United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R04-93/160
September 1993
3 EPA Superfund
Record of Decision:
Milan Army Ammunition Plant,
TN
-------
50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA/ROD/R04-93/160
3. Recipient's Accession No.
Title and Subtitle
SUPERFUND RECORD OF DECISION
Milan Army Ammunition Plant, TN
Second Remedial Action - Final
& RaportDat*
09/29/93
7. Authors)
a Performing Organization Rapt. No.
8. Performing Organization Nam* and Address
10 Project Task/Work Unit No.
11. Contr*ct(Q or Grant(G) No.
12, Sponsoring Organization Nam* and Addrwa
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
11 Type of Report* Period Covered
800/800
14.
15. Supplementary Note*
PB94-964049
16. Abstract (Limit: 200 words)
The 22,436-acre Milan Army Ammunition Plant site is an ammunition production and
storage facility located in Gibson and Carroll Counties, Tennessee. Land use in the
area is predominantly agricultural, with scattered residences located to the north and
east of the site. The Milan Army Ammunition Plant (MAAP) lies within the coastal plain
province of the Mississippi .Embayment, and contains numerous small streams, creeks, and
drainage ditches. The entire facility, except for the extreme southern portion, drains
via small creeks and ditches into the Rutherford fork of the Obion River, which empties
into the Mississippi River about 60 miles to the west. The 1,600 people presently
working at MAAP, as well as the population residing within the vicinity of the site,
use the Memphis Sand of the Clairborne Group aquifer as their main drinking water
supply. The O-Line Ponds area, addressed in this ROD, historically received wastewater
from the operations conducted at 0-Line and is located in the north central portion of
the site. Since 1941, the U.S. Army has used the site for the production and storage
of fuses, boosters, and small- and large-caliber ammunition. The types of explosives
handled in the facility include 2,4,6-trinitrotoluene (TNT) and RDX. From 1941 to 1978,
the function of the O-Line area was to remove explosives from bombs and projectiles by
injecting a high-pressure stream of hot water and steam into the steel shell of the
(See Attached Page)
17. Document Analysis a. Descriptors
Record of Decision - Milan Army Ammunition Plant, TN
Second Remedial Action - Final
Contaminated Media: soil, sediment, sw
Key Contaminants: organics; metals
b. Identifiers/Open-Ended Terms
c COSATI Reid/Group
ia Availability Statement
19. Security Class (This Report)
None
20. Security Class (This Pag*)
None
21. No. of Pag**
84
22. Price
(Se*ANS*-Z39.18)
SM Instruction* on A*tr«rs*
OPTIONAL FORM 272(4-77)
(Formerly NTB-35)
Department of Commerce
-------
EPA/ROD/R04-93/160
Milan Army Ammunition Plant/ TN
Second Remedial Action - Final
Abstract (Continued)
munitions. A 1978 investigation conducted under the U.S. Army water well sampling program
revealed that three of the MAAP's 11 water supply wells were contaminated with explosive
constituents. O-Line operations were ceased in 1978 and, beginning in 1981, effluent from
the ponds was pumped into a newly-installed pink water treatment facility (PWTF)
consisting of carbon adsorption and fabric filtration units. Effluent from the PWTF was
discharged to an open ditch, which was then covered with a PVC liner. In 1984, a closure
plan was implemented consisting of filling the ponds with clean inorganic fill followed by
the installation of a multilayered cover. The site is divided into three OUs for
remediation, all located within the O-Line area: GUI is the ground water beneath and
immediately downgradient from the former 0-Line Ponds contaminated by past disposal
practices; OU2 addresses the contaminated soil beneath and around the former ponds, and
surface water and shallow sediment in the drainage ditch that flows along the east and
north sides of the ponds; and OU14 addresses additional areas of ground water
contamination both upgradient and downgradient of OU1 and OU2. A 1992 interim ROD
addressed the remediation of contaminated ground water downgradient of the O-Line area.
This ROD addresses the contaminated soil beneath and around the former ponds and surface
water and shallow sediment in the drainage ditch, as OU2. A possible future ROD will
address the remediation of the ground water at OU14. The primary contaminants of concern
affecting the soil, sediment, and surface water are organics and metals.
The selected remedial action for this site includes extending the multilayered cap over
the contaminated soil around the perimeter of the existing cap to cover an area of 237,000
ft^; monitoring air during cap construction; monitoring ground water; and implementing
institutional controls, including deed and land use restrictions. The estimated present
worth cost for this remedial action is $1,833,000, which includes an estimated annual O&M
cost of $19,000 for 30 years.
PERFORMANCE STANDARDS OR GOALS:
Not provided.
-------
MILAN ARMY AMMUNITION PLANT (MAAP)
O-LINE PONDS AREA
SOIL, SEDIMENT, AND SURFACE WATER
OPERABLE UNIT
Milan, Tennessee
RECORD OF DECISION
FINAL DOCUMENT
September 29, 1993
In accordance with Army Regulation 200-2, this document is intended to
comply with the National Environmental Policy Act (NEPA) of 1969.
-------
DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
O-Line Ponds Area, Milan Army Ammunition Plant (MAAP), Milan, Tennessee
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for Operable Unit Two (OU2) at the
O-Line Ponds Area, 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 OU2 and the rationale for the final decision. The information supporting
this remedial action decision is contained in 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 the site, if not addressed by
implementing the response actions 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 overall cleanup activities at the site is to prevent migration of contaminants from
soil at the site and to prevent exposures to these contaminants, so that no adverse health effects will
result from current or future off-post or on-post use. Soil contaminated with explosives compounds is
known to exist in the O-Line Ponds area, and under current conditions, this contamination poses a
potential threat to groundwater at the site. Currently contaminated groundwater is being addressed by
separate remedial actions under different Operable Units (OUs).
The Operable Units at the O-Line Ponds area are defined as follows: Operable Unit One (OU1)
addresses contaminated groundwater beneath and immediately downgradient from the former ponds
which has been contaminated by past disposal practices at the ponds; OU2 addresses contaminated soils
beneath and around the former ponds, and surface water and shallow sediment in the drainage ditch that
flows along the east and north sides of the ponds, which have become contaminated as a result of past
disposal practices; and Operable Unit 14 (OU14) addresses additional areas of contamination both
upgradient and downgradient of OU1 and OU2. This Record of Decision presents the remedies that were
considered for OU2 only. A Record of Decision has already been issued for OU1, and the Army is
currently investigating the nature and extent of contamination in OU14.
The major component of the remedy selected for OU2 is an extension of the existing multi-media
cap to cover contaminated soil. The cap extension will be designed and constructed in accordance with
Resource Conservation and Recovery Act requirements for landfills. The entire capped area will be
-------
maintained to prevent degradation or erosion of the impermeable barriers. Groundwater monitoring will
be conducted in conjunction with OU1 and institutional controls will be implemented and/or maintained
to prevent access and exposures to the O-LJne Ponds site.
The principal threat at-tbis site is continued migration of contaminants to groundwater and
potential future exposures to contaminated groundwater. This threat will be addressed by capping all
areas of soil that are contaminated with explosives. The cap extension, along with the existing cap, will
provide an impermeable barrier to infiltrating water, thereby preventing downward movement of explosives
in the soil and protecting groundwater from further degradation.
The remedy specified herein will be one component of the overall remediation of the O-Line Ponds
area This action will be compatible with any current or planned future remedial actions for the site.
STATUTORY DETERMINATIONS
This action 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 cost-
effective. This remedy utilizes permanent solutions and alternative treatment technologies to the maximum
extent practicable for this site. However, because treatment of the principal threats of the site was not
found to be practicable, this remedy does not satisfy the statutory preference for treatment as a principal
element of the remedy. The large areal extent and depth of the contaminated soil at the site preclude a
remedy in which contaminants could be excavated and treated effectively.
Because this action will result in hazardous substances remaining on-site above health-based
levels, a review will be conducted within five years after implementation of this remedial action to ensure
that the remedy continues to provide adequate protection of human health and the environment
Additional remedial actions will be implemented to address contaminants in groundwater and to eliminate
potential future exposures.
B. Grumpier III Date
Lieutenant Colonel, U.S. Army
Commanding Officer, Milan Army Ammunition Plant
Lewis D. Walker Date
Deputy Assistant Secretary of the Army
(Environment, Safety, and Occupational Health)
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IV
4WD-FFB
rlED MAIL
345 COURTLAND STREET. N.E.
ATLANTA. GEORGIA 3O36S
RETURN RECEIPT REQUESTED
Mr. Lewis D. Walker
Deputy Assistant Secretary of the Army
(Environment, Safety and Occupational Health)
Attention: SAILE-ESOH _
The Pentagon, Room 2E577
Washington, D.C. 20310-0110
RE: Record of Decision for Operable Unit Two (2)
Milan Army Ammunition Plant, NPL Site
Milan, Tennessee
Dear Mr. Walker:
The U.S. Environmental Protection Agency (EPA) has reviewed the
above referenced decision document pursuant to the Comprehensive
Environmental Response, Compensation and Liability Act of 1980.
as amended and concurs with the proposed remedial action at
Operable Unit Two (2) as supported by the previously completed
Remedial Investigation and Baseline Risk Assessment Reports.
It is understood that the remedial action decision for Operable
Unit 2 (O-Line Ponds Area - Soil, Sediment and Surface Water
Operable Unit), is the final remedial action to address the above
referenced media potentially affected by past disposal practices
at the O-Line Ponds Area.
Sincerely,
Patrick M. Tobin
Acting Regional Administrator
cc: Commissioner J. A. Luna, Tennessee Department
of Environment and Conversation
LTC Everette B. Grumpier, III
Commanding Officer, MAAP
in
-------
STATE OF TENNESSEE
DEPARTMENT OF ENVIRONMENT AND CONSERVATION
NASHVILLE, TENNESSEE 37243-0435
NED MeWHERTER
GOVERNOR
J. W. LUNA
September 30, 1993
Mr. Lewis D. Walker
Deputy Assistant Secretary of the Army
OSHA-I, LE
Office of the Assistant Secretary
Department of the Army
Washington, D.C. 20310-0103
Ref. 27-505 MAAP O-Line Ponds OUf2 ROD
Dear Mr. Walker:
The Tennessee Department of Environment and Conservation has
reviewed the final Record of Decision submitted on August 26,
1993. This document has reference to the soil, shallow
sediment and surface water operable unit of the O-Line Ponds
Area at the Milan Army Ammunition Plant located in Milan,
Tennessee. The Department concurs with the findings and the
selected remedial action stated in this Record of Decision.
If you have any questions regarding this matter please
contact me at (615) 532-0900 or Mr. Ron Sells, TDEC Project
Manager at (9010 423-6600.
Sincerely/
r linton W. Wilier, Director
'Division of Super fund
Department of Environment and Conservation
IV
-------
TABLE OF CONTENTS
Sect/on 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 HYDROGEOLOGIC AND HYDROLOGIC SETTING 5-1
5.1.1 Soil Profile 5-1
5.1.2 Site Groundwater 5-1
5.1.3 Site Surface Water Hydrology 5-1
5.2 CONTAMINATION ASSESSMENT 5-2
5.2.1 Soil Contamination 5-2
5.2.1.1 Volume of contaminated soil under the cap 5-3
5.2.1.2 Routes of contaminant transport and exposure from soil
under the cap 5-3
5.2.1.3 Volume of contaminated soil around the perimeter of the
cap 5-3
5.Z1.4 Routes of contaminant transport and exposure from soil
around the perimeter of the cap 5-3
5.2.2 Surface Water and Shalllow Sediment Contamination 5-3
5.2.2.1 Volume of contaminated shallow sediment 5-4
5.2.2.2 Routes of contaminant transport and exposure 5-4
6.0 SUMMARY OF SITE RISKS 6-1
6.1 SELECTION OF CHEMICALS OF POTENTIAL CONCERN 6-1
6.1.1 Surface Soil 6-1
6.1.2 Surface Water 6-3
6.1.3 Shallow Sediment 6-3
6.2 HUMAN HEALTH EXPOSURE ASSESSMENT 6-3
6.2.1 Current and Hypothetical Future Land Use and Site Characterization ... 6-3
6.2.2 Potential Exposure Pathways 6-4
6.2.3 Quantification of Exposure 6-4
6.2.3.1 Estimation of Exposure Point Concentrations 6-7
6.2.3.2 Estimation of Chemical Intakes 6-7
6.3 TOXICITY ASSESSMENT 6-13
-------
TABLE OF CONTENTS (Continued)
Section Page
6.4 RISK CHARACTERIZATION 6-13
6.4.1 Incidental Ingestion of Soil 6-13
6.4.2 Dermal Exposures to Chemicals in Surface Soil 6-16
6.4.3 Incidental Ingestion of Shallow Sediment 6-16
6.4.4 Dermal Absorption of Chemicals in Shallow Sediment 6-16
6.4.5 Ingestion of Beef 6-16
6.4.6 Total Risks 6-16
6.5 EVALUATION OF EFFECTS OF INGESTION OF GROUNDWATER
CONTAMINATED BY OU2 6-16
6.5.1 Chemicals Of Potential Concern 6-17
6.5.2 Exposure Assessment 6-17
6.5.3 Risk Characterization 6-18
6.6 SUMMARY OF ECOLOGICAL RISK ASSESSMENT 6-18
6.7 RISK ASSESSMENT SUMMARY 6-21
7.0 DESCRIPTION OF ALTERNATIVES 7-1
7.1 APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS 7-1
7.2 TO-BE-CONSIDERED GUIDANCES 7-1
7.3 ALTERNATIVE A: NO ACTION 7-2
7.4- ALTERNATIVE B: LIMITED ACTION 7-2
7.5 ALTERNATIVE C: CLEAN SOIL COVER 7-3
7.6 ALTERNATIVE D: EXTENSION OF ENGINEERED CAP 7-4
7.7 ALTERNATIVE E: PARTIAL EXCAVATION/INCINERATION 7-6
7.8 ALTERNATIVE F: FULL EXCAVATION/INCINERATION 7-8
7.9 SUMMARY OF REMEDIAL ALTERNATIVES 7-9
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 8-3
8.4 LONG-TERM EFFECTIVENESS AND PERMANENCE 8-3
8.5 REDUCTION OF TOXICfTY, MOBILITY OR VOLUME THROUGH
TREATMENT 8-4
8.6 SHORT-TERM EFFECTIVENESS 84
8.7 IMPLEMENTABILJTY 8-5
8.8 COST 8-5
8.9 SUMMARY OF DETAILED EVALUATION 8-7
9.0 SELECTED REMEDY 9-1
9.1 ALTERNATIVE D: EXTENSION OF ENGINEERED CAP 9-1
9.1.1 Description 9-1
9.2 INSTITUTIONAL CONTROLS 9-2
9.3 REMEDIATION GOALS 9-2
9.4 COST OF SELECTED REMEDY 9-3
VI
-------
TABLE OF CONTENTS (Continued)
Sect/on Page
10.0 STATUTORY DETERMINATIONS 10-1
10.1 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT 10-1
10.2 COMPLIANCE WTTH APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS 10-1
10.2.1 Action-Specific ARARs 10-1
10.Z2 Chemical-Specific ARARs 10-2
10.2.3 Location-Specific ARARs 10-2
10.2.4 Other Criteria, Advisories or Guidance To Be Considered for the
Remedial Action (TBCs) 10-2
10.3 COST-EFFECTIVENESS 10-2
10.4 UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE
TREATMENT TECHNOLOGIES (OR RESOURCE RECOVERY
TECHNOLOGIES) TO THE MAXIMUM EXTENT PRACTICABLE 10-2
10.5 PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT 10-2
11.0 DOCUMENTATION OF SIGNIFICANT CHANGES 11-1
12.0 REFERENCES 12-1
APPENDIX A
Responsiveness Summary
vii
-------
LIST OF FIGURES
Figure _ _ Page
1-1 Location of MAAP in Western Tennessee 1-2
1-2 Active and Inactive Process Areas Within MAAP 1-3
2-1 O-Line and O-Line Ponds 2-2
2-2 Cross-Section of Existing Multi-Media Cover System, O-Line Ponds Area 2-3
7-1 Cap Extension Boundary 7-5
VIII
-------
LIST OF TABLES
Table Page
6-1 Chemicals of Potential Concern Adjacent to the O-Line Ponds 6-2
6-2 Potential Current Human Exposure Pathways at the O-LJne Ponds 6-5
6-3 Potential Future Human Exposure Pathways at the O-Line Ponds 6-6
6-4 Exposure Point Concentrations and Calculated CDIs, Surface Soil Exposure
Pathways 6-8
6-5 Exposure Point Concentrations and Calculated CDIs, Sediment Exposure Pathways
for a Child/Teenager 6-11
6-6 Exposure Point Concentrations and Calculated CDIs, Beef Ingestion Exposure
Pathway 6-12
6-7 Oral Toxicity Values for Chemicals of Potential Concern at the O-Line Ponds 6-14
6-8 Summary of Risks 6-15
6-9 Estimated Exposure Point Concentrations, CDIs, and Potential Risks: Groundwater
Exposure Pathways, Scenario 1 6-19
6-10 Estimated Exposure Point Concentrations, CDIs, and Potential Risks: Groundwater
Exposure Pathways, Scenario 2 6-20
7-1 Summary of Remedial Alternatives 7-10
8-1 Comparison of Costs for Remedial Alternatives 8-6
9-1 Summary of Costs for the Selected Remedy, Alternative D: Extension of
Engineered Cap 9-4
-------
1.0 SITE NAME. LOCATION. AND DESCRIPTION
Milan Army Ammunition Plant (MAAP) is located in western Tennessee, 5 miles east of Milan,
Tennessee, and 28 miles north of Jackson, Tennessee (Figure 1-1). MAAP is a government-owned,
contractor-operated installation with Martin Marietta Ordnance Systems, Inc., 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.
MAAP lies within the coastal plain 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 area is gently rolling to flat. It slopes regionally westward and contains numerous small
streams, creeks, and drainage ditches. The elevation of the plant varies from a high of approximately 590
feet above mean sea level (ft-msf) on the south side to a low of approximately 320 ft-msl on the north
boundary of the plant.
Numerous perennial and ephemeral surface water features occur within the installation and flow
to the north-northwest The entire facility, except for its extreme southern portion, drains via small 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 installation. The two parent streams, the Forked Deer River and the Obion River, empty
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.
At MAAP, the Memphis Sand of the Ciaibome Group is the major aquifer, and is thick, laterally continuous,
and highly transmissfve. 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
general scale, there are no abrupt hydrologic boundaries in the aquifer. The formation is recognized as
sand with clay lenses and clay-rich zones.
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. North of the facility, the nearest
residences are located north of the Rutherford Fork. These residences are downgradient from the 0-Line
Ponds area and are approximately 1.5 miles from the O-LJne Ponds. On the east side of the facility,
residences are located along the facility property line.
At present, approximately 1,600 people work within the MAAP facility. With the exception of 2
Army officers and 31 civilian employees, the work force is composed of Martin Marietta Ordnance
Systems, Inc., employees.
Of the thirteen process areas that were active at the end of World War II, only seven lines are in
use today. As shown in Figure 1-2, the active process areas are distributed throughout the northern half
of the facility. O-Line is located in the north central portion of MAAP. Immediately north of O-Une are the
O-Line Ponds (now closed), which historically received wastewater from the operations conducted at O-
LJne. This ROD addresses contamination that is present in the surface and subsurface soil around the
former ponds, and in the surface water and shallow sediments in the ditches that drain the O-Line Ponds
area This area is described in more detail in the following section.
1-1
-------
N
MISSISSIPPI
ALABAMA
FIGURE 1-1
LOCATION OF MAAP IN WESTERN TENNESSEE
1-2
-------
3 National Guard Area
D Operating Units of MAAP
O Private Ownership
0-LINE
3964
341 342 343 344 345 346 347 348 349 350 351 352
UTM Coordinates (kilometers)
FIGURE 1-2
ACTIVE AND INACTIVE PROCESS AREAS WITHIN MAAP
1-3
-------
2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES
The O-LJne area (Figure 2-1) at MAAP was built as part of the initial plant construction activity in
1941, and has operated since 1942 as an ordnance demilitarization facility. From the start, the major
function of the line has been to remove explosives from bombs and projectiles by injecting a high-
pressure stream of hot water and steam into the steel shell of the munitions. The types of explosives
handled in the facility include 2,4,6-trinitrotoluene (TNT) and RDX.
Wastewater contaminated with explosives was discharged from the O-Une washout operations
through a series of baffled concrete sumps where cooling caused significant amounts of explosives to
precipitate out of the waste stream. Effluent from the sumps was initially discharged to an open ditch
which ran through the O-Line area In 1942, 11 individual surface impoundments were excavated to
receive the O-Line effluent before discharge to the open ditch. The ponds reportedly were excavated into
native soil and the excavated material was used to form the pond dikes.
The ponds were 3-5 feet deep, had a total capacity of 5.5 million gallons, and covered an area
of about 280,000 square feet (USATHAMA, 1982a). The ponds were interconnected with a series of
spillways, open ditches, and distribution boxes allowing several pond configurations to be used in series.
Effluent from the last pond flowed through a bank of sawdust-filled tanks before discharge to Ditch B.
The drainage ditch that received effluent from the final pond discharged to the Rutherford Fork of the
Obion River which runs along the northern boundary of MAAP.
In 1978, the U.S. Army Toxic and Hazardous Materials Agency (USATHAMA) conducted an
Installation Assessment of MAAP (USATHAMA, 1978), which consisted of a records search and interviews
with employees. It was reported in this document that between 300 to 500 pounds of explosives could
be washed out in an 8-hour shift, and that many types of explosive materials were handled in this area
At the time of the survey, all of the wastewater ponds were full and signs of overflow were obvious. The
overflow entered the open ditch near O-Line.
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
explosive constituents. The affected wells were near a number of production areas, including O-Line.
MAAP facility personnel ceased using the O-Line Ponds because the ponds were determined to
be one of the most likely sources of groundwater contamination. As a result, the O-Line operation was
placed in a standby status in December 1978, and effluent has not been discharged to the ponds since
that time. The impounded effluent remained in the ponds until 1981, when the supernatant was pumped
out and treated in a newly constructed pink water treatment facility (PWTF), consisting primarily of carbon
adsorption units and fabric filtration units. The effluent from the PWTF was discharged to the open ditch
under the facility's National Pollutant Discharge Elimination System (NPDES) permit A PVC liner was
placed on top of the pond sediments in 1981 and the liner was filled with fresh water to stabilize it Pond
sediments that had previously been removed from the ponds and placed near the northwest comer of
the ponds were placed on top of the PVC liner prior to pond closure.
MAAP subsequently prepared and submitted a closure plan for the pond site (USATHAMA,
1982b). The closure plan was approved by the Tennessee Department of Health and the Environment
(TDHE) and implemented in 1984. The closure plan called for the construction of a multilayered cover
system for the ponds. A cross-section of this cap is shown in Figure 2-2. The ponds were filled with
clean inorganic fill, and two clay layers were placed on top and compacted. A gravel drainage layer was
placed between the clay layers. Topsoil was placed on top of the upper clay layer, and a vegetative cover
was then established.
2-1
-------
O-UNE PONDS
(CLOSED)
ROAD
••• — DITCH
RAILROAD
FENCE
FIGURE 2-1
O-UNE AND O-UNE PONDS
2-2
-------
o
460
455
'50
445
440
FENCE
6" PERFORATED
PVC PIPE
4" OF TOP SOIL
14" OF CLAY
8" GRAVEL FILTER
30" CLAY
ENCAPSULATED SOIL
r PLASTIC FILTER BLANKET
FENCE
PVC LINER
460
455
450
445
440
ORIGINAL SOIL
40' 20' 0 40' 80'
HORIZ.
5' 0 5' 10'
VERT.
SCALE IN FEET
FIGURE 2-2
CROSS-SECTION OF EXISTING MULTI-MEDIA COVER SYSTEM
0-LINE PONDS AREA
-------
The rationale for taking the ponds out of service and placing a liner on top of the contaminated
pond sediment was to decrease hydraulic loading on the source area, thereby reducing the amount of
explosives migrating to groundwater. The cap was designed to minimize hydraulic loading on the source
of explosives contamination by providing a multilayered cover system.
However, 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 EPA's list of hazardous waste sites
that present the greatest potential threat to human health and the environment if remediation does not
occur. Final listing on the NPL took place in August, 1987.
In 1990-1991, USATHAMA conducted a Remedial Investigation (Rl) at MAAP (USATHAMA, 1991).
The Rl was conducted to identify the type, concentration, and extent of contamination. Some of the
results of the Rl are as follows:
• The contaminants of concern in soil, surface water, shallow sediment, and groundwater
include explosives such as 2,4,6-TNT, 2,4-dinitrotoluene and 2,6-dinitrotoluene (DMT),
RDX, HMX, nitrobenzene, 1,3,5-trinitrobenzene (TNB), and 1,3-dinitrobenzene (DNB).
• The surface soil around the perimeter of the O-Line Ponds cap is contaminated with low
levels of explosives compounds, probably as a result of overflows during use of the O-
Line Ponds or from earthmoving activities that took place during pond closure. The
subsurface soil around the perimeter of the cap is also contaminated with low to
moderate levels of explosives compounds.
• The levels of explosives compounds immediately below the PVC liner (in the undisturbed
pond sediments) are much lower than those measured before pond closure, but
-contained the highest levels of explosives detected in soil at MAAP during the Rl.
• Concentrations of metals in the surface and subsurface soils are within the background
range, or exceed background levels infrequently and only by a small amount, suggesting
that detected metals are not related to past disposal activities in this area
• The measured hydraulic conductivity of the cap material and the moisture content data
indicate that water is not percolating through the contaminated soil. Therefore, the
capped area of the former ponds is currently not a significant source of groundwater
contamination. Leaching of contaminants to the aquifer most likely occurred between
initiation of pond usage to shortly after pond closure, as indicated by the greatly reduced
levels of explosives compounds immediately below the PVC liner.
• Surface water and shallow sediment samples collected from the ditches downstream of
O-Line suggest that there is low-level explosives contamination. Explosives contamination
found in the shallow sediment of the drainage ditches is at or below the levels attributable
to permitted discharges. Metals contamination occurs in some ditches, but at generally
tow levels. No site-related contamination of concern was found in the perennial streams
(i.e., the Rutherford Fork of the Obion River) below the outfalls of Ditch B. The levels of
explosives detected in surface water were well within the facility's NPDES permit limits
and, therefore, can be attributed to discharges from the O-Line PWTF.
To address the potential risks posed by the O-Line Ponds area as quickly as possible, the Army
has elected to divide the O-LJne Ponds area into three separate operable units (OUs) and to
investigate/remediate the site in a phased approach. The OUs are defined as follows:
2-4
-------
• OU1 consists of groundwater beneath and immediately downgradient from the former CD-
line Ponds which has been contaminated by past disposal practices at the ponds;
• OU2 consists of contaminated soils beneath and around the former ponds and surface
water and shallow sediment in the drainage ditch that flows along the east and north
sides of the ponds. Through sampling and consideration of former site activities, the area
of OU2 has been defined as consisting of the area that has been impacted by use and/or
closure of the former ponds at O-LJne. To be conservative, the boundary of this area has
been identified as the fence that encircles the capped area, excluding the area south of
the access road to the O-LJne Pink Water Treatment Facility (PWTF). The area of OU2
is approximately 582,000 ft2. The tributary of the drainage ditch (Ditch 5) that flows along
the east and north sides of the O-LJne cap, which received pond effluent while the ponds
were in use and currently receives treated water from the O-Line PWTF, is included from
the O-Line PWTF outfall to Route 104. Because the exposure pathways for both humans
and aquatic life associated with sediment are limited to direct contact only the shallow
zone (to a maximum depth of 2 feet) is included in OU2. Deeper sediments are currently
being investigated as part of the overall drainage ditch study and will be addressed in
future remedial actions as needed.
• OU14 consists of the area of contaminated groundwater between Route 54 (which
separates the northern industrial areas from the southern storage areas) and the northern
extent of groundwater contamination, which may reach the Rutherford Fork of the Obion
River. The extent of OU14 in the east-west direction is from Line B to Line C on the south
side, and from Line E to Ditch 7 on the north side. All intermediate source areas are
included in OU14.
To address the potential risks associated with OU1, a groundwater extraction and treatment
remedial action has been selected. An Interim Action Record of Decision (ROD) was signed in September
1992. This groundwater treatment system, when operational, will extract the highly-contaminated
groundwater immediately downgradient of the O-Line Ponds area, treat the water to meet discharge limits,
and reinject the treated water upgradient of the ponds. This system is designed to protect off-site users
of groundwater by reducing the levels of explosives compounds in the existing area of contaminated
groundwater and establishing hydraulic control over this area
Potential risks associated with OU2 and possible methods for reducing risks at the site were
investigated in the Focused Feasibility Study (FFS) for Operable Unit Two (USAEC, 1993a). Based on the
information gathered and presented in the FFS report, the Army has selected a preferred remedy for the
O-LJne Ponds area soils operable unit The rationale behind the remedy was presented to the public in
a Proposed Plan (USAEC, 19935).
2-5
-------
3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION
The Rl report for MAAP was released to the public in December 1991 and presented at a public
meeting held during the same month. Based on the results of the Rl, work then began on the Focused
Feasibility Study for OU1 (contaminated groundwater in the immediate vicinity of the O-Line Ponds). After
completion of treatability studies, an additional hydrogeological investigation of the area, and finalization
of a Proposed Plan and Record of Decision for OU1, work then began on OU2. The Focused Feasibility
Study (FFS) Report and Proposed Plan for OU2 were released to the public in July 1993. All of these
documents are available in both the Administrative Record and the information repositories maintained
at the Army Chief Engineer's Office at MAAP and the Mildred G. Fields Library, Milan, TN. The notice of
availability of these documents was published in The Mirror Exchange on June 30 and July 7,1993 and
The Jackson Sun on July 6,1993.
A 45-day public comment period was held from July 1, 1993 through August 16, 1993. In
addition, a public meeting was held on July 13,1993. At this meeting, representatives from MAAP, EPA,
and TDEC presented a summary of the site conditions and the remedial alternatives under consideration.
A response to the comments received during this period is included in the Responsiveness Summary,
which is part of this Record of Decision.
This decision document presents the selected remedial action for OU2 of the O-Line Ponds Area,
Milan Army Ammunition Plant, Milan, TN. The remedy has been chosen in accordance with CERCLA, as
amended by SARA, and, to the extent practicable, the National Contingency Plan. In addition, this
decision incorporates the findings of the FFS, which evaluated potential remedial alternatives for OU2.
The decision for this site is based on the Administrative Record.
3-1
-------
4.0 SCOPE AND ROLE OF OPERABLE UNIT OR RESPONSE ACTION
Past disposal practices at the O-Line Ponds contaminated soil and groundwater near the former
O-Line Ponds and released contaminants to ditches in the vicinity of the ponds. The Army has decided
to manage environmental contamination in the different media at the O-Line Ponds area in a phased
approach. This separation of environmental media into Operable Units allows the Army to begin
remediation prior to full assessment of the O-Line Ponds site.
An Operable Unit (OU) is defined by the National Oil and Hazardous Substances Pollution
Contingency Plan (40 CFR 300.5) as a discrete action which is an incremental step toward
comprehensively mitigating site problems. The Operable Units for the O-Line Ponds site at MAAP have
been defined as follows:
OU1: Contaminated groundwater beneath and immediately downgradient from the
former ponds which has been contaminated by past disposal practices at the
ponds.
OU2: Contaminated soil beneath and around the former ponds, and surface water and
shallow sediment in the drainage ditch that flows along the east and north sides
of the ponds, which have become contaminated as a result of past disposal
practices.
OU14: Contaminated groundwater between Route 54 (which separates the northern
industrial areas from the southern storage areas) and the northern extent of
groundwater contamination, which may reach the Rutherford Fork of the Obion
River. The extent of OU14 in the east-west direction is from Line B to Line C on
the south side, and from Line E to Ditch 7 on the north side.
The Army has already selected a remedy for OU1. The contaminated groundwater is a principal
potential threat at this site because of the high levels of explosives compounds detected in groundwater
samples collected from the O-LJne Ponds area This action is in the Remedial Design stage and
construction of extraction and reinjection wells is scheduled to begin in November, 1993. The award of
a construction contract for the treatment plant is expected to occur in December, 1993.
This ROD addresses contamination within OU2. OU14 requires additional investigations and will
be handled as a separate action.
OU2 consists of the soil, surface water, and shallow sediment that has been contaminated by
explosives-contaminated wastewaters that overflowed, drained, or seeped from the ponds during past
waste disposal operations. The primary contaminants are RDX, 2,4,6-TNT, and 1,3,5-TNB.
Access to the O-Line Ponds is currently restricted by a locked security fence and institutional
controls preclude the possibility of residential or industrial use of the area In addition, levels of
contamination in surface soil, surface water, and shallow sediment pose risks at levels less than EPA's
acceptable risk range. The principal threat posed by the site is the potential for leaching of contaminants
from soil to the water table, which results in an adverse impact on groundwater quality in the area
The Rl data indicate that the existing cap over the former ponds is effectively preventing infiltration
of water through the contaminated pond sediments. However, the data also indicate that the existing cap
does not cover all areas of contaminated soil, and the continued leaching of contaminants from the soil
around the perimeter of the cap to the water table would have an adverse impact on groundwater quality.
4-1
-------
The purpose of this response is to prevent current or future exposure to the contaminated soils around
the perimeter of the existing cap and to reduce contaminant migration into the groundwater.
Because this remedial action will eliminate further migration of contaminants from soil to
groundwater within the O-Line Ponds area, and will also eliminate all potential surface soil exposure
pathways, it is consistent with any planned future actions.
4-2
-------
5.0 SITE CHARACTERISTICS
This section provides a summary of the physical characteristics of the O-Line Ponds area,
including the setting, the nature and extent of soil, surface water, and shallow sediment contamination,
and the potential routes of contaminant migration and exposure. The information presented in this section
has been summarized from the Rl (USATHAMA, 1991) and FFS (USAEC, 1993a).
5.1 HYDROGEOLOGIC AND HYDROLOGIC SETTING
5.1.1 Soil Profile
The surface soils at MAAP consist chiefly of a brown silty clay that extends to a depth of 10 to 20
feet below the surface. This surface silt/clay unit is present across the facility except where it has been
eroded or otherwise removed (e.g., the ditches and engineered ponds). The hydrologic unit below the
surface soils is the Memphis Sand unit of the Claibome Group of Tertiary age. The Memphis Sand
consists of a thick body of non-marine fine- to coarse-grained sand that includes interbedded lenses of
clay and silt The clay and silt lenses were observed to vary in thickness from 0.5 to 6 inches and cannot
be correlated between adjacent boreholes; therefore, they are considered to be discontinuous. The lower
confining unit of the Memphis Sand is the Flour Island Formation, which is estimated to occur at an
approximate depth of 260 feet below ground surface in the O-Line Ponds area
5.1.2 Site Groundwater
The Memphis Sand aquifer is thick, laterally continuous, and highly transmissive. Based on results
of aquifer tests and grain size analyses of soil samples, the horizontal conductivity is estimated to be 27
ft/day. Due to the stratified nature of the aquifer, which contains numerous discontinuous lenses of silt
and clay, the vertical conductivity is estimated to be an order of magnitude smaller than the horizontal
conductivity. Thus, the conductivity is relatively high in both the horizontal and vertical directions.
Despite the high conductivity, the groundwater flow velocity is low because of a small gradient
Based on groundwater elevation contours developed during the Rl, groundwater in the O-Line Ponds area
flows toward the north-northwest (USATHAMA, 1991), and the horizontal gradient is estimated to be
approximately 0.0015 ft/ft. Using an estimated effective porosity of 20% for the soils, the average
groundwater velocity at the site is estimated to be 0.20 ft/day. The vertical gradient is also small (on the
order of -0.004 ft/ft), but because its magnitude is equal to or larger than the horizontal gradient,
groundwater flows downward at nearly the same rate that it travels laterally.
5.1.3 She Surface Water Hydrology
The O-Line Ponds area of the installation drains to the Rutherford Fork of the Obion River. This
portion of MAAP contains several well-developed, ephemeral, natural drainage bodies that join the
Rutherford Fork along the northern boundary of the installation. A small tributary receives effluent from
the O-Line Pink Water Treatment Facility (PWTF) and drains the capped area of the O-Line Ponds, then
empties into Ditch 5 near Route 104. Ditch 5 is renamed Ditch B upon passing Route 104, and this ditch
drains into the Rutherford Fork of the Obion River. The parent stream, the Obion River, empties into the
Mississippi River about 60 miles west of MAAP.
It was observed during the surface water and sediment sampling conducted during the Rl that
the interior drainage ditches, such as Ditch B and Ditch 5, are 'losing* ditches; that is, the base flow is
zero. Surface water flow occurs only as a result of storm water runoff and PWTF discharge, and surface
5-1
-------
water recharges groundwater at these times. *
5.2 CONTAMINATION ASSESSMENT
The results of the Rl (USATHAMA, 1991) and subsequent investigations (USAEC, 1993a) indicate
that the soil and groundwater in the vicinity of the former 0-Une Ponds and surface water and shallow
sediment in the ditches downgradient of the former ponds are contaminated with the explosives
compounds 2,4,6-TNT, RDX, HMX, nitrobenzene, 2,4-DNT, 2,6-DNT, 1,3,5-TNB, and 1,3-DNB. 2,4,6-TNT
and RDX are primary explosives and their presence at the site is due to the washout activities that have
taken place at O-Line since 1941. The other explosives compounds are degradation compounds or
contaminants of 2,4,6-TNT and RDX.
5.2.1 Soil Contamination
The O-Line Ponds were initially excavated in native soil, and were unlined through their operating
life. The result of constant hydraulic loading on the pond bottoms was the transport of explosives
compounds through the vadose zone and into the water table via infiltration of contaminated water
through the porous soils and aquifer material. During pond usage, the moisture content of the soil under
the ponds increased due to this infiltrating water. The analysis of soil samples collected from the pond
sediments prior to pond closure indicates that usage of the ponds resulted in high concentrations of
explosives compounds and high moisture content in the underlying soil.
In January-February of 1992, additional field work was conducted to evaluate the nature and
extent of soil contamination at the O-Line Ponds area This work included the drilling of boreholes,
collection of soil samples, and both physical and chemical analysis of the soil samples. These data were
used to evaluate the cap performance, vertical and horizontal extent of soil contamination, and the
potential for further leaching of explosives compounds from soil.
Seven boreholes were drilled around the perimeter of the cap to evaluate the lateral extent of soil
contamination. In addition, three boreholes were drilled through the cap and terminated at the water
table. The results of the soil investigation are the following:
• The surface soil around the perimeter of the O-Line Ponds cap is contaminated with low
levels of explosives compounds, probably as a result of overflows during use of the O-
Line Ponds or from sediment removal and earthmoving activities that took place during
pond closure.
• The subsurface soil around the perimeter of the cap is also contaminated with low to
moderate levels of explosives compounds.
• The levels of explosives compounds immediately below the PVC liner (in the undisturbed
pond sediments) are much lower than those measured before pond closure. The
moisture content of the soil is also reduced, which implies that drainage of excess
moisture has occurred since pond closure, and the bulk of the contaminants may have
been transported downward with the draining water.
• Concentrations of metals in the surface and subsurface soils are in the background range
and exceeded background only infrequently, and by a small amount Those samples
which had levels of metals above background levels were randomly located. The overall
results for heavy metals suggest that detected metals are not related to past disposal
activities in this area
5-2
-------
• The measured hydraulic conductivity of the cap material and the moisture content data
indicate that water is not percolating through the contaminated soil. Therefore, the
capped area of the former ponds are currently not a significant source of groundwater
contamination. Leaching of contaminants to the aquifer most likely occurred between
initiation of pond usage to shortly after pond closure, as indicated by the greatly reduced
levels of explosives compounds immediately below the PVC liner.
A biological/ecological assessment of the O-Une Ponds area concluded that a variety of
terrestrial species may be exposed to chemicals in soil at this area Because of their
intimate contact with the soil, soil-dwelling invertebrates are the terrestrial species most
likely to be impacted by chemicals in the soil. A series of bioassays were conducted to
evaluate the potential impacts of surface soil to the earthworm Eisenia foetida, indicating
no adverse impacts to the earthworms as a result of chemicals in the soil. It is therefore
concluded that terrestrial invertebrates are unlikely to be impacted by chemicals in the
soil.
5.2.1.1 Volume of contaminated soil under the cap. The area under the cap is approximately
280,000 ft2 and the depth to groundwater is approximately 45 feet. Therefore, the volume of contaminated
soil under the cap is approximately 12,600,000 ft3. Based on the limited sampling and analysis performed
under the cap, it has been estimated that the following quantities of principal contaminants are present
in the soil: 2,4,6-TNT, 17,600 IDS; RDX, 35,000 Ibs; and 1,3,5-TNB, 3,500 Ibs.
5.2.1.2 Routes of contaminant transport and exposure from soil under the cap. The Rl data
indicate that the existing cap over the former O-Une Ponds is effectively preventing infiltration of rainwater
through the contaminated pond sediments. However, if the existing institutional controls are relaxed and
the cap is allowed to fail, then humans could potentially be exposed to contaminants that would partition
to infiltrating-rainwater and would be transported to the water table.
5.2.1.3 Volume of contaminated soil around the perimeter of the cap. Although the levels of
contamination detected in soil around the perimeter of the cap are lower than those detected under the
cap, this contaminated soil also has the potential to impact groundwater quality. The surface area of the
contaminated area around the perimeter of the cap is estimated to be 302,000 ft2. The average depth
to water is 45 feet, so the volume of contaminated soil around the perimeter of the cap is estimated to
be 13,600,000 ft3. Based on the sampling and analysis performed around the perimeter of the cap, it has
been estimated that the following quantities of principal contaminants are present in the soil: 2,4,6-TNT,
1,900 Ibs; RDX, 2,800 Ibs; and 1,3,5-TNB, 340 Ibs.
5.2.1.4 Routes of contaminant transport and exposure from soil around the perimeter of the
cap. Humans could potentially be exposed to contaminants that could partition from soil to percolating
rainwater and be transported to the water table. Because the soil around the perimeter of the cap is
relatively permeable and is not protected by a low-permeability cover, this migration of contaminants is
occurring even under the current institutional controls. In addition, because contaminants are detectable
in surface soil around the perimeter of the cap, humans could be exposed to the explosives compounds
through dermal contact, inhalation, and ingestion.
5.2JJ Surface Water and Shalllow Sediment Contamination
Surface water and shallow sediment samples collected from the ditches downstream of O-LJne
suggest that there is low-level explosives contamination of these media. The levels of explosives detected
in the shallow sediment of the drainage ditches (to a depth of 2 feet) is at or below the levels attributable
to NPDES permitted discharges. Heavy metals On particular, cadmium, chromium, and lead) were
detectable in shallow sediment samples collected from Ditch 5 and Ditch B, but at generally low
5-3
-------
concentrations. Explosives compounds were not detected in samples found in the perennial stream (i-e.,
the Rutherford Fork) below the outfalls of Ditch B. The levels of explosives detected in surface water were
well within the facility's NPDES permit limits and, therefore, can be attributed to discharges from the ID-
Line PWTF.
Ditch 5 is dry throughout much of the year and is not a viable aquatic habitat However, Ditch
B drains into the Rutherford Fork of the Obion River where aquatic species occur. Surface water and
shallow sediment acute bioassays were conducted with Ceriodaphnia dub/a to evaluate potential impacts
to aquatic species in the Rutherford Fork of the Obion River. No mortality occurred in the surface water
bioassay and it was concluded that impacts to aquatic species are unlikely to occur as a result of surface
water from the O-Line Ponds Area Results of the shallow sediment elutriate bioassay indicated that the
shallow sediment in the tributary to Ditch 5 is toxic to the sensitive indicator species, although shallow
sediment samples collected downgradient from this point were not toxic. Based on the absence of toxicity
immediately downgradient from the O-Line Ponds Area, it was concluded that aquatic species are not
likely to be impacted in the Rutherford Fork of the Obion River (located approximately 12,000 feet
downstream) as a result of chemicals associated with the shallow sediments in OU2. Therefore, the
ditches downgradient of the O-LJne Ponds do not pose an environmental threat.
5.2.2.1 Volume of contaminated shallow sediment The length of the Ditch 5 tributary that
receives effluent from the O-Line PWTF and surface runoff from the O-Line Ponds cap (and which in the
past received wastewater directly from the ponds) from its source to its confluence with Ditch 5 is
approximately 2,800 feet. The length of Ditch 5 from the confluence with the tributary to Route 104 (where
the bioassay samples showed no toxicity) is approximately 125 feet The ditches are relatively narrow and
deeply-cut, with an approximate average width of 5 feet
5.2.2.2 Routes of contaminant transport and exposure. Contaminants in surface water and
shallow sediment could be transported to the Rutherford Fork when the ditches are flowing (i.e., when the
O-Line PWTF is discharging treated effluent or during a storm event). However, samples collected in the
Rutherford Fork indicate that the explosives compounds are not detectable in either surface water or
shallow sediment. In Ditch 5 and Ditch B, humans could be exposed to contaminants in the surface water
and shallow sediment via dermal contact while hunting or working in the ditches. Because workers are
in the ditches only infrequently, and because hunters are not permitted within the O-Line Ponds fenced
area (where the higher levels of contamination have been detected), these exposures are not expected
to be significant.
5-4
-------
6.0 SUMMARY OF SITE RISKS
This section contains an evaluation of potential human health and environmental impacts
associated with residual contamination in OU2. Risk assessment consists of the evaluation of the types
and levels of contaminants present within the Operable Unit, the pathways by which receptors could
potentially be exposed to these contaminants, and the toxicity and/or carcinogenicity of the contaminants.
A quantitative estimate of the potential for adverse health effects to occur in the future can be constructed
from these data In estimating these risks, the assumption was made that no remedial action would be
taken to address contamination within the Operable Unit; the resulting analysis is referred to as a baseline
risk assessment. The main focus of the baseline risk assessment (USAEC, 1993a) was to evaluate
potential risks associated with contaminated soil, surface water, and sediment from OU2 at the 0-Line
Ponds.
This risk assessment was conducted using generally conservative assumptions, including the
concept of 'reasonable maximum exposure,* as outlined by the U.S. Environmental Protection Agency
(USEPA, 1989a, 1990). The general purpose of using conservative assumptions is to ensure that the
decisions made will be protective of human health, even in the absence of comprehensive and definitive
health studies. Thus, the risks calculated in this section do not necessarily represent the true risks which
are or may be experienced by the exposed population; rather, they are upper-bound risks, which are
designed to provide a high level of protectiveness against adverse health effects. This is compatible with
EPA's policy of protecting all members of the population, including sensitive subgroups, from adverse
effects associated with exposures to hazardous chemicals.
The first five sections of the assessment review potential exposures associated with exposure to
chemicals in surface soil, surface water, and sediment at the O-LJne Ponds, and provide a conservative
evaluation of-potential risks associated with the exposure pathways evaluated. Section 6.6 presents a risk
assessment of potential exposures and risks from groundwater ingestion exposures associated with
groundwater from OU2 at the O-LJne Ponds.
6.1 SELECTION OF CHEMICALS OF POTENTIAL CONCERN
Chemicals of potential concern are those chemicals believed to be associated with past activities
at the O-LJne Ponds area of MAAP. The soil, surface water, and shallow sediment investigations
conducted from July to November 1990, in January and February 1992, and in July 1992, were the
sources of sampling data used in this risk assessment. All samples were analyzed for cadmium,
chromium, lead, mercury and nine explosives compounds (1,3-DNB, 2,4-DNT, 2,6-DNT, HMX,
nitrobenzene, RDX, tetryl, 1,3,5-TNB, and 2,4,6-TNT). Table 6-1 summarizes chemicals of potential
concern that were detected in surface soil, surface water, and shallow sediments.
6.1.1 Surface Soil
Soil samples were collected from seven locations around the perimeter of the O-LJne Ponds. Soil
samples were not collected on the cap of the O-LJne Ponds, which is comprised of clean fill. All soil
samples, with the exception of SS-1, consisted of vertically composite samples collected from 0-2 feet
Based on previous sampling results, as well as the historical data and knowledge of activities at
the site (no volatile or semi-volatile organic chemicals were used in the past at the O-LJne Ponds), soil at
the O-LJne Ponds was sampled primarily for the nine explosives compounds listed above and four target
inorganic compounds (Le., cadmium, chromium, lead, and mercury). In addition to the nine explosives
compounds and the four inorganic chemicals, the soil samples were analyzed for nitroglycerine and
6-1
-------
TABLE 6-1
CHEMICALS OF POTENTIAL CONCERN ADJACENT TO THE O-UNE PONDS
SURFACE SOIL (a)
Chemical
Organic Chemicals (pg/kg):
2,4-DNT
HMX
RDX
1,3,5-TNB
2,4,6-TNT
Inorganic Chemicals (mg/kg):
Manganese
Range of Detected
Concentrations
470
900-1,470
930-11.000
1,110
920-21,100
992
Frequency of
Detection (b)
1/8
4/8
4/8 .
1/8
4/8
1/1
Background
concernrauon (c/
-
-
_
-
-
200
SURFACE WATER (d)
Chemical
Organic Chemicals (pg/L):
HMX
1 ,1 2-Trichloroethane
Inorganic Chemicals (WJ/L):
Aluminum
Arsenic
Barium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Nickel
Potassium
Sodium
Vanadium
Zinc
Range of Detected
Concentrations
1.5
3.3
256-110,000
152
400-4,940
7,630 - 35,700
61.5
76.6
76
207 - 120,000
6.5 - 140
2,050 - 10.900
32.8 - 6,100
87.7
4,850-13,700
27,800 - 177,000
207
329
Frequency of
Detection
1/3
1/1
3/3
1/3
3/3
3/3
1/3
1/3
1/3
3/3
3/3
3/3
3/3
1/3
3/3
3/3
1/3
1/3
Background
Concentration (e)
-
-
282
5.08
39.6
4,200
12.0
50.0
162
1.114
2.52
2,080
462
68.6
3,380
6,680
7.64
422
SHALLOW SEDIMENT
-------
pentaerythritol tetranitrate. Soil sample SS-1, which was a discrete sample collected at a depth of 0-6
inches, was analyzed for the TAL compounds in addition to the nine explosives compounds.
As shown in Table 6-1, five explosives (1,3,5-TNB, 2,4,6-TNT, 2,4-DNT, HMX and RDX) were
detected in the surface soil, at concentrations ranging from 470 /jg/kg to 21,100 pg/kg. RDX HMX and
2,4,6-TNT were the most frequently detected explosives compounds, each detected in four of eight
samples. All five explosives compounds were retained as chemicals of potential concern. The maximum
concentrations for 1,3,5-TNB, 2,4,6-TNT, 2,4-DNT and RDX were detected at location SB-5. Manganese,
which was detected at a concentration greater than two times the single background concentration, was
the only inorganic chemical retained as a chemical of potential concern.
6.1.2 Surface Water
Surface water data used in the human health risk assessment were collected during Rl sampling
(USATHAMA, 1991) from a point adjacent to the O-line Ponds Area (designated as DTCH 5-2), and during
the FS from two points immediately downstream from the O-LJne Ponds Area and designated SW-2 and
SW-3.
The only explosives compound detected in surface water was HMX at SW-3, at a concentration
of 1.5 figlL. One other organic chemical (1,1,2-trichloroethane) was detected at DTCH5-2, at a
concentration of 3.3 pg/L Sixteen inorganic chemicals detected in surface water were present at
concentrations above the available background concentration, and were thus retained as chemicals of
potential concern. The maximum inorganic chemical concentrations were all detected at DTCH5-2, except
for calcium and sodium where maximum concentrations were detected at SW-2.
6.1.3 Shallow Sediment
One organic chemical was detected in the shallow sediment samples (trichlorofluoromethane),
at concentrations of 19 /*g/kg and 23 /*g/kg. Based on historical data and knowledge of activities at the
site where trichlorofluoromethane was not used, it is believed that this chemical is a sampling artifact
rather than associated with past activities.
Eleven inorganic chemicals were detected in shallow sediment Only sodium was present at
concentrations above background, and was therefore retained as a chemical of potential concern.
6.2 HUMAN HEALTH EXPOSURE ASSESSMENT
This section identifies the potential pathways by which human populations may be exposed to
the chemicals of potential concern, and quantifies exposures for selected pathways. This exposure
assessment discusses current and hypothetical future land use of the O-LJne Ponds and surrounding
area, identifies the pathways by which human populations may be exposed to chemicals of potential
concern at the O-Une Ponds under current and hypothetical future land use, selects pathways for further
evaluation, and presents quantitative exposure estimates for those pathways selected for quantitative
evaluation.
6.2.1 Current and Hypothetical Future Land Use and Site Characterization
Currently, no operations occur at the O-LJne Ponds that present the opportunity for significant
human exposures. The area is fenced and fully vegetated with grass. The only activity at the O-Une
Ponds is mowing, which occurs two to four times per year. To the east of the O-Une Ponds is a field
6-3
-------
leased for farming by a local farmer; to the north and west is mainly brush, where hunters have access,
but where there is no other human activity. To the south of the O-Line Ponds are the O-Une buildings,
where employees work indoors.
There are three hypothetical future land uses that could occur at the O-Line Ponds: continued
active MAAP industrial operations, agricultural land use, and residential land uses. If the O-Line Ponds
area remained as pan of the active MAAP installation, the most plausible future worker exposure scenario
would be one that was assumed for current land-use conditions (i.e., mowing). Another plausible future
land use would be agricultural, given that many other tracts of land at MAAP are leased to farmers and
are used for growing crops for livestock feed and for grazing cattle. No crops currently grown at MAAP
are used for human consumption. The third hypothetical land use is residential, whereby a house might
be built directly on the O-Line Ponds.
Because of the quality and availability of shallow groundwater, homeowners in this area of
Tennessee obtain their drinking water from the shallow aquifer. Surface water is not used as a source
of drinking water.
6.2.2 Potential Exposure Pathways
Table 6-2 summarizes the exposure pathways by which current populations could be exposed
to chemicals at the O-Line Ponds, and Table 6-3 summarizes the pathways by which hypothetical future
populations could be exposed. As noted earlier, no pathways were evaluated for exposure to
groundwater because this was conducted in the FS Report for OU1 (USATHAMA, 1992). All potential
exposure pathways that do not have negligible potential exposures are evaluated further in the following
section.
6.2.3 Quantification of Exposure
The following human exposure pathways were selected for quantitative evaluation:
• Surface Soil. Incidental ingestion and dermal absorption of chemicals in surface soil were
evaluated for hypothetical future residents living at the O-Line Ponds.
• Shallow Sediment. Dermal absorption and incidental ingestion of chemicals in shallow sediment
were evaluated for hypothetical children and teenagers playing in the streams and ditches near
the O-Line Ponds.
• Beef Cattle. Ingestion of beef from cattle that have consumed crops grown at the O-Line Ponds
was evaluated for hypothetical nearby residents.
To assess quantitatively the potential exposures associated with these pathways, estimates of
chemical concentrations at the exposure point are combined with exposure parameters describing the
extent, frequency, and duration of exposure to estimate chronic daily intakes (GDIs). Based on EPA
(1989a) guidance, GDIs should be quantified by estimating the reasonable maximum exposure (RME)
associated with the pathway of concern. The RME is intended to represent a possible upper-bound
exposure to a typical individual and is combined with upper-bound toxicity criteria to estimate risks.
Exposure point concentrations are presented first, then combined with exposure parameters to
estimate intakes for each of the selected exposure pathways.
6-4
-------
TABLE 6-2
POTENTIAL CURRENT HUMAN EXPOSURE PATHWAYS AT THE O-LINE PONDS
Exposure)
Medium
Potential Exposure
Pathway . :.;J,:H_...
Receptor Population
Potential for Significant Exposure
Method of Evaluation
Surface Soil
Dermal absorption and/or
Incidental Ingestion of
chemicals In surface soil.
MAAP personnel who mow
grass at the O-Llne Ponds.
Negligible. The O-Llne Ponds are
vegetated, and mowing typically
would not involve any contact with
surface soil.
None, given the low
potential for exposure.
Subsurface
Soil
Dermal absorption and/or
incidental Ingestion of
chemicals In subsurface
soil.
MAAP personnel who mow
grass at the O-Line Ponds.
Negligible. No activities (e.g.,
excavation) take place that involve.
contact with subsurface soil.
None, given the low
potential for exposure.
Ol
Surface Water
Dermal absorption and/or
Incidental Ingestion of
chemicals In surface
water.
MAAP personnel.
Negligible. Elevated surface water
concentrations were detected, but
there is no human activity at the O-
Line Ponds that involves contact
with surface water in ditches.
None, given the low
potential for exposure.
Shallow
Sediment
Dermal absorption and/or
Incidental Ingestion of
chemicals In shallow
sediment.
MAAP personnel.
Negligible. Chemical
concentrations in the
creeks/ditches were low, and there
is no human activity involves
contact with shallow sediment in
these creeks/ditches.
None, given the low
potential for exposure.
-------
TABLE 6-3
POTENTIAL FUTURE HUMAN EXPOSURE PATHWAYS AT THE O-LINE PONDS
Exposure
Medium
Surface Soil
Surface Soil
Subsurface Sol)
Subsurface Soil
Surface Water
Shallow Sediment
Air (dusts)
Air (dusts)
Agricultural
Produce
Beef/Dairy
Produce
Potential Exposure Pathway
Dermal absorption and/or
Incidental Ingestlon of chemicals In
surface soil.
Dermal absorption and/or
Incidental Ingestlon of chemicals In
surface soil.
Dermal absorption and/or
Incidental Ingestlon of chemicals In
subsurface soil.
Dermal absorption and/or
Incidental Ingestlon of chemicals In
subsurface soil.
Dermal absorption and/or
Incidental Ingestlon of chemicals In
surface water In ditches and
creeks near the O-Llne Ponds.
Dermal absorption and/or
Incidental Ingestlon of chemicals In
shallow sediment In ditches and
creeks.
Inhalation of wind-blown dusts.
Inhalation of wind-blown dusts and
dusts generated during plowing/
harvesting.
Ingestlon of crops that are grown
at the O-Llne Ponds.
Ingestlon of dairy milk or beef from
livestock that has consumed crops
grown on the O-Llne Ponds.
Receptor Population
Residents Irving at the O-Llne
Ponds.
Agricultural workers farming at the
O-Llne Ponds.
Residents living at the O-Llne
Ponds.
Agricultural workers farming at the
O-Llne Ponds.
Individuals living at the O-Llne
Ponds.
Individuals Irving at the O-Llne
Ponds.
Individuals living at the O-Llne
Ponds.
Agricultural workers plowing fields
at the O-Llne Ponds.
Residents living In or near MAAP.
Residents living In or near MAAP.
Potential fbif Significant Exposure
Moderate. Chemicals of concern were detected In surface
soil at the O-Llne Ponds. Individuals residing at the O-Llne
Ponds could have frequent dermal and Incidental Ingestlon
exposures.
Negligible. Although chemicals of concern were detected In
surface soil, farmers would most likely be exposed to
chemicals In soil only for short periods of time (e.g., during
planting and harvesting).
Negligible. Individuals would not be expected to come Into
contact with subsurface soil (greater than 2 feet deep) at the
O-Llne Ponds.
Negligible. Although farmers could come Into contact with
soil greater than 2 feet deep (due to tilling of the soil),
exposures would be expected to occur Infrequently.
Negligible. Standing water Is present In the ditches and
creeks for only about to hours following a rainfall, thus
there Is little potential for exposure.
Moderate. Children could play In the ditches and creeks
and Incidentally Ingest or dermally absorb chemicals
present In the shallow sediment.
Negligible. The O-Llne Ponds would be vegetated If
residents were to live there, thus chemicals would not be
released from the soil.
Negligible. Exposures would be of very short duration.
Further, based on other studies, It Is unlikely that farmers
would experience high Inhalation exposures while plowing.
Negligible. Virtually all crops currently grown at MAAP are
used for livestock feed, and this Is considered the most
likely use In the future.
Moderate. H Is possible that the O-Llne Ponds area could
be leased for agricultural purposes, and that beef cattle,
more prevalent than dairy cows In the area, could consume
this feed.
Method of Evaluation
Quantitative evaluation
for Ingestlon and dermal
exposures.
None, given the low
potential for exposure.
None. No complete
exposure pathway exists.
None, given the low
potential for exposure.
None, given the low
potential for exposure.
Quantitative evaluation
for Ingestlon and dermal
exposures.
None, given the low
potential for exposure.
None, given the low
potential for exposure.
None, given the low
potential for exposure.
Quantitative evaluation
for Ingestlon of beef.
-------
6.2.3.1 Estimation of Exposure Point Concentrations. Calculation of exposures to the
chemicals of potential concern requires the combination of exposure concentrations with assumptions
regarding the frequency, duration, and magnitude of receptor contact. Exposure point concentrations
for soil and shallow sediment pathways were determined using the RI/FS data, while exposure point
concentrations for beef were calculated using monitoring data from surface soil in combination with
environmental fate and transport models. Exposure point concentrations in surface soil, shallow sediment,
and beef are presented in the following sections along with estimation of chemical intakes for each
exposure pathway.
6.2.3.2 Estimation of Chemical Intakes. Chronic daily intakes (CDIs) are expressed as the
amount of a substance taken into the body per unit body weight per day, or mg/kg-day. To assess
quantitatively the potential exposures associated with these pathways, estimates of chemical
concentrations at the exposure point are combined with values describing the extent, frequency, and
duration of exposure. The CDIs, which incorporate the RME concentrations and conservative assumptions
and are intended to represent a possible upper-bound exposure to a typical individual, are combined with
toxicity criteria (presented later in Table 6-7) to estimate risks.
The generic equation for calculating chemical intakes is
Intake* C
where Intake = the amount of chemical entering the body (mg/kg body weight-day);
C = chemical concentration;
CR = contact rate; the amount of contaminated medium contacted per unit time;
EF = exposure frequency (days/year);
ED- = exposure duration (years);
BW = body weight (kg); and
AT = averaging time; period over which exposure is averaged (days).
For each of the exposure pathways to be quantified, the pathway-specific exposure parameters are
discussed below.
Incidental Ingestlon of Surface Soil. Chronic daily intakes (CDIs) for ingestion of surface soil
by residents at the O-Une Ponds were calculated by combining the RME exposure point concentrations
with the exposure parameters discussed below. For each chemical, the concentration used in the generic
equation for intake is the exposure point concentration of the specific chemical in surface soil as
presented in Table 6-4.
Residential soil ingestion exposures were evaluated for a hypothetical future resident living at the
O-Line Ponds. Exposures were evaluated for individuals 0-30 years of age. An exposure frequency (EF)
of 350 days/year (i.e., 50 weeks per year) and an exposure duration (ED) of 30 years were used. The
exposure frequency is the standard default parameter recommended by EPA (1991), and the exposure
duration is the national upper-bound time at one residence (USEPA, 1991, 1989a). The standard
assumption for a lifetime (AT) of 70 years (USEPA, 1989b) also was used.
The contact rate (CR) in the intake equation is equivalent to the soil ingestion rate. A soil
ingestion rate OR) of 120 mg/day was used for residents who may incidentally ingest surface soil. The
soil ingestion rate value is an age-weighted average, assuming 6-year olds ingest soil at a rate of 200
mg/day, and older individuals ingest 100 mg/day (USEPA, 1989a, 1991). A time-weighted average body
weight (BW) of 48 kg for a resident (0-30 years) was based on data provided in EPA (1 989b). To estimate
the CDIs, it was assumed that the fraction of total daily soil intake from the contaminated source was
6-7
-------
TABLE 6-4
EXPOSURE POINT CONCENTRATIONS AND CALCULATED GDIs
SURFACE SOIL EXPOSURE PATHWAYS
Chemical
Chemicals Exhibiting Carcinogenic Effects
Organic Chemicals
2,4-DNT
ROX
2.4,6-TNT
Chemical* Exhibiting Noncarclnogenlc Effects
Organic Chemicals
2,4-DNT
HMX
RDX
1,3,5-TNB
2,4,6-TNT
Inorganic Chemicals
Manganese
RME Exposure Point
Concentration (mg/kg)
4.40E-01
1.10E+01
2.11E+01
4.40E-01
1.11E+00
1.10E+01
7.50E-01
2.11E+01
9.92E+02
GDI: Incidental Ingeatlon
of Surface Soil (mg/kg-day)
4.52E-07
1.13E-05
2.17E-05
1.0SE-06
2.66E-06
2.64E-05
1.80E-06
5.06E-05
2.3BE-03
GDI: Dermal Absorption of
Chemicals In Soil (mg/kg-day)
1.08E-07
2,71 E-06
5.20E-06
2.53E-07
6.39E-07
6.33E-06
4.32E-07
1.21E-05
5.71 E-05
-------
100%' This factor assumes that all of the daily soil intake is from soil in the contaminated yard (at the O-
Line Ponds). It was also assumed that the oral absorption factor for each of the chemicals in soil was 1.0
(i.e., 100% is absorbed into the body from the soil). Therefore, the bioavailability for the chemicals of
concern was conservatively assumed to be 1.0. This assumption of 100% absorption in the
gastrointestinal tract may over-estimate ingestion exposures.
The exposure point concentrations and resulting GDIs for chemicals exhibiting carcinogenic effects
and chemicals exhibiting noncarcinogenic effects due to the incidental ingestion of soil are summarized
in Table 6-4.
Dermal Absorption of Chemicals from Surface Soil. Potential exposures through dermal contact
with chemicals of potential concern in soil may occur by a hypothetical future resident at the O-LJne
Ponds. The parameters describing exposure frequency (EF), duration of exposure (ED), body weight
(BW), and averaging time (AT) are identical to those used for estimating incidental ingestion of soil. The
RME exposure point concentrations (i.e., surface soil concentrations) used in the dermal absorption
pathway are presented in Table 6-4, along with the GDIs.
The product of several parameters determines the contact rate for this exposure pathway: skin
surface area (SA); adherence factor (AF); and dermal absorption fraction (Ab). It is assumed that the skin
surface area (SA) available for contact for a resident 0-30 years of age is 4,800 cm2/day. This value is
an age-weighted average 50th percentile surface area value from EPA (1985,1989a), assuming that the
surface area of the hands, one-half of the arms and one-half of the legs are uncovered and exposed. The
recommended default soil-to-skin adherence factor (AF) of 0.6 mg/cm2, which is the median of 0.2-1.0
mg/cm2 (USEPA, 1992, USEPA IV, 1992), was used for this exposure scenario (USEPA, 1989a).
The amount of chemical absorbed through the skin into the body from contacting soil is required
for estimating dermal exposures. For a chemical to be absorbed through the skin from soil, it must be
released from the soil matrix, pass through the stratum comeum, the epidermis, the dermis, and into the
systemic circulation. For the purposes of this assessment, the amount of exposure due to dermal
absorption considers the fraction of absorption from contacted soil that may occur for the selected
chemicals of potential concern. In accordance with EPA Region IV guidance, a default value of 1% for
all organic and 0.1% for inorganic chemicals of concern was used (USEPA IV, 1992). Using this
absorption fraction assumed that 1% of the organic chemical in the soil matrix was absorbed through the
skin and entered the systemic circulation.
GDIs (expressed as absorbed doses) for the chemicals of potential concern were estimated using
the exposure parameters discussed above, and are summarized in Table 6-4. The GDIs are calculated
differently for chemicals exhibiting carcinogenic and noncarcinogenic effects (with respect to averaging
time).
Incidental Ingestion of Shallow Sediment Under future land use conditions, a childAeenager
(6-16 years) at the O-Une Ponds is assumed to be exposed to chemicals of potential concern through
incidental ingestion of shallow sediment in the ditches and creeks adjacent to the O-Line Ponds. It was
considered unlikely that adults would be present in the ditches and creeks, thus this pathway was
evaluated only for children/teenagers. Intakes due to incidental ingestion of shallow sediment for
chemicals of concern were estimated using the same equation as for Incidental Ingestion of Surface Soil.
It was assumed that shallow sediment may be contacted while playing in the ditches and creeks
for 3 days/week during the warmer months of the year (June, July and August) and 2 days/week during
the spring and fall (May and September); thus, the exposure frequency (EF) is 52 days/year, and the
exposure duration (ED) is 10 years (i.e., 6 to 16 years of age for a child/teenager). A soil ingestion rate
(IR) of 110 mg/day was used for the children/teenagers. As discussed earlier, the soil ingestion rate value
6-9
-------
is an age-averaged value and assumes 6 year olds ingest soil at a rate of 200 mg/day and older
childrenAeenagers ingest soil at 100 mg/day (USEPA, 1989a, 1991). A time-weighted average body
weight (BW) value of 40 kg for a chiloVteenager (6-16 years) is based on data provided in EPA (1989b).
As before, it was conservatively assumed that all chemicals of concern were 100% absorbed through the
gastrointestinal tract.
RME exposure point concentrations and calculated GDIs for shallow sediment exposure pathways
are presented in Table 6-5.
Dermal Absorption of Chemicals from Shallow Sediment. This scenario evaluates potential
exposures through dermal contact with chemicals of potential concern in shallow sediment by a
childAeenager 6-16 years of age in the ditches and creeks. GDIs estimated for dermal contact with
chemicals of potential concern in shallow sediment are calculated using the same equation and
parameters as for Dermal Absorption of Chemicals in Surface Soil.
The exposure parameters describing frequency and duration of contact, body weight, and lifetime
are identical to those used for estimating incidental ingestion of shallow sediment by a childAeenager (6-
1 6 years). For this pathway, however, it was assumed that the skin surface area (SA) available for contact
for a childAeenager was 4,200 cm2/day. The recommended default soil-to-skin adherence factor (AF) of
0.6 mg/cm2 was also used for this exposure scenario (USEPA, 1992, USEPA IV 1992).
As discussed previously, exposures due to dermal absorption are evaluated by estimating the
fraction of absorption from contacted shallow sediment that may occur for the selected chemicals of
potential concern. Due to insufficient data on dermal absorption of organic chemicals of concern, EPA
Region IV's default value of 1.0% was used, in accordance with EPA Region IV guidance (USEPA IV,
1992).
The RME exposure point concentrations and GDIs (expressed as absorbed doses) for the
chemical of potential concern absorbed from shallow sediment are summarized in Table 6-5 for a
childAeenager.
Inqestion of Beef. GDIs were calculated for the ingestion of beef using the exposure point
concentrations presented in Table 6-6, and the beef ingestion exposure parameters as presented below.
Exposures due to beef ingestion were calculated using the following equation:
where
GDI = chronic daily intake (mg/kg-day)
Cb = exposure point concentration in beef (mg/kg)
IR = ingestion rate of beef (g/day)
CF = conversion factor (kg/103)
EF = exposure frequency (days/year)
ED = exposure duration (years)
FL = fraction of beef ingested that is locally produced (unitless)
BW = average body weight over period of exposure (kg)
AT = averaging time over which risk is being estimated (a lifetime [70 years] for
potential carcinogens and the period of exposure for noncarcinogens)
Days = days in a year (365 days/year)
6-10
-------
TABLE 6-5
EXPOSURE POINT CONCENTRATIONS AND CALCULATED GDIs
SEDIMENT EXPOSURE PATHWAYS FOR A CHILD/TEENAGER
Chemical
Chemical* Exhibiting Noncarclnogenlc Effect*
Organic Chemicals
Trlchlorofluoromethano
RME Expoaure Point
Concentration (mg/kg)
GDI: Incidental Ingeatlon
of Sediment (mg/kg-day)
2.3E-02
9.01 E-09
GDI: Dermal Absorption of
Chemicals In Sediment
(mg/kg-day)
2.06E-09
-------
TABLE 6-6
EXPOSURE POINT CONCENTRATIONS AND CALCULATED GDIs
BEEF INGESTION EXPOSURE PATHWAY
Chemical
Chemicals Exhibiting
Carcinogenic effects
Organic Chemicals
2,4-DNT
RDX
2.4,6-TNT
Chemicals Exhibiting
Nonearcinogenic Effects
Organic Chemicals
2,4-DNT
HMX
RDX
1,3,5-TNB
2,4,6-TNT
Inorganic Chemicals
Manganese
RME Exposure Point
Concentration (mg/kg) (a)
2.28E-05
1.00E-O4
6.79E-04
228E-05
4.92E-06
1.00E-04
1.02E-05
6.79E-O4
1.19E+00
GDI: Ingestion of Beef
(mg/kg-day)
5.78E-09
2.54E-08
1.72E-07
1.35E-08
Z91E-09
5.93E-08
6.03E-09
4.02E-07
7.05E-04
(a) - The concentrations in beef reflect ingestion of hay and com silage grown at the O-Line Ponds area.
6-12
-------
Beef ingestion exposures were evaluated for individuals between the ages of 1-30. Average body
weights for the age periods were based on data provided by EPA (1989b), and ingestion rates were
derived from USDA (1982). Individuals aged 1-8 were assumed to have an average body weight of 20
kg and an ingestion rate of 92 g/day, individuals aged 9 to 18 were assumed to have an average body
weight of 52 kg and an ingestion rate of 152 g/day, and individuals aged 19 to 30 were assumed to have
an average body weight of 70 kg and an ingestion rate of 166 g/day. All exposed individuals were
assumed to eat beef 3 times a week throughout the year (156 days/year), and obtain 44% of their beef
from cattle that consume crops grown at the O-Une Ponds {USEPA, 1989b). Individuals were assumed
to be exposed for 30 years (the upper bound estimate of the time a person is likely to spend in any one
residence [USEPA, 1989a]) and assumed to live for 70 years (USEPA, 1989a).
It was assumed conservatively that no reductions in concentrations occur during preparation of
the beef (i.e., cooking). Table 6-6 presents the estimated chemical concentrations in beef and the
resulting GDIs that were derived using the assumed exposure parameters for ingestion of beef. A
complete derivation of the chemical concentrations in beef can be found in the FFS (USAEC, 1993a).
6.3 TOXICFTY ASSESSMENT
Table 6-7 presents chronic oral health effects criteria (slope factors and RfDs) for the chemicals
of potential concern quantitatively evaluated in this assessment Detailed toxicity profiles for chemicals
detected in soil, surface water, and shallow sediment at the O-LJne Ponds area are provided in Appendix
B of the FFS (USAEC, 1993a).
No oral health effects criteria are available for sodium, thus potential risks associated with
exposure to sodium will not be quantitatively evaluated. Exclusion of this chemical from the quantitative
evaluation is not anticipated to result in significant underestimation of risk, because it is an essential
nutrient, and it is not likely to pose adverse health effects at the concentrations present in the media
evaluated for the O-LJne Ponds.
6.4 RISK CHARACTERIZATION
Risk estimates were calculated by combining GDIs with reference doses (RfDs) or slope factors
(SFs) to derive noncarcinogenic hazard indices or excess lifetime cancer risks, respectively. For
carcinogens, potential risks are presented as the product of the GDI and slope factor. Risks were
compared to EPA's target risk range of 10"4 to 10"6. For noncarcinogens, potential hazards are presented
as the ratio of the GDI to the reference dose (CDkRfD), and the sum of the ratios is referred to as the
hazard index In general, hazard indices that are less than one are not likely to be associated with
adverse health effects, and are therefore less likely to be of regulatory concern than hazard indices
greater than one. The remainder of this section presents potential risks and hazards for five different
exposure pathways. Table 6-8 summarizes the estimated risks for all exposure pathways.
6.4.1 Incidental Inoestlon of Soil
Excess lifetime cancer risk estimates associated with incidental soil ingestion exposures for future
residents at the O-Une Ponds are 2x10"6, due primarily to RDX and 2,4,6-TNT. This value is within the
EPA target risk range of 10"4 to 10"6. The hazard index for incidental ingestion of soil from the 0-Line
Ponds is below one. This indicates that adverse noncarcinogenic effects are unlikely to occur for those
who incidentally ingest soil at the O-Une Ponds.
6-13
-------
TABLE 6-7
ORAL TOXICITY VALUES FOR CHEMICALS OF POTENTIAL CONCERN AT THE O-UNE PONDS
Chemical
Chronic
Reference
Dose
(mg/kg-day)
Uncertainty
Factor (a)
Toxicological
Endpoint (b)
Reference
Dose
Source
Cancer
Slope Factor
(mg/kg-day>-1
EPA weight
of Evidence Slope
Classification Factor
(c) Source
Organic Chemicals:
DNT (2.4-. 2.6-}
HMX
RDX
1,1,2-Trichloroethane
TrichIorofIuoromethane
1,3.5-TNB
2,4.6-TNT
Inorganic Chemicals:
2E-03
5E-02
3E-03
4E-03
3E-01
5E-05
5E-04
100
1000
100
1,000
1,000
10,000
1,000
Neurotoxicity
Liver
Prostate
Liver
Mortality
Spleen
Liver
IRIS
IRIS
IRIS
IRIS
IRIS
IRIS
IRIS
6.8E-01
1.1E-01
5.7E-02
3E-02
62
D
C
C
HEAST
IRIS
IRIS
IRIS
IRIS
Aluminum
Arsenic
Barium
Berylliun
Calcium
Chromium (VI) and compounds (e)
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury, inorganic
Nickel
Potassium
Sodium
Vanadium
Zinc
..
3E-04
7E-02
5E-03
--
5E-03
.-
3.7E-02 (f)
--
--
--
1E-01
3E-04
2E-02
• -
--
7E-03
2E-01
'..
3
3
100
--
500
--
1
--
--
• -
1
1,000
300
--
--
100
10
..
Skin
> Blood Pressure
None Observed
--
CNS
--
Gastrointestinal
Tract
--
CNS
--
CNS
Kidney
Body Weight
--
--
None Observed
Blood (Anemia)
HEAST
IRIS 1.75E+00 (d)
IRIS
IRIS 4.3E*00
-.
IRIS
IRIS
HEAST
HEAST
IRIS
..
IRIS
HEAST
IRIS
.-
..
HEAST
HEAST
A
-.
82
-.
--
--
--
--
B2
•-
D
D
--
--
--
--
IRIS
--
IRIS
--
IRIS
--
--
--
IRIS
--
IRIS
IR"~
r
-
--
--
(a) Safety factors are the products of uncertainty factors and modifying factors. Uncertainty factors used to develop reference dos«
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 the variation in sensitivity among the members of the human population;
- a 10-fold factor to account for the uncertainty in extrapolating arrimel data to the case of humans;
- a 10-fold factor to account for the uncertainty in extrapolating from less than chronic MOAELs 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) The lexicological endpoint is the organ most sensitive to a chemical's toxic effect. RfOs are based on toxic effects in the
target organ. If an RfO was based on a study in which a target organ was not identified, an organ or system known to be affect*
by the chemical is listed.
(c) EPA Weight of Evidence for Carcinogenic Effects:
CAI » Human carcinogen based on adequate evidence from human studies;
CB21 > Probable hunan carcinogen based on inadequate evidence from human studies and adequate evidence from animal studies;
CC1 = Possible human carcinogen based on limited evidence from animal studies in the absence of human studies; and
ID1 = Not classified as to human carcinogenicity. .
(d) A unit risk of 5E-5 (ug/L)-1 has been proposed by the Risk Assessment Forum and thi* recommendation has been scheduled for SAB
review. This value is equivalent to 1.75 (mg/kg-day)-1 assuming a 70-kg individual ingests 2 liters of water per day.
(e) Chromium (VI) was used as a surrogate to evaluate total chromium.
(f) Drinking water standard reported in mg/L was converted to mg/kg-day by assuring a 70 kg adult drinks 2 liters of water per day.
NOTE: IRIS * Integrated Risk Information System - September 1, 1992.
HEAST - Health Effects Assessment Susmary Tables - First Quarter 1992.
e HO information available.
CNS = Central Nervous System
> * Increase
6-14
-------
TABLE 6-8
SUMMARY OF RISKS
Pathway Hazard Index (a) Upper Bound Excess
Lifetime Cancer Risk
Soil. Shallow Sediment, and Beef Pathways
Incidental Ingestion
Surface Soil
Shallow Sediment
Dermal Absorption
Surface Soil
Shallow Sediment
Ingestion of Beef
TOTAL RISK
<1 (2E-01)
<1 (3E-08)
<1 (5E-02)
<1 (7E-09)
<1 (8E-03)
<1 (3E-01)
2E-06
NA
6E-07
NA
1E-08
3E-06
(a) - The hazard index is the sum of the intake:RfD ratios for the listed chemicals.
NA = Not applicable.
6-15
-------
6.4.2 Dermal Exposures to Chemicals in Surface Soil
Excess lifetime cancer risk estimates associated with dermal absorption of chemicals in soil for
future residents at the O-Line Ponds are 6x10"7. This value is below the EPA target risk range of 10"* to
10"6. The hazard index for dermal absorption of chemicals in soil from the O-Line Ponds is below one.
This indicates that neither carcinogenic nor adverse noncarcinogenic effects are likely to occur for those
who are dermally exposed to chemicals in surface soil at the O-Line Ponds.
6.4.3 Incidental Ingestlon of Shallow Sediment
No carcinogens were detected in shallow sediment, so no cancer risks were calculated for this
exposure pathway. The hazard index for incidental ingestion of shallow sediment is much lower than one.
This indicates that adverse noncarcinogenic effects are unlikely to occur for those who incidentally ingest
shallow sediment at the O-Line Ponds. Risks associated with exposure to sodium were not included,
because oral toxicity criteria have not been developed for this chemical. This may slightly under-estimate
the risks and hazards associated with this pathway, although this is unlikely to change the conclusions
regarding this pathway.
6.4.4 Dermal Absorption of Chemicals in Shallow Sediment
No carcinogens were detected in shallow sediment; thus, only a hazard index was calculated for
dermal absorption of chemicals in shallow sediment. The hazard index for this pathway was much lower
than one, indicating that adverse noncarcinogenic effects are unlikely to occur for persons dermally
exposed to chemicals in shallow sediment. Once again, the risk evaluation does not include risks
associated with exposure to sodium, because oral toxicity criteria have not been developed for this
chemical.
6.4.5 Inoestlon of Beef
The excess lifetime cancer risk estimate associated with consumption of beef is 1x1O"8, two orders
of magnitude below the lower end of the EPA target risk range of 1O"4 to 1O"6. All of the individual hazard
indices as well as the total hazard index were below a value of one. This indicates that adverse
noncarcinogenic effects are unlikely to occur for those who ingest beef from cattle that have consumed
crops grown at the O-Line Ponds.
6.4.6 Total Risks
Risks associated with all exposure pathways evaluated in this assessment were added for
hypothetical future receptors at the O-Line Ponds. As shown in Table 6-8, total risks associated with
exposures to chemicals in soil, shallow sediment, and beef were 3x10"6, within the EPA target risk range
of 10"* to 10"6. In addition, the hazard index for these pathways combined was less than one, indicating
that adverse noncarcinogenic effects were unlikely to occur.
6.5 EVALUATION OF EFFECTS OF INGESTION OF GROUNDWATER CONTAMINATED BY OU2
Two scenarios were used to estimate the level of groundwater contamination that could occur due
to residual soil contamination in OU2:
• Scenario 1 consists of continued maintenance of the existing cap (which prevents migration
of the contaminants under the cap) but allows rainwater to infiltrate the contaminated soil around
6-16
-------
the perimeter of the cap. Under these conditions, the explosives compounds will partition from
subsurface soil to the percolating water, and will be transported to the aquifer.
• Scenario 2 consists of a discontinuation of maintenance of the existing cap. In developing this
scenario, it was assumed that the cap would eventually erode and fail to prevent water infiltration
through the contaminated soil currently under the cap. Calculations were performed to estimate
the rate of migration of contaminants to the water table.
As required by the NCP, this evaluation of potential risks was performed under the assumption
of the absence of institutional controls (e.g. controlled access to and usage of the O-Line Ponds area) and
in the absence of other remedial actions (e.g. the groundwater treatment system for OU1). Therefore, the
potential risks estimated in this section are those that could result solely from continued contaminant
migration from OU2 and uncontrolled residential use of the area
6.5.1 Chemicals Of Potential Concern
Chemicals of potential concern for the groundwater exposure pathway are those chemicals which
were detected in more than one sample in the subsurface soil of OU2: 1,3,5-TNB, 2,4,6-TNT, and RDX.
The resulting concentrations of explosives compounds in the shallow groundwater are shown in Tables
6-9 and 6-10, for Scenarios 1 and 2, respectively.
6.5.2 Exposure Assessment
In this section, the potential pathways by which individuals could be exposed to the chemicals
of potential concern in groundwater are identified and exposure is quantified. This risk assessment
focuses solely on potential human health risks associated with ingestion of untreated groundwater from
OU2. As described above, two hypothetical scenarios were evaluated.
Chronic daily intakes (GDIs) were calculated for residential drinking water exposures using the
estimated exposure point concentrations presented in Tables 6-9 and 6-10 for Scenarios 1 and 2,
respectively. GDIs were estimated using the equation and assumptions presented below for groundwater
ingestion:
BW*AT*Days
where:
GDI = chronic daily intake (mg/kg-day),
Cw = chemical concentration in groundwater (mg/L),
X = conversion factor (mg/IO3^)
IR = water ingestion rate (L/day),
EF = frequency of exposure (days/year),
ED = duration of exposure (years),
BW = average body weight (kg),
AT = averaging time (70 years for carcinogens, 30 years for noncarcinogens), and
Days = conversion factor (365 days/year).
Drinking water exposures are evaluated for a hypothetical future resident between the ages of 0
to 30. For individuals 0-30 years of age, a time-weighted average body weight of 48 kg (based on data
in EPA 19898), and a drinking water rate of 1.9 liters/day are used as parameters for the reasonable
6-17
-------
maximum exposure (RME) case. The drinking water consumption rate has been calculated assuming a
consumption rate of 1 liter/day for individuals up to 10 kg (approximately 3 years of age), and a rate of
2 liters/day for those over 3 years of age. An exposure duration of 30 years, the upper-bound time at one
residence, is assumed for residents (USEPA, 1991, USEPA, 1989a).
GDIs calculated using these exposure assumptions for chemicals exhibiting carcinogenic effects
and chemicals exhibiting noncarcinogenic effects due to ingestion of groundwater from OU2 are
presented in Tables 6-9 and 6-10.
6.5.3 Risk Characterization
Risks and hazards were calculated using methods similar to those described in Section 6.4.
Tables 6-9 and 6-10 present the exposure point concentrations, GDIs, toxicity data, and estimated risks
for Scenarios 1 and 2, respectively.
Carcinogenic and noncarcinogenic risks associated with the ingestion of untreated groundwater
during Scenarios 1 and 2 by future residents were calculated. The estimated upper-bound excess lifetime
cancer risk for ingestion of groundwater during Scenario 1 is 2x10"3, while estimated upper bound excess
lifetime cancer risk for groundwater ingestion during Scenario 2 is 1x10"1. The risks from both scenarios
exceed EPA's target risk range of 10"6 to 10"4 range for human health protectiveness. For
noncarcinogenic chemicals, the hazard index exceeded one for all chemicals in both Scenarios 1 and 2.
6.6 SUMMARY OF ECOLOGICAL RISK ASSESSMENT
This section summarizes potential impacts to nonhuman receptors resulting from exposure to the
chemicals of potential concern at the 0-Line Ponds area The approaches used in this environmental
assessment roughly parallel those used in the human health risk assessment. In this section, potentially
exposed populations (receptors) are identified, and then information on exposure and toxicity is combined
to derive qualitative or quantitative estimates of impact.
The area within several miles of the O-Line Ponds is rural and is used for agriculture, with some
residential areas. Much of the land is used for crop and pastureland. The terrain of MAAP consists
mainly of gently rolling hills and numerous small drainage courses. The potential receptors, potential
pathways by which plants and wildlife may be exposed, and the potential ecological impacts are
summarized. The pathway analysis is limited to potential exposures to chemicals of potential concern in
surface and shallow subsurface soils, shallow sediments, and surface waters. Plants and wildlife will not
be exposed to chemicals of potential concern in deep subsurface soils or groundwater because these
media are not accessible to the potential receptors. Discussions of potential impacts include results of
bioassays conducted for surface soil, surface water, and shallow sediment elutriate during the RI/FS. The
potential risks to the terrestrial invertebrates and aquatic life associated with the O-Line Ponds area were
evaluated based on the outcomes of these bioassays.
Absolute conclusions regarding the potential environmental impacts of the O-Line Ponds cannot
be made because there are many uncertainties surrounding the estimates of toxicity and exposure.
However, given the available data and limitations, several general conclusions regarding the potential for
environmental impacts are presented below.
6-18
-------
TABLE 6-9
ESTIMATED EXPOSURE POINT CONCENTRATIONS, GDIs, AND POTENTIAL RISKS
GROUNDWATER EXPOSURE PATHWAYS, SCENARIO 1
Chemicals Exhibiting
Carcinogenic Effects
RDX
2,4,6-TrlnHrotoluene (246TNT)
TOTAL
Chemicals Exhibiting
Noncarclnogenlc Effects
RDX
1,3,5-TrlnHrobenzene (135TNB)
2,4,6-Trlnttrotoluene (246TMT)
Hazard Index
RME Exposure Point
Concentration (jig/L)
9.6E+02
6.96E+02
RME Exposure Point
Concentration (jig/L)
9.6E+02
1.25E+02
6.96E+02
CD): Ingestlon of
Oroundwater (mg/kg-day)
1.6E-02
1.1E-02
CD): Ingestlon of
Qroundwater (mg/kg-day)
3.6E-02
4.7E-03
2.6E-02
Cancer Slope Factor
(mg/kg-day)'1
1.1E-01
3E-02
RfD
(mg/kg-day)
3E-03
5E-05
5E-04
Upper Bound Excess
Lifetime Cancer Risk
2E-03 i
3Ej)4
2E-03
1E+01
9E+01
SE+01
2E+02
2
to
-------
TABLE 6-10
ESTIMATED EXPOSURE POINT CONCENTRATIONS, GDIs, AND POTENTIAL RISKS
GROUNDWATER EXPOSURE PATHWAYS, SCENARIO 2
Chemicals Exhibiting
Carcinogenic Effect*
RDX
2,4,6-TrlnHrototuene (24BTMT)
TOTAL
Chemical* Exhibiting
Noncarclnogenlc Effects
RDX
1,3.5-TrlnHrobenzene (135TNB)
2,4,6-Trlnttrotoluene (246TNT)
HAZARD INDEX
RME Exposure Point
Concentration (pg/L)
6.00E+04
1.02E+04
RME Exposure Point
Concentration fjtg/L)
6.00E+04
2.04E+03
1.02E+04
GDI: Ingestlonof
Qroundwater (mg/kg-day)
9.8E-01
1.7E-01
GDI: Ingestlonof
Qroundwater (mg/kg-day)
2.3E+00
7.7E-02
3.9E-01
Cancer Slope Factor
(mg/kg-day)'1
1.1E-01
3E-02
RfD
(mg/kg-day)
3E-03
5E-05
5E-04
Upper Bound Excess
Lifetime Cancer Risk
1E-01
5E-03
1E-01
CDhRfD
Ratio
8E+02
2E+03
8E+02
3E+03
-------
Given the lack of phytotoxicity data, a quantitative assessment of potential plant impacts was not
done. However, it can be concluded that chemical concentrations at the site are below levels that are
likely to impact at least some terrestrial plant species. This conclusion is based upon the observation that
vegetation was present throughout the O-Une Ponds area, including the region adjacent to the landfill cap
where chemicals were found at the highest concentration within the surface soil.
A variety of terrestrial species may be exposed to chemicals at the O-LJne Ponds Area. Because
of their intimate contact with the soil, soil-dwelling invertebrates are the terrestrial species most likely to
be impacted by chemicals in the soil. Accordingly, a series of bioassays were conducted to evaluate the
potential impacts of surface soil to the earthworm Eisenia foetida. The results of the bioassay indicated
no impacts to the earthworms as a result of chemicals in the soil. It is therefore concluded that terrestrial
invertebrates are unlikely to be impacted by chemicals in the soil.
Terrestrial vertebrates may also be exposed to chemicals through the ingestion of chemicals that
have accumulated in food items (e.g., soil-dwelling invertebrates). Because of their prevalence and high
concentrations, explosives compounds have the greatest potential to bioaccumulate at the O-Une Ponds
Area However, tissue residue analysis of soil-dwelling invertebrates from the O-LJne Ponds Area indicated
that the accumulation of explosives compounds is not occurring and this pathway is considered to be
incomplete.
Ditch 5/B is dry throughout much of the year and is not a viable aquatic habitat. However, Ditch
5/B drains into the Rutherford Fork of the Obion River where aquatic species occur. Surface water and
shallow sediment acute bioassays were conducted with Ceriodaphnia dubia to evaluate potential impacts
to aquatic species in the Rutherford Fork of the Obion River. No mortality occurred in the surface water
bioassay and it was concluded that impacts to aquatic species are unlikely to occur as a result of surface
water from the O-LJne Ponds area Results of the shallow sediment elutriate bioassay indicated toxicity
in the O-Line Ponds Area tributary, though no toxicity occurred downgradient from this point Based upon
the absence of toxicity immediately downgradient from the O-IJne Ponds Area it was concluded that
impacts to aquatic species in the Rutherford Fork of the Obion River (located approximately 12,000 feet
downstream) are unlikely to occur as a result of chemicals associated with the shallow sediments.
6.7 RISK ASSESSMENT SUMMARY
The following conclusions may be drawn from the risk analysis presented above:
• Incidental ingestion and dermal absorption of chemicals in surface soils at the O-LJne Ponds,
assuming future residential exposures, do not result in risks in exceedance of the EPA target risk
range.
• Exposure to shallow sediments near the O-Line Ponds, assuming future residential exposures,
does not pose unacceptable risks to human hearth.
• Ingestion of beef from cattle that have consumed crops grown on the O-Line Ponds, assuming
a future agricultural exposure scenario, would result in risks that are not above unacceptable
levels.
• Although inorganic chemical concentrations in surface water were elevated above background
concentrations, there is no significant potential for such exposures by human receptors.
• Chemical concentrations in soil at the O-Une Ponds are below levels that are likely to impact
plants and soil dwelling invertebrates.
6-21
-------
• Terrestrial invertebrates are not likely to be impacted by chemicals that have accumulated in food
items (e.g.. soil dwelling invertebrates).
• Chemicals in surface water and shallow sediment are not likely to impact aquatic species in the
Rutherford Fork of the Obion River.
• Human health risks that could potentially result from ingestion of groundwater contaminated by
the continued leaching of explosives compounds from the soil around the perimeter of the existing
cap are at high levels (above EPA's acceptable risk range.)
• Human health risks that could potentially result from a discontinuation of cap maintenance and
eventual cap failure are predicted to be at high levels (under the assumption of residential land
use of the O-U'ne Ponds area)
The baseline risk assessment indicates that residual explosives contamination in soil at OU2 may
adversely affect groundwater quality, resulting in unacceptable future risks. The containment of these
contaminants and the prevention of hydraulic loading on this source area will prevent these unacceptable
risks.
This remedial action will stop further migration of contaminants of soil to groundwater and will
prevent any potential exposures to contaminated soils. The cap extension will significantly reduce or
eliminate the mobility of contaminants of concern in soil. Therefore, implementation of this remedial action
will result in significant reduction of risks potentially posed by Operable Unit Two. Implementing this
action concurrently with the interim remedial action for OU1 will provide the most effective and feasible
approach to protecting human health and the environment from the contamination targeted under these
remedial actions.
Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response action selected in this ROD, may present an imminent and substantial
endangerment to public health, welfare, or the environment
6-22
-------
7.0 DESCRIPTION OF ALTERNATIVES
During the technology screening conducted as part of the Focused Feasibility Study (USAEC,
1993a), applicable remedial technologies were identified, evaluated, and assembled into remedial
alternatives. These remedial alternatives address the following general response actions:
• No Action;
• Limited Action;
• Containment; and
• Excavation, On-Site Treatment, and Disposal.
This section briefly describes the alternatives that were considered for remediating OU2.
7.1 APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS
As required by the NCP, the selected alternative must be in compliance with all applicable or
relevant and appropriate requirements (ARARs). ARARs are the cleanup standards, standards of control,
and other substantive environmental protection requirements, criteria, or limitations promulgated under
Federal or State law that specifically address a hazardous substance, pollutant, contaminant, remedial
action, location, or other circumstance at a Superfund site.
The contaminated soil in the O-Une Ponds area is not a RCRA-listed waste, nor is the
contaminated soil expected to exhibit the characteristic of reactivity. Therefore, Federal RCRA and
Tennessee hazardous waste requirements are not applicable. However, due to the similarity of the
contaminated soil to RCRA-listed waste, the RCRA requirements for closure of surface impoundments (40
CFR 264.228) and closure of landfills (40 CFR 264.310) are relevant and appropriate. In addition, the
requirements of 40 CFR 264.91 (Subpart F - Releases from Solid Waste Management Units, Groundwater
Monitoring Requirements) are relevant and appropriate.
The Tennessee Hazardous Waste Management Act (Title 68, Chapter 46), which govern the
transport, storage, treatment, and disposal of hazardous waste are also relevant and appropriate. The
Tennessee Solid Waste Processing and Disposal Regulations (Rule 1200-1-7), which lay out the closure
and post-closure requirements of landfills and other disposal facilities, are applicable requirements.
For all actions that involve earthmoving (e.g., construction and excavation activities) or
incineration, the State air quality requirements are applicable. These consist of Tennessee Air Quality
Control Regulations for Fugitive Dust (Rule 1200-3-8.01), Visible Emissions (Rule 1200-3-5.01), Paniculate
Emissions (Rule 1200-3-7.03(2)), and Non-Process Emissions Standards (Rule 1200-3-6.02(3)).
For construction activities that disrupt more than 5 acres of land, the Tennessee Water Pollution
Control Regulations - General Stormwater Permit for Construction Activities (Rule 1200-4-10.05) are
applicable. For Stormwater discharges associated with industrial activities, including incineration, the
Tennessee Water Pollution Control Regulations - General Stormwater Permit for Industrial Activities (Rule
1200-4-10.04) are also applicable.
7.2 TO-BE-CONSIDERED GUIDANCES
The major to-be-considered guidances (TBCs) consist of the use of the EPA cancer slope factors
and reference doses listed in Section 6.0. The EPA Health Advisories for 2,4,6-TNT (2 fjg/L) and RDX (2
7-1
-------
fjg/L) in drinking water are also TBCs.
These TBCs have been used to derive risk-based cleanup levels for soil. For surface soil, cleanup
levels have been calculated using the identical exposure assumptions discussed in Section 6.0 for
incidental ingestion and dermal contact Because these assumptions include residential land use of the
O-LJne Ponds area, these surface soil cleanup levels are very conservative. For subsurface soil, cleanup
levels have been derived by estimating the total mass of explosives in soil, calculating the average rate
of contaminant transport to the water table, and using mass balance calculations to estimate the potential
concentration of each contaminant in shallow groundwater at the downgradient edge of the O-LJne Ponds
area These estimates of cleanup levels for subsurface soil are based on very conservative assumptions
(e.g., residential land use of the O-LJne Ponds area and use of shallow groundwater as drinking water)
so that the resulting cleanup levels would be fully protective.
7.3 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 alternative, no further action would be taken to address contamination at the site. The risks that were
calculated in the baseline risk assessment are based on the scenario presented by this alternative (i.e.,
no active reduction of present or future potential risks). For the No Action alternative, it is assumed that
the area may be used for any purpose, including residential land use. Therefore, existing institutional
controls (access restricted by the fence and maintenance of the existing cap) are not assumed under this
alternative. The potential human health risk associated with cap failure, leaching of contaminants currently
under the cap to groundwater, and use of the shallow groundwater as drinking water by residents, is
estimated to be 1x10~1. This level of risk is in exceedance of EPA's acceptable risk range of 10"4 to 10"6.
There is no implementation time or cost associated with the No Action alternative because no
additional remedial activities will be implemented at the site. This alternative is not in compliance with the
ARARs because the post-closure care requirements for the existing cap would not be met.
7.4 ALTERNATIVE B: UNITED ACTION
The Limited Action alternative would include implementation of the following actions:
• institutional controls to restrict site access;
• maintenance of existing cap;
• public education programs; and
• five-year reviews.
Institutional controls would include continued access restrictions (including maintenance of the
existing security fence around the O-Line Ponds area), deed restrictions, and land use restrictions. Deed
and land use restrictions would limit the future uses of the site and require permits, qualified supervision,
and health and safety precautions for any activities conducted in the vicinity of the site. Long-term
maintenance of the multi-media cap currently in place at the O-Une Ponds area would be performed to
prevent infiltration of rainwater through the contaminated soil under the cap. Five-year reviews are
required by the NCP at all sites where hazardous chemicals remain untreated. The review will analyze
available data to make a determination as to whether additional remedial actions are required at the site.
The Limited Action alternative would address potential exposures to contaminants in surface soil
7-2
-------
and would prevent the leaching of contaminants from soil under the existing cap to the water table.
However, no action would be taken to prevent the migration of contaminants from soil around the
perimeter of the existing cap to groundwater. The baseline risk assessment indicates that the potential
risk associated with human ingestion of groundwater contaminated by the explosives compounds that
could leach from the soil around the perimeter of the cap is 2x1 fJ3, which is in exceedance of EPA's
acceptable risk range.
Because the Limited Action alternative includes care of the existing cap, it is in compliance with
the ARARs identified in Section 7.1. However, because no action would be taken to remove the
explosives compounds from soil around the perimeter of the cap or to prevent the migration of
contaminants from the soil around the perimeter of the cap to groundwater, the action would not meet
the cleanup levels (TBCs) for soil.
All components of Alternative B could be implemented within one year of the initiation of the
remedial action. The cost estimate for this alternative does not include groundwater monitoring of the O-
Line Ponds area, which would be performed as part of the Groundwater Operable Unit (OU1) remedial
action. The capital cost of Alternative B is estimated to be $26,000, and the annual operating and
maintenance (O&M) cost is approximately $19,000. The net present worth for this alternative, based on
a 30 year implementation period (at a 5% discount rate), is $318,000. Maintenance of the existing cap
and fence is included in the annual operating cost for this alternative.
7.5 ALTERNATIVE C: CLEAN SOIL COVER
Alternative C consists of maintaining the current institutional controls and existing cap to minimize
human exposure to the site and, in addition, covering the area of contaminated soil around the perimeter
of the existing O-Une Ponds cap with a layer of clean soil. A covering of clean soil would provide a simple
and effective barrier which would prevent human and environmental exposures to contaminated surface
soils.
Clean cover soil would be obtained from an uncontaminated area of MAAP. Testing would be
performed to ensure that the soil does not have detectable concentrations of explosive compounds or
other organic contaminants and that the concentrations of metals are within the background range. This
soil would have a lower permeability than soils to be covered, which could be achieved by compaction
of the clean soil during placement Surface settlement of placed soils would be minimal because of the
small thickness of the clean soil layer. After placement of soil, the new surface would be seeded with
grasses and other durable vegetation. Other measures to control erosion, such as placement of geotextile
erosion control materials on the perimeter of the soil cover, would be taken to ensure the integrity of the
covering. Maintenance of the area would continue as described under Alternative B.
This action would prevent human exposure to contaminated surface soil and would prevent the
migration of contaminants in soil under the existing cap to the water table. However, the newly-
constructed surface covering would not be an engineered cap, so this action may reduce, but not prevent,
the percolation of rainwater through the contaminated soil around the perimeter of the cap. To be
conservative, the human health risk associated with implementation of this action is estimated to be
identical to that of Alternative B (Limited Action), or 2x10"3. This level of risk exceeds EPA's acceptable
risk range of 10"4 to 10"6.
The clean soil cover does not meet the requirements of 40 CFR 265.310 because of the lack of
a low-permeability layer and proper drainage. This action would not remove explosives compounds from
soil around the perimeter of the cap, nor would it prevent the percolation of rainwater through the
contaminated soil around the perimeter of the existing cap. Therefore, the TBC cleanup levels for soil
7-3
-------
would not be met
The soil cover would require approximately 2 to 4 months to construct The capital cost of
Alternative C is estimated to be $551,000, and the annual O&M cost is approximately $19,000. The net
present worth of this alternative, based on a 30 year implementation period (at a 5% discount rate), is
$843,000. These costs include all activities listed under Alternative B (Limited Action). The cost estimate
does not include material costs for clean cover soil, as this is expected to be borrowed from a clean area
of MAAP.
7.6 ALTERNATIVE D: EXTENSION OF ENGINEERED CAP
Alternative D consists of continued maintenance of the existing cap and the construction of a
lateral extension of the cap over the contaminated soil around the perimeter of the existing cap. This
alternative would extend the existing cap to the boundaries shown in Figure 7-1. As shown in this figure,
the total area of the cap extension would be 237,000 ft2. The boundary of this area is based on the data
that are currently available and therefore is subject to change during the remedial design process. The
cap extension boundary has been selected based on the following rationale:
• The purpose of the cap extension is to reduce the area of uncovered contaminated soil such that
the potential human health risk associated with the migration of contaminants from the uncovered
soil to the water table and use of the shallow groundwater as drinking water is within EPA's
acceptable risk range.
• The Army performed a study of the levels of contaminants in soil in July 1993. These data were
obtained by drilling boreholes in the area outside of the existing cap, collecting subsurface soil
samples, and analyzing these soil samples for concentrations of explosives compounds. The
chemical data were then analyzed to evaluate the required size of the cap extension such that
the potential risk associated with leaching of contaminants from uncapped areas would be within
EPA's acceptable risk range.
The chemical analysis of subsurface soil samples collected from the east side of the
ponds indicates that only negligible levels of contamination are detectable east of the
Ditch 5 tributary. Therefore, the cap extension will cover the soil between the existing cap
and the Ditch tributary.
On the south side of the existing cap, contaminants were not detected in soil samples
collected farther than 50 feet south of the existing cap. The cap extension will cover the
soil within 50 feet of the existing cap.
On the west side of the cap, contaminants were detected in several locations west of the
security fence; therefore, the residual risk associated with the continued leaching of
contaminants from the soil west of the security fence was estimated. The results indicate
that the risk associated with this potential pathway is 5 x 10'10, which is below EPA's
acceptable risk range. Therefore, the cap extension will cover the area between the
existing cap and the security fence.
On the north side of the existing cap, explosives compounds were detected in many
locations south of the Ditch 5 tributary. Based on the results of soil samples collected
east of the ponds (where only negligible levels of explosives were detected beyond the
Ditch 5 tributary), the cap extension will cover the area between the existing cap and the
Ditch 5 tributary.
7-4
-------
* N-
EXISTING CAP (445 FT.
ELEVATION CONTOUR LINE)
BOUNDARY OF EXTENSION
DRAINAGE DITCH
FENCE
PAVED ROAD
GRAVEL ROAD
04302CAP.DWG
09-03-93
FIGURE 7-1
CAP EXTENSION BOUNDARY
-------
The primary objective of extending the impermeable cap at the O-Line Ponds is to prevent
stormwater infiltration through the contaminated soil around the perimeter of the existing cap, thereby
eliminating continued contaminant loading to groundwater. Additionally, human and animal contact with
the contaminated surface soil surrounding the existing cap would be eliminated.
The cap extension would conform to RCRA requirements and would effectively tie in to the existing
multi-media cap. After completion, regular maintenance will be required to maintain the integrity of the
entire cap. The vegetative layer must be maintained and mowed to provide continual erosion control.
The cap must be inspected for differential settling, which may cause breaching of the impermeable layers.
Contingency plans for responding to subsidence problems would be devised as part of a long-term
maintenance plan for the cap. Groundwater monitoring of the area would be performed as part of the
OU1 remedial action.
The cap extension would serve to eliminate the migration of contaminants from the soil around
the perimeter of the cap to the water table. Human exposures to contaminated surface soil would be
prevented. At the same time, maintenance of the existing cap will prevent the migration of contaminants
under the cap. The estimated potential human health risk associated with the residual soil contamination
around the perimeter of the cap extension is 5x1 0"10, which is less than EPA's acceptable risk range of
This alternative would meet all of the major ARARs for landfill closure and post-closure,
groundwater monitoring, and all State ARARs identified in Section 7.1. Implementation of this action
would not result in the removal of explosives compounds from soil; however, by preventing the percolation
of rainwater through the contaminated soil under the existing cap and cap extension, risks to human
health and the environment will be reduced to levels within EPA's acceptable risk range. Accordingly,
EPA cancer slope factors, reference doses, and health advisories are not necessary to protect human
health and the environment, and are therefore not TBCs for this alternative.
Implementation of this option would take approximately 12 to 18 months for the design phase,
and 6 to 9 months for the construction phase. These time estimates include regulatory review of the
design.
The total capital cost for installation of the cap is estimated to be $1,733,000. The total annual
cost is estimated to be $1 9,000. The net present worth of the project, over a 30-year period and at a 5%
discount rate, is estimated to be $1,833,000. A major assumption for this estimate is that earthen
materials, such as sand and gravel, will be borrowed from clean areas of MAAP.
7.7 ALTERNATIVE E: PARTIAL EXCAVATION/INCINERATION
This alternative includes partial excavation of the contaminated soil in the O-Une Ponds Area
around the perimeter of the existing capped area. The excavated soil would be thermally treated in a
transportable incinerator located on-site. The thermally treated soil would be used as backfill along with
clean soil to resurface this area.
The following partial excavation scenarios were evaluated in this alternative:
Scenario 1: Excavation of 10% of the perimeter area to a depth of 2 feet (It has
been estimated from the soil analytical data that this fraction of the area
contains explosives compounds at levels corresponding to 1 0 risk and
above for surface soil exposure pathways.) Approximately 3,420 tons of
soil would be excavated and treated under this scenario.
7-6
-------
Scenario 2: Excavation to a depth of 2 feet around the perimeter of the existing
capped area Approximately 34,200 tons of soil would be excavated and
treated under this scenario.
Treatability studies have been performed on explosives-contaminated soil at Savanna Army Depot
Activity, Savanna, Illinois. Full-scale remediation of explosives-contaminated soil has been performed at
Louisiana Army Ammunition Plant. These studies indicate that high-temperature thermal treatment is
effective in removing explosives compounds from soil with a destruction and removal efficiency (ORE) of
99.99%. This efficiency would reduce the concentrations of explosives compounds in surface soil to
below the 10*6 risk level.
The treatment goal for this alternative is to reduce the concentrations of explosives compounds
to meet risk-based levels, which were derived using EPA's cancer slope factors for the principal
carcinogens detected in surface soil. The calculation of these treatment goals was performed under the
assumption that humans could be exposed to contaminants both through incidental ingestion and dermal
absorption. The concentrations estimated to result in a risk level of 10"6 are: for 2,4-DNT, 0.69 j*g/g; for
RDX, 0.70 //g/g; and for 2,4,6-TNT, 1Z41
Conventional earthmoving equipment would be used for excavation of the contaminated soils.
The rate of excavation would be determined by the volume of soil required to ensure a 1.5 week buffer
volume that would be stored in the stockpile area and which would be incinerated in case of inclement
weather that prevents excavation. Excavation would be performed in sections to minimize the possibility
of windblown emissions. Confirmatory sampling and analysis of the soil would be performed to verify that
all surface soil that exceeds the contaminant cleanup levels has been removed from the excavated
section. Also, confirmatory sampling ensures that the remaining soils do not exceed the treatment goals.
The- excavated section would be backfilled prior to proceeding to the next section of excavation.
Treated soils may be used as backfill after confirming that the treatment goals have been met The
reduction in volume of the treated soils after incineration is not expected to be greater than 10%. Clean
soil obtained from other areas of MAAP or off-site will also be used as backfill. Reseeding of the soil
section would be required to prevent erosion.
Because of the large volume of soil to be treated, a transportable incineration system with a
design soil feed rate of 15 tons per hour or greater would be used. Mobilization, set-up, and
demobilization of the transportable system would be required. This alternative also includes institutional
controls, maintenance of the existing cap and fence, public education programs, and five-year reviews
as described in Alternative B.
Implementation of this alternative would result in maintenance of the existing cap and the
remediation of surface soils only. Although the risk associated with exposure to contaminants in surface
soil would be reduced, and the contaminants in soil under the existing cap would be prevented from
migrating to the water table, the contaminants in subsurface soil around the perimeter of the cap would
not be prevented from migrating to groundwater. Therefore, the potential human health risk after
implementation of this remedy would be essentially equal to the risk under Alternative B (Limited Action),
or 2x1 0"3. This risk level is in exceedance of EPA's acceptable risk range.
For excavation and incineration options, the major ARARs consist of the RCRA requirements for
incinerators (Subpart O), including 40 CFR 265.345 (General Operating Requirements), 265.347
(Monitoring and Inspection), and 265.351 (Closure). Because the contaminated soil to be excavated and
treated is not a hazardous waste but is similar to a listed hazardous waste, these requirements are
relevant and appropriate. All State ARARs for an excavation and incineration action are listed in Section
7.1. This action will meet all Federal and State ARARs. However, because no action would be taken to
7-7
-------
remove explosives compounds from subsurface soil, this action would not meet the TBC cleanup levels
for soil.
Implementation of this alternative, from design to construction, will require approximately 20 - 24
months for completion. The thermal treatment technology is commonly used and commercially available.
The design, review, and procurement of the thermal treatment system will require roughly 15 months, and
mobilization and set-up of the transportable unit will require 1 to 2 months. Startup bums typically require
2 to 3 months for completion. Remediation of the O-Line Ponds area is expected to be completed in a
total of 2 years for either scenario.
Capital costs included in the alternative are site preparation, mobilization/set-up, demobilization,
and startup costs. For Scenario 1, the capital cost is estimated to be $2,672,000 and the annual O&M
cost is estimated to be $315,000. The net present worth of this action, over a project lifetime of 30 years
and a discount rate of 5%, is estimated to be $4,096,000. For Scenario 2, the capital cost is estimated
to be $2,672,000 and the annual O&M cost is estimated to be $11,594,000. The net present worth of
Scenario 2 is estimated to be $47,371,000.
7.8 ALTERNATIVE F: FULL EXCAVATION/INCINERATION
This alternative consists of the excavation and treatment of all of the contaminated soil in the O-
Line Ponds Area, such that the residual risk would not exceed a level of 10"6. The excavated soil would
be thermally treated in a fixed-site incinerator located on site. The thermally treated soil would be used
as backfill to resurface the area The following full excavation scenarios were evaluated in this alternative:
Scenario 1: Excavation to 20 feet including the existing capped area This scenario
will treat nearly half of the contaminated soil in the O-Line Ponds area
including the most-contaminated soil that is currently under the cap. The
total volume excavated would be 676,000 cubic yards.
Scenario 2: Excavation to 45 feet including the existing capped area This scenario
provides the highest level of removal and treatment of contaminated soil.
All explosives-contaminated soil from ground surface down to the water
table would be removed and treated. The total volume excavated would
be 1,322,000 cubic yards.
High-temperature thermal treatment is proposed for this alternative, and the system would operate
in a manner similar to the process described in Alternative E, with the major difference being the size of
the proposed incineration units. For Alternative F, two 30 ton per hour incinerators will be utilized to
decrease processing time for the large quantity of soil to be treated. Rather than using a single,
transportable unit, this alternative will use two units built and fixed at the site. The total capacity (60 tons
per hour) will significantly reduce treatment time for this large quantity of soil.
Alternative F also includes institutional restrictions, maintenance of the fence, public education
programs, and five-year reviews as described in Alternative B. Following completion of excavation,
incineration, and backfilling, the site (at least the top 20 feet) would be acceptable for unrestricted use
and the majority of the institutional and access controls could be eliminated.
The goal of this alternative is to remediate the site fully to allow for unlimited future land use.
Therefore, the treatment goals for the explosives compounds in soil are those concentrations which will
not result in unacceptable levels of risk following migration of the contaminants to groundwater. Because
of the large volume of soil to be remediated in this manner, the maximum allowable concentrations in soil
7-8
-------
are less than the detection limits of explosives in soil. In order to allow backfill of the soil after treatment,
the concentrations of explosives compounds must be reduced to non-detectable levels.
This action would meet the Federal and State ARARs for incineration listed in Section 7.1 and 7.7
for both Scenario 1 and Scenario 2. Implementation of Scenario 1 would reduce, but not eliminate, the
potential for migration of contaminants from subsurface soil to the water table. Because of the large
volume of soil remaining untreated at the site (the depth interval between 20 feet and the water table,
which occurs at an average depth of 45 feet below ground surface), and because of the elimination of
the cap, the contaminants left at the site would continue to migrate to the water table. The resulting
concentrations in groundwater are expected to exceed the EPA Health Advisories. Therefore, Scenario
1 would not meet the TBC cleanup levels for soil. Implementation of Scenario 2 would eliminate both
surface and subsurface through treatment This action would meet ARARs and TBCs.
Implementation of this alternative, from design to construction, will require approximately 27 to 30
months for completion. The thermal treatment technology is commonly used and commercially available.
The design, review, and procurement of the thermal treatment system will require roughly 15 months. The
mobilization and set-up of the fixed site unit will require 10 to 12 months. Startup test bums typically
require 2 to 3 months for completion. Complete remediation of the O-LJne Ponds area is expected to be
completed in about 24 to 26 months for the 20 foot depth, and 48 to 60 months for the 45 foot depth.
Capital costs included in the alternative are site preparation, mobilization, set-up, and startup bum
costs. The capital cost for Scenario 1 is estimated to be $33,700,000 and the annual O&M cost is
estimated to be $43,600,000. The net present worth of this alternative is estimated to be $239,000,000,
based on a 30-year project life and a 5% discount rate. The capital cost of Scenario 2 is estimated to be
$33,700,000 and the annual O&M cost is estimated to be $65,900,000. The net present worth of Scenario
2 is estimated to be $436,000,000, based on a project life of 30 years and a 5% discount rate.
7.9 SUMMARY OF REMEDIAL ALTERNATIVES
Six alternatives have been developed, including a No Action alternative (Alternative A), a Limited
Action alternative (Alternative B), and four treatment alternatives varying from containment to on-site
treatment (Alternatives C through F). A summary of these alternatives is presented in Table 7-1. Section
8 provides a comparison of these alternatives with respect to nine evaluation criteria
7-9
-------
TABLE 7-1
SUMMARY OF REMEDIAL ALTERNATIVES
Alternative
A
B
C
D
E
F
Description
• No Action
• Limited Action
• Clean Soil Cover
• Extension of Existing Cap
Scenario 1 :
• Partial Excavation of 10% of
Soil to 2 feet
• Incineration
Scenario 2:
• Partial Excavation to 2 feet
• Incineration
Scenario 1:
• Full Excavation to 20 feet
• Incineration
Scenario 2:
• Full Excavation to 45 feet
• Incineration
Implementation Time
Design
(months)
0
less than 6
4 to 6
18
18
18
18
18
Construct
(months)
0
less than 12
4
9
4
4
24 to 26
48 to 60
Costs In 1992 Dollars
Capital Cost
$0
$26,000
$551,000
$1,733,000
$2,672,000
$2,672,000
$33,700,000
$33,700,000
Annual
O&M Cost
$0
$19,000
$19,000
$19,000
$315,000
$11,594,000
$43,600,000
$65,900,000
Present Worth*
$0
$318,000
$843,000
$1,833,000
$4,096,000
$47,371,000
$239,000,000
$436,000,000
NOTE: All times and costs are estimates and are subject to change.
* - Present worth calculated over 30 years at an annual discount rate of 5%.
-------
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 discussed below. All of the alternatives were evaluated for their
ability to meet the threshold criteria of protection of human health and the environment and compliance
with ARARs. The alternatives meet the other criteria to different degrees. To aid in identifying and
assessing relative strengths and weaknesses of the remedial alternatives, this section provides a
comparative analysis of alternatives. As previously discussed, the alternatives are as follows:
• Alternative A, No Action
• Alternative B, Limited Action
• Alternative C, Clean Soil Cover
• Alternative D, Extension of Engineered Cap
• Alternative E, Partial Excavation/Incineration
• Alternative F, Full Excavation/Incineration
These six alternatives are compared to highlight the differences between the alternatives, and determine
their relative value in meeting the criteria for the detailed evaluation of alternatives.
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 adequate 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 requirements of Federal and State environmental statutes and/or
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 Toxictty, Mobility, or Volume through Treatment is the anticipated
performance of the remedial actions employed for each alternative.
• Short-term Effectiveness refers to the speed with which the remedy achieves protection,
as well as the remedy's potential to create adverse impacts on human health and the
environment that may result during the construction and implementation period.
• Implementablltty is the technical and administrative feasibility of a remedy, including the
availability of materials and services needed to implement the chosen solution.
8-1
-------
• Cost includes both capital and operation and maintenance 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 assesses the public comments received on the RI/FS Report
and the Proposed Plan for the Operable Unit.
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' which 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 weighed. The preferred alternative will be that 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
Because current levels of contamination pose unacceptable levels of potential human health risk,
Alternative A, No Action, will not meet this criterion because no actions are taken to eliminate, reduce or
control exposure pathways. The threshold criterion of protection of human health and the environment
is not achieved by Alternative A.
Alternative B, Limited Action, provides some additional protection from contaminated surface soil
by implementing and maintaining restrictions such as the site fencing and the existing multi-media cap,
which limit site access and human exposure to the contaminated soil. Although actions would be taken
to minimize exposures to contaminants in surface soil, the migration of contaminants in the soil around
the perimeter of the existing cap to the water table would not be prevented. The continued migration of
contaminants to groundwater has been evaluated to have an adverse impact on groundwater quality and
human consumption of this water would result in a risk level of 2x10"3, which is above EPA's acceptable
risk range. Therefore, Alternative B would not be protective of human health and the environment
Alternatives C and E provide additional protection of human health and the environment by
eliminating the surface soil exposure pathway. Alternative C provides protection by covering the
contaminated surface soil with a clean layer of topsoil and vegetation. Alternative E would treat surface
soil to a depth of 2 feet by incineration. Although each of these alternatives provides protection of human
health via the surface soil exposure pathway, Alternative C and Alternative E do not include impermeable
barriers or treatment of the contaminated soil and therefore do not prevent leaching of contaminants to
groundwater. The level of human health risk posed by the continued migration of contaminants to the
water table has been estimated to be 2x10"3, which is above EPA's acceptable risk range. Alternatives
C and E are therefore not protective of human health and the environment
Both Alternative D and Alternative F would be protective of human health by preventing the
leaching of contaminants from soil, thereby eliminating contaminant loading to groundwater. Potential
surface soil exposure pathways would also be eliminated. Alternative D would prevent infiltration of
precipitation by extending the existing cap over the contaminated soil around the perimeter of the cap
and by providing for continued maintenance and institutional controls. Alternative F would be protective
of human health and the environment by removing the explosives compounds from the soil through
excavation and treatment of the soil.
8-2
-------
8.3 COMPLIANCE WITH ARABS
Compliance with ARARs is a threshold criterion which must be met by the proposed remedial
action. The No Action alternative (Alternative A) does not meet this criterion because the existing cap
would not be maintained. The Limited Action alternative (Alternative B) meets this criterion because the
post-closure care requirements of the existing cap would be met. Alternative C (Clean Soil Cover) would
not meet the ARARs because the landfill closure requirements (40 CFR 265.310) would not be met.
Alternatives D, E, and f involve further actions to eliminate exposures to contaminated soil.
Implementation of these alternatives would meet the ARARs identified in Section 7.1 and Section 7.7.
Alternative D (Extension of the Existing Cap) would meet the Subpart N landfill closure requirements (40
CFR 265.310) and the Subpart F groundwater monitoring requirements (40 CFR 265.91). Alternatives E
and F would meet the Subpart O incineration requirements (40 CFR 265.345,265.347, and 265.351). In
addition, State ARARs for solid waste management, hazardous waste management, air quality control, and
stormwater management (listed in Section 7.1) would be met.
8.4 LONG-TERM EFFECTIVENESS AND PERMANENCE
Alternatives A, B, C, and E do not provide long-term effectiveness and permanence because the
magnitude of the residual risk after the remedial objectives have been met would be at unacceptable
levels. None of these alternatives provides sufficient, effective protection of groundwater quality.
Alternative D, extension of the existing cap, provides long-term effectiveness and permanence by
isolating the contaminated soil using institutional controls (maintenance of site fencing), maintenance of
the existing multi-media cap, and construction and maintenance of a cap extension. The maintenance
activities required to assure effective cap performance consist of regular mowing of the vegetative cover,
inspection of the cap for subsidence, repair (as needed), and groundwater monitoring.
The design and construction of a cap extension capable of preventing the infiltration of rainwater
through the contaminated soil would be a relatively straightforward task, as this technology is well-
understood and commonly-applied. Provided that the cap and cap extension are properly maintained,
the magnitude of the residual risk following implementation of this remedial action would be within EPA's
acceptable risk range. Because contaminants would remain on site, 5-year reviews would be performed
to evaluate the site conditions.
Because MAAP is a currently-operating facility, the institutional controls that are currently in place
to limit access to the site and prevent exposures to the contaminated media are adequately and reliably
enforced. Should MAAP be closed in the future, the requirements of the Base Realignment and Closure
Act, as well as this Record of Decision, would preclude the dismantling of these institutional controls.
Therefore, the long-term reliability of management controls for Alternative D is excellent
Alternative F incorporates incineration as the treatment method to provide the greatest degree of
long-term effectiveness and permanence. Incineration achieves long-term effectiveness by the irreversible
destruction of greater than 99.99% of the explosive contaminants in soil. Because incineration has been
successfully used to treat explosives-contaminated soil, the reliability of the technology and the certainty
that the treatment goals will be met are high. The magnitude of residual risk following implementation of
this action would be within EPA's acceptable risk levels. Maintenance of the area would not be required
after the project is complete.
Under Alternative F, residual contaminants would be removed down to levels that do not pose an
unacceptable level of risk, so management controls to prevent exposures would not be needed. Long-
8-3
-------
term monitoring of groundwater also would not be needed.
8.5 REDUCTION OF TOXICHY, MOBILITY OR VOLUME THROUGH TREATMENT
Alternatives A and B provide no reduction of toxicity, mobility, or volume of the contaminants
through treatment
Alternative C does not meet the statutory preference for treatment, but will reduce the mobility of
contaminants via the surface runoff and erosion pathways. However, implementation of Alternative C will
not preclude the infiltration of rainwater through the contaminated soil and the subsequent leaching of
contaminants to groundwater.
Alternative D also does not meet the statutory preference for treatment However, implementation
of this alternative will prevent contaminant migration to groundwater through extension of the existing
impermeable cap.
Alternative E would meet the statutory preference for treatment by permanently destroying
contaminants in surface soil through the excavation and incineration of surface soil around the perimeter
of the cap. An estimated volume of 34,200 ft3 would be treated in this manner. The toxicity, mobility, and
volume of contaminants in surface soil would be irreversibly reduced through treatment However, the
alternative would not affect the toxicity, mobility, or volume of contaminants in subsurface soil.
Alternative F provides the greatest reduction of toxicity, mobility, and volume because the
explosives compounds in the soil would be permanently destroyed through treatment. An estimated
volume of 1,322,000 ft3 of soil would be treated. Full excavation (the 45 foot excavation scenario) would
result in complete reduction of contaminant toxicity, mobility and volume through treatment.
8.6 SHORT-TERM EFFECTIVENESS
Implementation of Alternatives A and B would pose the lowest risks to the community, site
workers, and the environment, as well as require the shortest implementation time. These actions would
not require excavation, construction, or transport of hazardous materials.
Alternative C (Clean Soil Cover), also would not pose a risk to the community because the amount
of dust generated during placement of the soil is expected to be minimal. Because workers would be
engaged in covering the area around the perimeter of the existing cap with clean soil, their level of
exposure to contaminants in the soil would be small. Environmental impacts are expected to be minimal.
Alternative D (Extension of the Existing Cap) would not pose a risk to the community because
dust generation during construction of the cap is expected to be minimal, and only non-hazardous
construction materials would be transported to the site. Because workers would be engaged in
construction activities rather than excavation activities, their level of exposure to the contaminated soil is
expected to be minimal. Environmental impacts are not expected to occur under this alternative.
Both Alternatives E and F involve the excavation and incineration of the contaminated soil. During
the implementation of these alternatives, the community could potentially be exposed to dust generated
during excavation activities and to flue gas stack emissions, both of which could be reduced through the
use of engineering controls. Workers at the site would also be exposed to contaminants in soil. For
Alternative F, where the cap would be removed and the highly-contaminated sediments under the cap
would be exposed, methods to prevent accidental detonation of deflagration and exposures would need
8-4
-------
to be deployed (e.g., use of non-sparking equipment and adequate personal protective equipment) Also,
the excavation, backfilling, and stockpiling activities would require extensive use of sediment and erosion
control measures.
The length of time required to implement and complete the remedial alternatives follow in
increasing order. Alternative C, Alternative D, Alternative E, and Alternative F. Alternative C would require
4 to 6 months to design and 4 months to construct the clean soil cover. Alternative D would require
approximately 18 months to design and 9 months to construct. Alternative E would require 18 months
to design and approximately 4 months to complete the remediation process. Alternative F would require
18 months to design and approximately 4 years to complete the remediation of the O-Une Ponds area
8.7 IMPLEMENTABILJTY
Alternatives A and B would be the most easily implemented of the alternatives under
consideration. Alternative A requires cessation of existing institutional controls, and many components
of Alternative B are already in place.
Alternative C would be relatively easy to design and construct because of the simplicity of the
concept, the availability of clean soil at MAAP, and the fact that the earthmoving equipment needed for
the project is readily available. The construction of a soil cover would be effective and reliable in
preventing human exposure to surface soil. Because all construction activities would take place on site,
permits would not be needed for this alternative.
Alternative D would require detailed engineering to ensure that the existing cap and the cap
extension function together effectively. The layering within the cap extension must tie in to the layers of
the existing cap. The technology is widely available, and the materials (either natural or synthetic) are
also available from a large number of sources. Properly designed and constructed, this technology is
expected to be very reliable. Because all construction activities would take place on site, permits would
not be required.
Alternatives E and F utilize incineration, which has been successfully utilized for the treatment of
explosives-contaminated soil. The technology is expected to be very reliable in reducing the levels of
explosives compounds to the soil cleanup levels. However, these alternatives are most susceptible to
schedule delays due to inclement weather and mechanical failure. Due to the fact that coordination of
excavation, incineration, and backfilling activities must be performed within a relatively limited area, these
alternatives pose the greatest technical feasibility problems. Although permits would not be required, the
substantive requirements of air permits must be met These alternatives would require the expertise of
specialists in excavation and operation of the incineration equipment Both fixed-site and mobile
incineration units are available from a number of vendors.
Excavation to the depths proposed in Alternative F would make this the most difficult alternative
to implement Although feasible, excavation to groundwater (approximately 45 feet below ground surface)
would pose a challenge because vertical constraints are required to ensure stability and safety and to
maintain access to the excavation area for the earthmoving equipment Shoring or bracing would be
required for excavation below four feet
8.8 COST
Table 8-1 provides a comparison of the costs of the remedial alternatives. Total capital and
annual costs and present worth (discount rate of 5%) for each alternative are presented. The progression
8-5
-------
TABLE 8-1
COMPARISON OF COSTS FOR REMEDIAL ALTERNATIVES
Alternative
A
B
C
0
E
F
Description
• No Action
• Limited Action
• Clean Soil Cover
• Extension of Existing Cap
Scenario 1:
• Partial Excavation Hot
Spots only to 2 feet
• Incineration
Scenario 2:
• Partial Excavation, to 2 feet
• Incineration
Scenario 1:
• Full Excavation to 20 feet
• Incineration
Scenario 2:
• Full Excavation to 45 feet
• Incineration
Costs In 1992 Dollars
Capital Cost
$0
$26,000
-$551,000
$1,733,000
$2,672,000
$2,672,000
$33,700,000
$33,700,000
Annual
O&M Cost
$0
$19,000
$19,000
$19,000
$315,000
$11,594,000
$43,600,000
$65,900,000
Present Worth*
$0
$318,000
$843,000
$1,833,000
$4,096,000
$47,371,000
$239,000,000
$436,000,000
NOTE: All times and costs are estimates and are subject to change.
- Present Worth calculated over 30 years at an annual discount rate of 5%.
8-6
-------
of total present worth from least expensive to most expensive alternative is: Alternative B, Alternative C,
Alternative D, Alternative E, and Alternative F. Alternative D is more costly than Alternative C because it
uses specialized materials to create the impermeable cap extension. Alternative F is more costly than
Alternative E because of the greater depth and volume of excavation for Alternative F. The greater degree
of treatment causes higher total capital, annual, and present worth costs as seen in a comparison of the
scenarios in Alternative E and Alternative F.
8.9 SUMMARY OF DETAILED EVALUATION
The following is a brief summary of the evaluated alternatives:
• Alternatives A, B, C, and E are not protective of human health and the environment and
therefore are eliminated from consideration.
• Alternative D provides for protection of human health and the environment by
eliminating the infiltration of rainwater through the contaminated soil and
preventing additional adverse impacts on groundwater quality. Surface exposure
pathways are also eliminated.
• Alternative F permanently removes all contaminants from surface soil and
subsurface soil within OU2 through excavation and incineration. This alternative
would protect groundwater quality and eliminate all potential future exposures to
contaminants associated with OU2.
• For the same level of risk reduction, comparison of Alternative D and
Alternative F reveals that Alternative D poses fewer short-term risks, is
more implementable, and is more than 200 times less costly.
Based on the comparative analysis of alternatives, the selected remedy is Alternative D, Extension
of the Existing Cap.
8-7
-------
9.0 SELECTED REMEDY
Based upon consideration of CERCLA requirements, the detailed analysis of the alternatives, and
public comments, the Army, with the concurrence of EPA and TDEC, has determined that extension of
the existing cap is the most appropriate remedy for OU2 at the O-Line Ponds Area of Milan Army
Ammunition Plant, Tennessee. This section presents details of the selected remedy with the
understanding that some changes may be made during the subsequent remedial design and construction
processes.
9.1 ALTERNATIVE D: EXTENSION OF ENGINEERED CAP
9.1.1 Description
The primary objective of extending the impermeable cap at the O-line Ponds is to prevent
stormwater infiltration through the contaminated soil around the perimeter of the existing cap, thereby
eliminating continued contaminant loading to groundwater. Human and animal contact with the surface
soil surrounding the existing cap would also be eliminated. A simple soil cap may prevent direct contact
exposures and surface runoff of contaminants, but will not adequately prevent infiltration and leaching of
contaminants. Therefore, a multi-media cap system such as that prescribed in RCRA guidance and which
functions similarly to the existing cap will be constructed. Although the current cap effectively isolates the
contaminated sediments and the soils with the highest levels of explosives contamination, it does not
cover areas of contaminated soil beyond the boundary of the former ponds, which were contaminated
from pond overflows, from mis-handling of explosives-contaminated dredge spoils, and from earthwork
during cap construction.
Prior to construction, the site will be prepared for installation of the cap extension by establishing
site security, clearing of vegetation from the site, and the establishment of equipment and material staging
areas.
Based on the results of analysis of soil samples collected in July, 1993, the cap extension will
cover a total area of 237,000 ft2. The boundary of this area is based on the data that are currently
available and therefore is subject to change during the remedial design process. As stated in Section
7.6, the cap extension would cover the following areas: from the northern limit of the cap to the Ditch B
tributary; from the existing cap eastward to the Ditch B tributary; from the existing cap southern limit to
a distance of 50 feet south of the existing cap; and from the existing cap westward to the security fence.
This cap extension will cover the contaminated soil around the perimeter of the cap such that the resulting
risk in groundwater is within EPA's acceptable risk range. .
RCRA guidance for landfill covers specifies that the minimum layering for a cap consists of a
vegetated top cover, a middle drainage layer, and a low permeability bottom layer. The cap extension
proposed under this alternative will include these required layers. During construction of the cap, air
monitoring for paniculate releases will be conducted to ensure compliance with dust-emission ARARs.
Sediment and erosion control measures will also be implemented and maintained until the vegetative
cover is fully established. Following completion of the cap extension construction, the security fence will
be extended around the entire capped area
After completion, regular maintenance will be conducted to maintain the integrity of both the
existing cap and the cap extension. The vegetative layer will be maintained and mowed to provide
continual erosion control. The cap must be inspected occasionally for differential settling, which may
cause breaching of the impermeable layers. Contingency plans for responding to subsidence problems
9-1
-------
will be devised as part of a long-term maintenance plan for the cap. Groundwater monitoring will be
conducted in association with OU1 groundwater remediation, and will meet the requirements of RCRA
Subpart F.
9.2 INSTITUTIONAL CONTROLS
Institutional controls will include continued access restrictions, deed restrictions, and land use
restrictions. Long-term maintenance of the fence and multi-media cap currently in place at the O-LJne
Ponds area will occur. Deed and land use restrictions will limit the future uses at the site and require
permits, qualified supervision, and health and safety precautions for any activities conducted in the vicinity
of the site. To make these restrictions more permanent, a Memorandum of Agreement could be
negotiated between the facility, EPA Region IV, and the State of Tennessee.
The Army will ensure protection of on-site future users of groundwater. The cap extension will
be supplemented with institutional controls to prevent direct contact with contaminated soil and ingestion
of groundwater that is potentially contaminated by OU2. These institutional controls will consist of the
following specific measures for cases where the Army maintains ownership and where the property may
be excessed, respectively:
• The groundwater affected by OU2 will not be used for potable purposes while the levels
of contaminants are higher than health-based levels; this will be ensured by Milan Army
Ammunition Plant Environmental Office review of all projects and leases involving well
installation and usage at the facility. Any well installed within the facility will be tested
prior to use.
• - In accordance with Army Regulation 200-1, entitled Environmental Protection and
Enhancement, the Army is required to perform preliminary assessment screening for any
parcel being excessed. This screening will evaluate potential use of the property, identify
any remedial activities required, and/or place restrictions on the property to protect the
future landowners through a document entitled Statement of Condition. The Army will
implement the recommendations in the Statement of Condition prior to property transfer.
In either case, a continuing program of public awareness will be used to inform the public of the hazards
associated with contaminants that remain within or that may migrate from OU2.
Five-year reviews are required by the NCP at all sites where hazardous chemicals remain
untreated. The review will analyze available data to make a determination as to whether additional
remedial actions are required at the site. Groundwater monitoring data collected in conjunction with OU1
at the site will be used to determine if OU2 continues to release contaminants from the unsaturated zone
into the groundwater.
9.3 REMEDIATION GOALS
The purpose of this response action is to reduce the area of uncovered contaminated soil such
that the potential human health risk associated with the migration of contaminants from the uncovered
soil to the water table and use of the shallow groundwater as drinking water is within EPA's acceptable
risk range. Existing conditions at the site have been estimated to pose an excess lifetime cancer risk of
2x10"3 from the potential ingestion of contaminated groundwater. Because no Federal or State ARARs
exist for soil, the size of the cap extension was determined through a site-specific analysis. Fate and
transport calculations were performed to evaluate the risk reduction capability of the response action.
9-2
-------
The basis for these remediation goals is a calculation of potential risk using EPA's cancer slope factors
for 2,4,6-TNT and RDX (the principal contaminants at the site).
The results of the risk assessment discussed in Section 3.0 indicate that the level of risk posed
to human health and the environment by the residual contamination in surface soil, surface water, and
shallow sediment within OU2 are at acceptable levels. Therefore, remedial action objectives for cleanup
of surface water and shallow sediment are not considered.
9.4 COST OF SELECTED REMEDY
The total capital costs for installation of the cap is estimated at $1,733,000. The total annual costs
are estimated at $19,000. Total present worth of capital and annual costs are estimated at $1,833,000.
The cost estimates are preliminary and are subject to change. The estimates were developed based on
generic unit costs and vendor information. These costs are outlined in Table 9-1. A major assumption
for this estimate is that earthen materials, such as sand and gravel, will be borrowed from clean areas of
MAAP.
Implementation of this option would take approximately 12 to 18 months for the design phase,
and 6 to 9 months for the construction phase. These time estimates include regulatory review of the
design.
Assumptions were made for several factors that affect the time and cost estimates for this
alternative, including:
• Materials and construction methods selected. The cost estimate and schedule were
based on a multi-media cap extension employing both natural and synthetic layers for
minimum thickness.
• Overlap with other construction projects. It was assumed that the construction of the
groundwater treatment plant will not interfere with construction of the cap extension.
Health and safety considerations. For the cost estimation, health and safety measures
were assumed to be 10% of the capital subtotal. Based on actual conditions at the site
and actual investigation and construction methods, health and safety measures may
result in lower or higher costs.
9-3
-------
TABLE 9-1
SUMMARY OF COSTS FOR THE SELECTED REMEDY
ALTERNATIVE D: EXTENSION OF ENGINEERED CAP
*nai
COST
Capital Costs
Administrative Actions
Site Preparation and General Actions
Installation of Cap Extension
Air Monitoring During Construction
$ 20,000
$ 180,000
$ 766,000
$ 10,000
Subtotal $ 976,000
Contingencies (40% of Capital Subtotal)
Engineering & Design (25% of Capital Subtotal plus
Contingencies)
Permitting and Coordination
$ 390,000
$ 342,000
$ 25,000
Total Capital Costs $1,733,000
Annual Operation and Maintenance Cost
Quarterly Mowing and Lawn Maintenance, Five Year
Reviews, and Program Oversight
O&M Contingency (25% of Annual O&M)
Present Worth of Annual O&M (30 years, 5% discount
rate)
Total Present Worth (Capital and Annual Costs @ 30
years, 5% discount rate)
$ 15,000
$ 4,000
$ 100,000
$1,833,000
9-4
-------
10.0 STATUTORY DETERMINATIONS
The selected remedialjaction for this site must comply with applicable or relevant and appropriate
environmental standards established under Federal and State environmental laws unless a statutory
waiver is justified. The selected remedy must also be cost-effective and utilize permanent solutions and
alternative treatment technologies or resource recovery techniques to the maximum extent practicable.
Finally, the statutory preference for remedies that permanently and significantly reduce the volume,
toxicrty, or mobility of hazardous wastes through treatment as their principal element should be satisfied.
The following sections discuss how the selected remedy meets these statutory requirements.
10.1 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
The risk assessment identified potential risks to human health and the environment from the
continued leaching of contaminants from the soil around the perimeter of the cap, migration of these
contaminants to groundwater, and ingestion of the contaminated groundwater as drinking water. The risk
assessment also identified potential risks from discontinued maintenance of the existing cap, which would
result in cap failure. The selected remedy addresses these risks and protects human health and the
environment through maintenance of the existing cap and capping the explosives-contaminated soil
around the perimeter of the existing cap. The cap extension will be consistent with the existing cap and
will meet RCRA landfill closure requirements to prevent the leaching of contaminants from soil, thereby
reducing risks posed to groundwater. There are no short-term risks associated with the selected remedy
that cannot be readily controlled. In addition, no cross-media impacts are expected from the remedy.
10.2 COMPUANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS
The selected remedy of extension of the existing cap will comply with all applicable or relevant
and appropriate chemical-, action- and location-specific requirements (ARARs). The ARARs are presented
below.
10.2.1 Action-Specific ARARs
RCRA requirements for closure of surface impoundments (40 CFR 264.228) and closure of
landfills (40 CFR 264.310) (relevant and appropriate).
RCRA requirements for groundwater monitoring (40 CFR 264.91) (relevant and appropriate).
Tennessee Hazardous Waste Management Act (Title 68, Chapter 46), which govern the transport,
storage, treatment, and disposal of hazardous waste (relevant and appropriate).
Tennessee Solid Waste Processing and Disposal Regulations (Pule 1200-1-7), which lay out the
closure and post-closure requirements of landfills and other disposal facilities (applicable).
Tennessee Air Quality Control Regulations for Fugitive Dust (Rule 1200-3-8.01), Visible Emissions
(Rule 1200-3-5.01), Paniculate Emissions (Rule 1200-3-7.03(2)), and Non-Process Emissions
Standards (Rule 1200-3-6.02(3)) (applicable).
Tennessee Water Pollution Control Regulations - General Stormwater Permit for Construction
Activities (Rule 1200-4-10.05) (applicable).
10-1
-------
10.2L2 Chemlcal-Soecffic ARARs
None.
10.2.3 Location-Specific ARARs
None.
10.2.4 Other Criteria. Advisories or Guidance To Be Considered for the Remedial Action (TBCs)
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 $1,833,000. The estimated costs
of the selected remedy are far less than the cost of the alternative that uses treatment of the soil as a
principal element. Implementation of the selected remedy will result in risk reduction identical to the more
expensive remedy, yet its costs are less than 0.5% of the alternatives involving incineration.
10.4 UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE TREATMENT
TECHNOLOGIES (OR RESOURCE RECOVERY TECHNOLOGIES) TO THE MAXIMUM EXTENT
PRACTICABLE
The Army, EPA, and the State of Tennessee have determined that treatment is impracticable and
that the selected remedy represents the maximum extent to which permanent solutions and treatment
technologies can be utilized in a cost-effective manner for Operable Unit Two. Of those alternatives that
are protective of human health and the environment and comply with ARARs, the Army, EPA, 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, ft will significantly reduce the risks posed by the contaminated
soils around the perimeter of the existing cap by preventing direct contact with these soils and minimizing
contaminant transport to groundwater. The selected remedy offers fewer short-term risks to the
community and site workers, and a shorter timeframe for project implementation. The implementability
of the selected remedy is significantly better than the incineration options. The selected remedy is also
less expensive 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 more quickly, with less difficulty,
and at less cost than the incineration alternative and is determined to be the most appropriate solution
for the contaminated soils at Operable Unit Two.
10.5 PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT
The statutory preference for remedies that employ treatment as a principal element is not satisfied.
10-2
-------
11.0 DOCUMENTATION OF SIGNIFICANT CHANGES
The Proposed Plan for Operable Unit Two, Milan Army Ammunition Plant, was released for public
comment in July 1993. The Proposed Plan identified Alternative D, Extension of the Existing Cap, as the
preferred alternative. The Army, EPA, and the State of Tennessee reviewed and considered all comments
received during the Public Meeting (written comments were not received during 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.
11-1
-------
12.0 REFERENCES
TDHE, Tennessee Department of Health and Environment. 1991. Rules of the Tennessee Department
of Health and Environment, Bureau of Environment, Division of Water Pollution Control. Chapter
1200-4-3. January 1991.
USAEC, U.S. Army Environmental Center, 1993a Milan Army Ammunition Plant O-Une Ponds Area
Feasibility Study. Focused Feasibility Study for Operable Unit Two. Final Document. Contract
Number DAAA15-91-D-0014.
USAEC, U.S. Army Environmental Center, 1993b. Milan Army Ammunition Plant O-Line Ponds Area
Proposed Plan for Operable Unit Two. Final Document. Contract Number DAAA15-91-D-0014
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 Milan
Army Ammunition Plant. Report No. 122. June 1978.
USATHAMA, U.S. Army Toxic and Hazardous Materials Agency. 1982a Milan Army Ammunition Plant
Contamination Survey. Report DRXTH-FS-FP-82131. Pugh, D.L: Envirodyne Engineers. January
1982.
USATHAMA, U.S. Army Toxic and Hazardous Materials Agency. 1982b. Milan Army Ammunition Plant
O-hine Settling Ponds Closure Plan. Wirth, P.K. September 1982.
USATHAMA, U.S. Army Toxic and Hazardous Materials Agency. 1984. Incineration Test of Explosives
Contaminated Soils at Savanna Army Depot Activity, Savanna, Illinois. U.S. Army Toxic and
Hazardous Materials Agency, Aberdeen Proving Ground, MD. Report Number DRXTH-TE-CR-
84277. April 1984.
USATHAMA, U.S. Army Toxic and Hazardous Materials Agency. 1991. Milan Army Ammunition Plant
Remedial Investigation Report. Final. Okusu, N., et al.: ICF Kaiser Engineers, Inc., Fairfax, VA.
December, 1991.
USATHAMA, U.S. Army Toxic and Hazardous Materials Agency. 1992. Milan Army Ammunition Plant O-
LJne Ponds Area Feasibility Study. Focused Feasibility Study for Operable Unit One Groundwater
Alternatives. Final Document Contract Number DAAA15-91-D-0014.
USDA, U.S. Department of Agriculture. 1982. Foods Commonly Eaten by Individuals: Amount Per Day
and Per Eating Occasion. Poa, E.M., Fleming, K.H., Guenther; P.M. and Mickle, S.J. Home
Economics Research Report Number 44.
USEPA, U.S. Environmental Protection Agency. 1985. Developmental Statistical Distribution or Ranges
of Standard Factors Used in Exposure Assessments. Office of Health and Environmental
Assessment, Washington, D.C. March 1985. Final Report OHEA-E-161.
USEPA, U.S. Environmental Protection Agency. 1989a Risk Assessment Guidance for Superfund.
Volume I: Human Health Evaluation Manual. Interim Final. OSWER Directive 9285.7-01 a
12-1
-------
September 29,1989.
USEPA, U.S. Environmental Protection Agency. 1989b. Exposure Factors Handbook. Office of Health
and Environmental Assessment, Washington D.C. July.
USEPA, U.S. Environmental Protection Agency. 1990. National Oil and Hazardous Substances
Contingency Plan. Final Rule. Federal Register. 55:8666-8865.
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, D.C. OSWER Directive 9285.6-03. March 25, 1991.
USEPA, U.S. Environmental Protection Agency. 1992. Dermal Exposure Assessment: Principles and
Applications, USEPA Interim Report, Exposure Assessment Group, Office of Health and
Environmental Assessment. EPA/600/8-91 /011B. January.
USEPA IV, U.S. Environmental Protection Agency (Region IV). (USEPA IV). 1992. Letter from Mr. Elmer
Akin, Office of Health Assessment, Region IV EPA, to Mr. Yazdi, ARCS Contract Manager, Bechtel
Environmental, Inc. March 13.
12-2
-------
APPENDIX A
Responsiveness Summary
-------
RESPONSIVENESS SUMMARY
The Focused Feasibility Study and the Proposed Plan were made available to the public in the
administrative record file located at the Mildred G. Fields Library in Milan, Tennessee, and at the Army
Chief Engineer's Office at the Milan Army Ammunition Plant. In addition, a public meeting was held at
the Milan Senior Citizens' Center on July 13,1993. At this meeting, representatives of the U.S. Army
and its contractor, the U.S. Environmental Protection Agency, and the State of Tennessee discussed
with the public the preferred remedy as well as all remedial alternatives under consideration. The
public was invited to comment between July 1 and August 15,1993, on ajl alternatives.
This Responsiveness Summary addresses comments received during the public meeting. The
comment is summarized and a response is provided. Written comments were not received during the
public comment period.
Public Comment 1.
Of the alternatives under consideration, only one (Alternative F) represents true cleanup of the site,
such that the area may be used for any purpose. The selection of any other alternative would require
maintenance of the site and limited use of the land.
Response to Public Comment 1.
The selected alternative has been evaluated as being protective of human health and the environment,
and in compliance with all environmental regulations. Although it would be preferred to be able to
remediate the site so that the land may be used for any purpose and would not have to be managed
as a contaminated site, the major reasons for selecting Alternative D are the following:
• Alternative D results in the same level of risk reduction as Alternative F, at less than 1 /200th
the cost;
• The short-term risks posed to the community and to site workers are significantly less for
Alternative D than for Alternative F; and
• Alternative D could be implemented in a much shorter timeframe than Alternative F.
Public Comment 2.
Treatment of the soil would be the preferred alternative if the cost were not so great. Were treatment
options considered that are less expensive that incineration?
Response to Public Comment 2.
A large number of treatment technologies were identified and considered during the Feasibility Study
stage of this project, including a variety of innovative and emerging technologies. However, none of
the other technologies is currently capable of achieving the low cleanup levels required at the site to
reduce the potential human health risks to within EPA's acceptable risk range.
-------
Public Comment 3.
Because there is a remedial alternative that can solve the problem of contaminated soil in the area,
that alternative should be selected.. The cost of the treatment alternative should not play such a large
part in the selection of the preferred remedy.
Response to Public Comment 3.
The National Contingency Plan requires that cost be considered when selecting a remedial alternative.
Cost is not considered to be a primary criterion, but is a balancing criterion that is considered when
weighing the relative advantages and disadvantages of each alternative. Although the cost difference
was one reason that Alternative D was selected over Alternative F, other factors were considered as
well, namely that implementation of Alternative D would result in lower short-term risks and a shorter
implementation time. Also, the large magnitude of the cost difference between Alternative D and
Alternative F, for the same reduction in risk, was considered.
Public Comment 4.
Even if the incineration alternative were selected, would that completely solve the problem? Does use
of this technology guarantee that the soil will be remediated to safe levels?
Response to Public Comment 4.
Incineration of~explosives-contaminated soil has been demonstrated to achieve destruction and
removal efficiencies of 99.99%. Use of this technology would result in complete remediation of the
excavated soil, such that no human health risks would be posed by contaminants remaining in this
soil.
------- |