united states environmental protection agency … · five-year review milan army ammunition plant...

UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION 4

ATLANTA FEDERAL CENTER61 FORSYTH STREET

ATLANTA, GEORGIA 30303-8960

4WD-FFB

MEMORANDUM

SUBJECT: Milan Army Ammunition PlantMilan, TennesseeFive-Year Review

FROM: Peter Dao, Remedial Project ManagerFederal Facilities Branch

THRU: Jon Johnston, ChiefFederal Facilities Branch

TO: Richard D. Green, DirectorWaste Management Division

Attached please find the Five-Year Review report for the Milan Army Ammunition Plant NPLsite in Milan, Tennessee. Section 121(c) of the Comprehensive Environmental Response, Compensation,and Liability Act (CERCLA), as amended, requires that if a remedial action is taken that results in anyhazardous substances, pollutants, or contaminants remaining at the site, the Environmental ProtectionAgency (EPA) shall review the remedial action no less often than each five years after initiation of theremedial action to assure that human health and the environment are being protected by the remedialaction being implemented.

Contaminated media are being addressed at the Milan Army Ammunition Plant Site’s fourOperable Units. Operable Unit One (OU- 1) addresses the O-Line Ponds groundwater. A pump and treatsystem addresses the groundwater source beneath the O-Line Ponds and prevents it from migrating offsite. Construction started in 1993. In 1999 the Remedial action was completed after a performanceevaluation of the operating parameters. Minor modifications to the system were made before it operatedcontinuously. Monitoring of the groundwater shows that the plume has not migrated further and that thesystem is performing as designed. An ESD to the ROD was performed to add the health based level asthe clean up goal, and the use only the carbon absorption unit without the UV-oxidation unit when theinfluent concentration is not sufficiently high.

Operable Unit Two (OU-2) consist of soil and sludge source material in the O-Line Pond. Thesoil and sludge were originally capped under a clay cover in 1984. In 1994 an impermeable capextension was added to the existing cap to cover additional contaminated soil. These actions eliminatedthe contaminant’s migration to ground water. Routine inspections and maintenance

Internet Address (URL) • http://www.epa.gov

4WD-FFB

MEMORANDUM

SUBJECT: Milan Army Ammunition PlantMilan, TennesseeFive-Year Review

FROM: Peter Dao, Remedial Project ManagerFederal Facilities Branch

THRU: Jon Johnston, ChiefFederal Facilities Branch

TO: Russell S. Wright, Acting DirectorWaste Management Division

Attached please find the Five-Year Review report for the Milan Army Ammunition PlantNPL site in Milan, Tennessee. Section 121(c) of the Comprehensive Environmental Response,Compensation, and Liability Act (CERCLA), as amended, requires that if a remedial action is takenthat results in any hazardous substances, pollutants, or contaminants remaining at the site, theEnvironmental Protection Agency (EPA) shall review the remedial action no less often than eachfive years after initiation of the remedial action to assure that human health and the environment arebeing protected by the remedial action being implemented.

Contaminated media are being addressed at the Milan Army Ammunition Plant Site’s fourOperable Units. Operable Unit One (OU- 1) addresses the O-Line Ponds groundwater. A pump andtreat system addresses the groundwater source beneath the O-Line Ponds and prevents it frommigrating off site. Construction started in 1993. In 1999 the Remedial action was completed after aperformance evaluation of the operating parameters. Minor modifications to the system were madebefore it operated continuously. Monitoring of the groundwater shows that the plume has notmigrated further and that the system is performing as designed. An ESD to the ROD was performedto add the health based level as the clean up goal, and the use only the carbon absorption unitwithout the UV-oxidation unit when the influent concentration is not sufficiently high.

Operable Unit Two (OU-2) consist of soil and sludge source material in the O-Line Pond.The soil and sludge were originally capped under a clay cover in 1984. In 1994 an impermeable capextension was added to the existing cap to cover additional contaminated soil. These actionseliminated the contaminant’s migration to ground water. Routine inspections and maintenance

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of the cap are being performed as well as a baseline ground water monitoring of up gradient and downgradient wells. Remedial activities associated with OU-1 were completed in July 1997.

For Operable Unit Three (OU-3) Groundwater a pump and treat system similar to that of OU-1without the UV-oxidation unit is being utilized to prevent further off-site migration of the northernboundary plume. Remedial action was completed in September 1999, and O&M is continuing with thesystem operating as designed.

Operable Unit Three and Four (OU-3&4) soils consist of the contaminated soils at the load linesand sumps. The OU-3&4 is a result of the re-designation and regrouping of the Sumps, Closed Landfill,Former Borrow Pit and B-Line Area OUs soil into two OUs. This was done because of the similarnature and extent, and some overlap of contamination at these different areas. It was determined that itwill be more economical to address these together. The remedies consisted of digging contaminated soildown to a maximum depth of ten feet, treatment through windrow composting, and disposal of treatedsoil in a solid waste landfill. The Remedial action was completed in September 1999. O&M activitiesare continuing with the area by area removal and composting of the soil.

After review of the remedial objectives for OU-1, OU-2, OU-3 groundwater and OU-3&4industrial area soils, no areas of non compliance have been identified. O&M activities are beingconducted as outlined in the O&M plans. The remedy remains protective of human health and theenvironment. The contractor for the Army made the following recommendation for actions that shouldbe taken between this and the next five-year review due in 2004:

• Refinement of the OU-l groundwater plume with additional monitoring wells andextraction wells if needed if the capture zone is determined to be inadequate.

• Install additional wells at OU-3 for performance monitoring and better plume definition.Also, identify residential wells for inclusion into the monitoring program if necessary.Add extraction well if needed based on the result.

• Consider other disposal option for treated soil from the OU-3&4 soil composting

• Identify new and innovative technologies that may better address all the above in termsof time and money

EPA also recommended that the Army re-evaluate the extraction wells location and depthperiodically to maximize the efficiency of the pump and treat system as the plume contract. The Armyshould also develop a monitoring plan and criteria for determining when clean up goals have beenachieved.

Attached to this memorandum is the report which presents the data for the five-year review forthe Milan Army Ammunition Plant site. The report which is titled Five-Year Review,

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Milan Army Ammunition Plant, was prepared by Environmental Science & Engineering Inc., on behalfof the United States Army Corps of Engineer, in December 1999.

Attachment

Approved by:Richard D. GreenDirectorWaste Management DivisionUS EPA Region 4

Draft FinalFive-Year Review

Milan Army AmmunitionPlant (MAAP)

Milan, Tennessee

Provided to:

U.S. Army Corps of EngineersMobile District

Mobile, Alabama

Provided by:

Environmental Science & Engineering, Inc.Gainesville, Florida

ESE Number: 3196301G

May 2000

MAAP, 5 Year Review

p/MAAP/5yrrev/draft.doc i Environmental Science & Engineering, Inc.

Table of Contents

1.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

2.0 Site Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1 Physical Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12.1.1 Physiography and Topography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12.1.2 Climatology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12.1.3 Soil Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12.1.4 Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32.1.5 Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2.2 Site History and Facility Mission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-52.2.1 Historical Review of Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-52.2.2 Current Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-82.2.3 Description of Onpost Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8

2.3 Physical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-92.3.1 OU1 – O-Line Ponds Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-92.3.2 OU2 – O-Line Ponds Soil, Sediment and Surface Water . . . . . . . . . . . . . . . . . . . . . 2-102.3.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-102.3.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

2.4 Land and Resource Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-112.4.1 OU1 – O-Line Ponds Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-112.4.2 OU2 – O-Line Ponds Soil, Sediment and Surface Water . . . . . . . . . . . . . . . . . . . . . 2-122.4.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-122.4.4 OU3 and OU4 Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

2.5 Site Operations and Chemicals of Concern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-132.5.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-132.5.2 OU2 – O-Line Ponds Soil, Sediment and Surface Water . . . . . . . . . . . . . . . . . . . . . 2-142.5.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-142.5.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

2.6 Initial Responses and Current Waste Disposal Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-162.6.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-162.6.2 OU2 – O-Line Ponds Soil, Sediment, and Surface Water . . . . . . . . . . . . . . . . . . . . . 2-162.6.3 OU3 - Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-172.6.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

2.7 OUs Not Currently in Remedial Action Phase or Work, NFA ROD, and RemovalActions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-182.7.1 Other OUs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-182.7.2 NFA ROD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-202.7.3 Removal Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

3.0 Development and Implementation of the Remedy and Operation andMaintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.1 Remedy Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13.1.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13.1.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33.1.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33.1.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

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Table of Contents (continued)

3.2 Remedy Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-73.2.1 OU1 - O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-73.2.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83.2.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83.2.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

3.3 Operation and Maintenance Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83.3.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83.3.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-93.3.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-93.3.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

3.4 Operational and Maintenance Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-103.4.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-103.4.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-113.4.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-113.4.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

3.5 Progress Since the Last Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

4.0 Five -Year Review Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1 Five -Year Review Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14.2 Interviews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.2.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14.2.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24.2.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24.2.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.3 Site Visit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34.3.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34.3.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34.3.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34.3.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.4 Remedial Action Objectives Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44.4.1 OU1 - O Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44.4.2 OU2 - O Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44.4.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-54.4.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.5 Data Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-54.5.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-54.5.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-74.5.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-74.5.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

5.0 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.1 Appropriateness of Remedial Action Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15.1.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15.1.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-75.1.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-75.1.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

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5.2 Achievement of Remedial Action Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-95.2.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-95.2.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-95.2.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-95.2.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

5.3 Whether the Remedy is Effective and Functioning as Designed . . . . . . . . . . . . . . . . . . . . . 5-105.3.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-105.3.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-115.3.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-125.3.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-13

5.4 Adequacy of O&M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-145.4.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-145.4.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-145.4.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-145.4.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14

5.5 Early Indicators of Potential Remedy Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-155.5.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-155.5.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-155.5.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-155.5.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-16

6.0 Deficiencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.1 O&M Record Keeping and Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.1.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.1.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.1.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.1.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2 O&M Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.2.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.2.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.2.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26.2.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

6.3 Institutional Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26.3.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26.3.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26.3.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26.3.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

6.4 Cleanup Levels/Contaminant Delineation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26.4.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-36.4.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-66.4.3 OU3 – K Line (NE) Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-86.4.4 OU3/OU4 – Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10

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7.0 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.1 OU1 – O-Line Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17.2 OU2 – O-Line Ponds Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17.3 OU3 – Northern Boundary Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17.4 OU3 and OU4 – Northern Industrial Area Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2

8.0 Protectiveness Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1


9.0 Next Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1


10.0 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1

List of Appendices

Appendix A OU3 Extraction Well Construction LogsAppendix B Operable Unit Review DocumentsAppendix C Five-Year Reviews, Site Visit Checklist(s)Appendix D Examples of OU2 Pond Cap Quarterly Inspection ChecklistAppendix E Photographs of Operable UnitsAppendix F Groundwater Model Outputs

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List of Tables

Table 3-1 Chronology of Remedy Development and Implementation . . . . . . . . . . . . . . . . . . . . 3-2Table 3-2 Summary of Soil Risk-Based Remediation Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5Table 3-3 Soil Risk-Based Remediation Goals for Residents . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6Table 3-4 Effluent Discharge Limits, OU3 Northern Boundary Groundwater Treatment Plant

Discharge into the Rutherford Fork of the Obion River; Discharge FlowRate 1.73 MGD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13

Table 4-1 Design Influent Concentration and Effluent Standards . . . . . . . . . . . . . . . . . . . . . . . . 4-6Table 5-1 Identification of Action-Specific ARARs and TBC Guidance . . . . . . . . . . . . . . . . . . 5-2Table 5-2 Identification of Chemical-Specific ARARs and TBC Guidance for

Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5Table 5-3 Identification of Location-Specific ARARs and TBC Guidance . . . . . . . . . . . . . . . . . 5-6Table 6-1 Review of OU1 Discharge Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4Table 6-2 Estimate of Acceptable Groundwater Concentration in Vicinity of OU1

Extraction Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7Table 6-3 Review of OU3, Line K (NE) Grondwater Cleanup Standards . . . . . . . . . . . . . . . . . . 6-9Table 6-4 Summary of Soil Risk-Based Remediation Goals, OU3/OU4 Industrial

Area Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11Table 6-5 Observed Vertical Distribution of COCs in the Vadose Zone at Line B . . . . . . . . . . . 6-13Table 6-6 Comparison of Observed Soil Concentrations with Csat . . . . . . . . . . . . . . . . . . . . . . . 6-16Table 6-7 Depth of Contaminant Penetration Through the Vadose Zone Under

Various Infiltration Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21Table 6-8 Mass of COCs Remaining in soil Column After Completion of Remedial

Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-22

List of Figures

Figure 1-1 Facility Map with Operable Units and Areas of Concern . . . . . . . . . . . . . . . . . . . . . . 1-4Figure 2-1 Location of MAAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2Figure 6-1 Comparison of Actual Concentrations to CSAT for RDX . . . . . . . . . . . . . . . . . . . . . 6-17Figure 6-2 Comparison of Actual Concentrations to CSAT for TNT . . . . . . . . . . . . . . . . . . . . . 6-18

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List of Acronyms

ABA Ammunition Burnout AreaAO American OrdnanceARAR Applicable or Relevant and Appropriate RequirementsASTM American Society for Testing and MaterialsATSDR Agency for Toxic Substances and Disease RegistryCERCLA Comprehensive Environmental Response, Compensation, and Liability ActCDAP Chemical Data Acquisition Plancm centimeterCOC chemical of concernECWTP explosives-contaminated wastewater treatment plantEE/CA Engineering Evaluation and Cost AnalysisEPA U.S. Environmental Protection AgencyERM Environmental Resources Management, Inc.ESD Explanation of Significant DifferencesESE Environmental Science & Engineering, Inc./F degrees FahrenheitFFS Focused Feasibility StudyFS Feasibility Studyft footft2 square footft-bls feet below ground surfaceft/day feet per dayft-msl feet above mean sea levelGAC granular activated carbonGOCO government-owned, contractor-operatedGPM gallons per minuteHMX cyclotetramethylene tetranitramineHSWA Hazardous and Solid Waste AmendmentsIWWTP industrial wastewater treatment plantkg/L kilograms per literLAP loading, assembly, and productionLDR Land Disposal RestrictionsLHA Lifetime Heath AdvisoryLMOS Lockheed Corporation (merged with Martin Marietta, Inc.)MAAP Milan Army Ammunition Plant

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MeV million electron voltmg/L milligrams per literMGD million gallons per daymm millimeterMMOS Martin Marietta Ordnance Systems, Inc.MOD Milan Ordnance DepotNCP National Oil and Hazardous Substance Contingency PlanNFA No Further ActionNPDES National Pollutant Discharge Elimination SystemNPDWS National Primary Drinking Water StandardNPL National Priorities ListingNSA Northern Study AreaO&M operation and maintenanceOU operable unitPlexus Plexus Scientific CorporationPRG preliminary remediation goalPWTF pink water treatment facilityRAB Remedial Advisory BoardRAO Remedial Action ObjectiveRCRA Resource Conservation and Recovery ActRfD reference doseRI Remedial InvestigationROD Record of DecisionSARA Superfund Amendments and Reauthorization Act of 1986STP sewage treatment plantTBC to-be-consideredTCLP Toxicity Characteristic Leaching ProcedureTCRA Time Critical Removal ActionTDEC Tennessee Department of Environment and ConservationTDHE Tennessee Department of Health and the EnvironmentTSD treatment, storage, and disposal:g/cm2 micrograms per square centimeter:g/cm3 micrograms per cubic centimeter:g/cm2/yr micrograms per square centimeter per year:g/g micrograms per gram:g/L micrograms per literUSACE U.S. Army Corps of Engineers

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USAEHA U.S. Army Environmental Hygiene AgencyUSATHAMA U.S. Army Toxic and Hazardous Materials AgencyUSC United States CodeUV ultravioletWCOP Wolf Creek Ordnance PlantWWII World War II

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1.0 Introduction

Environmental Science and Engineering, Inc. (ESE) was authorized by the US Army Corps of Engineers(USACE), Mobile District to conduct a 5-year review of the remedial action(s) implemented at alloperable units (OUs) located at Milan Army Ammunition Plant (MAAP), located in Milan, Tennessee.An OU is defined by the National Oil and Hazardous Substance Contingency Plan [(NCP) 40 CFR (Codeof Federal Regulation) 300.5] as a discrete action which is an incremental step toward comprehensivelymitigating site problems. At the present time, remedial actions have been implemented at:

• OU1 – O-Line Ponds Groundwater,• OU2 – O-Line Ponds Soil,• OU3 – Northern Boundary Groundwater, and• OU3/OU4 – Northern Industrial Area Soil.

Additional OUs will be incorporated into the future 5-year reviews when a Record of Decision (ROD) isapproved and the selected remedial action is initiated at that OU.

Other operable units currently in the pre-remedial action stages of work are as follows:• Non-Industrial Area Soils (Ditches) in OU3 and OU4;• OU4, Region 1 Groundwater (X-Line Groundwater Plume);• OU4, Regions 2 and 3 Groundwater (City of Milan Groundwater Plume);• OU5, Southern Study Area; and• OU3, 4, and 5 Groundwater (Onpost Groundwater).

MAAP has also finalized one No Further Action (NFA) ROD. This ROD was prepared for thefollowing sites at MAAP:

1. Sanitary landfill,2. Former Ammunition Burnout Area (ABA) (Sunny Slope), and 3. Salvage Yard.

This review has been conducted on behalf of the U.S. Army. The primary purpose of the review is todetermine whether the remedy remains protective of human health and the environment. Five-year reportsidentify deficiencies, if any, and recommendations to address them. Five-year review reports documentthe evaluation of the implementation of the remedy and operation and maintenance (O&M), as well as thecontinued appropriateness of remedial action objectives, including cleanup levels at a site.

Section 121(c) of the Comprehensive Environmental Response, Compensation, and Liability Act of1980 (CERCLA), as amended by the Superfund Amendments and Reauthorization Act of 1986(SARA), and Section 300.430 (f) (4) (ii) of the NCP, require that periodic (no less often thanevery 5 years) reviews be conducted for sites where hazardous substances, pollutants or

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contaminants remain at the site above levels that allow for unlimited use and unrestricted exposurefollowing the completion of all remedial actions.

This is the first 5-year review for the MAAP site and generally, for sites with multiple OUs, a 5-yearreview should be conducted for the entire site, rather than 5-year reviews for each OU. The rationale forthis policy is to show the evolution of the implemented remedies for each OU and to present the site as acoherent whole. The 5-year review is triggered by the first OU that requires a 5-year review.

This statutory review is triggered by the March 1995 construction of the OU1 groundwater treatmentfacility. The methodology used for the trigger determination was selection of the actual remedial actiononsite construction date with a review conducted after July 26, 1994 [NPL Sites ROD 5-Year ReviewGuidance, U.S. Environmental Protection Agency (EPA), March 1998]. Explosives-contaminatedgroundwater, soil, sediment, and/or surface water are being addressed at the respective OUs and are beingadministered under a ROD specific to those media. A ROD was signed for OU1 – O-Line PondsGroundwater on September 30, 1992, for OU2 – O-Line Ponds Soil on September 30, 1993, for OU3 –Northern Boundary Groundwater on September 30, 1994 and for OU3 and 4 – Northern Industrial AreaSoil on September 30, 1995. The NFA ROD for the Salvage Yard, Former ABA, and Sanitary Landfillwas signed on February 3, 1998.

The EPA has established a tiered approach to conducting 5-year reviews, which allows reviews to betailored to the status of activities onsite and to site-specific considerations. Four levels (1, 2, 3, and 1a) ofreview have been established that detail the type of activities which should take place. Level 1 representsthe fundamental review type, and is appropriate for most sites where construction is complete. Levels 2and 3 represent enhanced levels of review, needed to address site-specific considerations. A recalculationof risk is a typical feature of a Level 2 review. A new risk assessment is a typical feature of a level 3review. Level 1a reviews, which were developed for sites with an ongoing response, generally apply tosites where construction is not complete. A site visit, interviews, and an Applicable or Relevant andAppropriate Requirements (ARARs) review are not needed at the level 1a review.

A Level 1 review was conducted for OUs at MAAP. The OUs included in this 5-year review are: 1. OU1 – O-Line Groundwater2. OU2 – O-Line Ponds Soil, Sediment and surface Water3. OU3 – Northern Boundary Groundwater4. OU3/OU4 – Northern Industrial Area Soil

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There is also a discussion in Sec. 2.0 of other OUs where remedial action has not been initiated (or is notplanned) at the time this document was prepared. Included in this discussion are the following sites:

• NFA sites (Salvage Yard, Former ABA, and Sanitary Landfill),• Onpost Groundwater (OU3, OU4, OU5),• OU4 – Region 1 Groundwater,• OU4 – Regions 2 and 3 Groundwater,• OU5 – Southern Study Area, and• Removal Action Sites – Water Towers.

See Fig. 1-1 for site locations.

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2.0 Site Background

This section describes the physical setting, climate, geology, and hydrology of the installation as providedfrom the Environmental Resources Management, Inc. (ERM), Remedial Investigation (RI), (1995). Asummary of the history, mission, and operations of the site and specific information on the loading,assembly, and production (LAP) lines and ditches are also included.

2.1 Physical Setting

MAAP is located in portions of Gibson and Carroll Counties in western Tennessee (see Fig. 2-1). TheCity of Milan lies approximately 1 mile west of MAAP; Humboldt lies 17 miles southwest; Trenton lies18 miles northwest; and Jackson lies 28 miles south. The site is approximately 50 miles east of theMississippi River. MAAP encompasses 22,436 acres and is bordered on the northeast and east by landowned by the Tennessee National Guard and on the northwest by land owned by the City of Milan andthe University of Tennessee.

2.1.1 Physiography and Topography

MAAP lies within the Coastal Plain Province of the Mississippi Embayment. The topography of MAAPand the surrounding area is characterized by gently rolling hills with elevations ranging fromapproximately 590 feet above mean sea level (ft-msl) at the southern boundary to approximately 320ft-msl at the northern boundary.

2.1.2 Climatology

The MAAP area is characterized by a temperate climate. Rainfall averages about 50 inches per year. Theaverage evaporation is approximately 40 inches. Relative humidity averages 60 to 70 percent. Themonthly mean temperature ranges from 40 degrees Fahrenheit (/F) in the winter to 80/F in July. Theaverage frost-free season is 215 days per year. Prevailing winds are from the south at an averagewindspeed of 6 to 10 miles per hour.

2.1.3 Soil Types

The surface soils at MAAP consist chiefly of a reddish-brown to yellow mottled silty clay that grades intoa clay unit with depth. The soil types include the Memphis, Loring, Grenada, Calloway, Henry, Falaya,and Waverly soil associations. Based on topography, the Memphis and Loring series occur on higherelevations and are well-drained soils. The Henry soil series is poorly drained and is usually associatedwith flat terrain, and the Falaya and Waverly soils occur in the low areas and are poorly drained.

Boring logs at the site indicate that the upper 12 to 15 feet (ft) of soil consists of reddish-brown to tan,silty, low-plasticity clay with some layers of sandy and highly plastic clay. Below these

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depths, sands with varying amounts of silts and clays have been encountered. Occasional gravel, up to3/8-inch-diameter, has been encountered during boring operations. A more sandy alluvium of lesserthickness (5 to 10 ft) was observed in several areas near surface drainage features in the Northern StudyArea (NSA). Natural and artificial drainage systems have incised into the alluvium in several locations.

2.1.4 Geology

Western Tennessee (including MAAP) lies on the eastern flank of the Upper Mississippi RiverEmbayment. Structurally, the embayment is a downwarped, downfaulted trough whose axis approximatesthe present course of the Mississippi River. Sediments ranging in age from Cretaceous to Recent havebeen deposited in this trough. These sediments consist of sand, gravel, lignite, clay, chalk, and limestoneunits that vary in thickness.

MAAP is situated on the Memphis Sand of the Claiborne Group of Tertiary age in the Gulf Coastal Plainof western Tennessee. The elevation and thicknesses of stratigraphic units beneath the City of Milan, areinferred on the cross section from the data for observation wells in Gibson and Carroll Counties.

The Memphis Sand outcrops in a broad belt across western Tennessee, but is covered in most places byfluvial deposits of Tertiary and Quaternary age and loess and alluvium of Quaternary age (Parks andCarmichael, 1990b). The eastern boundary of the Memphis Sand was mapped by Parks and Russell(1975a) as the contact between the Wilcox and Claiborne Formations. This boundary was mappedbecause of the uncertainty of the equivalence of strata outcropping with the units that make up the Wilcoxand Claiborne Groups in the subsurface, as subdivided by Moore and Brown in 1969 (Parks andCarmichael, 1990b). The western boundary of the outcrop belt is not well established because the contactbetween the Memphis Sand and the overlying Cook Mountain Formation is covered by fluvial deposits,loess, or alluvium (Parks and Carmichael, 1990b).

The Memphis Sand consists of a thick body of sand that includes subordinate lenses or beds of clay andsilt at various depths. The clay and silt locally are carbonaceous and lignitic; thin lenses of lignite alsooccur locally. Thick beds of clay and silt in the upper part of the Memphis Sand may, in some places, beconfused with the overlying Cook Mountain Formation.

Sand in the Memphis Sand ranges from very fine to very coarse, but is commonly fine to coarse. The Memphis Sand ranges from 0 to 900 ft in thickness, and where the original thickness is preserved, it is about 400 to 900 ft thick (Parks and Carmichael, 1990b). The formation is thinnest along the eastern limits of the outcrop belt in Hardeman, Madison, Carroll, and Henry Counties. In western Tennessee, the base of the Memphis Sand dips westward at rates of 20 to 50 ft per mile. The variation in the thickness of the Memphis Sand aquifer cannot be accurately mapped in

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the MAAP area since, with the possible exception of MI085 (312 ft total depth), no well in the study areahas penetrated the top of the Flour Island Clay. The Memphis Sand aquifer generally thickens to the westacross the study area, with thickness values ranging from 182 ft to over 300 ft (ERM, 1995). TheMemphis Sand aquifer is at least 360 ft thick near MI091 (382 ft total depth).

The Claiborne Group is underlain by the Wilcox Group, which is approximately 60 ft thick. The FlourIsland Formation, where present, acts as a confining layer between the Claiborne and Wilcox Groups. TheFlour Island Formation appears to be a continuous formation across Carroll and Gibson Counties.Underlying the Wilcox is the Porters Creek Clay, which acts as a confining unit between the Fort PillowSand of the Wilcox Group and the McNairy Sand of the Cretaceous age.

The exact depth to bedrock under MAAP is not known. A test well drilled to 1,289 ft approximately 20miles south-southwest of MAAP near Jackson, Tennessee, was stopped in a sandy clay marl. It wasestimated that rock (possibly limestone) would be encountered between 500 to 800 ft below thecompleted depth of the test well.

2.1.5 Hydrology

2.1.5.1 Surface Water

Numerous perennial and ephemeral surface water features occur within the installation and flowto the north-northwest. Wolf Creek, the largest interior drainage body, originates as the East Fork of WolfCreek near Pine Lake at the southeastern boundary. Along with two other tributaries (Dry Creek and WestFork of Wolf Creek), Wolf Creek drains the southern and central portions of the installation. It exits alongthe northwest boundary and empties into the Rutherford Fork of the Obion River. The extreme southernportion of the installation drains south to the Middle Fork of the Forked Deer River. The northeasternportion of the installation drains to Halls Branch, Johns Creek, and the Rutherford Fork of the ObionRiver. The northern portion of MAAP contains several well-developed, ephemeral, natural drainagebodies (defined alphabetically as Ditches A through E) that join the Rutherford Fork along the northernboundary of the installation. The two parent streams, the Forked Deer River and Obion River, empty intothe Mississippi River about 50 miles west of MAAP.

Under the authority of the Tennessee Water Quality Control Act, the Tennessee Water Quality ControlBoard has classified the three primary streams near the NSA (Rutherford Fork of the Obion River, theEast Fork of Wolf Creek, and Wolf Creek) for the following uses: maintenance of healthy fish andaquatic life populations, human recreation, irrigation, and livestock and wildlife watering [TennesseeDepartment of Health and the Environment (TDHE), now known as Tennessee Department ofEnvironment and Conservation (TDEC), 1991].

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2.1.5.2 GroundwaterSands in the Claiborne and Wilcox Groups are principal sources of groundwater in western Tennessee. AtMAAP, the Memphis Sand of the Claiborne Group is the major aquifer. Although groundwater is alsoabundant in the underlying Wilcox and Cretaceous sediments (i.e., McNairy Sands), it has not beennecessary to tap these deeper sources in most areas. Within the NSA, depth to groundwater ranges from10 to 70 feet below land surface (ft-bls), depending on topography and hydraulic location. The majorcontrols on groundwater movement in the Memphis Sand are the dip of the sediments, surfacetopography, and surface recharge and discharge patterns. Groundwater in the western Tennessee areagenerally flows to the west, in the direction of regional dip of these sands, and can also trend to the northbecause of topographic influences. The gradient of the groundwater flow is estimated at 7.5 to 11 ft permile to the northwest within the northern portion (ERM, 1993). On a general scale, there are no abrupthydrologic boundaries in the aquifer. The formation is recognized as sand with clay lenses and clay richzones, which may locally alter vertical groundwater flow; stratification of the sediments tends to makevertical conductivities lower than horizontal conductivities. The sands range from very fine to verycoarse-grained, and the grain size may vary both horizontally and vertically over short distances. Thethickness of Memphis Sand aquifer in the study area ranges from approximately 180 ft to more than 360ft, based on the drilling logs from ERM and ESE drilling activities. The thickness of the Fort Pillow Sandaquifer is estimated at 60 to 100 ft in the study area (Parks and Carmichael, 1990b).

The clay units that dominate the stratigraphic section below the Wilcox Group to the top of theCretaceous McNairy Sands are known as the Porters Creek Clay, the Clayton Formation, and the OwlCreek Formation. Collectively, these formations constitute a stratigraphic unit that is approximately 425 ftthick and begins at approximately 250 ft-bls at MAAP. The McNairy Sand is an artesian aquifer thatunderlies the installation and begins approximately 500 ft below the Claiborne Group. The McNairy Sandis approximately 200 ft thick near the Tennessee-Mississippi border and contains cross-bedded,variegated sands with lenses and interbeds of clay and lignite (Cushing et al., 1964). Clays are common inthe McNairy Sand, and relatively large clay bodies occur stratigraphically near the middle of theformation (Parks and Russell, 1975b).

2.2 Site History and Facility Mission

The name, size, and mission of MAAP have changed since its beginning in 1940. This section brieflydescribes the original site operations, changes that have occurred over the years, and current operations.

2.2.1 Historical Review of Operations

Construction of MAAP was authorized on December 18, 1940, started in January 1941, and completedin January 1942. The H.K. Ferguson Engineering Company, Cleveland, Ohio, and the

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Oman Construction Company, Nashville, Tennessee, formed a company, The Ferguson-Oman Company,to design and construct the installation. The original land area encompassed 28,521 acres. The installationcurrently encompasses 22,436 acres, as tracts of land have been sold, deeded, leased, or transferred.Approximately 548 acres enclose the various production lines, while the storage areas total 7,930 acres.The field service portion includes approximately 9,897 acres, and approximately 1,395 acres are used foradministrative, shop maintenance, housing, recreation, and other functions. Other acreage is necessary toallow safe distances between areas containing explosives.

Initially, the plant was divided into two separate units: the Wolf Creek Ordnance Plant (WCOP), and theMilan Ordnance Depot (MOD). In July 1943, the WCOP and MOD merged into a single integralordnance facility, Milan Ordnance Center, and the Proctor and Gamble Defense Corporation became theoperating contractor for the facility.

During World War II (WWII), the mission of the facility included the production of fuzes, boosters, andminor and major caliber ammunition; the operation of an ammonium nitrate plant; and the receipt,storage, and shipping of ammunition. Peak employment reached approximately 11,000 people.

The Milan Ordnance Center was designated Milan Arsenal on October 30, 1945, and during the followingmonth, the plant reverted to Government operation and placed on standby status. The plant’s mission thenincluded receipt, storage, and processing of ammunition from overseas; maintenance, surveillance,renovation and demilitarization; and a limited amount of new production.

During the early part of the Korean Conflict, the Proctor and Gamble Defense Corporation assumedoperation of the facility. On April 29, 1953, the plant was placed on active status, and employmentreached approximately 8,000 people. Principal changes to the plant’s mission were the increased outputof new ammunition, inclusion of experimental ammunition, and the Phase II Industrial EngineeringStudies of all ordnance command loading plants.

Effective July 1, 1954, Milan Arsenal was designated a Permanent Installation. Production lines wereplaced on layaway due to sharp decreases in production schedules in 1954. In 1955, two more productionlines were placed on standby status. By 1957, production had ceased, and only a small demilitarizationprogram continued at Line B.

On October 1, 1957, the industrial activity of Milan Arsenal was placed on inactive status. An economy and austerity program was put into effect and remained until January 1, 1960, when theindustrial portion of the Milan Arsenal returned to active status. Later that same month, the

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Proctor and Gamble Defense Corporation terminated their contract with the Government, and HarveyAluminum Sales, Inc., Torrance, California, became the operating contractor.

On November 2, 1961, the industrial portion of Milan Arsenal was designated Milan Ordnance Plant, andthe field service portion was designated as Milan Depot Activity. The depot activities were discontinuedon November 16, 1962; however, the field service mission is still being performed. On August 1, 1963,the Milan Ordnance Plant became officially known as Milan Army Ammunition Plant.

During the 1960s, existing facilities were rehabilitated, and the plant was modernized to produce fuzes,primers, delay plungers, delay elements, and boosters; 40 millimeter (mm), 60mm, 81 mm, 90mm,105mm, 106mm, and 155mm ammunition; mine, grenade, and cluster bomb unit dispensers; demolitionkits; shell metal parts; pelletizing explosives; and to renovate various items.

Martin Marietta, Inc., gained controlling interest of Harvey Aluminum Sales, Inc., on December 22, 1969.

During 1971, Lines E, F, and H were placed on layaway. Production was transferred to other lines, andequipment used to produce metal shell parts was transferred to private industry.

In December 1975, production of items on Line Z was canceled. Line Z was reactivated in April 1992 andis currently on active status. In 1977, production of items from Line C was transferred to Line B. Line Cwas then placed on standby status.

In December 1977, a portion of Line H was reactivated to load, assemble, and pack M739 fuzes. Thesefuzes required a temperature- and humidity-controlled environment that was available at Line H.

An extensive modernization program began in 1978 and continued through 1985. Production Lines A, C,E, and Z were updated during this program. A project to automate manufacturing 60mm and 81mmpropellant increments at Line C was also completed during this time. This project led to the developmentof a melting system at MAAP. Prove out/production was completed in October 1983, and Line C wasplaced on layaway in August 1984. Limited production of 60mm and 81mm mortar rounds wastransferred to Line D.

The X-ray facility at Line V was built to consolidate the plant’s X-ray operations in one location.Previously, X-ray facilities existed at Lines C, D, and K. Line V contains an underground 4-millionelectron volt (MeV) X-ray unit, a 2-MeV unit, a 0.420-MeV unit, and a fluoroscope. This is the world’slargest facility dedicated solely to nondestructive testing of ammunition.

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Other upgrades to MAAP included the construction of explosives-contaminated wastewater treatmentplants (ECWTPs), which were built at six production lines under a contract issued by USACE.Construction began in October 1979 and was completed on March 13, 1981. An additional ECWTP wasconstructed in Area J for pretreatment of the laundry wastewater. Construction began in April 1992 andwas completed in November 1993. These plants remove explosive contaminants from process waterbefore discharge using activated carbon filtration. These discharges are regularly monitored by anenvironmental laboratory constructed in 1980. The spent carbon generated by the ECWTPs is a listedhazardous waste (EPA No. K045). Spent carbon is stored in the hazardous waste storage igloos in Area Dbefore transport to an offsite treatment, storage, and disposal (TSD) facility.

Effective January 7, 1985, Martin Marietta, Inc. sold its interest in the aluminum business and organizedanother company, Martin Marietta Ordnance Systems, Inc. (MMOS), to operate MAAP. During 1995,Lockheed Corporation merged with Martin Marietta, Inc. (LMOS). In January 1997, General Dynamics,Inc. acquired operation of MAAP.

2.2.2 Current Operations

MAAP is a government-owned, contractor-operated (GOCO) military industrial installation under thejurisdiction of the Commanding General, Headquarters, U.S. Army Armament, Munitions and ChemicalCommand. MAAP is currently under the local command of the U.S. Army Ordnance Corps and isoperated by American Ordnance, LLC (AO). The current level of employment is approximately 900people.

The current mission includes:• Loading, assembling, and packaging of conventional ammunition items, as assigned;• O&M, as directed, of active facilities in support of current operations;• Maintenance and/or layaway, in accordance with regulations for standby facilities, including any

machinery and packaged items received from industry, in such condition as will permitrehabilitation and resumption of production within the time limitations prescribed;

• Receipt, surveillance, maintenance, renovation, demilitarization, salvage, storage, and issue ofassigned field service stocks and Groups V and W items of industrial stocks, as required ordirected; and

• Procurement, receipt, storage, and issue of necessary supplies, equipment, components, andessential materials.

2.2.3 Description of Onpost Sites

Several onpost sites may be impacted by past disposal practices. The LAP line areas are addressedunder a final Record of Decision [ICF Kaiser Engineers, Inc. (ICF Kaiser), 1995], and theECWTPs and WCOP sewage treatment plant (STP) are permitted under a National Pollutant

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Discharge Elimination System (NPDES) permit. The locations of these outfalls are presented in Fig. 2-6of the 1991 RI by ICF Kaiser. Previous RI reports have identified numerous potential sources ofgroundwater contamination at MAAP.

MAAP facilities include nine ammunition LAP lines, one washout/rework line, one experimental line,one central X-ray facility, one test area, two shop maintenance areas, storage areas, demolition andburning grounds area, an administrative area, a family housing area, and recreational facilities. Inaddition, there are medical facilities, fire/ambulance stations, 10 high-pressure heating/process steamplants, 16 low-pressure heating plants, 1 solar pond, and 7 ECWTPs.

Two STPs are located on the facility: the WCOP STP in the northern portion of the site, and the MODSTP in the southern portion of the site. A laundry facility for clothing used by onsite personnel workingwith explosives/propellants is located in Area J. A large power plant, a coal pile, and an evaporation pondfor coal pile runoff are located near Line K.

Of the 14 process areas active by the end of WWII, only 9 lines (A, B, D, H, I, O, V, X, and Z) are in usetoday. In the past, wastewater from production activities in the lines was discharged to open ditches thatdrained from sumps or surface impoundments into both intermittent and perennial streams and rivers.Currently, all explosives-contaminated wastewater generated by the LAP Lines is treated in the sevenECWTPs. This wastewater is processed by an activated carbon absorption system and discharged underthe authority of a NPDES permit. Specific areas of potential contamination included in the SiteCharacterization Report (ERM, 1993) are described in the following subsections. For descriptions ofother sites investigated previously, refer to the ICF Kaiser RI (1991).

Acreage not designated as a LAP line or process area is often used for agricultural purposes.Approximately 13,600 acres within the MAAP boundary are leased for agricultural use; approximately3,984 acres are used as cropland. Cotton, corn, and soybean are the main crops, with smaller amounts ofgrain sorghum and wheat also grown. In 1990, there were 2,746 head of cattle grazing on the facility. Thecattle graze between April and November on approximately 8,700 acres. In addition, MAAP has morethan 6,000 acres of managed timberland.

2.3 Physical Characteristics

2.3.1 OU1 – O-Line Ponds Groundwater

OU1 is located in the northeastern portion of MAAP along Route 104 approximately 1 mile westof Building T, the MAAP headquarters building. The OU1 consists of the groundwater underlying approximately 50 acres of a gently sloping, hilly area located north (down-gradient) of O-Lineand south of K Line and Route 104. The site is bordered by Ditch B on the west and a

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narrow drainage ditch (also referred to as OU2 Ditch) on the east, which merges into Ditch B. The cappedO-Line ponds (OU2) are located on the southeast portion of the OU1 site.

The site generally slopes from the southeast to northwest with elevations decreasing from approximately450 to 430 ft-msl. The site, which is slightly mounded due to the capping of the ponds, is drained by thenarrow OU2 Ditch with surface water discharging from OU2 Ditch into Ditch B, which flows underRoute 104 to the north. The ditches are typically dry and only contain water after rainstorms. The depth togroundwater ranges from approximately 55 to 35 ft-bls, and the flow direction, north to northwest,generally mimics the local topography.

2.3.2 OU2 – O-Line Ponds Soil, Sediment and Surface Water

OU2 is situated in the southeast portion of the OU1 area. OU2 is comprised of the contaminated soilbeneath and around the former ponds and surface water and shallow sediments in the drainage ditch (OU2Ditch) that flows along the east and north sides of the former ponds. Through sampling and considerationof former site activities, the area of OU2 has been defined as consisting of the area that has been impactedby use and/or closure of the former ponds at O-Line. To be conservative, the boundary of this area hasbeen identified as the fence that encircles the capped area, exclusive of the area south of the access road tothe O-Line industrial wastewater treatment plant (IWWTP). The area of OU2 is approximately 582,000square feet (ft2), or a little more than 13 acres. The OU2 Ditch, that flows along the east and north sides ofthe O-Line cap, which received pond effluent while the ponds were in use and currently receives treatedwater from the O-Line IWWTP, is included in OU2. See Sec. 2.3.1 for site topography and depth togroundwater.

2.3.3 OU3 – Northern Boundary Groundwater

The OU3 consists of the northeastern portion of the MAAP facility; the area north of Route 54 to theRutherford Fork of the Obion River, and is bordered on the east by Ditch 7 (also known as Ditch A) andon the west by Lines B and E.

The topography is hilly and approximately at an elevation of 500 ft-msl in southern area and slopesgradually to the north, with an elevation of about 370 ft-msl at the Rutherford Fork River. The depth togroundwater ranges from 50 to 60 ft-bls in the southern area of OU3 to approximately 3 ft-bls near theRutherford Fork. The OU3 area is primarily drained by Ditches A, B and C, all of which flow to the northand into the Rutherford Fork.

2.3.4 OU3 and OU4 – Northern Industrial Area Soil

The northern industrial area, as described in the ROD (OU3 and OU4 Soil), includes the following loadlines, storage areas, and disposal areas:

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1. Load Lines A, B, C, D, E, K, O, X, and Z 2. Closed Sanitary Landfill 3. Former Borrow Pit

Other areas within the northern industrial area have not yet been investigated but are included in thisremedial action; Area M (storage), Area N (storage), Area S (storage), Area J (maintenance/fabrication),and Lines F, H and V. These areas are all industrial areas in the northern portion of the facility locatednorth of Route 54. Although the southern portion of the facility contains storage areas, a test area, an openburning ground and an operating landfill, most industrial operations occur in the northern portion of thefacility.

The northern industrial area topography generally slopes from southeast to the northeast with elevationsranging from approximately 500 to 320 ft-msl on the northern installation boundary near the RutherfordFork. Numerous perennial and ephemeral surface water features occur with the OU3 and OU4 area andflow is to the north-northwest. The entire facility, except for the extreme southern portion, drains viasmall and medium-sized creeks and ditches to the Rutherford Fork of the Obion River, which flows westeventually discharging into the Mississippi River about 60 miles to the west.

2.4 Land and Resource Use

2.4.1 OU1 – O-Line Ponds Groundwater

The actual OU1 site is entirely on MAAP installation property, although Route 104, a state secondaryroad runs through the installation just to the north of OU1. The site is restricted to the public and access isgated and an official identification pass, approved by MAAP personnel, is necessary to gain access to thesite. There are no industrial or agricultural activities onsite at OU1. The only building onsite is the OU1groundwater treatment plant (Building O-18).

MAAP is located in a rural area, with agriculture being the primary land use. Installation property isleased for agricultural purposes, down-gradient of OU1. However, groundwater is not used for irrigationon the leased land. There are scattered residences to the north and east of the facility boundary. North ofthe facility, the nearest residences are located north of Rutherford Fork, which probably acts as a shallowgroundwater divide. These residences are down-gradient of OU1 and are approximately 1.5 to 2 milesnorth. At the eastern side of the facility, residences are located along the facility property line andhomeowners are not at risk from contaminated OU1 groundwater because they are cross-gradient andup-gradient from OU1. On the westem/northwestern side of the facility, residential and commercial wellsare more than 3 miles from OU1 and OU2. No explosive compounds were detected in any of the 32offsite private wells sampled, twice each, during 1996/1997 (Final Residential Well Survey Report,October 1997).

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There is no residential or commercial use of land within a 1-mile radius of OU1 and OU2. There are nopublic or private water wells within the 1-mile radius. Within the facility, the Army performs regularmonitoring of potable water production wells to insure that no contamination is present. Three installationsupply wells are located within a 1-mile radius of OU1; supply wells C-100, K-100, and T-99. However,only T-99 is in operation and located side-gradient from OU1 and OU2. Therefore, under current land-useconditions, humans are not exposed to any contaminated OU1 groundwater within a 1-mile radius of OU1and OU2.


OU2 lies within the physical boundaries of OU1. See Sec. 2.4.1 for land and resource use.


See Sec. 2.4.1 for land and resource use. OU3 consists of a much larger area than OU1 and OU2, both ofwhich are located physically in the area described as OU3. However, there are no public or privategroundwater wells located within the OU3 and there are no MAAP supply wells in operation in ordowngradient of the OU3 area (T-99 is also located side-gradient of OU3).

There are four active ammunition lines (B, D, H and O) and three inactive lines (C, E and K) within theOU3 area. There is no commercial or residential use of land within the OU3 area. However, there areseveral residences within one mile north of OU3, beyond the installation boundary and across theRutherford Fork of the Obion River. The river appears to function as a shallow groundwater divide in theregion of OU3. There is agricultural use of land in the OU3 area, but no groundwater is used for irrigationor drinking purposes. Under current land use conditions, humans are not exposed to contaminated OU3groundwater within the OU3 area. However, the down-gradient extent of the explosive’s contaminatedplume is unknown at this time (and additional groundwater monitoring is currently being conducted).

2.4.4 OU3 and OU4 Northern Industrial Area Soil

The facility is located in a rural area, with agriculture being the primary land use. MAAP leases land foragricultural purposes onsite and private land, offsite in the northern boundary area is also used foragriculture. There is no residential or commercial property usage within the MAAP facility, except atLine G (aluminum recycling operation). There are scattered residences to the north and east of the facilityboundary, while the City of Milan lies just to the west. North of the facility, the nearest residences arelocated north of the Rutherford Fork. These residences are approximately 1 to 1.5 miles from the northernfacility boundary. On the east and west sides of the facility, residences are located along the facilityboundary.

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The only groundwater usage in the OU3 and OU4 area is the MAAP supply well S-99, located near AreaS and F-100 (at Line F), which is used for industrial and well drilling purposes. Wells B-100, C-100,K-100, T-100, and X-100 are no longer in operation.

2.5 Site Operations and Chemicals of Concern

A chronology of the National Priorities Listing (NPL) listing activities and interim remedial actionscompleted at each OU is presented in Table 2-1.

Table 2-1. Chronology of NPL Listing and Removal Actions

Event

Date

OU1 OU2 OU3 OU3/4Water Towers

(OU5)Initial discovery of problem orcontamination Jun-78 Jun-78 Jun-78 Jun-78 Jul-82

Pre-NPL responses --- Feb-79 --- --- ---NPL listing Nov-84 Nov-84 Nov-84 Nov-84 Nov-84Removal actions Mar-96 Jun-84 Mar-79 Feb-99 Apr-94/Oct-97Source: ESE.

2.5.1 OU1 – O-Line Groundwater

The O-Line area at MAAP was built as a part of the initial plant construction and has operated since 1942as an ordnance demilitarization facility. From the start, the major function of the line has been to removeexplosives from ordnance by injecting a high - pressure stream of hot water and steam into the steel shellof munitions. Wastewater contaminated with explosives was discharged from the O-Line washoutoperations through a series of baffled concrete sumps where cooling caused significant amounts ofexplosives to precipitate out of the waste stream. Effluent from the sumps was initially discharged to anopen ditch, which ran through the O-Line area. In 1942, eleven individual surface impoundments wereexcavated to receive the O-Line effluent. The ponds reportedly were excavated into native soil and theexcavated material was used to form the pond dikes. In 1978, the US Army Environmental HygieneAgency’s (USAEHA) water well sampling program (USAEHA, 1978) revealed that three of MAAP’swater supply wells were contaminated with explosive constituents. The affected wells were near a numberof production areas, including O-Line.

The chemicals of concern (COCs) in groundwater included the following explosives: 2,4,6-trinitrotoluene(TNT), 2,4-dinitrotoluene (DNT) and 2,6-DNT, RDX, cyclotetramethylene tetranitramine (HMX),nitrobenzene, 1,3,5-trinitrobenzene (TNB), and 1,3-DNB. Carbon disulfide was originally a COC, butwas subsequently determined to be in too low of concentrations to cause adverse health affects.

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As described above, the eleven O-Line ponds received wastewater contaminated with explosives from theO-Line demilitarization facility. The ponds were 3 to 5 ft deep, had a total capacity of approximately 5.5million gallons and covered an area of 280,000 ft2 [US Army Toxic and Hazardous Materials Agency(USATHAMA), 1982a]. The ponds were interconnected with a series of spillways, open ditches, anddistribution boxes allowing several pond configurations to be used in series. Effluent from the last pondflowed through a bank of sawdust-filled tanks before discharge to OU2 Ditch and then Ditch B. As aresult of the USAEHA investigation in 1978, MAAP ceased using the O-Line Ponds. The impoundedeffluent remained in the ponds until 1981.

The chemicals of potential concern were those chemicals believed to be associated with past activities ofthe O-Line area: cadmium, chromium, lead, mercury and nine explosive compounds (1,3-DNB, 2,4-DNT,2,6-DNT, HMX, nitrobenzene, RDX, tetryl, 1,3,5-TNB, and 2,4,6-TNT).


The OU3 area received explosive’s contaminated wastewater discharged from LAP lines into the ditchoutfalls prior to 1981, when the practice was discontinued. The Ditch A (also known as Ditch-7) areareceived wastewater from Line C. Ditch B received wastewater from Lines C, D, K, and O. Ditch Creceived wastewater from Lines B, D, and H. Lines C, E, and K are currently inactive. Explosive’scontaminated wastewater from all LAP lines has been treated at the ECWTPs since 1981. The wastewateris processed by activated carbon adsorption systems and is discharged under MAAP’s NPDES permit.

The results of chemical analysis of groundwater collected during the RI (USAEC, 1991) in 1990 to 1991indicated that explosives compounds were detectable at several locations near the northern facilityboundary. One of the groundwater samples (well MI060) contained a total explosives concentration of9.33 micrograms per liter (µg/L). During the summer of 1993, a sample from MI060 contained a totalexplosive’s concentration of 68.1 µg/L, more than seven times the concentration in MI060 during 1990.Due to that increase, the Army accelerated the investigation of groundwater quality at the northernboundary of MAAP.

The chemicals of potential concern were: the same nine explosive compounds listed in the precedingsection and nitrate, which has a National Primary Drinking Water Standard (NPDWS) of 10,000 µg/L asnitrogen. Inorganics (metals), above background concentrations, were considered during the baseline riskassessment, but were not COCs (did not pose a significant health risk and were below drinking watercriteria) after data were analyzed. The concentrations of metals in groundwater were evaluated because ofthe low limits that must be achieved if the groundwater is extracted, treated, and discharged to surfacewater.

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All wastewater from industrial operations have been treated at the ECWTPs or IWWTPs since 1981. AllResource Conservation and Recovery Act (RCRA) wastes are handled, disposed, and shipped accordingRCRA policies. The following are descriptions of OU3 and OU4 site operations.

Line A: Line A has been in operation since 1941 and activities have included the renovation of 60-mmmortar rounds, loading of fuses, press-loading of 40-mm rounds, and rocket assembly. Explosiveshandled at this site included 2,4,6-TNT, RDX, and tetryl.

Line B: Line B has been in operation since 1941 and activities have included the renovation of highexplosive rocket and artillery rounds; demilitarization of 37-, 40-, and 75-mm rounds; disassembly of40-mm shells and 4.5-inch rockets; production of 4.5-inch rockets; and segregation and handling ofcordite. The primary explosive compound used at this site was RDX.

Line C: Line C operated from 1941 until the 1970s. Past activities included the operation of a melt/pourfacility, renovation of rockets, loading of rockets and mortars and the disassembly of howitzer shells. AnX-ray facility was also here. The primary explosive compounds used at the site included RDX, 2,4,6-TNTand tetryl.

Line D: Line D has been in operation since 1941 and activities have included a melt/pour facility,renovation of howitzer and mortar shells, and loading of howitzer shells. A former photography lab andX-ray facility also were located here. The explosive compounds used included RDX, 2,4,6-TNT, andtetryl.

Line E: Line E operated from 1941 until the 1970s and past operations included assembly of fuzes andbooster leads, and the blending and pelletizing of tetryl. Explosive compounds used here included RDXand tetryl.

Line F: This line operated from 1941 to the 1970s and past activities included the assembly of fuzes,pressing of booster pellets and lead charges, and blending and pelletizing of tetryl. Explosive compoundsused included RDX and tetryl.

Line H: This active line has been used for the assembly of delay charges, loading of fuzes, pressing ofsmall mortar propellants and pressing of black powder. Explosive compounds used include RDX andtetryl.

Line K: This line has been used for both metal parts production and munitions production. Both activitiesare inactive and the line is now used for storage. An X-ray facility also was previously located here.Explosive compounds used here included RDX, 2,4,6-TNT, and tetryl.

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Line O: Line O has been in operation since 1941. See Secs. 2.3.1 and 2.3.2.

Line X: This line has been in operation since 1941. Past and present operations have included the loadingof mortar rounds, rockets and fuzes; demilitarization of 20- and 37-mm munitions; renovation of fuzes;and production of mortar and artillery shells. Explosive compounds used included RDX, 2,4,6-TNT, andtetryl.

Line Z: This line was in operation from 1941 until the late 1970s, and production resumed in 1993.Operations have included the loading of fuzes. Explosives used here include RDX and tetryl.

Closed Sanitary Landfill: This closed landfill, located between Lines H and K north of Route 104,operated from the 1960s until 1974. The landfill was used as a general-purpose disposal area for paper,construction material, and miscellaneous items including RDX-contaminated packing material.

Former Borrow Pit: Located south of Line H and immediately north of Route 104, this former borrow pitwas used to excavate sand for construction purposes. Discarded building materials from construction andrenovation activities were placed here. The pit now contains ponded water.

The primary COCs are the principal explosive compounds found in soil within the OU3 and OU4 area;2,4,6-TNT and RDX. Also, tetryl where ever it was handled.

2.6 Initial Responses and Current Waste Disposal Operations


MAAP personnel ceased using the O-Line ponds in 1978 since the ponds were determined to be one ofthe most likely sources of the groundwater contamination. As a result, the ponds were closed and cappedin 1984. O-Line effluent has been pumped and treated at one of MAAPs ECWTP since 1981 anddischarged according to the facility’s NPDES permit. A further history of the O-Line ponds (OU2 – O-Line Ponds Soil, Sediment, and Surface Water) is provided in the following section.

2.6.2 OU2 – O-Line Ponds Soil, Sediment, and Surface Water

In 1981, the impounded effluent in the ponds was pumped out and treated in the newly constructed pink water treatment facility (PWTF). A PVC liner was placed on top of the pond sediments 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 corner of the ponds were placed on top of the PVC liner, prior to pond closure. MAAP subsequently prepared and

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submitted a closure plan for the pond site to TDEC, which was approved and implemented in 1984. Theclosure plan called for the construction of a multi-layered cover system for the ponds. The ponds werefilled with clean inorganic fill, and two clay layers with a gravel drainage layer in between and thencompacted. Topsoil was placed on top of the upper clay layer and a vegetative cover was established.

However, in May 1984, because the level of explosives contamination in groundwater was increasing, thefacility was proposed for listing on the NPL. Final listing occurred in August 1987. In 1990 and 1991,USATHAMA conducted a RI to identify contaminants at OU2. Potential risks associated with OU2 andpossible methods for reducing risks at the site were investigated during the Focused Feasibility Study(FFS). Based on the FFS report, the Army selected the installation of an impermeable cap extension as thepreferred remedy for the O-Line Ponds area soils operable unit. The results of the risk assessmentindicated that the level of risk posed to human health and the environment by residual contamination insurface soil, surface water, and shallow sediment within OU2 were at acceptable levels. Therefore,Remedial Action Objectives (RAOs) for cleanup of surface water and shallow sediment were notconsidered.

2.6.3 OU3 - Northern Boundary Groundwater

After the increase in explosives concentrations was detected in the northern boundary area (OU3)monitoring wells during the summer of 1993, the Army accelerated the groundwater RI in the OU3 area.To respond as rapidly as possible to potential off-site migration and threat posed by contaminatedgroundwater, the Army elected to address remediation at OU3, while further investigations of other areasof MAAP continues. In 1994, an FFS (USAEC, 1994a) of the northern boundary area was conductedwhich identified remedial technologies that were capable, singly or in combination, of mitigating thegroundwater contamination.

There were two primary areas of concern at OU3 that were identified during the RI: the eastern regionand western region. The eastern area of concern is located at the Milan National Guard Training Area andthe western area is directly north of Area M and the WCOP sewage treatment plant. Groundwatercontamination down-gradient of these areas is still not fully characterized. Also, several monitor wellslying between these two areas had elevated total explosives concentrations; MI146 (near Ditch B and KLine) at 7,790 µg/L, MI046 (near Ditch C) and MI051 (near the OU3 groundwater treatment facility).These three wells are screened in the lower intermediate to deep aquifer zone at approximately 140 to 160ft-bls.

There are currently no waste disposal operations (into the environment) at any of the LAP lines or otherareas in OU3. Spent GAC and other treatment sludge from groundwater or wastewater treatment facilitiesare disposed of in compliance with RCRA requirements (40 CFR 260-270).

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During the 1990 to 1991 RI, all sumps within each load line were investigated and soil samples wereanalyzed for explosives, select metals, and volatile organic compounds. A more detailed study of Line Bwas conducted in 1994. Explosive compounds were detected in soil at levels up to 100,000 microgramsper gram (µg/g). However, the average total concentration of explosive compounds was in the range of 10to 100 µg/g. As expected from the history of the facility, 2,4,6-TNT and RDX accounted forapproximately 95 percent of the total mass of explosives detected in soil. Tetryl was detected only whereit was used; Lines A, E, and Z.

All current waste operations at OU3 and OU4 are conducted according to RCRA requirements with allwastewater going to either the ECWTPs or IWWTPs.

2.7 OUs Not Currently in Remedial Action Phase or Work, NFA ROD, and RemovalActions

MAAP is currently in the RI/FS/RD stages of work on several OUs. The OUs are as follows:• Non-Industrial Area Soils (Ditches) in OU3 and OU4;• OU4, Region 1 Groundwater (X-Line Groundwater Plume);• OU4, Regions 2 and 3 Groundwater (City of Milan Groundwater Plume);• OU5, Southern Study Area; and• OU3, 4, and 5 Groundwater (Onpost Groundwater).

MAAP has also finalized one No Further Action (NFA) ROD. This ROD was prepared for the followingsites at MAAP:

• Sanitary landfill,• Former ABA (Sunny Slope), and• Salvage Yard.

Additionally, MAAP has completed several removal actions. Each of the above sites is briefly describedbelow.

2.7.1 Other OUs

This section addresses defined OUs at MAAP that have not proceeded to the RA phase of work.

2.7.1.1 Non-Industrial Area Soils (Ditches) in OU3 and OU4In the past, wastewater from various production activities in the lines A, F, G, V, X, and Z wasdischarged to open ditches that drained from sumps or surface impoundments into both intermittentand perennial streams. Currently, MAAP treats all process water from the lines that generateexplosives-contaminated wastewater in IWWTPs. There are, however, several ditches

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p/MLAAP/5yrReview/Review.doc 2-19 Environmental Science & Engineering, Inc.

that were possibly affected by past activities and may be potential contaminated source areas in this unit.These are ditches 1, 2, D, E, and Wolf Creek.

A RI was finalized in September 1998. The Draft Final Feasibility Study (FS) was submitted for agencyreview in November 1999. This OU is currently in the Final FS phase of work.

2.7.1.2 OU4, Region 1 Groundwater (X-Line Groundwater Plume)OU4 (Northern Study Area) - This unit encompasses all aspects of contamination due to past dischargesemanating from Line-X. These discharges are migrating north and northwest toward the City of Milan.The primary source of groundwater contamination in this OU is that associated with contaminated soilsleaching to the groundwater.

Although a final ROD has been prepared for this site, it has not yet been signed and made a part of theAdministrative Record.

2.7.1.3 OU4, Regions 2 and 3 Groundwater (City of Milan Groundwater Plume)This OU encompasses all aspects of contamination due to past discharges emanating from X-Line intoDitch E and Wolf Creek. These discharges are migrating north and northwest toward the City of Milan.The primary source of groundwater contamination in this OU is that associated with industrial wastedischarges to Ditch E and subsequent transport and infiltration into the creek beds of Ditch E and WolfCreek.

A Final RI for this site was submitted in May 1999. The Draft FS was submitted in May 1999. This OU iscurrently in the Draft Final FS phase of work.

2.7.1.4 OU5, Southern Study AreaOU5 (Southern Study Area) - This unit consists of all portions of the facility located south of Route 54.Suspected contaminant sources include: (1) Open Burning Ground, (2) Current Ammunition DestructionArea, (3) Former Ammunition Destruction Area, (4) Ammunition Test Area, (5) Closed ABA, (6)Ammunition Storage Areas, and (7) the Plant’s five elevated potable water towers.

A final RI was submitted in February 1999. This OU is currently in the Draft FS phase of work.

2.7.1.5 OU3, 4, and 5 Groundwater (Onpost Groundwater)This unit emcompasses all onsite groundwater at MAAP that is not addressed as part of OU1, OU3, andOU4 Regions 1, 2, or 3. This OU is currently in the RI phase of work.

MAAP, 5 Year Review


2.7.2 NFA ROD

One NFA ROD has been prepared at MAAP. This ROD, finalized in February 1998, addresses thefollowing areas at MAAP:

• Sanitary landfill,• Former ABA (Sunny Slope), and• Salvage Yard.

The above three areas were determined to pose no unacceptable threat to human health and theenvironment. Therefore, no further action was considered warranted at these sites.

2.7.3 Removal Actions

As part of the IRP Program at MAAP, several removal actions have been completed.

2.7.3.1 Off-Post Removal ActionThe City of Milan, Tennessee, supplies drinking water to approximately 4,000 customers. Environmentalinvestigations conducted by the Army have detected concentrations of the explosive compound RDX inthree city water supply wells. Based on the levels of RDX detected, the Army funded a project for thelocation and construction of a new well field for the City of Milan. Construction of the new well field andwater treatment plant have been completed. Milan residents began receiving potable water from the newsystem in March 1999.

2.7.3.2 Original Capping of O-Line Ponds in 1984The O-Line ponds were capped in 1984.

2.7.3.3 Water Tower Lead ContaminationA removal action for lead contamination associated with past sandblasting activities at MAAP’s fivewater towers was initiated 1994. The soils were excavated and sent off-site for treatment and disposal. In1997, another removal action was completed (grading of site) to prevent erosion and provide properdrainage to prevent the ponding of water in the area where contaminated soils were removed.Additionally, soil samples were collected around the perimeter of the water tower bases to confirm thatsoil in the area did not exceed the residential exposure concentration for lead.

2.7.3.4 On-Post Removal Action Due to Lead ContaminationA removal action was initiated to shut down the Area I water system due to lead contamination associatedwith sandblasting activities of the water tower in Area I. The action extended the plant’s main waterlineinto Area I so that potable water could be pumped to the Area. This action was completed in 1996.

MAAP, 5 Year Review


3.0 Development and Implementation of theRemedy and Operation and Maintenance

MAAP has been the focus of numerous environmental investigations since 1978, when the USATHAMA(1978) conducted a records search and interviewed facility employees. A chronology of events from theinitiation of the installation assessment through the selected remedies and construction at each OU ispresented in Table 3-1.

3.1 Remedy Selection


In May 1984, because of the explosive contamination in the groundwater, MAAP was proposed for listingon the NPL. The NPL is EPA’s list of hazardous waste sites that present the greatest potential threat tohuman health and the environment if remediation does not occur. Final listing on the NPL took place inAugust 1987. In 1990 to1992 USATHAMA conducted a RI at MAAP (USATHAMA 1991). The RIconfirmed that the level of explosives in groundwater were more then 10,000 times higher than the EPA’shealth advisory levels; as high as 30,000 µg/L in some monitor wells. The explosives groundwater plumewas estimated to be 2,500 ft in length, 1,500 ft in width, and extending approximately to 170 ft-bls. Theprimary contaminants were HMX, RDX, 2,4,6-TNT, 1,3,5-TNB, 2,4-DNT, 2,6-DNT, 1,3-DNB, andnitrobenzene. In order to respond as rapidly as possible to the potential threat posed by groundwatercontamination, the Army separated the O–Line groundwater from the remainder of the facility to addressremediation of that area – OU1.

In 1991 to 1992, a FFS of the O-Line Ponds area groundwater was conducted by USATHAMA toidentify remedial technologies that were capable, singly or in combination, of mitigating the risks posedby the contaminated groundwater. Treatability studies were performed in 1992 to further evaluate theeffectiveness, implementability, and cost of the most promising technologies.

Eight alternatives were evaluated in accordance to Section 300.430 (e) of the NCP. The acceptability orperformance of each alternative against the criteria was evaluated so the relative strengths and weaknessescould be identified. These criteria were:

1. Overall Protection of Human Health and Environment, 2. Compliance with ARARs,3. Long-term Effectiveness and Permanence,4. Reduction of Toxicity, Mobility, and Volume,5. Short-term Effectiveness,6. Implementability,7. Cost,

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Table 3-1. Chronology of Remedy Development and Implementation

Event

Date

OU1 OU2 OU3 OU3/4Water Tower

(OU5)

RI/FS complete Mar-93 Jun-92 May-95 Apr-95 ---ROD signature Sep-92 Sep-93 Sep-94 Sep-95 ---ROD Amendments or ESDs Jun-98 --- Feb-96 --- ---Enforcement document (CD, AOC, UAO) --- --- --- --- ---Remedial design complete Nov-93 Jul-94 Mar-96 May-97 Feb-94Construction start date Mar-96 Nov-94 Feb-97 Apr-98 Mar-94Construction completion date Mar-96 May-96 Jan-99 Jan-99 Oct-97Close Out Report Dec-97Superfund State Contract or Federal Facility Oct-89 Oct-89 Oct-89 Oct-89 Oct-89Agreement signed

Note: ESD = Explanation of Significant Differences. CD = Consent Decree. --- = Not applicable.

Source: ESE.

MAAP, 5 Year Review


8. State Acceptance, and9. Community Acceptance.

Based on the consideration of the requirements of CERCLA, the NCP, the detailed analysis ofalternatives, and public comments, the Army (with the concurrence of EPA and TDEC) determined thatthe extraction of groundwater with treatment by precipitation, ultraviolet (UV)-oxidation, and granularactivated carbon (GAC) and re-injection was the most appropriate interim remedy for OU1 groundwater.The interim action ROD was approved on September 30, 1992.

The selected remedy originally was to consist of the following components:1. Extraction of explosives contaminated groundwater via six large-diameter extraction wells, which

would pump the water to the treatment site. The total extraction rate was estimated at 500 gallonsper minute (GPM), based on the extraction rate needed to reverse the groundwater gradient.

2. Treatment of the recovered groundwater (from 170 ft-bls to the water table) by series ofelectrochemical precipitation, UV-oxidation and GAC. Groundwater is first pretreated byelectrochemical precipitation to reduce the level of inorganics to levels acceptable for re-injection. UV-oxidation is then used to remove the bulk of the organic compounds from thewater, and GAC is then used as a polishing step to reduce the level of explosive compounds tobelow discharge levels.

3. Re-injection of the treated water into the aquifer up-gradient of the capped ponds. 4. Performance monitoring of influent groundwater and effluent prior to re-injection. 5. Institutional controls.6. A performance evaluation at the end of 1-year operation and preparation of the final remedy ROD

for OU1.

3.1.2 OU2 – O-Line Ponds Soil

Based on consideration of CERCLA requirements, the detailed analysis of six alternatives and publiccomments, the Army, with concurrence of EPA and TDEC, determined that an extension of the existingcap was the most appropriate remedy for OU2 at the O-Line Ponds area. This evaluation was performedin accordance with Sec. 300.430(e) of the NCP. The Final ROD was signed in September 1993. Theselected remedy was to consist of the following:

1. A cap extension using geo-synthetic materials and soil cover.2. Institutional controls.3. Post-closure requirements, such as quarterly inspections of the cap.


The Army elected to perform groundwater cleanup at OU3 under an Interim Action ROD, signedin September 1994, which allows for the design, construction, and operation of a treatment

MAAP, 5 Year Review


system that addresses only part of the OU3 groundwater contamination. The cleanup objectives forgroundwater at the northern boundary area are to control the migration of contaminated groundwater fromMAAP to other areas and to reduce the levels of explosives compounds in the OU3 area. Five remedialalternatives were evaluated according to the nine criteria of Section 300.430 (e) of the NCP. The overallstrategy consists of extracting contaminated groundwater and treating it to reduce the levels of explosivecompounds to concentrations that are safe for discharge to the Rutherford Fork of the Obion River. Inpursuit of the overall goal of reducing the levels of contaminants to acceptable health-based levels, GAC,a proven technology, was selected to remove explosive compounds from extracted OU3 groundwater.This remedy was selected because of its ability to adequately and economically remove explosivecontaminants to meet State of Tennessee effluent discharge levels.


Based on the results of the overall MAAP RI, and the representative Line B investigation, the type anddistribution of contaminants throughout the OU3 and OU4 area was generalized as follow:

1. The principal explosives compounds found in soil with OU3 and OU4 are 2,4,6-TNT and RDX.With the exception of those areas where only tetryl was handled, other explosive compoundsoccur at a concentration equal to or less than 5 percent of the principal explosives compoundsconcentrations.

2. In general, surface soil contains the highest concentration of explosives compounds as comparedto the subsurface collected at the same location. The concentration of explosive compoundsdecreases by approximately one order of magnitude per 5 ft of depth.

3. Approximately 0.1 percent of the total area within a load line is contaminated.

A FFS (USAEC,1995a) was conducted to determine soil remediation goals. The human health-basedremediation goals for explosives compounds in soil are summarized in Table 3-2. The soil remediationrisk-based goals selected for groundwater protection at the OU3 and OU4 area of MAAP are 10 :g/g forRDX, 25 :g/g for 2,4,6-TNT and 500 :g/g for tetryl. The overall remediation goal (Table 3-3) based onsoil contact was 55 :g/g for RDX, 130 :g/g for 2,4,6-TNT and 2,600 :g/g for tetryl. However, all soilscontaminated with explosive contamination above the groundwater protection-based levels (10 :g/g forRDX, 25 :g/g for 2,4,6-TNT, and 500 :g/g for tetryl) are to be removed to a maximum depth of 10 ft andtreated, unless engineered capping is necessary.

Remedial alternatives for OU3 and OU4 soil were developed to satisfy the following RAOs: 1. Protect human health and the environment.2. Attain risk-based soil remediation goals to protect workers and groundwater quality in the OU3

and OU4 area.


Table 3-2. Summary of Soil Risk-Based Remediation Goalsa

ChemicalSoil Contact Remediation Goals

(ug/g)

Soil RemediationGoals for Groundwater

Exposures(ug/g)

IndustrialWorker

ExcavationWorker

Resident Resident

RDX 220 3,500 55 10Tetryl 9,400 12,000 2,600 5002,4,6-TNT 4,700 600 130 25

aThe most conservative remediation goals for each receptor are presented in this table.

Source: MLAAP ESD Document (#12), 1996.


Table 3-3. Soil Risk-Based Remediation Goals for Residentsa

ChemicalResidential Soil Contact Remediation Goalb

(ug/g)Carcinogenic Noncarcinogenic Overall Remediation

Goalc

RDX 90 (I) 1,300 (I) 55140 (D) 2,000 (D)

Tetryl - - (I) 4,200 (I) 2,600- - (D) 6,600 (D)

2,4,6-TNT 320 (I) 200 (I) 130620 (D) 400 (D)

a Remediation goals are in concentrations of mg/kg, and were rounded to twosignificant figures. The remediaiton goal for carcinogens was based on a target riskof 1x10-5, while the remediation goal for noncarcinogens was based on a hazardquotient of 1.0.

b Remediation goals for soil contact were calculated for both ingestion and dermalpathways:

I = remediation goal calculated for ingestion of chemicals in soil;D = remediation goal calculated for dermal absorption of chemicals in soil.

c The overall remediation goals are based on a resident simultaneously beingexposed to chemicals via the soil ingestion and dermal pathways.

Source: MLAAP ESD Document (#12), 1996.

MAAP, 5 Year Review


3. Use permanent solutions and treatment methods to the maximum extent possible. 4. Achieve a remedy in a cost-effective manner.

Four alternatives were compared, based on the nine criteria of Sec. 300.430(e) of the NCP, and a remedywas selected that included excavation, onsite treatment, and disposal of soils containing explosivescompounds at concentrations higher than the risk-based soil remediation goals. A method of biologicalsoil treatment known as windrow composting would be used to reduce the concentrations of explosives inthe soil. This method consists of mixing the soil with sources of organic carbon and bulking agents suchas chips, straw, and manure (amendment mixture). The mixture would be formed into long piles calledwindrows. Microoganisms would biotransform and biodegrade the explosives compounds within themixture. The concentrations of the principal explosives compounds would be reduced by approximately90 percent.

The ROD was finalized in September 1995. Under the ROD, the explosives contaminated soil of OU3and OU4 are to be removed and treated to reduce explosive concentrations in the soil to below thecalculated risk-based levels. The cleanup levels were established to prevent potential contamination ofgroundwater and to reduce the risk to hypothetical future residents due to groundwater ingestion. Toachieve these goals, the ROD requires the excavation of the explosives contaminated soil, biotreatmentvia windrow composting to remove the contaminants, and disposal of the treated soil in an engineeredlandfill. The ROD also allows for engineered caps to be constructed over any contaminated soils that arenot suitable for excavation due to proximity to buildings or other structures. The engineered caps will bedesigned and maintained to prevent the infiltration of water through the contaminated soil.

Based on results from bioremediation testing, the ROD concluded that the treated soils would be suitablefor disposal when the maximum concentrations of RDX and 2,4,6-TNT are 20 :g/g and tetryl is 500:g/g. Additionally, the treated soil must comply with the Toxicity Characteristic Leaching Procedure(TCLP) and Paint Filter Liquid Test requirements.

3.2 Remedy Implementation

3.2.1 OU1- O-Line Groundwater

The treatment facility design was completed in November 1993 and the construction contract wasawarded in December 1993. Construction was completed and start-up occurred on March 1996. Afteroperating the plant for about a year, an Explanation of Significant Differences (ESD) was submitted bythe Army and approved by the EPA and TDEC in January 1998. The ESD allows the Army a moreflexible approach to operating the treatment system using all or part of the approved methods includingprecipitation, UV-oxidation, and GAC.

MAAP, 5 Year Review



The cap extension design was completed in August 1994 and the construction contract awarded inSeptember 1994. Construction was completed in May 1996. The Post-Closure Care Plan [an addendum tothe Chemical Data Acquisition Plan (CDAP), 1997], which contained changes to the approved plan andspecifications and the as built drawing, was approved by EPA as the Final Remedial Action Post ClosureReport in July 1997. A quarterly inspection of the site is currently in place.


The design for the OU3 remedy was completed in August 1996, the project was awarded for constructionin September 1996, and construction was completed in January 1999. The operation’s startup at thefacility was on March 1, 1999. The selected remedy uses pH adjustment, filtration, GAC to treat theextracted groundwater and a gravity-feed discharge to the Rutherford Fork.


The remedial design for the selected remedy was completed in May 1997. A Composting Treatment Planwas submitted to the EPA and TDEC by Plexus Scientific Corporation (Plexus) under contract to USAECin October 1998. Plexus designed the full-scale composting facility at MAAP and prior to the startup offull-scale operations, would conduct treatability testing. Piles of explosives-contaminated soil aboutone-tenth the size of full-scale piles would be composted and closely monitored to allow optimization ofoperating procedures.

The composting facility was completed in January 1999 and the operation startup was initiated after thefinal inspection of the facility on March 17, 1999. The treatability testing, conducted by Plexus, continueduntil September 1999. The facility operations were then shut down temporarily until full-scale startupwould begin, under management of AO personnel. AO began operating the facility in October 1999.

3.3 Operation and Maintenance Requirements


The following is a summation of the selected remedy as installed and planned O&M activities asoriginally planned. The primary goals of the selected remedy are that the remediation facility will 1)capture and treat the explosives-contaminated groundwater at OU1 to meet re-injection limits, and 2) thatthe remediation system is properly operating and meeting the guidelines specified by the EPA. In order toreach these goals, the ROD required that an O&M Manual be prepared for the system. The objectives ofthe OU1 O&M Manual were to:

MAAP, 5 Year Review


1. Inform operators of compliance and performance goals;2. Provide the operators with guidance on normal operation; 3. Ensure consistency in operating practices;4. Provide a guide for troubleshooting problems that is based on past operating history; 5. Provide a tool to train operators on system startup, shutdown, and emergency situations; and6. Provide a guide for conducting major maintenance activities.

Compliance monitoring includes groundwater monitoring and analysis of the effluent from thegroundwater treatment system. Chemical analytical support is provided at MAAP by AO LLCEnvironmental Laboratory, and by the OU1 facility laboratory. Field operating procedures and laboratorymethods are specified in the CDAP. The operators maintain records of operating data and testing resultsfrom the facility laboratory on daily log sheets. The daily log sheets are to be filed in the OU1 controlroom for 3 years.


The primary goals of the selected remedy for OU2 were to prevent storm-water infiltration through thecontaminated soil around the existing cap, thereby eliminating continued contaminant loading togroundwater and to minimize the formation of leachate. Post-closure requirements included maintainingthe integrity of the cap through quarterly inspections and repair, monitoring the groundwater for thirtyyears (semiannual the first year and annually thereafter), and maintaining surface water control (through abiannual preventative maintenance schedule). The details of these O&M procedures are found in the FinalPost-Closure Care Plan, which is an addendum to the CDAP (1997).

Maintaining and operating a leachate collection system is not a requirement since no leachate collectionsystem exists. Monitoring of gas emissions is not required because the wastes at OU2 are not gasgenerators.


The following is a summation of the selected remedy as installed and planned O&M activities asoriginally planned. The primary goals of the selected remedy are that the OU3 remediation facility willcapture and treat the explosives contaminated groundwater to meet discharge requirements and that theremediation system will properly operate and meet the guidelines specified by EPA. In order to meetthese goals, the ROD required that an O&M manual be prepared for the system. The objectives of theOU3 O&M manual are the same as for the OU1 system (see Sec. 3.3.1).

MAAP, 5 Year Review


Compliance monitoring includes groundwater monitoring and analysis of the effluent from thegroundwater treatment system prior to discharge to the Rutherford Fork. Chemical analytical support isprovided by the AO Environmental Laboratory and by the OU3 facility laboratory. Field operatingprocedures and laboratory methods are specified in the CDAP and testing results are kept on daily/weeklylog sheets that are to be kept on file in the OU3 control room for 3 years.


The O&M requirements to assure that the selected remedy operates as directed by the ROD, include thefollowing:

1. Testing and excavation of explosives compounds contaminated soil from OU3 and OU4 sites.Clean fill into excavation.

2. Delivery of contaminated soil to compost facility.3. Delivery of amendments (cow manure, com silage, sawdust and woodchips) from local sources.4. Storage for up to 30 days in covered storage building (soil and each amendment are separated)

and screening of rocks and debris from contaminated soil.5. Soil and amendments are combined and piles formed in the climate-controlled compost building.6. Piles are composted for approximately 30 days (and turned and monitored for temperature,

oxygen, and moisture).7. Compost is moved to the storage area for a 30-day curing phase while it cools and matures.8. Following analytical confirmation for explosives concentrations, TCLP and Paint Filter Liquid

Test, the compost is disposed of in an onsite landfill.

3.4 Operational and Maintenance Activities


The ROD originally specified six extraction and three re-injection polyvinyl (PVC) wells to attain thegoal of extracting 500 GPM and re-injecting the treated water into the aquifer. However, the layout of thewells as designed by ICF Kaiser included two (Wells A and B) extraction wells and six injection wells(Well A through F). All the wells are stainless steel: the extraction wells are each installed to 90 ft-blswith 45 ft of screen and the injection wells are installed to 190 ft-bls with 145 ft of screen. Subsequently,two additional extraction wells were installed based on HSI Geo Trans recommendation to provide thesystem with operational flexibility. However, one of those wells did not perform effectively and wasabandoned.

MAAP, 5 Year Review


An overview of O&M activities at OU1 are described in App. A of the Performance Evaluation of OU1Groundwater Treatment Plant Report (ICF, 1999). The electrochemical and UV-oxidation units are notnecessary to achieve discharge limits and are not in operation at this time.


The final cover for the ponds is composed of two separate cover systems: the original soil cover and the1996 cap extension. The majority of the cap consists of a compacted clay liner system constructed duringthe initial closure of the ponds. The cap extension consists of a 2-ft-thick composite layer of compactedsoil and geo-synthetic materials. Both portions of the cap contain a drainage layer, a vegetative supportlayer and a low permeability layer. The final layer is graded to provide slopes, which aid in directinginfiltration and surface-runoff water toward the perimeter of the site where it is channeled into existingand/or improved natural drainage features.

The as-built changes from the original contract design documents include: 1. The clearing and grubbing on the west side of the site was reduced by moving the security fence

closer to the cap extension. 2. The perimeter erosion control silt fence was eliminated and replaced with a silt fence placed

perpendicular to the existing wet weather ditches. 3. The location and elevation of the tie-in to the original cap gravel drainage layer was adjusted in

various locations to match field conditions. 4. As a result of a contractor value engineering proposal, the lower geo-textile in the geo-synthetic

liner system was eliminated from the project. 5. Seams in the upper geo-textile were changed from sewn to heat tacked and the seam overlap was

increased to 12 inches. 6. The perimeter security fence was relocated in several areas to avoid crossing drainage ditches and

resulted in elimination of three security grills.

Operation of this cover requires no external support. Preventative maintenance includes quarterly visualinspection of the complete landfill cap and drainage system at the site. A biannual preventativemaintenance schedule is used to identify and correct problems with the surface water control systemelements; however, inspections are periodically held after major rainfall events or damaging storms.


The OU3 extraction system included six stainless steel (eight-inch diameter) groundwater wells, eachwith submersible pumps with a 200 to 250 GPM capacity. The well completion diagrams withconstruction details are presented in App. A. All piping from the extraction wells to the OU3 treatmentfacility (Building K121) is below grade (underground). The wells each have fenced-in and secure pumphouses, which are inspected daily for any malfunctions to the well and/or pump.

MAAP, 5 Year Review


The extracted water is sand filtered (and metals are settled out), pre-treated with sodium hydroxide toraise the pH, treated with GAC in one of the three GAC beds and gravity discharged to the RutherfordFork, approximately 1 mile north of Building K121. The monitoring frequency and discharge analyticalrequirements are shown in Table 3-4.

The OU3 treatment plant can be operated from the OU3 or OU1 control room via a computer-operatedprogram, which provides computer monitor graphics of the extraction and treatment system with pumpingand flow rates. There are also alarms for out-of-range pH and water levels.


During the treatability testing at the OU3 and OU4 compost facility, three test windrows (300 ft each) ofcomposted explosives-contaminated soil were evaluated to determine the optimal amendment mixture andamount of compost turning during the 30-day composting. A fifty-fifty mixture of contaminated soil andamendment is typically prepared.

In the first trial, the following amendment compositions were used:1. Windrow 1: 40% sawdust, 30% cow manure, 30% corn silage.

2. Windrow 2: 15% woodchips, 30% sawdust, 28% cow manure, 27% corn silage.3. Windrow 3: 30% woodchips, 20% sawdust, 25% cow manure, 25% corn silage.

In trial 1, all windrows were turned each day during composting.

In the second trial, all windrows were constructed with the recipe that performed best during the first trial.However, windrow 1 was turned every day; windrow 2, every 3 days; and windrow 3 followed a variedturning schedule. Windrows were watered to maintain the microorganisms and floor drains collected thewater in a sump for reuse.

After the 30-day composting and 30-day storage, the soil is tested and if remedy explosive concentrationsare met, along with TCLP and filter testing, the soil is landfilled onsite at the Subtitle D landfill in theSouthern Area at MAAP.

3.5 Progress Since the Last Review

This section is not applicable, as this is the first review for the site.


Table 3-4. Effluent Discharge Limits, OU3 Northern Boundary GroundwaterTreatment Plant Discharge into the Rutherford Fork of the Obion River;Discharge Flow Rate 1.73 MGD

Analyte

Effluent Limit1

Monthly AverageConcentration

(ug/L)

SampleType

MonitoringFrequency

Cadmium, Total 1.19 Composite 1/WeekChromium, Total 395.0 Composite 1/WeekCopper, Total 9.65 Composite 1/WeekCyanide, Total 3.0 Composite 1/WeekLead, Total 1.53 Composite 1/WeekMercury, Total 0.01352 Composite 1/WeekNickel, Total 329.65 Composite 1/WeekSilver, Total 0.333 Composite 1/WeekZinc, Total 302.75 Composite 1/WeekTotal Nitrobodies4 100 Composite 1/WeekpH5 Maintained between

6.0 and 9.0Standard Units

Composite 5/Week

48-Hour LC506 Survival in 100%Effluent

Composite 1/Quarter

1 Effluent samples will be collected at the end of the reaeration tank. Samples will be collected at theindicated frequency.

2 The State of Tennessee Required Detection Limit (RDL) of 0.2 ug/L will be used.3 The State of Tennessee Required Detection Limit (RDL) of 1.0 ug/L will be used.4 Total nitrobodies consists of the sum of 2,4,6-trinitrotoluene; 1,3,5-trinitrobenzene; 2,4-dinitrotoluene;

2,6-dinitrotoluene; RDX; HMX; and all other explosive compounds that are known to be present andfor which toxicity data are available.

5 pH analysis shall be performed immediately after sample collection.6 This test shall be performed using the standard methodology and sampling procedures as found in

Part III of the Milan Army Ammunition Plant NPDES permit.

Source: MAAP ESD Document (#12), 1996.

MAAP, 5 Year Review

p/MLAAP/5yReview/Review.doc 4-1 Environmental Science & Engineering, Inc.

4.0 Five -Year Review Findings

4.1 Five -Year Review Process

The 5-year review of OU1 was conducted by ESE personnel during the week of September 20, 1999, atOU1, OU2, OU3, and OU3 and OU4. The primary objectives of the review were to determine if theimplemented remedy and remedial action objectives continued to be protective of human health and theenvironment. Activities during this process included document review, personnel interviews and OU sitevisits.

Document review consisted of the review of all documents, reports, and files relevant to each OUincluding the initial environmental investigations, RI/FS, selection of the operating remedy, decisiondocuments, O&M documents, monitoring reports, and other pertinent documents. A list of all documentsreviewed is presented in App. B. The Five-Year Review Site Visit Checklist form for each OU is found inApp. C.

4.2 Interviews


The OU1 treatment plant supervisor and an operator were interviewed onsite during September 22, 1999to ascertain the performance of the implemented remedy at OU1. Subsequent telephone conversationswere also conducted to gather additional information on OU1 performance. The influent concentration atthe plant averaged approximately 4 to 5 milligrams per liter (mg/L) total explosives during September1999 and was lower than originally projected (Knott, personal interview). The flow-weighted averageduring performance evaluation testing in October 1997 was 7.6 mg/L total explosives (ICF Kaiser, 1999).

Since the issuing if the ESD, various combinations of the UV-oxidation and GCA treatment were tested.The GAC, alone, was able to remove the explosives necessary for re-injection. Also, it was discoveredthat the pretreatment electrochemical unit was not needed to precipitate the inorganics out of the influentsince natural settlement and sand filtration was adequate. The electrochemical unit and UV-oxidationreactors were taken offline in November 1998.

The effluent continues to be below the detection limits for total explosives. Typically, three extractionwells (renamed EXT-1, EXT-2, and EXT-3) extract approximately 580 GPM and four injection wells (A,B, D, and E) can inject up to about 600 GPM (125 GPM per well). The extracted water is stored in thefeed tank, which has a nominal capacity of 25,000 gallons or a residence time of about 40 minutes.

MAAP, 5 Year Review



The OU2 site inspector and supervisor were interviewed on September 22 and 23, 1999 to ascertain theperformance of the implemented remedy. The extended cap had good integrity and, other than someoccasional erosion problems, the remedy appears to be effective. Some erosion problems were noted onMay 19, 1999; erosion on the north end of the cap and southeast and northern end of the side slopes. Aninspection checklist from September 1, 1999, showed that the erosion problems were corrected. Examplesof the quarterly checklist for OU2 are shown in App. D. The main items include inspection of the finalcover, side slopes, groundwater monitoring wells, ditches and channels and service road.

Restorative maintenance includes backfilling, grading, reseeding, and dressing of slopes and surfaces toprevent breaching of the cover system and to prevent depressions from becoming ponded areas.Maintenance also includes normal mowing operations to prevent the growth of trees and/or shrubs thatcause pathways for infiltration through root penetration of the cover materials.


The OU3 treatment plant supervisor and an operator were interviewed on September 22, 1999 onsite toinspect the performance of the implemented remedy at OU3. Subsequent telephone conversations werealso conducted to gather additional information pertaining to the facilities operation. At the time of theinterview, the facility was in its seventh month of operation. The GAC treatment of the explosivescontaminated groundwater was successful in reducing the influent explosive concentration in OU3groundwater from its weekly average in September 1999 of 2 to 4 mg/L to a discharged explosivesconcentration of below detection.

The six extraction wells were pumping 1,030 GPM (an average of approximately 172GPM per well) intothe plant during time of the visit. The holding tank at the facility has a 57,000-gallon capacity. Thedischarge rate to the river was 900 GPM at the time of the visit. The discharge water had a pH of 6.54 anda dissolved oxygen level of 10.4 mg/L. All operations were running according to the O&M manual. Theonly minor problem that recently occurred was some farm equipment cut a fiber-optic cable that providedinformation from one of extraction wells, and although the computer program and screen provided noinformation on the well, it was operating properly. A contractor was onsite, during the interview, toprovide a cost estimate to repair the cable.


The AO environmental coordinator for the OU3 and OU4 was interviewed at the compost facility, located on the north side of Route 54 just south of Line A, on September 23, 1999. The

MAAP, 5 Year Review


treatability testing had been completed at the compost facility and the operation was temporarilyshutdown. The AO coordinator explained that the composting was successful and the remediation goalshad been achieved for the landfilling of the treated soil. No major problems or deficiencies wereencountered. However, the Composting Treatment Report had not been completed at that time. The Armywas also investigating possible reuse of the treated soil instead of landfilling.

4.3 Site Visit


ESE visited the OU1 site during September 22 and 23, 1999 to assess the operational status of theimplemented remedy. The plant supervisor and operator were interviewed by an ESE senior projectmanager. Photographs (see App. E) were taken of various site operations, equipment, and site conditions.Onsite documents were inspected including: O&M manual, Health and Safety Plan, Contingency Plan,Emergency Response Plan, O&M logs, and other daily logs.


ESE personnel visited the OU2 site on September 22 and 23, 1999 to assess the operational status of theremedy. The OU2 inspection supervisor was interviewed and photographs (in App. E) were taken of thesite. O&M manuals, maintenance logs, inspection logs and other documents were viewed at the OU1treatment facility, where they are stored.


ESE personnel visited the OU3 site on September 23, 1999 to assess the operational status of the remedy.The OU3 plant supervisor and a treatment plant operator were interviewed and ESE took photographs(App. E) of the treatment facility at Building K121, extraction wells and the discharge outfall at theRutherford Fork. O&M manuals, maintenance and inspection logs, and other documents were viewed atthe facility control room.


ESE personnel visited the OU3 and OU4 Compost Facility site on September 23, 1999 to assess theoperational status of the remedy. Although the facility was not operating at that time, the AO coordinatorexplained that the remedy was successful and no major problems were encountered during the treatabilitytesting during the 90-day test. ESE took photographs (App. E) of the facility during the site visit. O&Mmanuals, maintenance and inspection logs, and other documents are kept filed and locked in the siteoperations office.

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4.4 Remedial Action Objectives Review

The Department of Defense plans to utilize MAAP for military purposes for the foreseeable future.Consequently, certain land and water use scenarios that were considered in the remedial planning processare not reasonable future uses.

The Department of Defense (DOD) will not use contaminated groundwater under the affected OUs withinthe boundaries of MAAP as a drinking water supply. The DOD utilizes groundwater at MAAP that isunaffected (upgradient or sidegradient) by explosives contamination and analyzes the drinking watersupply weekly for the presence of explosives. The nearest point(s) of exposure to explosives-contaminated groundwater as a drinking water supply is at the MAAP facility boundary. The westernboundary of MAAP abuts the City of Milan and this area is supplied water by the community watersystem. Groundwater at the western boundary is unlikely to be used as a potable supply by residential,industrial, or commercial receptors. The low probability of exposure to groundwater at the westernboundary supports selection of health risks at the upper end of the acceptable risk range, i.e., 10-4 lifetimecarcinogenic risk, and a cumulative hazard index of 1. The northern boundary of MAAP, on the otherhand, includes some residential land use and is not supplied by the community water system; and a targetrisk of 10-5 for individual carcinogenic contaminants is appropriate at the northern boundary.

In addition, land use scenarios that included residential exposure to the site are not practical.

4.4.1 OU1 - O Line Groundwater

O-Line groundwater discharges to MAAP’s northern boundary. The RAO should be to achieve risk-basedcleanup levels (cumulative HI of 1, individual carcinogens at 10-5 risk levels, cumulative risk less than 10-4 in the City of Milan) at the MAAP boundary.

4.4.2 OU2 - O Line Ponds Soil

The remedial action objectives for this OU were to eliminate:• Direct contact with contaminated surface soils, and• Infiltration of rainwater through contaminated soils to groundwater.

The objective was achieved by installation of a cap.

Based on an evaluation of soils data from other OUs (see Sec. 6.4.3), it is likely that substantial oil contamination under the O-Line Ponds extends through the full vadose zone thickness to thewater table. Insofar as the water table fluctuates on seasonal and annual cycles, fluctuatinggroundwater levels may leach significant quantities of COCs from soils near the water table for a period of many years, even though the cap is effective in eliminating infiltration of rainwater. As a result, the groundwater extraction and treatment systems downgradient of OU2 may need to be

MAAP, 5 Year Review


operated and maintained for an excessive duration unless soils near the water table are treated to removethe groundwater COCs. The downgradient groundwater remediation systems are intended to intercept thisleachate, but it may be more efficient to eliminate the source.


RAOs for OU3 should be modified as recommended for OU1.


The RAOs for this OU (ROD, Section 7.0) included remediation of surface soils to protect workers bydirect contact pathways and groundwater quality in the northern industrial areas of MAAP. Ultimately,the controlling remedial objectives for soils were based on their potential to leach to groundwater. Thisobjective should be modified such that soils are remediated sufficiently to protect onsite workers andgroundwater quality at the MAAP boundary. If this objective were to be modified, an Explanation ofSignificant Difference must be executed with review by all parties to the ROD and public comment.

4.5 Data Review


All relevant and appropriate documents associated with the OU1 site investigations, remedy development,and remedy operation were reviewed during the development of this report. Table 4–1 lists the designinfluent concentration and effluent standards.

Although influent concentration levels are less than predicted and are decreasing, the treatment facility isreducing the influent explosive concentrations to below detection for re-injection. The addition of treatedwater to the explosives groundwater plume may have some dilution effect on the aquifer. RDXconcentrations are still as high as 24,317 :g/L (MW-14S-97) and 19,206 :g/L (MI058) in OU1groundwater. Between September 22 and October 8, 1997, influent groundwater samples were analyzedby the onsite laboratory. The influent from the western extraction well (Well A) averaged 6.5 mg/L andthe eastern extraction well (Well B) averaged 10.8 mg/L, total explosives. The flow - weighted averageinto the plant was 7.6 mg/L, which reflects the higher flow from Well A, typically 55 percent of the totalplant feed. Groundwater explosives relative compositions from each well are very similar (within 2percent of each other) with the major constituents being RDX (50 to 52% by weight) and 2,4,6-TNT(38% by weight). This compares to the design basis influent of RDX (32% by weight) and 2,4,6-TNT(50% by weight). The difference in composition between the actual influent and design basis influent isnot expected to impact operating efficiencies of the treatment plant equipment. The lowered measuredlevel reduces the required explosives removal efficiencies while still meeting effluent standards. Thus,operating costs for treatment are expected to be lower.

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Table 4-1. Design Influent Concentration and Effluent Standards

ParameterDesign Influent

Concentration (:g/L)Effluent

Standard(:g/L)Explosive Compounds1,3-Dinitrobenzene 71.5 52,4-Dinitrotoluene 117 0.52,6-Dinitrotoluene 7.44 0.5HMX 1,160 2,000Nitrobenzene 240 18RDX 9,250 101,3,5-Trinitrobenzene 1,440 202,4,6-Trinitrotoluene 12,300 10Inorganic AnalytesAluminum < 141 to 3,020 NTGAntimony < 38.0 6Arsenic < 2.54 to 50 50Barium 26.1 to 193 1,000Beryllium 5.00 4Cadmium < 4.01 to 5 56Calcium 14,600 to 15,600 NTGChromium < 6.02 to 7.80 50Cobalt < 25.0 NTGCopper < 8.09 to 10.9 1,300Cyanide 4.04 to 31.2 200Iron 200 300Lead < 1.3 to 2.19 15Magnesium 5,180 NTGManganese 13.7 to 20 50Mercury < 0.2 to 0.36 2Nickel < 34.3 to 35.7 100Nitrate + Nitrite as Nitrogen 21,000 10,000*Potassium 5,020 NTGSelenium < 3.02 to 3.02 50Silver < 4.60 to 6.36 100Sodium 19,500 to 293,000 NTGThallium < 81.4 2Vanadium < 11.0 to 11.9 NTGZinc < 21.1 to 41.1 2,000

Note: NTG = No treatment goal for this chemical.

*Treatment goal only.

Source: ICF, 1999.

MAAP, 5 Year Review



All relevant and appropriate documents associated with OU2 investigations, remedy development andoperation were reviewed for this 5-year report. Surface water and shallow sediment samples collectedfrom downstream of O-Line suggest there is low- level explosives and metals contamination. However,the levels are generally at or below levels attributable to permitted discharges from the O-Line facility’sNPDES permit limits and therefore, can be attributed to discharges from the O-Line PWTF. ESE iscurrently determining if explosives and metals levels in OU2 Ditch are at risk to aquatic receptors [OU2Ditch Characterization Report (ESE, 1999)]. There is no risk to human health.

As discussed above, the explosives contamination in the influent of the OU1 treatment facility isdecreasing; in October 1997, the average influent concentration was 7.6 mg/L. Recently (September1999), it has been averaging 4 to 5 mg/L (phone conversation with E. Knotts, 1999). However,fluctuations in the water table could cause contaminant migration from the unsaturated zone.


All available, relevant and appropriate documents associated with OU3 site investigations, remedydevelopment and operations were reviewed during the preparation of this report. The OU3 areaexplosives contamination is not fully characterized at this time (see Sec. 2.4.3) and additional monitorwell installations and groundwater sampling are currently being conducted by International Technology,Inc. The remedy is operating properly, and explosives-contaminated groundwater is being treated tobelow detection. However, the capture of the entire explosives groundwater plume is not occurring.Groundwater explosives contamination is reported to have extended to and beyond the currentgroundwater extraction and monitoring network (Conversation, September 23, 1999).


All relevant and appropriate documents associated with OU3 and OU4 investigations, remedydevelopment, and operation were reviewed for this 5-year report. The 1991 to 1992 RI identified severalareas, primarily inside load lines, which contained explosives-contaminated soil. Under the OU3 and OU4Northern Industrial Area soil ROD, the soils in the immediate vicinity of wastewater surveys, ditches, andoutside doors of buildings where washout activities occurred are to be removed and treated to reduceexplosive concentrations in the remaining soil to below the risk-based levels (25 :g/g for 2,4,6-TNT, 10:g/g for RDX, and 500 :g/g for tetryl).

It was originally anticipated that the excavations would be near the surface soil and would not exceed 10ft bls. An estimated 38,000 tons of explosives-contaminated soil was based on

MAAP, 5 Year Review


sampling soils at Line B and comparing those results to the sampling and historical information for LoadLines A, C, D, E, K, O, S, and Z.

The maximum concentration of explosive compounds detected at Line B was approximately 100,000:g/g. The average concentration of explosive compounds is in the range of 10 to 100 :g/g.Approximately 95 percent of the total mass of explosive compounds detected in the soil are 2,4,6-TNTand RDX. At certain load lines and sumps, only tetryl was detected; Lines A, E, and Z.

The remedy (excavation, treatment, and disposal) for the OU3 and OU4 soils is protective of humanhealth and is partially removing a source of groundwater contamination. However, as presented in Sec.6.0, soils deeper than 10 ft are saturated with contaminants and will continue to be a source ofgroundwater contamination for many years.

MAAP, 5 Year Review


5.0 Conclusions

5.1 Appropriateness of Remedial Action Objectives

EPA’s primary responsibility at NPL sites is to select remedial actions that are protective of human healthand the environment. In addition, Section 121 of CERCLA establishes several other statutoryrequirements and preferences. These specify that when complete, the selected remedy for this site mustcomply with ARARs established under Federal and State environmental laws unless a statutory waiver isjustified. The selected remedy must also be cost-effective and utilize permanent solutions and alternativetreatment technologies or resource recovery technologies to the maximum extent practicable. Finally, thestatute include a preference for remedies that employ treatment that permanently and significantly reducethe mobility, toxicity or volume (MTV) of hazardous wastes as their principal element.

As a part of this review, all remedial action objectives and associated ARARs were reviewed for each OUto determine if any changes had taken place at the site or within the regulatory environment which wouldchange the cleanup goals.


The ARARs and to-be-considered (TBC) guidance for OU1 are described in the sections that follow.

5.1.1.1 Action-Specific ARARs

This remedy is to be operated in accordance with all federal and Tennessee treatment facilityrequirements. A list of action-specific ARARs and TBC guidance is presented in Table 5-1.

According to Rule 1200-4-6-.14 of the State of Tennessee Water Laws, re-injection of treatedgroundwater is permissible. A Class V injection well may be used provided that no hazard to existing orfuture use of the groundwater as cited in Rule 12004-6-.05 exists. Groundwater usage under this later ruleincludes domestic water supply, industrial water supply, livestock watering and wildlife, surface waterdrainage, and irrigation. The rule stipulates that groundwater used for these purposes may be subject totreatment prior to the actual use. Treatment of extracted groundwater will take place prior to use of aClass V injection well for re-injection, and therefore, will not disqualify the groundwater from being usedfor any of the stated uses in the rule.

Since land re-surfacing and construction activities will be performed upon implementation of a treatmentalternative, air quality ARARs are applicable. For each technology within this remedy, applicable airquality regulations will be met. UV-oxidation requires the generation of ozone, a regulated substance, foruse as an oxidant. The Tennessee Ambient Air Quality Primary Standard for ozone is 0.12 mg/L byvolume (Rule 12-3-3-.03).

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Table 5-1. Identification of Action-Specific ARARs and TBC Guidance, Page 1 of 2

Authority Requirement Status Requirement Synopsls

Federal RegulatoryRequirement

NationalEnvironmental PolicyAct (NEPA)of 1969

Applicable Federal actions may not result in environmental damage.

Occupational Safetyand Health Act(OSHA) - GeneralIndustry Standards(29 CFR 1910)

Applicable These regulations specify the 8-hour time-weighted average concentration forvarious organic compounds. Training requirements for workers at hazardous wasteoperations are specified in 29 CFR 1910.120.

OSHA - Safety andHealth Standards (29CFR 1926)

Applicable This regulation specifies the type of safety equipment and procedures to befollowed during site remediation.

OSHA -Recordkeeping,Reporting, andRelated Regulations(29 CFR 1904)

Applicable This regulation outlines the recordkeeping and reporting requirements for anemployer under OSHA.

ResourceConservation andRecovery Act(RCRA), RCRASubtitle C (40 CFR260)

Relevant andAppropriate

RCRA regulates the generation, transport, storage, treatment, and disposal ofhazardous waste. CERCLA specifically requires (in section 104(c) (3) (B)) thathazardous substances from remedial actions be disposed at facilities incompliance with Subtitle C of RCRA.

RCRA - Standardsfor Owners andOperators ofPermitted HazardousWaste Facilities (40CFR 264.1 - 264.8)


General facility requirement include general waste analysis, security measures,inspections, and training requirements.

RCRA -Preparedness andPrevention (40 CFR264.30 - 264.31)


This regulation outlines requirements for safety equipment and spill control.

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Table 5-1. Identification of Action-Specific ARARs and TBC Guidance, Page 2 of 2


RCRA - ContingencyPlan and EmergencyProcedures (40 CFR264.50 - 264.56)


This regulation outlines the requirements for emergency procedures to be usedfollowing explosions, fires, etc.

RCRA - GroundwaterProtection (40 CFR264.90 - 264.109)


This regulation details requirements for a groundwater monitoring program to beinstalled at the site.

RCRA - Closure andPost-Closure (40CFR 264.110 -264.120)


This regulation details specific requirements for closure and post-closure ofhazardous waste facilities.

National AmbientAir Quality Standards(40 CFR Part 50)

Applicable Federal agencies are required to determine if the site is located in a non-attainment zone for ozone. Sites within non-attainment areas must consider theozone attainment status in designing remediation systems.

Federal Guidance USEPA GroundwaterProtection Strategy -USEPA PolicyStatement (August1984)

To be considered Identifies groundwater quality to be achieved during remedial based on the aquifercharacteristics and use.

State RegulatoryRequirement

State of TennesseeWater Laws (Rule1200-4-6-.14)

Applicable The requirements for a Class V injection well are listed.

State of TennesseeAmbient Air QualityPrimary Standards(Rule 1200-3-3-.03)

Applicable Identifies the air quality standards for ozone.

Source: ESE.

MAAP, 5 Year Review


In regards to disposal of the spent carbon and precipitation filter cake, important potential ARARs are theLand Disposal Restrictions (LDRs) implemented by EPA under the Hazardous and Solid WasteAmendments (HSWA). Under these restrictions, hazardous waste may not be landfilled without meetingthe prescribed treatment standard. If these restrictions are applicable (i.e., if the spent carbon and/or filtercake are determined to constitute a hazardous waste), then the disposal of the wastes will be performed incompliance with the LDRs.

5.1.1.2 Chemical-Specific ARARs

The selected interim remedy provides a means of reducing the levels of contamination in extractedgroundwater to below clean up levels set by ARARs and TBCs at the facility boundary and will achievethese levels within the facility for most contaminants. The remedy will significantly reduce theconcentrations of RDX 2,4,6-TNT, HMX, and 1,3-DNB within the OU; however, the health-based limitsapplicable to these constituents may not be achieved within the facility boundary during this interimaction. Further remediation of groundwater within the OU may be addressed in the subsequent finalremedial action. To ensure protection of human health and the environment while the subsequent action isbeing developed, institutional controls will be used to prevent use of the water.

More stringent maximum contaminant level goals (MCLGs), established by the Safe Drinking Water Act,are not relevant and appropriate standards given the risks posed by the OU.

All groundwater ARARs will be achieved through the implementation of the selected remedy. Applicablegroundwater ARARs and TBC guidance are listed in Table 5-2.

5.1.1.3 Location-Specific ARARs

The construction and operation of the treatment facility and extraction/re-injection wells incorporated inthis remedy will comply with all location-specific ARARs. A list of location-specific ARARs and TBCguidance is presented in Table 5-3.

No changes to the rules affecting the ARARs have occurred which would change the cleanup goals,except for the health-based discharge limit for 1,3,5-TNB, which has been recalculated (see Section 6.4.1)from a technically feasible level of 20 :g/L to a health based level of 1,050 :g/L. However, this change isnot consequential since the system as currently designed and operated, is achieving the more stringenteffluent limitation of 20 :g/L. The MTV is being reduced by the capture and treatment of explosive’scontaminated groundwater at OU1. As such, the implemented remedy and the cleanup goals remainappropriate at the time of this review.

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Table 5-2. Identification of Chemical Specific ARARs and TBC Guidance for Groundwater

Authority Requirement Status Requirement Synopsls


Safe Drinking WaterAct (SDWA) -MaximumContaminant Levels(MCLs), 40 CFR141.11-141.16


MCLs have been promulgated for a number of common organic and inorganiccontaminants. These levels regulate the concentration of contaminants in publicdrinking water supplies based on health effects and technical capabilities. MCLsmay also be considered relevant and appropriate for groundwater aquiferspotentially used for drinking water.

State RegulatoryRequirements

Rules of theTennesseeDepartment ofHealth and theEnvironment,Chapter 1200-5-1-.06


The State of Tennessee has adopted groundwater standards and public watersupply standards.

Federal Criteria,Advisories, andGuidance

EPA CarcinogenAssessment GroupPotency Factors

To Be Considered Potency factors are developed by EPA from health effects assessments orevaluation by the Carcinogen Assessment Group. Carcinogen potency factors areused in the baseline risk assessment to compute the individual incremental cancerrisk resulting from exposure to site contaminants.

EPA Office ofDrinking WaterHealth Advisories(HAs)

To Be Considered Health advisories developed from estimates of risk due to consumption ofcontaminated drinking water considering noncarcinogenic effects only. Healthadvisories are considered for contaminants in groundwater that may be used fordrinking water.

EPA Risk ReferenceDoses (RfDs)

To Be Considered RfD are dose levels developed by EPA for non-carcinogenic effects. RfDs areused in the baseline risk assessment to characterize risks due to exposure to non-carcinogenic contaminants in groundwater.

Source: ESE.

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Table 5-3. Identification of Location-Specific ARARs and TBC Guidance

Authority Requirement Status Requirement Synopsis


RCRA - LocationStandards (40 CFR264.18)


This regulation outlines the requirements for constructing a RCRA facility on a 100-yearfloodplain. The facility must be designed, constructed, operated, and maintained to avoidwashout by a 100-year flood, unless waste may be removed safely before floodwater canreach the facility or on adverse effects on human health and the environment would resultif washout occurred.

RCRA - LocationStandards (40 CFR264.18)


This regulation prohibits new treatment, storage, or disposal of hazardous waste within 61meters (200 feet) of a fault displaced in Holocene time.

Executive Order11988: FloodplainManagement (40CFR 6, Appendix A)

To be considered Federal agencies are required to reduce the risk of flood loss, to minimize the impact offloods and to restore and preserve the natural and beneficial value of floodplains.

Executive Order11990: Protection ofWetlands (40 CFR6, Appendix A)

To be considered Federal agencies are required to minimize the destruction, loss, or degradation ofwetlands, and preserve and enhance the natural and beneficial values of wetlands.

NationalArchaeological andHistoricPreservation Act (16USC 469): NationalHistoric LandmarksProgram (36 CFR65)


Federal agencies must take action to recover and preserve artifacts within areas whereaction may cause irreparable harm, loss, or destruction of significant artifacts.

Source: ESE.

MAAP, 5 Year Review



There are no chemical- or location-specific ARARs for OU2. The action-specific ARARs are:1. RCRA requirements for closure of surface impoundments (40 CFR 264.228) and closure of

landfills (40 CFR 264.310).2. RCRA requirements for groundwater monitoring (40 CFR 264.91).3. Tennessee Hazardous Waste Management Act (Title 68, Chapter 46).4. 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. 5. Tennessee Air Quality Regulations (applicable only during construction). 6. Tennessee Water Pollution Control Regulations – General stormwater permit of construction

activities (Rule 1200-4-10.05).

These ARARs have been met and there are no changes to cleanup goals. The remedy is cost-effectivewith minimal O&M costs. The MTV of soil contamination mobilizing into the groundwater has beenreduced effectively. However, a fluctuating water table could mobilize contaminants from the unsaturatedzone.


In February 1996, an ESD was issued for OU3 that represents a notice of change to the OU3 ROD that isconsidered by the Army to be significant, but not fundamental to the remedy. The EPA and TDECconcurred with the change, which was inclusion of final discharge limits (into surface water) for the OU3groundwater treatment facility (see Table 3-4). These discharge limits are being met by the OU3 facility.There have been no other changes to the ARARs and TBC guidance specified in the original ROD; thechemical-specific groundwater quality ARARs, the location-specific ARARs and action-specific ARARshave remained unchanged. The ARARs for OU3 are described in the sections that follow.

The ARARs for this remedial action include action-specific, chemical-specific, and location-specificrequirements. TBC guidances are also listed.

5.1.3.1 Chemical-Specific ARARs and TBC GuidanceThis remedy will be operated in accordance with all federal and state of Tennessee treatment facilityrequirements.

Groundwater Quality• The maximum contaminant level (MCL) for nitrate (40 CFR 141.23) is a relevant and appropriate

requirement.• EPA Lifetime Health Advisories (LHAs) and health-based cleanup standards calculated from

EPA’s Reference Doses and Cancer Slope Factors are TBC cleanup goals.

MAAP, 5 Year Review


Surface Water DischargeEffluent discharge limits assigned by the state of Tennessee Division of Water Pollution are applicalbe.These limits are based on federal Ambient Water Quality Criteria, as set by EPA under the Clean WaterAct [33 United States Code (USC) 1314(a)(1)] and the Rules of the TDEC (Chapter 1200-4-3). Fordischarge to the Rutherford Fork, an NPDES permit would be required. The permit limits are applicablerequirements.

5.1.3.2 Location-Specific ARARs

• RCRA requirements regarding the location of hazardous waste treatment plants are relevant andappropriate. These requirements cover placement on a floodplain and placement near a fault (40CFR 264.18).

• Regulations that require federal actions to protect floodplains and protect wetlands (40 CFR 6,App. A) are relevant and appropriate.

5.1.3.3 Action-Specific ARARs

The disposal of sludges and spent GAC will be performed in compliance with RCRA requirements (40CFR 260 through 270), which are relevant and appropriate.

The remedy is cost effective with minimal O&M costs. The MTV of groundwater contamination has beenreduced, although the capture of the explosives contaminated is not complete. The selected remedy isappropriate as well as the RAOs. There have been no changes that would affect the ARARs as they arepresented above.


ARARs have been used to develop the RAOs in the FFS (USAEC, 1995), to determine the appropriatecleanup levels, and govern the implementation of the remedy selected in the ROD. There are nochemical-specific or location-specific ARARs identified in the ROD. It determined that there are nofederal or Tennessee regulations governing the soil contaminants addressed by this remedy. Since thesoils are not reactive and the TCLP concentration of nitrobenzene does not exceed 2 mg/L, and 2,4-DNTextracted concentrations do not exceed 0.13 mg/L, the soils are also not considered to beRCRA-characteristic waste. Action-specific ARARs were identified as follows:

1. The excavation of soil and windrow composting will be performed in compliance with TennesseeAir Pollution Regulations [Fugitive Dust Standards, Rule 1200-3-8.01; Visible Emissions Rule1200-3-5.01; and Particulate Emissions, Rule 1200-3-7.03 (2)]

2. The disposal of a treated soil within a solid waste landfill will be performed in compliance withthe State of Tennessee solid waste requirements(Tennessee Solid Waste Processing and DisposalRegulations, Rule 1200-1-7-.04)

MAAP, 5 Year Review


3. Excavation activities within the northern industrial areas will be performed in compliance withthe substantive requirements of the Tennessee Water Pollution Control Regulations’ generalstorm-water permit program for construction activities (Rule 1200-4-10.05)

These ARARs appear to have been met thus far and cleanup goals have reportedly been achieved,although a full-scale operation has not occurred to date. The remedy, which is protective of human healthand the environment, appears to be appropriate at this time.

5.2 Achievement of Remedial Action Objectives


As a part of the review process, it is important to determine if the RAOs are being met through operationof the implemented remedy. OU1 groundwater is being successfully treated to below detection forexplosives and re-injected with adequate capture. Concentrations of explosives are being reduced in thegroundwater and institutional controls are effective.


The purpose of the implemented remedy at OU2 was to reduce the area of uncovered contaminated soilsuch that the potential human health risk associated with the migration of contaminants from theuncovered soil to the water table and use of the shallow groundwater as drinking water is within EPA’sacceptable risk range. The RAOs have been met by the OU2 remedy; exposure to uncoveredcontaminated soil has been reduced and release of contaminants from the unsaturated zone (under the cap)into the groundwater has been prevented. However, fluctuations in the water table may still mobilizeexplosive compounds in the soil under the cap (i.e., fluctuating groundwater levels could leachcontaminants out of the unsaturated zone).


The goal of this remedy is to reduce the potential health risks and restore the aquifer to the extentpracticable with the selected technology. The remediation goals for this action are to reduce the levels ofexplosives compounds in off-post groundwater to the chemical-specific, risk-based groundwaterstandards. The off-post performance monitoring is ongoing and not complete at this time. A capture zoneanalysis has not been performed at this time and additional groundwater monitoring is currently ongoing.The achievement of RAOs can not be determined at this time.


Although a full-scale operation to treat the explosives-contaminated soil in OU3 and OU4 usingbioremediation has not been implemented at this time, it appears that the technology will be successfuland achieve the RAOs.

MAAP, 5 Year Review


5.3 Whether the Remedy is Effective and Functioning as Designed


The current implemented remedy consists of groundwater recovery and treatment, re-injection,performance monitoring, and institutional controls. While there are minor deficiencies, the remedy as awhole continues to be effective as per the requirements of the ROD. The following is a review of theremedy components and an evaluation as to its effectiveness.

Extraction System: The three extraction wells are capable of pumping approximately 580 to 600 GPM toprovide adequate capture of the RDX plume at OU1. The extraction wells are currently pumping 24 hoursa day, 7 days per week. A groundwater simulation model predicted that pumping cyclically 4 days on – 3days off at a constant pumping rate of 330 GPM would provide adequate capture (HSI GeoTrans, 1999).

Treatment System: The ESD, approved by the EPA and TDEC, gave the Army flexibility in treating theexplosives contaminated groundwater at OU1. The electrochemical precipitation unit was not necessaryto remove inorganics prior to treatment (sand filtration and settlement are sufficient to remove inorganics)and the GCA units are effective in reducing the explosives concentration to below detection with use ofthe UV-oxidation units. Although more GAC may be necessary without use of the UV-oxidation units,the added expense should be covered by the savings in electricity to run the UV-oxidation units and UVlamp replacement. The cost for operating UV-oxidation and carbon adsorption is estimated to beapproximately $180,000 a year, regardless of the combination of the two units to attain effluent standardsfor explosives (ICF Kaiser, Performance Evaluation of OU1, 1999). If carbon can be reactivated andreused, then carbon adsorption is the most cost-effective method. The spent carbon, filter cake and otherresiduals are being tested, stored, and disposed of in accordance with all environmental laws andregulations that are applicable to the materials at this time.

Re-infection System: The six re-injection wells are designed to pump approximately 125 GPM each (750GPM total) and are performing efficiently at this time. Regular O&M is critical to continued designperformance.

Performance Monitoring: A monitoring program is in place to ensure that the hydraulic controlof groundwater within OU1 is maintained. Specifically, an inward and upward gradient within theaquifer must exist to prevent further migration of the contaminated groundwater from OU1. Thehydraulic control appears to be maintained. The water quality data indicates that explosivescontamination extends further north of the extraction wells than originally believed. Whether thecontaminants originated from the O-Line ponds or Ditch B is unclear. It is likely that the plume hasmigrated several hundred feet since the plume was last characterized in 1992. The contaminationobserved in the wells 400 feet north of OU1 is being captured by the extraction

MAAP, 5 Year Review


system, but the northern-most extent of the plume is unknown (HIS GeoTrans, 1999), and requires moredelineation.

Institutional Controls: The institutional controls are being effectively maintained. MAAP is a fenced andpublic-restricted Army military installation. Access to all active sites, including OU1, are restricted bylocked and/or guarded gates. The groundwater within OU1 is not being used for potable purposes and, inaccordance with Army Regulation 200-1, entitled Environmental Protection and Enhancement, the Armywill perform preliminary assessment screening for any parcel being excessed that is associated with OU1.Also, a continuing program of public awareness is being used to inform the public of hazards with anycontaminants that remain within OU1.


The current implemented remedy consists of the geo-synthetic cap extension (approximately 302,000square ft) which extends beyond the original soil (clay, gravel, and sand) cap (approximately 280,000 ft2),performance monitoring, and institutional controls. The remedy appears to be effective as per therequirements of the ROD. The following is a review of the components and an evaluation as to itseffectiveness.

Geo-Synthetic Cap Extension: The geo-synthetic cap, along with the original soil cap, has reduced thearea of uncovered, potentially contaminated soil and has minimized the infiltration of storm-water into theunderlying contaminated soil and also reduced the formation of leachate.

Performance Monitoring: Groundwater monitoring at OU2, in conjunction with OU1 monitoring, is theprimary means of determining whether the remedy is operating properly. The explosive concentrationsdown-gradient of OU2 have decreased since the implementation of the remedy, as revealed by thelowered explosive’s concentration in the influent of OU1 from 1997 to 1999 (7.6 mg/L to approximately5 mg/L). The annual monitoring, in conjunction with OU1 groundwater monitoring is effective at thistime. Surface water control is maintained by a biannual preventative schedule that identifies and correctsproblems with surface water control systems. Ditches and channels are also inspected during the quarterlyinspections and after major storm events. Performance monitoring is effective in maintaining the integrityand performance of the remedy.

Institutional Controls: OU2 institutional controls include continued access restrictions, deedrestrictions, and land use restrictions, which will limit future land uses at the site. Long-termmaintenance of the fence and multi-media cap is ongoing. MAAP is a fenced and public-restrictedArmy military installation. Access to all active sites, including OU2, are restricted by locked and/orguarded gates. The Army continues to ensure protection of onsite future users of groundwater andhas a public awareness program to inform the public of any hazards associated

MAAP, 5 Year Review


with contaminants from OU2 and all other sites at MAAP. Institutional controls, as currentlyimplemented, are effective at OU2.


The current implemented remedy at OU3 consists of groundwater recovery and treatment, discharge tosurface water (Rutherford Fork), performance monitoring and institutional controls. The technology ofthe remedy is effective. However, a performance evaluation (HIS GeoTrans, 2000) of the remedyindicates that the contamination extends north of the extraction wells and is not being captured at thistime. The following is a review of the remedy components.

Extraction System: The six extraction wells are capable of pumping approximately 200 GPM each andare functioning properly at this time; extracting approximately 1,000 to 1,100 GPM total. They arecapturing explosives contaminated groundwater (average concentration of 2 to 4 mg/L). However,additional extraction wells may be needed to provide adequate capture of the entire explosivescontaminated groundwater plume.

Treatment System: The GAC filtration treatment system is effectively reducing the explosive compoundsconcentration in the influent (2- to 4-mg/L range) to below detection and easily meeting the dischargerequirement for nitrobodies, which is 100 :g/L.

Discharge to Surface Water: Treated groundwater is meeting all discharge requirements and is beinggravity fed to the Rutherford Fork, approximately one mile north of the OU3 treatment facility.

Performance Monitoring: Effluent monitoring has been implemented and maintained in an effectivemanner. However, the monitoring network to ensure adequate capture of the contaminated groundwater isnot in place at this time.

Institutional Controls: The institutional controls are being effectively maintained. The institutionalcontrols for OU3 are as follows.

The Army will ensure protection of future users of groundwater. The active remediation will besupplemented with institutional controls to prevent ingestion of contaminated groundwater from the areasof concern at the northern boundary. These institutional controls will consist of the following:

• The groundwater at the northern boundary will not be used for potable purposes while the levelsof contaminants are higher than health-based levels; this will be ensured by MAAPenvironmental Office review of all projects and leases involving well installation and usage at thefacility. Any well installed within the facility will be tested prior to use.

MAAP, 5 Year Review


• A continuing program of public awareness will be used to inform the public of the hazardsassociated with contaminants that remain in groundwater along the northern facility boundary.

• MAAP is a fenced and public-restricted Army military installation. Military installation signs,warning visitors of restrictions and the requirement for authorized passes, are prominently placedthroughout the facility.


The remedy at OU3 and OU4 consists of excavation, engineered capping if necessary, bioremediationtreatment, institutional controls, landfill disposal, and monitoring of the landfill.

Excavation: Explosives contaminated soil has been excavated from OU3 and OU4 and used in treatabilitytesting to successfully reduce the explosives concentration to the remediation goals. No engineering capshave been utilized at this time.

Bioremediation Treatment: Explosives contaminated soil has been bioremediated by microorganisms in a90-day treatability test by composting the soil with varying mixtures of amendments for approximately 30days.

Institutional Controls: MAAP is a fenced and public-restricted Army military installation. Access to allactive sites, including OU3 and OU4, are restricted by locked and/or guarded gates. Explosivescontaminated soil is being removed to a maximum depth of 10 ft and remediated at the compost facility.With this remedy, the northern industrial areas, which are remediated, will be suitable for current use asindustrial areas and for future use as either industrial areas or residential areas. This remedy should alsoreduce the future leaching of explosive contaminants by stormwater to groundwater, which will helpprotect groundwater quality. (However, fluctuation of the water table may mobilize explosivecontaminants in the unsaturated zone.) Therefore, no institutional controls on future land use will beneeded. Institutional controls will only be required to maintain the engineered caps within the northernindustrial areas (if this option is exercised) and maintenance of the Subtitle D solid waste landfill.

Landfill Disposal: Treated soil is currently being landfilled onsite at MAAP. Reuse of the treated soil maybe an option.

Monitoring: Post-closure of the selected onsite or offsite landfill and cap will be performed for aminimum of 30 years after final closure. A post-closure groundwater monitoring program will beimplemented if contaminants from the landfill are entering the groundwater. One monitoring well will beinstalled up-gradient and two down-gradient of the landfill. The compounds to be monitored in thegroundwater will be determined during the design phase.

MAAP, 5 Year Review


The remedy appears to be effective but can not be evaluated as a whole at this time. The facility isdesigned to and capable of composting 1,000 tons of explosives contaminated soil per month and capableof operating 365 days per year. The facility has not operated on a full-scale basis at the time of thisevaluation.

5.4 Adequacy of O&M


As a part of the 5-year review, the O&M of the implemented remedy was evaluated to determine if it isadequate to maintain the effectiveness of the remedy. The responsibility for O&M activities belongs toAO personnel, under the guidance of the Environmental Branch, Facilities Division of MAAP. The O&Mmanual and activity records are filed and kept onsite. O&M activities have been greatly reduced byshutting down the electrochemical precipitation and UV-oxidation operations. The primary O&Mactivities are to maintain the good running order of the extraction and re-injection wells and pumps, toadjust and readjust the pH of influent and effluent, and to conduct the performance monitoring, includingsampling and analysis of the influent and effluent. The O&M activities, as currently implemented, areadequate to maintain the implemented remedy.


The responsibility for the O&M activities at OU2 belong to AO personnel, under guidance of the MAAPEnvironmental Branch. The post-closure requirements and O&M requirements and procedure arecontained in the Final Post-Closure Care Plan, which is kept onsite at the OU1 treatment facility officealong with records of O&M activities and inspections. The primary O&M activities are the inspection andmaintenance of the OU2 cap and performance monitoring. The O&M activities, as currentlyimplemented, are adequate to maintain the implemented remedy.


The responsibility for the O&M at OU3 belongs to AO personnel, under guidance of the EnvironmentalBranch, Facilities Division of MAAP. The primary O&M activities are to maintain the good runningorder of the extraction wells and pumps, to adjust the pH of the influent, avoid breakdown of GACquality, maintain the (gravity) discharge piping, and conduct the performance monitoring. The O&Mactivities, as currently implemented, are adequate to maintain the implemented remedy.


Plexus had the responsibility for the O&M during the treatability testing. AO personnel will assumeresponsibility for the operation and O&M of the facility when it begins full-scale

MAAP, 5 Year Review


operation. The O&M should be adequate to maintain the remedy as indicated from treatability O&Mperformance. However, a treatability test report has not been submitted at the time of this 5-yearevaluation.

5.5 Early Indicators of Potential Remedy Failure


Indicators of remedy failure at OU1 will be evident either with failure of the capture of the explosivescontaminant plume or the inability of the O&M activities to keep the implemented remedy operational.Currently the plume appears to be captured and the O&M activities are keeping the remedy operational.There may be some lack of delineation of the explosives plume to the north OU1. A modified monitoringnetwork could ascertain if the plume from OU1 is captured or if explosives contamination to the north ofOU1 is from another source.


Indicators of remedy failure at OU2 would be evident if explosive concentrations in groundwater wereincreasing due to a breach in the cap cover, thereby allowing infiltration of storm-water onto theunderlying contaminated soil. Also, failure of the remedy would occur if the cap was not maintainedproperly, allowing storm-water to impound on top of the cap. Groundwater monitoring shows explosivesconcentrations are decreasing at the site and that no impounded water was apparent during the site visit.The cap and vegetative cover are in good condition and the O&M activities are preventing any remedyfailure.


Indicators of remedy failure at OU3 would be evident either with the failure of the capture of theexplosives-contaminated plume or the inability of the O&M activities to keep the implemented remedyoperational. A capture analysis [Capture Zone Verification at the OU3 Northern Boundary GroundwaterTreatment System (HIS GeoTrans, 2000)] indicates that the capture of groundwater from the mostconcentrated portions of the two northern boundary plumes is occurring. However, the mostdown-gradient northern boundary monitor wells, which are outside the intended capture zone, haveexplosive compounds contamination. It is likely the western plume has migrated several hundred feetsince the plume was last characterized. The explosives contamination in the wells along the RutherfordFork of the Obion River is not being captured by the extraction system, and the contaminants flowpathand eventual discharge point is uncertain. It is an indication of remedy failure. The O&M activities areadequate.

MAAP, 5 Year Review



The remedy has not operated in a full-scale operation at this time. However, remediation goals wereachieved during the treatability testing and O&M activities were adequate to keep the remedy operationalwhen implemented on a full-scale basis.

MAAP, 5 Year Review


6.0 Deficiencies

The purpose of the 5-year review is to note deficiencies in the implemented remedy that prevent theremedy from being protective of human health and the environment and from achieving the RAOs.Deficiencies may result from changes to the site characteristics, change in the nature and extent of thecontaminants, failure of the implemented remedy to operate as designed, or failure of the remedy toachieve design specifications.

6.1 O&M Record Keeping and Reporting


O&M record keeping and reporting were well documented, organized, and accessible. No deficiencieswere noted.


O&M record keeping and reporting were well documented, organized, and accessible. No deficiencieswere noted.


O&M record keeping and reporting were well documented, organized and accessible. No deficiencieswere noted.


No deficiencies were noted during the preliminary treatability testing at the compost facility. However,the remedy has not been implemented on a full-scale operation at this time.

6.2 O&M Activities


O&M activities were conducted as specified in the O&M Manual and were well documented. The AOpersonnel that were operating the plant were very capable and knowledgeable of their O&Mrequirements.


O&M activities were conducted as specified in the Final Post-Closure Care Plan. The quarterlyinspections were up-to-date and the site well maintained. No deficiencies were noted.

MAAP, 5 Year Review



No deficiencies were noted in the O&M activities.


Additional performance monitoring is necessary to fully define the contaminant plume, andextraction-well performance must be optimized.

6.3 Institutional Controls

MAAP is a fenced and restricted Army military installation. Access to all active sites, including thefollowing OUs, are restricted by locked and/or guarded gates. Government authorized identificationpasses are required of all persons (employees and visitors) entering the MAAP facility. Militaryinstallation signs warning visitors of restrictions and the requirement for authorized passes areprominently placed throughout the facility. The Army keeps the public aware of all ongoing and proposedremedies at the Remedial Advisory Board (RAB) meetings in Milan.


Institutional controls were in effect as required by the ROD; there were no major deficiencies noted at thetime of the 5-year review.


Institutional controls were in effect as required by the ROD; there are no deficiencies noted at the time ofthis 5-year review.


Institutional controls were in effect as required by the ROD; there were no deficiencies noted at the timeof the 5-year review.


Institutional controls were in effect as required by the ROD; there were no deficiencies noted at the timeof this 5-year review.

6.4 Cleanup Levels/Contaminant Delineation

ESE has reviewed the cleanup levels established in the RODs in light of any changes in risk-basedstandards or toxicological information for the COCs for OUs 1, 2, 3, and 4. In addition,

MAAP, 5 Year Review


data on contaminant delineation has been reviewed to estimate the progress and probable outcomes ofongoing and/or planned remedial actions.


6.4.1.1 Discharge Limits for Groundwater Extraction and Treatment System

The ROD for OU1 specified discharge limitations for the groundwater treatment system based onhealth-based standards for drinking water and/or technical feasibility. The discharge levels identified inthe ROD are listed in Table 6-1. The basis for these levels was reviewed to determine if there had beenany changes in regulatory limits or underlying toxicological information that might result in modificationof any of these limitations. Results of this review are also summarized in Table 6-1. Only one COC(1,3,5-trinitrobenzene) has been affected by updated toxicological data, standards, or advisories. The oralreference dose (RfD) for 1,3,5-trinitrobenzene (TNB) was 0.00005 milligrams per kilogram per day(mg/kg/day) at the time of the ROD execution. The RfD for TNB was modified by EPA in 1997 (EPA,1997; or EPA, 1999) to a value of 0.03 mg/kg/day. At the now obsolete level of 0.0005 mg/kg/day, a safedrinking water concentration for TNB was estimated at 2 :g/L. It was determined (through the FS andROD) that achievement of this level in the groundwater treatment effluent was technically infeasible, sothe discharge limitation was established at the limit of technical feasibility (20 :g/L). Based on currentlyavailable toxicological data from EPA and following procedures for calculation of risk-based PreliminaryRemediation Goals (PRGs) (EPA, 1991), a limit of 1,100 :g/L is determined to be protective of humanhealth by the drinking water exposure pathway.

Based on the recent performance of the groundwater treatment system, this change is not consequential,because the system (as currently designed and operated) is achieving the more stringent effluent limitationof 20 :g/L. TNB is not a critical contaminant in terms of treatment system operation. Treatment toremove other COCs coincidentally removes TNB, which is not a “treatment driver.”

Cancer slope factors are not available for 2,4- and 2,6-dinitrotoluene individually. Ratherthe available slope factor applies to a mixture of 2,4- and 2,6-dinitrotoluene. Consequently, theestimated acceptable drinking water concentration applies to the sum of 2-4- and 2,6-dinitrotoluene(total dinitrotoluenes). The discharge limitation specified in the ROD of 0.5 :g/L for the twocompounds separately is approximately equivalent to a PRG of 1.3 :g/L for the sum of the two.The discharge limit of 10 :g/L for RDX is approximately equal to the 10-5 risk level. Attenuationduring transport to the boundary provides for an adequate margin of safety, so the use of theLifetime Health Advisory does not suggest an unacceptable risk. The Lifetime Health Advisoryof TNT is controlled by noncarcinogenic effects, so it is not acceptable to permit the 10-5 risklevel for this COC. Methods recommended by EPA (1991) indicate that the

P/mlaap/5yrReview/tables.doc6-4

Table 6-1. Review of OU1 Discharge Limits

Chemical of Concern

DischargeLimit(µg/L) Basis 5 Year Update

INORGANIC CONSTITUENTS

Nitrate 10,000 MCL NC

VOLATILE ORGANIC COMPOUNDS

Carbon Disulfide 3,5000 Health Based – RfD NC

EXPLOSIVES COMPOUNDS

1,3-Dinitrobenzene 5 Lifetime Health Advisory NC

2,4-Dinitrotoluene 0.5 Health Based – Cancer Risk NC

2,6-Dinitrotoluene 0.5 Health Based – Cancer Risk NC

HMX 2,000 Lifetime Health Advisory NC

Nitrobenzene 17.5 Health Based – RfD NC

RDX 10 Lifetime Health Advisory NC

1,3,5-Trinitrobenzene 20 Technical Feasibility 1,100 :g/LHealth-Based – RfD

2,4,6-Trinitrotoluene 10 Lifetime Health Advisory NC

Notes: MCL – Federal Maximum Contaminant Level.

Health Based – RfD – based on noncarcinogenic systemic health effects applying method ofEPA (1991).

Lifetime Health Advisory – EPA Office of Drinking Water Lifetime Health Advisory adjustedto the assumption that all exposure comes from drinking water.

Health Based – Cancer Risk – based on carcinogenic effects with a target risk of 10-5 applyingmethod of EPA (1991).

NC – No Change in Basis since execution of the ROD.

Source: ESE.

MAAP, 5 Year Review


maximum acceptable drinking water concentration for protection against the noncarcinogenic effects ofTNT is 18 :g/L.

Based on this review, the discharge limits specified in the ROD are confirmed to be adequately protectiveof human health, but not substantially overprotective, for the carcinogenic COCs if this water were to beused for drinking. In fact, groundwater at the point of discharge will not be used as a drinking watersupply. Attenuation during transport to the nearest point of potential exposure, the MAAP facilityboundary, could be taken into account to derive somewhat less stringent requirements that would still beprotective of human health and the environment. Evaluation of attenuation along this pathway ispresented in Sec. 6.4.1.

6.4.1.2 Remediation Goals for Groundwater Quality

The ROD applied a simple groundwater dilution model to demonstrate that achievement of the dischargelimits in groundwater near the O Line Ponds would result in the ultimate achievement of drinking waterstandards at the MAAP boundary, approximately 9,000 ft north of the O-Line Ponds. The ROD does not,however, indicate levels that should be achieved in monitor wells near the O-Line to ensure meetingdrinking water standards at the boundary. Furthermore, the ROD does not identify a completion criterion.

It would be useful, for planning purposes, to identify the conditions under which active groundwaterremediation could be discontinued, without posing an unacceptable risk to health or the environment. Atestimated groundwater flow velocities (133 ft per year, ICF Kaiser, 1997), the transport time from thecenter of the plume (near extractions wells EXT-1, -2, -3, and -4) is approximately 60 years.Consequently, a long time could transpire between the time that satisfactory groundwater quality isachieved in the source area and the time when the effects of the action would be observed at theboundary.

With this objective, ESE applied the steady-state groundwater contaminant attenuation model presentedby the American Society for Testing and Materials (ASTM) (1995) to estimate a site-specificdilution/attenuation factor (DAF). The model accounts for adsorption, dispersion, and contaminantdegradation in a uniform groundwater flow field. In this application, it was assumed that the COCs do notdegrade. When no degradation is simulated, the model is not sensitive to contaminant adsorption, so allCOCs will have the same DAF as a result of dispersion. Consequently, it was only necessary to apply themodel to any hypothetical constituent to derive a DAF, which could then be applied to all the COCs.

Model application is documented in App. F. Inputs for the model were estimated using data presented inthe ROD, ESE (1999), HIS GeoTrans, Inc. (1999), and ICF Kaiser (1997). Critical inputs are:

• Aquifer Thickness – 250 ft;

MAAP, 5 Year Review


• Plume Thickness in Source Area – 50 ft;• Plume Width in Source Area – 2,400 ft;• Hydraulic Conductivity – 105 feet per day (ft/day);• Hydraulic gradient – 0.0015;• Lateral Dispersivity – 0.002 x, where x is distance from the source; and• Vertical Dispersivity – 0.00004 x.

The dispersivities are consistent with values used by ESE (1999) to accurately calibrate the RDX plumemigrating west of MAAP from the X Line and Ditch E. All other values are representative of conditionsobserved in the vicinity of the O-Line Ponds and along the downgradient flow path to the boundary.

Model results indicate that concentrations at the boundary are expected to be lower than concentrations inthe vicinity of the OU1 extraction wells by a factor of 3.7 under hypothetical natural gradient conditions.This value represents a DAF that can be applied conservatively to all COCs associated with OU1 –O-Line Groundwater. This DAF does not “take credit for” any biodegradation that may be occurringalong the groundwater flow path. Consequently, it would be conservative for COCs that biodegrade ingroundwater. ESE (1999) observed that RDX appears to be degrading with a half-life of 20 years. If thisrate of degradation also occurs in OU1 groundwater, then the DAF for RDX may be as much as 14.

The conservative, nondegrading DAF of 3.7 is multiplied times the health-based drinking water goals thatapply at the MAAP boundary to produce estimated concentration targets for the OU1 source area (seeTable 6-2). When groundwater concentrations at the OU1 extraction wells fall to the levels indicated inTable 6-2, groundwater remediation may be discontinued. Dispersion during downgradient transportwould be expected to reduce concentrations to the indicated health based criteria at the MAAP boundaryunder natural gradient (no remediation) conditions. Table 6-2 does not present an alternate groundwatercriterion for nitrate because nitrate occurs naturally and participates in a variety of chemical reactionsduring groundwater transport. Consequently, the ASTM steady-state attenuation model may not berealistic for nitrate. In addition, an alternate target for RDX at the boundary was used (7.7 :g/L) which isthe 10-5 cancer risk PRG for drinking water.


It is likely that substantial soil contamination under the O-Line Ponds extends through the full vadose zone thickness to the water table. Insofar as the water table fluctuates on seasonal and annual cycles, fluctuating groundwater levels may leach significant quantities of COCs from soils near the water table for a period of many years, even though the cap is effective in eliminatinginfiltration of rainwater. As a result, the groundwater extraction and treatment systems downgradient of OU2 may need to be operated and maintained for an excessive duration unless


Table 6-2. Estimate of Acceptable Groundwater Concentration in Vicinity of OU1 Extraction Wells

Chemical of Concern

Health-Based TargetConcentration at

Boundary(:g/L)

Related GroundwaterConcentration in Vicinityof OU1 Extraction Wells

(:g/L)

Carbon Disulfide 3,500 13,000

1,3-Dinitrobenzene 5 18

2,4-Dinitrotoluene 0.5 1.8

2,6-Dinitrotoluene 0.5 1.8

HMX 2,000 7,400

Nitrobenzene 17.5 65

RDX 7.7 28

1,3,5-Trinitrobenzene 1,100 4,100

2,4,6-Trinitrotoluene 10 37

Source: ESE.

MAAP, 5 Year Review


soils near the water table are treated to remove the groundwater COCs. The downgradient groundwaterremediation systems are intended to intercept this leachate, but it may be more efficient to eliminate thesource.

6.4.3 OU3 – K Line (NE) Groundwater

In contrast to OU1, the ROD for OU3 – K Line (NE) Groundwater specifies Cleanup Standards forGroundwater, rather than treatment system effluent. The basis for the specified levels are similar to thebasis used in establishing OU1 discharge limitations, with one significant difference. The primarydifference between the health-risk-based standards at OU1 (O-Line) and OU3 (K Line) is that LifetimeHealth Advisories (LHAs) for HMX, RDX, and TNT were used without modification in OU3. For theOU 1 ROD, the LHAs were adjusted upwards by a factor of 5 in establishing effluent limitations. It maybe appropriate to adopt more stringent criteria for groundwater at OU3 (K Line) than for effluent at OU1for two reasons:

C K Line is closer to the facility boundary.C Effluent standards are frequently less stringent than receiving water standards; effluent can be

diluted further upon mixing with the receiving waters.

Notwithstanding these factors that could contribute to tighter standards for groundwater at Line K thanwere established for effluent at Line O, the O-Line standards are sufficiently protective of human healthand in accordance with CERCLA guidance (EPA, 1991). LHAs are calculated under the assumption thatonly 20 percent of a safe chronic dose should be permitted to come from drinking water, allowing 80percent of the acceptable chronic dose to come from other sources/exposure pathways. EPA (1991)methodology for determining PRGs under CERCLA permit 100 percent of the acceptable dose to comefrom drinking water, where drinking water is the predominant pathway associated with the site.Consequently, the adjustment that was made at OU1, increasing LHAs by a factor of 5, is consistent withCERCLA guidance. The adoption of unadjusted LHAs at OU3 is more stringent than required byCERCLA.

Table 6-3 summarizes the Cleanup Standards established for OU3 K Line (NE) groundwater, and presentsthe results of the same analysis presented for OU1 standards in Table 6-1. Specifically, the basis for thestandards was reviewed to determine in changes in regulatory standards of the primary toxicologicalinformation available for each COC has changed since execution of the ROD (see Sec. 6.4.1 for moredetailed discussion). Consistent with the findings of the similar evaluation conducted for OU1, the basisfor the standard established by the ROD has not changed for any COC except 1,3,5-TNB, whose RfD wasincreased by a factor of 600 by EPA in 1997.

Although the basis for these cleanup standards has not changed, they may be more stringent than isrequired for the protection of human health and the environment for this OU. Table 6-3 also providespotentially acceptable alternate cleanup standards under current EPA CERCLA guidance. Standardsbased on LHAs in the ROD were adjusted by a factor of 5 consistent with

P/mlaap/5yrReview/tables-H.doc 6-9

Table 6-3: Review of OU3, Line K (NE) Groundwater Cleanup Standards (µg/L)

Chemical ofConcern

PerROD

(:g/L) Basis5 Year Update

(same methodology)

PotentiallyAcceptable

Alternative undercurrent CERCLA

guidance

Basis

INORGANIC CONSTITUENTS

Nitrate 10,000 MCL NC 10,000 NC

EXPLOSIVES COMPOUNDS

1,2-Dinitrobenzene 1 Lifetime Health Advisory NC 5 LHA x 5

2,4-Dinitrotoluene 0.5 Health Based – Cancer Risk NC 0.5 NC

2,6-Dinitrotoluene 0.5 Health Based – Cancer Risk NC 0.5 NC

HMX 400 Lifetime Health Advisory NC 2000 LHA x 5

Nitrobenzene 20 Health Based – RfD NC 20 NC

RDX 2 Lifetime Health Advisory NC 7.7 Health Based – Cancer Risk

1,3,5-Trinitrobenzene

2 Health Based – RfD 1,050Health-Based – RfD

1,050 1,050 :g/LHealth-Based – RfD

2,4,6-Trinitrotoluene 2 Lifetime Health Advisory NC 10 LHA x 5

Note: MCL – Federal Maximum Contaminant Level.Health Based – RfD – based on noncarcinogenic systemic health effects applying method of EPA (1991).Lifetime Health Advisory – EPA Office of Drinking Water Lifetime Health Advisory.LHA x 5 – Lifetime Health Advisory adjusted to the assumption that all exposure comes from drinking water.Health Based – Cancer Risk – based on carcinogenic effects with a target risk of 10-5 applying method of EPA (1991).NC – No Change in Basis since execution of the ROD.

Source: ESE.

MAAP, 5 Year Review


EPA (1991) under the assumption that the drinking water route would be the predominant exposure routefor these COCs. Note that 5 times the LHA for RDX would exceed limit required to achieve a 10-5

lifetime cancer risk, so the more stringent standard based on cancer risk has been used.

The center of the Line K plume is within 3,000 ft of the MAAP boundary, and its downgradient limit hascrossed the boundary, so there is little potential for attenuation of this plume prior to reaching theboundary. Consequently, the steady-state attenuation model used to evaluate the O-Line plume was notapplied to K Line.

Additional contaminant plume delineation is necessary since performance evaluation (HSI GeoTrans,2000) indicates that the contamination extends further north of the extraction wells than originallybelieved.

6.4.4 OU3/OU4 – Industrial Area Soil

The PRGs established for OU3/OU4 Industrial Area Soils were developed to be protective of humanhealth and the environment. Human health risks resulted in the most stringent, and therefore controlling,remediation goals. Remediation goals were established for three COCs – RDX, tetryl, and 2,4,6-TNT.The underlying toxicological information pertaining to these chemicals has not changed since executionof the ROD.

Health risk-based remediation goals were developed to protect three potential receptor groups – industrialworkers, excavation workers, and residents. Remediation goals were developed in accordance withcurrent CERCLA guidance for these receptors, accounting for cumulative exposure by the ingestion anddermal exposure routes. In addition, remediation goals were developed for soil to protect potential futureresidents from exposure via drinking water by the soil to groundwater exposure pathway. The remediationgoals established in the OU3/OU4 ROD are presented in Table 6-4.

The residential scenario is not plausible for onsite exposure because planned future use isindustrial/military. Consequently, the remediation goals developed to protect onsite residents are nolonger relevant under the potential future land use scenario. Residential exposure is possible for thesoil-to-groundwater pathway after migration of groundwater to the MAAP facility boundary. The valuespresented in the ROD, however, were based on onsite residential exposure (to onsite groundwater) sothese values were reevaluated.

6.4.4.1 Evaluation of Soil–To–Groundwater Pathway

Distribution of COCs in Industrial Area SoilsDetailed information on the horizontal and vertical distribution of soil contamination in the IndustrialArea Soils is principally limited to samples collected at Line B. These data formed the

P/mlaap/5yrReview/tables.doc.6-11

Table 6-4. Summary of Soil Risk-Based Remediation Goals, OU3/4 Industrial Area Soils

Chemical

Soil Contact Remediation Goals

(:g/g)

Soil Remediation Goalsfor Groundwater

Exposures

(:g/g)IndustrialWorker

ExcavationWorker Resident Resident

RDX 220 3,500 55 10

Tetryl 9,400 12,000 2,600 500

2,4,6-TNT 470 600 130 26

Source: ESE.

MAAP, 5 Year Review


basis for the evaluation of the soil to groundwater pathway that supported the ROD. The distribution ofcontaminants in Line B is assumed to be similar to the distribution within the other lines (A, B, C, D, E,F, G, H, K, O, X; and Z). Different lines have produced different munitions so the relative amounts of thevarious COCs may vary from line to line. On the other hand, the layout of industrial processes and thewaste handling at Line B is representative of the other lines, so the horizontal and vertical distribution ofcontamination may be expected to be similar, even if the relative amounts of the various COCs differsfrom that found in other lines. Recent assessments of contaminant delineation in groundwater at theO-Line and X Line indicate that these Lines are not similar to Line B. Both Lines exhibit much higherconcentrations of RDX in groundwater than observed at Line B, and TNT levels in groundwater at Line Xare much higher than observed at either Line B or Line O. Groundwater concentrations at Line O appearto be higher due to management of wastes in lagoons. Enhanced recharge from the lagoons caused muchhigher recharge rates than occurred at Line B. At Line X, discharge of waste to sumps may have had asimilar effect to the lagoons at Line O, causing enhanced recharge rates, however most of the lines hadsumps. Line X has been used more intensively than most other lines, so the sumps may have receivedmore discharge at Line X than at other lines.

Fifteen soil borings were completed at Line B, and samples were analyzed from the following intervals: 0to 2 ft, 5 to 7 ft, 10 to 12 ft, 15 to 17 ft, and 20 to 22 ft. COCs were detected in eight of the 15 borings.The remaining seven were uncontaminated. Additionally, 19 surface soil samples were collected. COCswere detected in 9 of the 19 surface soil samples. The sampling was biased to emphasize locations wheresoil contamination was expected. Based on the analytical results it was concluded (ROD) that 0.5 percentof the area within the Industrial Area was contaminated by the COCs. Further evaluation of the data inthis document will focus only on the locations where COCs were detected in soil. The assumption used inthe ROD that 0.5 percent of the surface area is contaminated will be adopted for this assessment.

The data were grouped into, and assumed to represent contaminant levels in, four layers:• 0 to 2 ft – 0 – 2 ft intervals in borings and all surface soil samples,• 2 to 10 ft – 5 – 7 ft intervals in borings,• 10 to 20 ft – 10 – 12 ft intervals and 15 – 7 ft intervals in borings, and• 20 to 50 ft – 20 – 22 ft intervals in borings.

These layers were defined based on the distribution of depth intervals in the available data, the observedvertical distribution of contamination, observed stratigraphy of the vadose zone, and the total thickness ofthe vadose zone (50 ft).

The average concentrations of the COCs within these layers are provided in Table 6-5. Tetryl was notdetected in Line B soils and will not be further evaluated. The concentrations of both RDX and TNTdecrease dramatically below the 0- to 2-ft interval. The concentrations of RDX are


Table 6-5. Observed Vertical Distribution of COCs in the Vadose Zone at Line B (:g/g)

Layer \ COC RDX TNT Tetryl

0 to 2 ft 10,000 ± 7,000 30,000 ± 20,000 ND

2 to 10 ft 70 ± 40 70 ± 40 ND

10 to 20 ft 50 ± 40 60 ± 60 ND

20 to 50 ft 40 ± 30 10 ± 9 ND

Values are arithmetic means ± standard errors (standard deviation ÷ N1/2). ND – Tetryl was not detected in Line B soils.

Source: ESE.

MAAP, 5 Year Review


nearly uniform from 2 to 50 ft, while the concentration of TNT appears to be uniform from 2 to 20 ft, thendecline significantly below 20 ft.

Chemical Saturation Potential of COCs in Vadose Zone SoilsTo gain a better understanding of the observed concentrations, ESE estimated the chemical saturationpotential of the soil with respect to these COCs. The chemical saturation potential, Csat, of soil is theconcentration of the COC that results when the soil moisture is at the aqueous solubility and the solidphase is at chemical equilibrium with the moisture. Where observed concentrations exceed Csat, it can beassumed that the COC is present as a separate organic phase. The COCs are solids at environmentaltemperatures, so the separate phase would consist of crystalline particles within the soil pores.

For semi-volatile compounds, such as the COCs, the chemical saturation potential (mg/kg or :g/g) isgiven by (EPA, 1996, or ASTM, 1995):

6-1

where: Sol = solubility of COC in water (mg/L),Kd = adsorption coefficient (L/kg),nw = volumetric moisture content of soil (L/L), andp = dry bulk density of soil [kilograms per liter (kg/L)].

Soil PropertiesSoil properties were estimated using a combination of site-specific data and representative characteristicsof soils of similar texture. Site-specific data were used to estimate foc (ESE has analyzed 13 vadose zonesamples ranging in depth from 2 to 42 ft for foc; USCS, 1984 and USCS, 1994 provide site-specific dataon foc in surface soils). Bulk density and moisture retention properties were assumed to be similar to othersoils of the same type/texture. Plausible ranges for these values are shown below:

Interval Soil Type foc nw D

0 – 2 ft -- CL or SC -- 0.003 < 0.011 0.23 < 0.54 1.22 – 10 ft -- SC or ML -- 0.001 < 0.003 0.23 < 0.54 1.210 – 20 ft -- SM or SP -- 0.0011 < 0.0015 0.22 < 0.49 1.3520 – 50 ft -- SM or SP -- 0.0011 < 0.0015 0.05 < 0.35 1.7

MAAP, 5 Year Review


Chemical-Specific Properties for TNT and RDXSolubility – Three literature sources were reviewed for solubility of the COCs – Layton et al. (1987) andAgency for Toxic Substances and Disease Registry [(ATSDR) 1995a, 1995b]. The average of thereported values for TNT is 127 ± 4, and for RDX is 47 ± 7.

Kd—For organic COCs, Kd is usually assumed to be proportional to the soil organic carbon

Kd = Koc foc

content foc (kg/kg):6-2

where: Koc = adsorption coefficient to soil organic carbon (L/kg).Koc of RDX and TNT has been measured experimentally in 18 different soils, as summarized by Layton,et al. (1987). The average Koc observed for RDX was 130 ± 30, and for TNT, 900 ±200.

Below 2 ft at this site, foc is generally less than 0.003. At low foc, Tucker et al. (1985) found that theadsorption coefficients of TNT and RDX did not follow the relationship expressed in Equation 6-2.Specifically, they found a non-zero intercept, i.e., for RDX, Kd = 0.61 + 48 foc; and for TNT, Kd = 2.2 +210 foc. At an foc of 0.001, application of Equation 6-2 yields Kd of 0.13 ± 0.03 for RDX and 0.9 ± 0.2 forTNT, while the equations derived by Tucker et al. (1985) provide a Kd of 0.7 ± 0.4 for RDX and 2.4 ± 1.8for TNT. The Tucker et al. (1985) equations imply that, at very low organic carbon content, sorbentsother than organic carbon (e.g., clays) become relatively more important as adsorption sites for theexplosives compounds, presumably because there is so little organic material available.

Estimation of Csat

The parameters defined above were applied in Equation 6-1 to estimate Csat for each of the layers.Alternative estimates were made using Equation 6-2 or the Tucker et al. (1985) equations for Kd. Resultsare presented, and compared to the observed concentrations, in Table 6-6. These results are alsoillustrated in Figs. 6-1 (RDX) and 6-2 (TNT). Propagated errors were evaluated by methods summarizedby Lyman et al. (1982).

For both COCs, the observed concentrations in the 0 to 2 ft interval are much greater than Csat. This canonly occur where crystalline explosives are present within the soil pores. The fine particles of TNT, RDX,or a mixture of the two, cannot migrate downward through the soil profile. Consequently, this conditionoccurs only in the 0- to 2-ft interval. Below 2 ft, the vertical distribution of RDX, relative to its Csat, isdifferent from the pattern for TNT.

Below 2 ft, the observed concentrations of RDX are approximately equal to the Csat values in each layer.Although the Tucker et al. (1985) formula for Csat (Kd) matches the observed distribution somewhat moreclosely than the Koc (Equation 6-1) values, both estimates of Csat are

P/mlaap/5yrReview/tables-H.doc 6-16

Table 6-6. Comparison of Observed Soil Concentrations with Csat

LAYER

RDX TNT

ObservedCsat, Kd fromEquation 1

Csat, Kd fromTucker, et al,

(1985) ObservedCsat, Kd fromEquation 1

Csat, Kd fromTucker, et al,

(1985)

0 to 2 ft 10,000 ± 7,000 60 ± 30 60 ± 20 30,000 ± 20,000 800 ± 500 500 ± 300

2 to 10 ft 70 ± 40 30 ± 15 50 ± 20 70 ± 40 300 ± 200 400 ± 200

10 to 20 ft 50 ± 40 19 ± 6 40 ± 20 60 ± 60 160 ± 50 300 ± 200

20 to 50 ft 40 ± 30 13 ± 5 40 ± 20 10 ± 9 140 ± 50 300 ± 200

Notes: All concentrations in (:g/g).

Source: ESE.

MAAP, 5 Year Review


equivalent to the observed concentrations, considering the overall uncertainties, as represented by theerror bars in Fig. 6-1. From these comparisons, it can be concluded that the soils are at their chemicalsaturation potential, and are expected to generate leachate at the solubility limit of RDX (i.e., 47 mg/L).

• The observed concentrations of TNT, on the other hand, are consistently lower than the estimatedCsat values, even after accounting for the potential errors in the estimates. The concentrations ofTNT in soil decline consistently with depth, both in the actual concentrations and in the ratio ofthose concentrations to Csat. The latter ratio is important because the concentration of TNT inleachate can be estimated as that ratio times its solubility. In the 2- to 10-ft interval and the 10- to20-ft intervals, the actual concentrations are approximately 20 percent of Csat; while in the 20- to50-ft interval, the observed concentrations are less than 10 percent of Csat. The reductions withdepth could be due to two factors:

• TNT has not had sufficient time to migrate downward through the soil column, in which case theconcentrations could increase with time (if no further action); or TNT is degrading in the vadosezone, in which case concentrations might stay constant.

Consequently, it is useful to evaluate the time for RDX and TNT to migrate downward through the soilcolumn. The depth of penetration of a front of contamination through a homogeneous soil layer can beestimated by:

Depth (ft) =Infiltration Rate (ft / yr) × Time (yr)

6-3Effective Porosity × Retardation Factor

In the Offsite Groundwater RI, ESE (1999) estimated the infiltration rate within the RutherfordFork/Obion River watershed at 1 to 6 inches per year, with a best estimate of 3.5 inches per year. ERM(1993) estimated the infiltration rate at 9.5 inches/year. ICF Kaiser (1999) estimated infiltration underditches, which are areas with known or suspected soil/sediment contamination, of 24 inches/year. Thedivergence in these values indicates that the infiltration rates are not well defined. Historical watermanagement practices may have also caused higher infiltration rates in portions of the Industrial Areathan the rates that may be occurring today.

Under unsaturated flow conditions, the effective porosity of the vadose zone is estimated to beapproximately 0.15. As a result, the vertical migration of water through the vadose zone would beapproximately 7 times the infiltration rate.

The migration of TNT and RDX through the vadose zone would be retarded due to adsorption. TheRetardation Factor is given by (1 + D Kd/n), where n is total porosity. Using the Tucker et al. (1985)method for Kd yields retardation factors for the four soil layers as follows:

MAAP, 5 Year Review


RDX TNT0 to 2 ft 3 92 to 10 ft 3 710 to 20 ft 3 820 to 50 ft 4 13

Table 6-7 presents estimates of the depth of penetration of RDX and TNT during the 50-year history ofindustrial operations at MAAP under various hypothetical infiltration rates. The results in Table 6-7indicate that the lower range of infiltration rates reported by ESE (1999) are not consistent with theobserved distribution of RDX, which has penetrated 50 ft to the water table from areas away from ditches.Only the highest infiltration rates, appropriate for recharge from ditches, allow TNT to migrate to thewater table during the history of the facility. Higher recharge rates are also likely under the O Linelagoons and X Line sumps. Consequently, the observed distributions of RDX and TNT are consistentwith watershed-wide infiltration rates of 6 to 10 inches per year, with enhanced recharge under the ditchesand sumps. It is possible that recharge of TNT to the aquifer would increase with time if no further actionwere taken. Although biodegradation of TNT may be occurring in the vadose zone, the observeddistribution of TNT is consistent with that of an adsorbing, but nondegrading, constituent.

Implications for Effectiveness of Soil RemediationThe ongoing soil remediation is intended to reduce soil concentrations of TNT, RDX, and tetryl to theremediation goals listed in Table 6-4 through the upper 10 ft of soil. When this has been accomplished,the lower 40 ft of the vadose zone may continue to generate leachate for a considerable period of time.The mass of COCs per unit area [micrograms per square centimeter (:g/cm2)] is given by:

Mass / Area = Cs × D × T 6-4

where: Cs = concentration of COC in soil (:g/g), andT = thickness of soil layer [centimeter (cm)].

Table 6-8 shows the mass of TNT and RDX within each soil layer after completion of the ongoing remediation. Upon completion of the remedial action, approximately 95 percent of the remaining RDX will be in the 10 to 50 ft interval, and approximately 80 percent of the total TNT. The remaining deep contamination of RDX will be generating leachate at the solubility limit of 47 mg/L [47 micrograms per cubic centimeter (:g/cm3)]. At an infiltration rate of 9.5 inches per year = 24 centimeters per year (cm/yr), leaching will remove 1,100 micrograms per square centimeter per year (:g/cm2/yr). With a total mass remaining of 88,000 :g/cm2 (Table 6-8), it will takeapproximately 80 years (88,000 :g/cm2 ÷ 1,100 :g/cm2/yr) for leaching to remove the remaining RDX from the soil column. During most of those 80 years, the leaching rate will


Table 6-7: Depth of Contaminant Penetration Through the Vadose Zone Under Various Infiltration Rates

Possible Infiltration Rates Depth of Penetration, RDX Depth of Penetration, TNT

(in/yr) (ft) (ft)

Reported Rates Outside of Ditches

1 9 3

3.5 29 13

6 43 21

9.5 > 50 29

Reported Rate in Ditches

24 > 50 > 50

Source: ESE.


Table 6-8. Mass of COCs Remaining in Soil Column After Completion of Remedial Action (:g/cm2)

LAYER RDX TNT

0 to 2 ft 700 1,800

2 to 10 ft 2,900 7,300

10 to 20 ft 21,000 25,000

20 to 50 ft 63,000 16,000

Total Mass in Vadose Zone 88,000 50,000

Source: ESE.

MAAP, 5 Year Review


remain approximately the same, limited by the solubility, as infiltrating rainwater moves throughchemically saturated soils.

With respect to TNT, it is less obvious what the future leachate concentrations will be. It is estimated thatthe present-day leachate quality percolating to the water table is approximately 3 percent of the solubility(since observed concentrations in the lower layer are about 3 percent of Csat). At the solubility of 127mg/L, leachate quality is estimated to be 4 mg/L. It is possible that this could increase toward the ratioobserved in the 10 to 20 ft layer of 20 percent, which would lead to leachate levels of 25 mg/L. For thepurpose of the simple mass balance calculations, it is assumed that the average leachate concentrationswill be 15 mg/L. Applying the same infiltration rate of 24 cm per year, TNT will be removed from thevadose zone at an average rate of 360 :g/cm2/yr. With 50,000 :g/cm2 remaining in the soil column aftersoil remediation (see Table 6-8), it would take 140 years to remove this contamination via leaching.During that time, groundwater concentrations would be expected to be stable or increasing.

Remediation targeted at source removal to protect the groundwater resource should be reevaluated. Itappears that deeper portions of the vadose zone may need to be addressed, or the groundwater remedialactivities may be extended for an excessive duration.

On the other hand, the soil remediation goals were designed to produce drinking water quality ingroundwater within the installation. Probable future use of the installation for military/industrial usesuggests that it is not necessary to meet this objective.

ESE has applied methods used to develop the EPA Soil Screening Levels (EPA, 1996) and the steadystate groundwater attenuation model to estimate soil concentrations in the lines that could result inachievement of human health risk-based groundwater objectives at the MAAP boundary. The modeladopts the assumption used in the ROD that Line B is representative of other lines in the NorthernIndustrial Area, with the exception of the X Line where historical discharge to sumps has apparentlycaused TNT to penetrate deeper through the vadose zone with resultant higher concentrations of TNTthan observed in the other lines. At Line X the current model assumes that leachate concentrations ofTNT are 10 times higher than at the other lines. The infiltration rate was assumed to be 7 inches/year, thelowest rate that results in RDX penetration through the full vadose zone. Aquifer thickness, hydraulicconductivity, hydraulic gradient, and dispersivities are the same as the values used for OU1 (see Sec.6.4.1.2). Plume thickness at the source and the concentration in the source area were calculated byformulas used by EPA (1996; Soil Screening Levels User’s Guide). Kd was estimated using the formulasof Tucker et al. (1985). ASTM (1995) steady-state attenuation model was used to predict concentrationsfrom each Line to the nearest downgradient boundary. Where plumes from more than one line overlap atthe boundary, the contributions from overlapping plumes were added.

MAAP, 5 Year Review


The model predicts concentrations of RDX in source areas of approximately 3,000 :g/L in source areasand a maximum concentration at the boundary of 1,300 :g/L downgradient of the X Line at current soilconcentrations. Maximum concentrations predicted at the MAAP north boundary under currentconditions are approximately 400 :g/L. These results are consistent with observations. Maximum RDXconcentrations downgradient of O-Line are considerably higher than the model estimated value at thatlocation, but the observed concentrations are believed to represent historical recharge conditions from thelagoons when they were active, and not a response to current leachate/recharge conditions. The modelpredicts maximum concentrations of TNT in source areas of approximately 3,000 :g/L at the X Line andmaximum concentrations at the MAAP boundary downgradient of X Line of approximately 1,300 :g/Lunder current leachate generation conditions. Maximum TNT concentrations under the other lines areestimated to be about 300 :g/L, and the maximum concentrations predicted at the north boundary ofMAAP is approximately 100 :g/L, and these results are also in general agreement with observations.

The model has been applied to estimate concentrations of TNT and RDX that must be achievedthroughout the vadose zone that would result in attainment of risk-based standards in groundwater at thefacility boundary, discounting any effect of groundwater remediation systems. The risk-based targets forgroundwater quality at the boundary are 77 :g/L for RDX at the western boundary, 7.7 :g/L for RDX atthe northern boundary, and 10 :g/L for TNT. The risk-based target concentration for groundwater at thewestern boundary is higher than at the northern boundary because the western boundary is supplied withpotable water by the City of Milan. This limits exposure potential. Since RDX is the principalcarcinogenic COC in groundwater at the boundary, a risk-based standard based on 10-4 lifetime cancerrisk is appropriate at the western boundary. The north boundary is not serviced by the City of Milan, andresidents would obtain potable supply from wells in the water table aquifer. The nearest point of potentialexposure to groundwater north of MAAP is more than ½ mile north of the northern boundary of thefacility, because the area is undeveloped and in the flood plain of the Rutherford Fork of the Obion River.During transport to the nearest potential exposure point, the plume is expected to migrate to deeperportions of the Memphis Sand Aquifer, below the typical completion depths of private wells in the area. Ifthis assumption can be documented by further investigation, then groundwater at the north boundarycould be contaminated to a level equivalent to 10-5 cancer risk, without resulting in actual or potentialexposures above the NCP and TDEC risk target of 10 -6.

Groundwater affected by Lines A, B, D, E, F, G, X, and Z migrates to the western boundary, andgroundwater affected by Lines C, H, K, and O migrates to the northern boundary. Model application(see App. F) indicates that concentrations of RDX throughout the vadose zone must be reducedto 2 :g/g under Lines A, B, F, G, X, and Z to achieve the risk-based standards at the boundary,discounting the effects of any groundwater remediation systems. Lines D and E do not contributeto exceedances of risk-based standards for RDX in groundwater at the MAAP boundary undercurrent conditions, so the controlling RDX cleanup standard at Lines D and E

MAAP, 5 Year Review


would be the Industrial Worker Soil Contact Remediation Goal, identified in the ROD as 220 :g/g.Further investigation of the soil-to-groundwater pathway and the effect of specific source areas on theoverall pattern of groundwater contamination are needed, however, to determine the most cost-effectivestrategy that would be protective of human health and the environment.

Application of the model to TNT indicates that soil concentrations throughout the vertical extent of thevadose zone would have to be reduced to approximately 1 :g/g to achieve risk-based groundwater qualityobjectives at the MAAP boundary. TNT Concentrations could be higher, up to 2 :g/g, at Lines D and E,which experience greater dilution/attenuation during migration to the boundary.

The model used for RDX in groundwater in this assessment incorporated biodegradation with a half-lifeof 20 years. This rate is supported by evidence presented in the off post groundwater RI (ESE, 1999).Biodegradation was not incorporated in the model for TNT in groundwater because a site-specificbiodegradation rate for TNT is not available. It is likely that TNT also biodegrades slowly in groundwaterat the site. If the half-life of TNT in groundwater is 20 years, the cleanup standards for TNT at Lines C,H, K, and O could be increased to 3 :g/g, and the soil cleanup objectives for TNT at Lines D and E couldbe increased to 35 :g/g.

Contaminated vadose zone soils below the O-Line lagoons have been capped, reducing recharge rate tonegligible amounts. These soils may still contribute to groundwater contamination due to water tablefluctuations. The current model does not specifically account for the effect of the O-Line lagoons ongroundwater quality, but addresses only the portion of the O-Line industrial area that is similar to B Line.

The groundwater model that was applied in this 5-year review may not be sufficiently accurate to be thesole or even primary basis for setting cleanup objectives for industrial area soils. However, the overallassessment of conditions in the vadose zone and the predictable effects of vadose zone contaminants ongroundwater quality suggest that the planned remedial actions may not be completely effective ineliminating the sources of RDX and TNT to groundwater. Remediation of the upper 10 ft of the vadosezone may not result in a significant improvement in groundwater quality for approximately 100 years.Groundwater extraction and treatment systems or institutional controls may be required to be operatingand effective over the next century to protect human health. Cost effectiveness of the planned soilremediation action should be reviewed with consideration of the necessity to continue groundwaterinterception and treatment for an extended duration. Alternatively, a more aggressive in situ vadose zonetreatment could reduce the operation lifetime of associated groundwater systems.

MAAP, 5 Year Review


7.0 Recommendations

7.1 OU1 – O-Line Groundwater

It was noted in the Capture Zone Verification at Milan O-Line Ponds Groundwater Treatment SystemReport (HSI GeoTrans, 1999) that although the capture zone analysis indicated that all the area within theprojected 10-:g/L plume is captured and the capture zone extends approximately 400 ft north of theextraction system, “the northernmost of the extent of the plume in unknown.” The followingrecommendations are suggested for OU1:

1. The OU1 groundwater explosives plume should be better defined through additional monitoringand additional extraction wells added and/or optimized if the capture zone is not adequate.

2. A final remedy ROD should be prepared for OU1 to specifically address conditions under whichthe remedial action could be discontinued (i.e. the treatment system shut down).

3. New groundwater technologies should be utilized to cleanup OU1 groundwater, if they bettermeet NPL evaluation criteria than the current remedy.

4. A sampling method and plume concentration limits should be developed to determine theeffectiveness of the treatment system.

7.2 OU2 – O-Line Ponds Soil

The remedy is operating as designed and should continue to achieve its remediation goals as long as thepost-closure requirements and O&M activities are fulfilled. The following recommendations aresuggested for OU2:

1. If a treatment technology with a permanent solution to soil contamination is available and bettermeets the NCP criteria, that technology should be utilized (e.g., in situ soil treatment).

2. Additional data should be collected to determine if contaminants are being flushed out of thevadose zone soils into the groundwater by a fluctuating water table.

7.3 OU3 – Northern Boundary Groundwater

The remedy technology is operating as designed. However, a capture analysis indicates that a contaminantplume north of the extraction system (wells P101A and P101B) is not being captured by the extractionsystem and the contaminants flowpath and eventual discharge point is uncertain. The followingrecommendations are suggested:

1. Install additional groundwater monitor wells for performance monitoring at OU3. Sample andanalyze those wells and other existing wells for explosive compounds and define thegroundwater plume(s).

MAAP, 5 Year Review


2. Determine if additional extraction wells are needed to capture the OU3 explosive compoundsgroundwater plume. Also, the depths, screen intervals, and locations of existing extraction wellsshould be optimized for minimal extraction of clean water.

3. Identify and sample residential wells for explosive compounds that are located across theRutherford Fork (and down-gradient) from OU3 during future residential well sampling efforts.

4. Utilize innovative technologies, if available and cost-effective, that could provide better andquicker remediation of OU3 contaminant sources.

5. A groundwater model of the contaminant plume should be updated with additional data todetermine future risk, if any, to groundwater users north of the installation boundary.

7.4 OU3 and OU4 – Northern Industrial Area Soil

The remedy technology appears to be effective. However, until the remedy is implemented on a full-scalebasis, an overall assessment of the remedy can not be made. It is recommended that if the treated soil isnot a risk to human health and the environment, that its reuse be considered.

Consideration should be given to evaluate innovative soil treatment technologies that could effectivelyreduce contaminant concentration in that portion of the vadose zone between 10 ft-bls and the water table.Information presented in Sec. 6.4.4 shows the current remedy; although effective in reducing contaminantconcentrations in the upper 10 ft of soil, it may be ineffective in protecting groundwater. The deepercontaminated soils are expected to leach contaminants for the next 80 to 140 years. This would requirethat existing and new groundwater treatment systems operate an inordinate period of time. The analysisreported in Section 6.4.4 is still quite uncertain, and current information is insufficient to recommendalternative cleanup standards or any modification to the ROD. Additional investigation of the site-specificeffects of soil explosives on groundwater quality is recommended. Because Line X appears to have thegreatest effect on offsite groundwater quality, initial investigation should be targeted on thesoil-to-groundwater pathway at Line X.

MAAP, 5 Year Review


8.0 Protectiveness Statement


This selected remedy for OU1 Groundwater has undergone an initial 5-year review. No majordeficiencies were noted which detract from the ability of the selected remedy to protect human health andthe environment. While the remedial action is still underway, the remedy remains protective of humanhealth and the environment through extraction, treatment, and re-injection of groundwater in the affectedaquifer. Treatment of the groundwater continues to effectively reduce risk from exposure to thegroundwater as well as further migration of the explosives contaminated groundwater.

Upon completion of the remedial action, the remedy is expected to meet the requirements of the ROD toensure protectiveness.

NameRegional AdministratorEPARegion IV

Date

MAAP, 5 Year Review



This selected remedy for OU2 Soil has undergone an initial 5-year review. No deficiencies were notedwhich detract from the ability of the selected remedy to protect human health and the environment. Whilethe remedial action is still underway, the remedy remains protective of human health and the environmentthrough prevention of stormwater leaching of explosive contaminants from the unsaturated soil into thegroundwater and offsite into surface water. Although this remedy is not permanent, the naturalattenuation and degradation of explosives in soil, along with continued groundwater treatment at OU1may provide additional protection to human health and the environment.



Date

MAAP, 5 Year Review



The selected remedy has undergone an initial 5-year review. While the remedy is still underway, theremedy remains protective of human health and the environment through the extraction, treatment, andsurface discharge of the treated groundwater. Although treatment of the groundwater continues toeffectively reduce exposure to the groundwater, additional plume delineation and optimization of theextraction well network is necessary.



Date

MAAP, 5 Year Review



This selected remedy for OU3 and OU4 soil has undergone an initial 5-year review. No majordeficiencies were noted which would detract from the ability of the selected remedy to protect humanhealth and the environment, if soils can be removed to risk-based goals. While the remedy has not beenimplemented on a full-scale basis, the remedy remains protective of human health and the environmentthrough excavation, treatment via bioremediation and disposal in a Subtitle D solid waste landfill.Treatment (or capping, if exercised) of the explosives-contaminated soil should continue to effectivelyreduce the risk from exposure, as well as prevent further migration of the explosive compounds in the soilinto the groundwater via infiltration, if the soils can be removed to risk-based goals.



Date

MAAP, 5 Year Review


9.0 Next Review


As the continued implementation of the selected remedy results in hazardous substances remaining onsiteabove health based levels, a review will be conducted 5 years after commencement of this review toensure that this remedy continues to provide protection of human health and the environment.


See Sec. 9.1.


See Sec. 9.1.


See Sec. 9.1.

MAAP, 5 Year Review


10.0 References

Albright, J. and Walter, L.D. 1994. Record of Decision, Interim Remedial Action, Operable Unit 3, MilanArmy Ammunition Plant Northern Boundary Groundwater.

Albright, J.W. and Fatz, R.J. 1995. Record of Decision, Operable Units 3 and 4, Milan Army AmmunitionPlant, Northern Industrial Area Soil.

American Society for Testing and Materials (ASTM). 1995. Standard Guide for Risk-Based CorrectiveAction Applied at Petroleum Release Sites. ASTM Designation E 1739-95.

Agency for Toxic Substances and Disease Registry (ATSDR). 1995b. Toxicological Profile for TNT.

Agency for Toxic Substances and Disease Registry (ATSDR).1995a Toxicological Profile for RDX.

Crumpler, E.B. and Walker, L.D. 1993. Record of Decision, Milan Army Ammunition Plant O-Line PondsArea Soil, Sediment, and Surface Water, Operable Unit 2.

Crumpler, E.B. and Walker, L.D. 1992. Interim Action Record of Decision, Milan Army AmmunitionPlant O-Line Ponds Groundwater, Operable Unit 1.

Cushing, E.M., Boswell, E.H., and Hosman, R.L. 1964. General Geology of the Mississippi Embayment.Water Resources of the Mississippi Embayment. Geological Professional Paper 448-B. U.S.Government Printing Office, Washington, DC.

Environmental Science & Engineering, Inc. (ESE). 1997. Final Residential Well Survey Report. Preparedfor the U.s. Army Environmental Center, Aberdeen Proving Ground, MD.

Environmental Science & Engineering, Inc. (ESE). 1997. Offsite Groundwater Remedial Investigation,Milan Army Ammunition Plant. Draft. Prepared for the U.S. Army Environmental Center,Aberdeen Proving Ground, MD.

Environmental Resources Management, Inc. (ERM). 1995. Final Milan Army Ammunition PlantRemedial Investigation, OU4 Northern Study Area. ELIN AO13. Prepared for the U.S. ArmyEnvironmental Center, Aberdeen Proving Ground, MD.

MAAP, 5 Year Review


Environmental Resources Management, Inc. (ERM). 1993. Milan Army Ammunition Plant RemedialInvestigation Follow-On Site Characterization Report, Northern Study Area, Draft. Prepared forthe U.S. Army Environmental Center, Aberdeen Proving Ground, MD.

HSI GeoTrans, Inc. 1999. Capture Zone Verification at Milan O-Line Ponds Groundwater TreatmentSystem. Prepared for American Ordnance, TN.

HSI GeoTrans, Inc. 2000. Capture Zone Verification at the OU3 Northern Boundary GroundwaterTreatment System. Prepared for The IT Group, CA.

ICF Kaiser Engineers, Inc. (ICF). 1991. Remedial Investigation for Milan Army Ammunition Plant.Prepared for the U.S. Army Environmental Center. Aberdeen Proving Ground, MD.

ICF Kaiser Engineering, Inc. (ICF). 1999. Performance Evaluation of Operable Unit One GroundwaterTreatment Plant. Prepared for the U.S. Army Corps of Engineer, Mobile District, AL.

Layton D., B. Mallon, W. Mitchell, L. Hall, R. Fish, L. Perry, G. Snyder, K. Bogen, W. Malloch, C. Ham,and P. Dowd. 1987. Conventional Weapons Demilitarization: A Health and EnvironmentalEffects Data Base Assessment: Explosives and Their Co-Contaminants, prepared by LawrenceLivermore National Laboratory for U.S. Army Medical Research and Development Command.AD-A220 588. AD UCRL-21109.

Lyman, W.J., W.F. Reehl, and D.H. Rosenblatt. 1982. Handbook of Chemical Property EstimationMethods. McGraw-Hill, New York.

Parks, W.S. and Russell, E.E. 1975. Stratigraphy of the Outcropping Upper Cretaceous, Paleocene, andLower Eocene in Western Tennessee (Including Descriptions of Younger Fluvial Deposits).State of Tennessee, Department of Conservation, Division of Geology, Bulletin 75.

Parks, W.S. and Carmichael, J.K. 1990b. Geology and Ground Water Resources of the Memphis Sand inWestern Tennessee. U.S. Geological Survey Water Resources Investigations Report 88-4182.U.S. Government Printing Office, Washington, DC.

Parks, W.S. and Carmichael, J.K. 1990a. Altitude of Potentiometric Surface, Fall 1985, and HistoricWater-Level Changes in the Memphis Aquifer in Western Tennessee. U.S. Geological SurveyWater-Resources Investigation Report 88-4180.

MAAP, 5 Year Review


Tucker, W.A., Dose, E.V., Gensheimer, G.J., Hall, R.E., Koltuniak, D.N., Pollman, C.D., and Pollman,D.H. 1985. Evaluation of Critical Parameters Affecting Contaminant Migration Through Soils.Presented at the National Environmental Engineering Conference of the American Society ofCivil Engineers. Boston, MA. July 1-3; also DOD report of same title, Report No.AMXTH-TE-TR-85030.

U.S. Army Toxic and Hazardous Materials Agency (USATHAMA). 1982. Milan Army Ammunition PlantContamination Survey. Report DRXTH-FS-FP-82131. Pugh, D.L.: Envirodyne Engineers.January 1982.

U.S. Environmental Protection Agency (EPA). 1991. Risk Assessment Guidance for Superfund (RAGS).Volume 1: Human Health Evaluation Manual, Part B (Development of Risk-Based PreliminaryRemediation Goals). Office of Emergency and Remedial Response, Washington, DC. OERR9285.7-01B.

U.S. Environmental Protection Agency (EPA). 1996. Soil Screening Guidance: User’s Guide.EPA/540/R-96/018. PB 96-963505.

U.S. Environmental Protection Agency (EPA). 1997. Supplemental Guidance to RAGS: Region 4Bulletins. Waste Management Division, Office of Health Assessment, EPA Region IV, Atlanta,GA. June 1997.

U.S. Army Toxic and Hazardous Materials Agency (USATHAMA). 1978. Installation Assessment ofMilan Army Ammunition Plant. Report No. 122. June 1978.

U.S. Environmental Protection Agency (EPA). 1998. NPL Sites Record of Decision 5-Year ReviewGuidance (Second Interim Draft).

U.S. Army Toxic and Hazardous Materials Agency (USATHAMA). 1991. Milan Army Ammunition PlantRemedial Investigation Report. Okusu, N. et al: ICF Technology, Inc., Fairfax, VA. December1991.

U.S. Army Environmental Hygiene Agency (USAEHA). 1978. Potable/Recreational Water QualitySurvey No. 31-24-0163-79, Milan Army Ammunition Plant. March 28, 1978.

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

MAAP, 5 Year Review


U.S. Environmental Protection Agency (EPA). 1991b. Risk Assessment Guidance for Superfund (RAGS).Volume 1: Human Health Evaluation Manual, Supplemental Guidance (Standard DefaultExposure Factors). Interim Final. Office of Emergency and Remedial Response, Washington,DC. OSWER Directive 9285.6-03.

U.S. Environmental Protection Agency (EPA). 1996. Risk-Based Concentration Table, January-June1996. Prepared by R.L. Smith, Technical Support Section, EPA Region III, Philadelphia, PA.April 18, 1996.

U.S. Army Environmental Center (USACE). 1994. Milan Army Ammunition Plant Northern BoundaryGroundwater, Focused Feasibility Study, Final Document. Contract No. DAA15-91-D-0014.