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ATSDR Agency for Toxic Substances and Disease Registry
BRAC Base Realignment and Closure
CDC Centers for Disease Control and Prevention
CERCLA Comprehensive Environmental Response, Compensation and Liability Act of 1980
CREG Cancer Risk Evaluation Guides
CV comparison value (ATSDR)
DDD p,p'-dichlorodiphenyldichloroethane
DDE p,p'-dichlorodiphenyltrichloroethene
DDMT Defense Depot Memphis Tennessee
DDT p,p'-dichlorophenyltrichlorothane
DEHP bis(2-ethylhexyl)phthalate
DLA Defense Logistics Agency
EMEG Environmental Media Evaluation Guides
EPA U.S. Environmental Protection Agency
HOD Health Outcome Data
LTHA Lifetime Health Advisory
MCL Maximum Contaminant Level (for safe drinking water)
MLG&W Memphis Light, Gas and Water
NCEH National Center for Environmental Health (CDC)
NPL National Priorities List
OUs operable units
PAH(s) polynuclear aromatic hydrocarbons
PCP pentachlorophenol
PHA(s) public health assessment(s)
PHAP Public Health Action Plan
ppb parts per billion
ppm parts per million
RCRA Resource Conservation and Recovery Act
RI Remedial Investigation
RMEG Reference Media Evaluation Guide
SARA Superfund Amendments and Reauthorization Act of 1986
SVOCs semi-volatile organic compound(s)
TDEC Tennessee Department of Environment and Conservation
TDH Tennessee Department of Health
ug/l micrograms per liter (equals parts per billion)
USACDP U.S. Army Chemical Demilitarization Program
VOC(s) Volatile Organic Compounds


Over 90% of the land area within DDMT is graded and developed. Extensive modification has occurred, including the addition of fill material.

Regionally, the stratigraphy of this area includes, from the land surface downward, loess, fluvial deposits, Jackson Formation\Upper Claiborne Group clays and the Memphis Sand Aquifer. The surface sediments are glacially-derived loess, a fine-grain sediment consisting of silty clay, to fine sandy clayey silt. This loess ranges in thickness from six to forty feet. Although not a primary water-bearing unit, following rainfall, the loess may briefly contain perched water-bearing zones.

Fluvial (river-derived sediment) deposits underlie the loess. These consist of clayey sand to gravelly sand, and range in thickness from 40 feet to about 131 feet. These sediments comprise the shallow watertable aquifer. It is this aquifer that is contaminated by chemicals from DDMT. The fluvial aquifer is not believed to discharge to surface waters in the area of DDMT. Groundwater flow in the DDMT area is in two general directions. As stated in the 1995 CH2M Hill report: "In the Dunn Field area, a westerly direction of flow is apparent in the installation's shallow aquifer...". " At the Main Installation, a different flow regime is suggested by water level data...". "The closure of water level contours around MW-34 and STB-8 suggests that groundwater flow in this area is directed toward what may be a 'sink' or buried stream channel of poorly defined proportions...the flow is to the west." Current information supports that a general west to northwest groundwater flow is indicated for the rest of the Main Installation.

The Jackson Formation\Upper Claiborne Group underlies the fluvial deposits. Regionally, these sediments comprise a significant confining unit separating the shallow, fluvial aquifer from underlying major aquifers. Thickness of this unit ranges from 15 to about 92 feet in the area. This confining layer appears to extend across DDMT and vicinity. Although this is the case, as suggested above, evidence suggests that erosion of this unit may have resulted in stream channels or sinks in its surface that may allow leakage.

The Memphis Sand Aquifer is composed of fine to gravelly sand ranging in thickness from 500 to 890 feet. This is the primary source of water for the area, providing about 95 percent of the water supplies for the Memphis area. Most of the recharge to this aquifer is provided by outcroppings several miles to the east of DDMT. Water in this aquifer is under artesian conditions, Water in this aquifer is under regionally artesian conditions, which means that in many areas, however, as the Tennessee Department of Environment and Conservation (TDEC) points out, a local water level depression exists, indicating a negative head near the DDMT. This negative head is attributed to the presence of the Allen Well Field to the west. The presence of the local depression in the water level in the DDMT areas could be due to leakage from the fluvial aquifer into the deeper aquifer. The remainder of the local water supply is provided by the deeper Fort Pillow Sand aquifer, from a depth of about 1,400 feet.


Law Environmental, 1990, Defense Depot Memphis Tennessee (DDMT) Remedial Investigation Final Report, for U.S. Army Corps of Engineers, Huntsville Division, August 1990.

CH2M Hill, 1995, Defense Distribution Depot Memphis, Generic Remedial Investigation/Feasibility Study Work Plan Draft Final, March 1995.

English, Jordan, 1995, Tennessee Department of Environment and Conservation, Comments RE: Draft of the Public Health Assessment for Defense Depot, Memphis, TDFS#79-736, cc82, August 11, 1995.


The conclusion that a contaminant exceeds the CV does not mean that it will cause adverse health effects. CVs are contaminant concentrations in specific media that are used to select contaminants for further evaluation to determine the possibility of adverse public health effects.

Action Level

    An EPA Action Level is the contaminant concentration that is high enough to warrant action (such as water treatment) under CERCLA.

Background concentrations

    Background concentrations for the state, region, or nation can be used for comparison, when background samples for the medium of concern, such as soil, have not been collected and when other comparison values do not exist. Background concentrations can be used provided the medium has the same basic characteristics as the medium of concern at the site.

Cancer Risk Evaluation Guides (CREGs)

    CREGs are estimated contaminant concentrations that would be expected to cause no more than one excess cancer in a million (10E-6) persons exposed over a lifetime. CREGs are calculated from EPA's cancer slope factors (CSFs).

Environmental Media Evaluation Guides (EMEGs)

    EMEGs are based on ATSDR minimal risk levels (MRLs) and factor in body weight and ingestion rates. An EMEG is an estimate of daily human exposure to a chemical (in mg/kg/day) that is likely to be without an noncarcinogenic effects over a specified duration of exposure to include acute, intermediate, and chronic exposures.

Lifetime Health Advisory (LTHA)

    An LTHA represents contaminant concentrations that EPA considers protective of noncarcinogenic health effects during a lifetime (70 years) of exposure. Drinking water concentrations are developed to predict acceptable exposure levels for both adults and children when data on a NOAEL or LOAEL exist from animal or human studies. LTHAs are not legally enforceable standards.

Maximum Contaminant Level (MCL)

    The enforceable drinking water standard for a specific contaminant. This level is protective of long-term (lifetime) human health.

Reference Media Evaluation Guide (RMEG)

    RMEGs are derived by ATSDR from the EPA oral Reference Dose. It is the concentration in water or soil at which daily human exposure is unlikely to result in adverse noncancerous effects.


1. Mustard and lewisite were developed during World War I and cause blisters. Phosgene was also used in WW I and causes serious lung injury at high doses: it is now used in various industrial processes. Chloropicrin is a riot control agent which has been replaced by newer chemicals which are considered safer (40).

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