineered caps will reduce direct exposure to the contaminants
within the soil and protect groundwater guality. The engineered caps will be constructed of
low-permeability materials and will completely cover the contaminated soil.

9.4 MONITORING

Post-closure care of the landfill and cap will be performed for a minimum of 30 years
after final closure. The final contours and drainage of the cap and surrounding area will be
maintained. The vegetated cover will be maintained and mowed to prevent undermining of the cap
due to erosion. The cap will be inspected for differential settling, which could cause
breaching of the impermeable layers. Contingency plans for responding to subsidence problems
will be devised as part of a long-term maintenance plan for the cap.

A post-closure groundwater monitoring program will be implemented to determine if
contaminants from the landfill are entering the groundwater. One monitoring well will be
installed upgradient and two monitoring wells will be installed downgradient of the landfill.
Groundwater samples collected from the upgradient monitoring well represent the guality of
groundwater not affected by the landfill facility drainage. Groundwater samples collected from
the two downgradient wells represent groundwater guality passing beneath the landfill area. The
compounds to be monitored in the groundwater will be determined during the design phase.

9.5 INSTITUTIONAL CONTROLS

Implementation of Alternative D will result in the remediation of soil contaminated with

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explosives compounds in exceedance of the soil remediation goals, to a maximum depth of 10 feet.
Under this alternative, the northern industrial areas will be suitable for current use as
industrial areas and for future use as either industrial areas or residential areas.
Alternative D will also minimize the future leaching of explosives compounds to groundwater,
which will protect groundwater quality. Therefore, no institutional controls on future land use
will be needed. Institutional controls will only be required to maintain the engineered caps
within the northern industrial areas (if this option is exercised) and maintenance of the
Subtitle D solid waste landfill.

9.6 REMEDIATION GOALS

The goal of this remedial action is to protect current and future workers, future
hypothetical residents, and groundwater quality in the area by remediating soil in the northern
industrial areas that contains explosives compounds in exceedance of the soil remediation goals.
These goals are 10 Og/g for RDX, 25 0/g for 2,4,6-TNT, and 500 0/g for tetryl. These goals are
based on the Reference Dose and Cancer Slope Factor information in the USEPA's IRIS and HEAST
databases, as well as the conceptual model for soil contamination developed from the results of
chemical analysis of soil samples collected during the Remedial Investigation of the site and
other studies.

The bioremediation process is capable of reducing the concentrations of the principal
explosives compounds to very low levels. Based on the results from the bioremediation testing
that has been performed at other sites, it is expected that a composting time of 40 days will,
at a minimum, achieve the treatment goals of 20 0/g for 2,4,6-TNT and 20 0/g of RDX. The soil
undergoing bioremediation will be suitable for disposal when the following conditions are met:

• The soil contains a maximum concentration of 20 0/g for 2,4,6-TNT and 20 Og/g of RDX;
• The soil passes the TCLP test (i.e., does not display the characteristic of
toxicity); and
• The soil passes the Paint Filter Liquid Test.

9.7 COST OF THE SELECTED REMEDY

The total capital cost of the windrow composting option for Alternative D has been
estimated to be $15,800,000. The total annual costs are estimated at $44,000 per year. The
total present worth of capital and annual costs are estimated at $16,500,000. The cost
estimates are preliminary and are subject to change. The estimates were developed based on
construction unit costs and vendor information. These costs are outlined in Table 9-1.

The design and construction of the treatment system will take approximately 12 months.
This estimate includes time for the treatment system design and review, preparation of bid
packages, selection of contractors and equipment suppliers, construction, equipment
installation, and start-up.

Assumptions were made about several factors that affect the time and cost estimates for
this alternative. The major assumption for this cost estimate is the mass of soil to be
treated. It has been assumed that 38,000 tons of soil will require excavation, treatment, and
disposal. Other assumptions include:

• Contaminant concentrations have been estimated from existing data. If the actual
concentrations differ greatly from those assumed, then the volume of soil to be
excavated and treated, as well as the cost of the remedy, would change.

• Treatment costs were estimated based on the unit cost information available from
studies performed at other sites. These costs included all equipment, amendments,
buildings, and utilities required for windrow composting.

• The costs for health and safety measures were assumed to be 10% of the capital cost
subtotal. Based on actual conditions at the site and actual investigation and
construction methods, implementation of health and safety measures may result in
higher or lower costs.

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                                            Table 9-1
                    Summary of Costs for the Selected Remedy:  Alternative D
                     Excavation/Storage/Windrow Composting/On-Site Landfill

               ITEM                                                     COST

                                    Capital Costs
Administrative Actions                                                           $28,000
Site Preparation and General Actions                                             $14,000
Contaminated Soil Excavation/Clean Soil Backfill                                $985,000
Windrow Composting Operation                                                  $8,020,000
On-Site Landfill                                                                $751,000
Long-Term Monitoring                                                             $30,000
Contingencies  (40% of Capital Subtotal)                                       $3,940,000
Engineering & Design  (25% of System Subtotal)                                 $2,000,000
Permitting & Coordination                                                        $25,000

                             Annual Operation and Maintenance Costs
Administrative Actions                                                           $28,000
Long-Term Monitoring & Five-Year Reviews                                          $7,000
Contingencies  (25% of Annual Subtotal)                                             $9,000
Present Worth of Annual O&M  (30 years,  5% discount rate)                         $675,000
Total Present Worth (Capital and Annual Costs,  30 years at 5%                $16,500,000
discount rate)

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10.0 STATUTORY DETERMINATIONS

Executive Order 12580 delegates the authority for carrying out the reguirements of CERCLA
Sections 104 (a), (b), and (c) (4) and 121 to the Department of Defense, to be exercised
consistent with Section 120 of the Act. Therefore, under its legal authorities, the Army's
primary responsibility at MAAP is to undertake a remedial action that achieves adeguate
protection of human health and the environment. In addition, Section 121 of CERCLA establishes
several other statutory reguirements and preferences. These specify that when complete, the
final remedial action for the northern industrial area soil must comply with applicable or
relevant and appropriate environmental standards established under Federal and State
environmental laws unless a statutory waiver is justified. The final remedy also must be
cost-effective and utilize permanent solutions and alternative treatment technologies or
resource recovery technologies to the maximum extent practicable. Finally, the statute includes
a preference for remedies that employ treatment that permanently and significantly reduce the
toxicity, mobility, or volume of hazardous substances as their principal element. The following
sections discuss how the selected remedy is consistent with these statutory reguirements as far
as practicable given the limited scope of the action.

10.1 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT

The selected remedy consists of the remediation of soil within the northern industrial
areas that contains explosives compounds in exceedance of the risk-based soil remediation goals
(10 Og/g for RDX, 25 0/g for 2,4,6-TNT, and 500 0/g for tetryl), to a maximum depth of 10 feet.
The soil will be either treated using bioremediation and then placed in a Subtitle D landfill,
or will be left in place and covered with an engineered cap. This remedy will be protective of
current workers, future workers and hypothetical residents, and groundwater guality by
preventing direct exposure to the contaminated soil and minimizing the leaching of explosives
compounds from soil to groundwater. The selected remedy will reduce carcinogenic risks to less
than 10-5, which is within the USEPA's acceptable risk range of 10-4 to 10-6. The Hazard Index
for non-carcinogens will be reduced to less than 10. There are no short-term threats associated
with the selected remedy that cannot be easily controlled. In addition, no adverse cross-media
impacts are expected from the remedy.

10.2 COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS

The selected remedy of excavation, treatment of the excavated soil using windrow
composting, and placement of the treated soil in a Subtitle D solid waste landfill (supplemented
with construction of optional engineered caps on areas where excavation cannot safely be
performed), will comply with all applicable or relevant and appropriate chemical-, action-, and
location-specific reguirements (ARARs). The ARARs are presented below.

10.2.1 Chemical-Specific ARARs

None.

10.2.2 Action-Specific ARARs

The excavation of soil and windrow composting will be performed in compliance with
Tennessee Air Pollution Control Regulations (Fugitive Dust Standards, Rule 1200-3-8.01; Visible
Emissions, Rule 1200-3-5.01; Particulate Emissions, Rule 1200-3-7.03(2)), which are applicable
reguirements.

The disposal of treated soil within a solid waste landfill will be performed in compliance
with State of Tennessee solid waste reguirements (Tennessee Solid Waste Processing and Disposal
Regulations, Rule 1200-1-7.04), which are applicable reguirements.

Excavation activities within the northern industrial areas will be performed in compliance
with the substantive reguirements of the Tennessee Water Pollution Control Regulations' general
stormwater permit program for construction activities (Rule 1200-4-10.05), which are applicable
reguirements.

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10.2.3  Location-Specific ARARs

        None.

10.3   COST EFFECTIVENESS

       The selected remedy is cost-effective because it has been determined to provide overall
effectiveness proportional to its costs, the net present worth value being $16,500,000.  By
implementing windrow composting for the treatment of explosives-contaminated soil, the selected
remedy represents the best cost/benefit ratio, being less costly than the incineration
alternative, while providing egual protection of human health and the environment.

10.4   UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE TREATMENT TECHNOLOGIES  (OR RESOURCE
       RECOVERY TECHNOLOGIES) TO THE MAXIMUM EXTENT PRACTICABLE

       The Army,  the USEPA,  and the State of Tennessee have determined that the selected remedy
represents the maximum extent to which permanent solutions and treatment technologies can be
utilized in a cost-effective manner for the northern industrial area soil.  Of those
alternatives that are protective of human health and the environment and comply with ARARs, the
Army, the USEPA,  and the State of Tennessee have determined that this selected remedy provides
the best balance of tradeoffs in terms of long-term effectiveness and permanence, reduction in
toxicity, mobility, or volume achieved through treatment, short-term effectiveness,
implementability, cost,  while considering the statutory preference for treatment as a principal
element and State and community acceptance.

       While the selected remedy does not offer as high a degree of long-term effectiveness and
permanence as the incineration alternative, it will significantly reduce the risks posed by the
contaminated soil by preventing direct contact with the soil and minimizing contaminant
transport to groundwater.  Treatment of the excavated soil using bioremediation will reduce the
concentrations of the explosives compounds, the toxicity of the leachate, and will result in the
remaining organic compounds becoming tightly bound to the soil matrix.  This increases the
certainty that the treated soil can be contained in the long term.  Since the remaining
explosives compounds will be bound up in the soil and will continue to degrade over time, the
impact on human health and the environment would be minimal even if the solid waste landfill
were to fail.  The selected remedy offers fewer short-term risks to the community and site
workers when compared to incineration, and the implementability of the selected remedy is egual
to that of the incineration option.  The selected remedy is also more cost-effective than
incineration.

       The major tradeoffs that provide the basis for this selection are short-term
effectiveness, implementability and cost.  The selected remedy can be implemented with smaller
short-term risks, less difficulty, and at less cost than the incineration alternative and is
determined to be the most appropriate solution for the contaminated soil within the northern
industrial areas.

10.5   PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT

       By treating the explosives-contaminated soil using bioremediation, the selected remedy
addresses one of the principal threats posed by the site through use of treatment technologies.
Therefore, the statutory preference for remedies that employ treatment as a principal element is
satisfied.

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11.0   DOCUMENTATION OF SIGNIFICANT DIFFERENCES

       The Proposed Plan for the Northern Industrial Area Soil, Milan Army Ammunition Plant, was
released for public comment on April 14, 1995.  The Proposed Plan identified Alternative D,
Excavation/Storage/Biological Treatment/On-Site Landfill, as the preferred alternative.  The
Army, the USEPA, and the State of Tennessee reviewed and considered all comments received during
the Public Meeting and the public comment period.  Upon review of these comments, it was
determined that no significant changes to the remedy, as it was originally identified in the
Proposed Plan, were necessary.

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12.0 REFERENCES

Griest, W.H., Stewart, C.H., Ho, C.H., Tyndall, R.L., Vass, A.A. , Caton, J.E., and
W.M. Caldwell. Characterization of Explosives Processing Waste Decomposition Due to
Composting. Draft Report ORNL/TM-12812. September, 1994.

USAEC, U.S. Army Environmental Center, U.S. Department of the Army. 1988b. Field Demonstration
-- Composting of Explosives-Contaminated Sediments at the Louisiana Army Ammunition Plant
(LAAP). Report Number AMXTH-IR-TE.88242. U.S. Army Environmental Center, Aberdeen
Proving Ground, MD. September 1988.

USAEC, U.S. Army Environmental Center. 1991a. Milan Army Ammunition Plant Remedial
Investigation Report. Final Document. ICF Kaiser Engineers, Inc. Fairfax, VA.
December, 1991.

USAEC, U.S. Army Environmental Center, U.S. Department of the Army. 1991b. Optimization of
Composting for Explosives Contaminated Soil. Report Number CETHA-TS-CR-91053. U.S. Army
Environmental Center, Aberdeen Proving Ground, MD. November 1991.

USAEC, U.S. Army Environmental Center, U.S. Department of the Army, 1993. Windrow Composting
Demonstration for Explosives Contaminated Soils at the Umatilla Depot Activity, Hermiston,
Oregon.

USAEC, U.S. Army Environmental Center. 1995a. Milan Army Ammunition Plant Northern Industrial
Area Soil, Focused Feasibility Study, Final Document. ICF Kaiser Engineers, Inc.,
Abingdon, MD. April, 1995.

USAEC, U.S. Army Environmental Center. 1995b. Proposed Plan for the Milan Army Ammunition
Plant Northern Industrial Area Soil. Final Document. ICF Kaiser Engineers, Inc.
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USAEC, U.S. Army Environmental Center. 1995c. Milan Army Ammunition Plant Remedial
Investigation OU4 Northern Study Area. Draft Final Document. Environmental Resources
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USAEHA, U.S. Army Environmental Hygiene Agency, U.S. Department of the Army. 1978.
Potable/Recreational Water Quality Survey No. 31-24-0163-79, Milan Army Ammunition Plant.
March 28, 1978.

USATHAMA, U.S. Army Toxic and Hazardous Materials Agency. 1978. Installation Assessment of
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USATHAMA, U.S. Army Toxic and Hazardous Materials Agency. 1982. Milan Army Ammunition Plant
Contamination Survey. Report DRXTH-FS-FP-82131. Pugh, D.L.: Envirodyne Engineers.
January 1982.

U.S. Department of the Army. 1984. Military Explosives, Technical Manual TM 9-1300-214.
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USEPA, U.S. Environmental Protection Agency. 1986a. Guidelines for Carcinogenic Risk
Assessment. Federal Register 51:33992-34003.

USEPA, U.S. Environmental Protection Agency. 1986b. RCRA Facility Assessment Report, Milan
Army Ammunition Plant, EPA I.D. No. TN0210020582. A.T. Kearney and Geo/Resource
Consultants. August 21, 1986.

USEPA, U.S. Environmental Protection Agency. 1988. Integrated Risk Information System (IRIS).
Office of Health and Environmental Assessment. EPA/600/8-86/032a.

USEPA, U.S. Environmental Protection Agency. 1989a. Risk Assessment Guidance for Superfund.
Volume I: Human Health Evaluation Manual. Part A. Interim Final. EPA/540/1-89/002.

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       December 1989.

USEPA, U.S. Environmental Protection Agency.  1989b.  Federal Facility Agreement for Milan Army
       Ammunition Plant.

USEPA, U.S. Environmental Protection Agency.  1991.  Risk Assessment Guidance for Superfund.
       Volume I:   Human Health Evaluation Manual Supplemental Guidance.  Standard Default
       Exposure Factors.   Interim Final.   Washington,  DC.  OSWER Directive 9285.6-03.  March 25,
       1991.

USEPA, U.S. Environmental Protection Agency  (USEPA).  1994a.  Human Health Effects Assessment
       Summary Tables  (HEAST).   Office of Health and Environmental Assessment,  Environmental
       Assessment and  Criteria Office, Cincinnati,  Ohio.  Prepared for Office of Solid Waste and
       Emergency Response,  Office of Emergency and Remedial Response,  Washington, D.C.  FY-1994.

USEPA, U.S. Environmental Protection Agency.  1994b.  Integrated Resource Information Systems
       (IRIS).   Environmental  Criterion and Assessment Office,  Cincinnati, Ohio.

USEPA, U.S. Environmental Protection Agency.  1994c.  Technical Background Document for Soil
       Screening Guidance.   Review Draft.  Office of Solid Waste and Emergency Response,  U.S.
       Environmental Protection Agency.  Washington, D.C.  EPA/540/R-94/106.   December 1994.

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APPENDIX A

RESPONSIVENESS SUMMARY
COMMENTS RECEIVED AT THE PUBLIC AVAILABILITY SESSION
APRIL 25, 1995
Bob Parkins, 152 Medina Highway, Milan, Tennessee. I've kept up with the project for several
years. I reviewed the blueprints on the slide presentation on the display and after talking to
several of the experts, it appears that composting is the best idea-mixing manure and sawdust
and filtration products and the cost was staggering-$16 million dollars I believe-I was told. I
don't guess there's any simple solution to this but I know that it probably has to be done. The
most feasible way to protect environment and the safety of the people is the most important and
I would definitely recommend and endorse such a project.

I'm Mary Brew and from what I've looked at observing these charts and from what I understand,
alternative D would be the one I would opt for because it would have the same results as C but
it would be less expensive and I'm always for saving the taxpayers money. This chart was the
easiest for me to understand; the others were a little bit confusing.

I'm Andrew Hawkins and I think they are doing an excellent job on trying to clean it up. Nora
was very informative. I'm also employed out there and naturally I'd say they are doing a
wonderful j ob.

Karen Moore and I believe bioremediation is the most feasible method to use on this site. I
don't believe incineration would meet the public's expectations or would be acceptable to them.
I think bioremediation would be something that they could more easily understand and would
accept. Then the cost effectiveness of it is much better and that's something we have to
consider since the budget cuts are coming through the Congress.

I'm Howard Ezell. I represent Rotary and the community of Milan. I'd like to make this comment
so far as our way of handling the cleanup at the Milan Arsenal. It seems to me that it boils
down to incinerating or composting. After listening to the comments made by Nora and a few
other people, it seems in my way of thinking the composting is the best and that we can get a
very rapid deterioration in the TNT particularly-big effect after 5 days. By using this compost
piling that they are going to use and then distributing it to the landfill and then putting a
cap on it.
RESPONSES TO COMMENTS RECEIVED AT THE PUBLIC AVAILABILITY SESSION

The Army agrees with the commenters that the bioremediation option offers the best trade-off
between long-term and short-term effectiveness, implementability, and cost. Bioremediation of
the explosives-contaminated soil can be performed safely and in a cost-effective manner. This
alternative will reduce the risk associated with use of the northern industrial areas to a level
that is within EPA's acceptable risk range at a significantly lower cost than through the use of
incineration.
COMMENTS RECEIVED IN WRITING FROM MR. BILL OWNBY
RESTORATION ADVISORY BOARD CO-CHAIRMAN
(Received April 24, 1995)

The incineration/backfill offers the environment a soil free from contaminates and my children
or grandchildren should never have to worry about it again. 99.99% destruction.

Biological treatment/on-site landfall only offers a theoretical reduction of explosive compounds
of approximately 80%. An on site solid waste land fill which would include a cap, a liner and

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monitoring wells would still be necessary to protect the environment due to the lack of total
destruction of the explosive compounds.

Using Biological Treatment is a lot like the city selecting new well sites in the underground
water flow from the Southern Boundary of the MAAP, both are hoping that the inevitable will not
happen. Total removal and/or prevention of pollution is the only answer to protecting the
environment.

If cost is going to be the deciding factor then there is not need to spend all the extra money
and effort by citizens to work with the Army to help evaluate environmentally sound methods of
pollution clean-up. EPA uses the term BAT - Best Available Technology and I hope the Army
doesn't use the term CAT - Cheapest Available Technology.

I feel that all the citizens around the MAAP would like to be assured that the pollution would
be removed to the point that they would not have to ever hear the words arsenal soil and water
contamination. If the restoration is carried out in a manner to satisfy the above concern then
we can all go about our business without arsenal related health problem to worry about.
RESPONSES TO WRITTEN COMMENTS

Although incineration is a widely practiced technology, there is the potential for the
concentration of metals in the incinerator ash the release of concentrated metals into the
atmosphere as flue gas, and the incomplete combustion of organic compounds. Although the Army
does not believe that the risks associated with the incineration of contaminated soil are high,
it is believed that the short-term risks associated with the bioremediation process are lower
than those for incineration.

Furthermore, the Army disagrees that it is inevitable that the solid waste landfill will fail or
that such a failure would pose a risk to human health and the environment. Treatment of the
excavated soil using bioremediation will reduce the concentrations of the explosives compounds,
the toxicity of the leachate, and will result in the remaining organic compounds becoming
tightly bound to the soil matrix. This increases the certainty that the treated soil can be
contained in the long term. Since the remaining explosives compounds will be bound up in the
soil, the impact on human health and the environment would be minimal if the solid waste
landfill were to fail.

It is important to consider that the biological activity of the explosives/still/compost mixture
does not cease when landfilled. Ultimately, essentially all of the explosives residues will be
degraded. Until that happens, the landfill design offers a practical means to ensure protection
of groundwater resources.

While bioremediation does not offer as high a degree of long-term effectiveness and permanence
as the incineration alternative, it will significantly reduce the risks posed by the
contaminated soil by preventing direct contact with the soil and minimizing contaminant
transport to groundwater. The selected remedy offers fewer short-term risks to the community
and site workers, and the implementability of the selected remedy is egual to that of the
incineration option. The selected remedy is also significantly less expensive than
incineration.

Because the bioremediation option offers the same risk reduction as the incineration option yet
is less expensive, it offers the best cost-benefit ratio available. The public should be
assured that the Army's intention is not to save money at the expense of health risks to current
and future workers and residents; rather, the intention is to select the most appropriate remedy
based on all of the scientific data available, and to remediate the soil in a safe and
cost-effective manner.

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