PUBLIC HEALTH ASSESSMENT
USA DEFENSE DEPOT MEMPHIS
MEMPHIS, SHELBY COUNTY, TENNESSEE
The Defense Depot Memphis Tennessee (DDMT) is located on 642 acres in Memphis, Shelby County, Tennessee. It is about five miles east of the Mississippi River, and four miles east of the Memphis central business district.
DDMT was constructed in 1941. Operations began in 1942. DDMT has served as a supply, storage and maintenance facility for the U.S. Army since that time. The supplies include a broad range of commodities, such as clothing, food, medical supplies, electronic equipment, petroleum products, construction materials and industrial chemicals. Many of the supplies contain components which are now considered hazardous materials. During the course of normal activities leaks and spills occurred. Also, items were disposed in the onsite disposal area.
In 1981, the Defense Logistics Agency began evaluating the management of hazardous waste materials at its facilities, including DDMT. In 1988, DDMT began to investigate soil and groundwater contamination. To aid in the study, DDMT was divided into four operable units (OUs). The facility was proposed for placement on the National Priorities List in August, 1991, and placed on the NPL in October of 1992. The chemicals contaminants that have been most found are volatile organic compounds (VOCs- mainly cleaners and solvents), petroleum products, pesticides, and metals.
DDMT is not the type of facility generally associated with production large amounts of hazardous wastes. The types of contamination that exist are from burial of unusable industrial supplies and chemical agents in Dunn Field, from isolated spills, or from the normal application of pesticides and herbicides to the facility.
The contamination issues at DDMT that will be evaluated for public health implications are:
- contamination buried in Dunn Field (reaching the groundwater under that area);
- the possibility of contamination in drainage channels;
- the possibility of air contamination; and
- isolated areas of soil contamination on the Main Installation.
The possibility of contamination in the drainage ditches is an issue that is being investigated. Although it is very unlikely that enough contamination exists to present a public health threat, ATSDR is recommending that samples be analyzed to verify that no threat exists.
Operations at DDMT (for example, warehousing and shipping activities) are not generally associated with significant amounts of air contamination. However, over the years, isolated accidents and incidents have occurred that are evaluated in this public health assessment. For the most part, these do not appear have released enough contaminants to present a threat to public health. However, with the absence of air sampling information, ATSDR recommends that soil samples be analyzed from the area of the sandblasting operation. Soil samples in this area will provide information on whether metals from the sandblasting operation were transported by air currents and deposited outside the facility.
Access to areas containing contaminated soil is controlled by warning signs, fencing, or paving. As a result, the areas containing contaminated soil are not a threat to public health.
The Agency for Toxic Substances and Disease Registry (ATSDR) was established under the mandate of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980. (Note: Appendix A provides a listing of abbreviations and acronyms used in this report.) CERCLA, also known as the "Superfund" law, authorized the U.S. Environmental Protection Agency (EPA) to conduct clean-up activities at hazardous waste sites. EPA was directed to compile a list of sites considered hazardous to public health. This list is termed the National Priorities List (NPL). The 1986 Superfund Amendments and Reauthorization Act (SARA) directed ATSDR to perform a public health assessment for each NPL site. In 1990, federal facilities were included on the NPL.
Public health assessments (PHAs) are conducted by scientists from ATSDR (or from states with which ATSDR has cooperative agreements). The purpose of a PHA is to determine whether people have been (in the past) or are being exposed to (in contact with) hazardous substances and if so, whether that exposure is harmful and should be stopped or reduced.
In conducting the PHA, three types of information are used. A major source of information is the extensive environmental data collected for EPA. This information is examined to determine whether people in the community might be exposed to hazardous materials from the NPL facility. If people are being exposed to these chemicals, ATSDR will determine whether the exposure is at levels which might cause harm. A second source of information used in the PHA is community health concerns. ATSDR will evaluate health concerns of community members and determine whether health concerns could be related to exposure to chemicals released from the NPL facility. If ATSDR finds that harmful exposures have occurred, health outcome data (information from local hospitals and other medical organizations) can be used to further assess the occurrence of specific illnesses.
The PHA presents conclusions about whether exposures are occurring, and whether a health threat is presented. In some cases, if enough information is available, it is possible to determine whether exposures occurred in the past. If it is found that a threat exists, recommendations are made to stop or reduce the threat to public health. ATSDR is an advisory agency. Its recommendations identify actions which EPA, the facility or local agencies may undertake. If exposures are occurring at levels which could pose a threat to public health, ATSDR can undertake health education activities or certain additional follow-up studies. ATSDR can also identify types of information which might be needed to make public health decisions, if such information is lacking.
In order to evaluate the effect on public health of contaminants at NPL sites, the public health assessment focuses on examining whether people have been exposed to (in contact with) the contaminants. To this end, the two most important tasks in the public health assessment are:
- determining whether people have been exposed to hazardous materials from the NPL facility, and;
- if exposure is possible or has occurred, determining whether the exposure is at a level that could be a threat to public health.
In this PHA we will examine:
- whether contamination exists in the environment,
- whether contamination is in places where people in the surrounding community might
come in contact with the contaminants, and
- if there is exposure, whether it is at a level high enough to affect the health of people in the community.
To make these decisions, each of the possible environmental "pathways" will be examined. An environmental pathway can be described as the route that the contamination follows to get from the source to where people may be in contact with it. The environmental routes that this PHA will examine are:
- groundwater, or underground (well) water, in both public water supplies and private wells,
- surface water (creeks, ponds),and
- sediments under the creeks and ponds and on their banks;
- soil; and
- the "food chain", such as livestock, crops, game and fish (specifically, at DDMT, home gardens).
Figure 1 portrays the environmental routes we will investigate in this PHA. The numbers 1 through 6 on the figure match the numbers for the routes shown above, and will be referred to throughout the text as the pathways and possibility of exposure are discussed. Figure 2 shows the questions ATSDR asks about whether exposures could occur that would cause public health problems.
In the environmental exposure evaluation, ATSDR examines the TYPES and AMOUNTS of contaminants present at their SOURCES (such as spills, leaks or landfills). The ROUTE these contaminants might take is then determined (These are noted on the figure by the numbers 1 through 6). ATSDR looks at environmental data to decide whether it is likely that one or more of these ROUTES is in fact contaminated. If contamination is found, ATSDR decides whether people can be in CONTACT with these chemicals, by BREATHING, DRINKING, EATING, or TOUCHING them. Finally ATSDR determines whether the AMOUNT present is sufficient to be a public health problem.
ATSDR Exposure Evaluation Process
WHAT ARE THE CONTAMINANTS AT DDMT?
WHICH ENVIRONMENTAL MEDIA ARE CONTAMINATED?
HOW DO THE CONTAMINANTS TRAVEL TO WHERE PEOPLE
CAN BE IN CONTACT WITH THEM?
HOW COULD PEOPLE BE EXPOSED?
IF EXPOSURE IS OCCURRING, OR OCCURRED IN THE PAST
Another important factor is the way that people might contact the contaminant. By this we mean whether the chemical is:
- ingested (eaten or drunk); or
- absorbed through the skin.
Not all chemicals are a hazard for each of these methods of contact. For example, most metals
are not harmful, particularly in very low amounts, if the only contact is by way of the skin.
The Defense Depot Memphis Tennessee (DDMT) is located on 642 acres in Memphis, Shelby County, Tennessee. See Figure 3 for the location of the site (1). DDMT lies in the south central section of Memphis. It is about five miles east of the Mississippi River, and four miles east of the Memphis central business district.
Located on land that was previously used for growing cotton, DDMT was constructed in 1941. Operations began in 1942. DDMT has served as a supply, storage and maintenance facility for the U.S. military since that time. In 1962, the Defense Logistics Agency (DLA) assumed command of DDMT. The supplies include a broad range of commodities, such as clothing, food, medical supplies, electronic equipment, petroleum products, construction materials and industrial chemicals (2). Many of the supplies contain components which are now considered hazardous materials. Over the 50+ year history of the facility, during the course of normal activities and due to the large volumes handled, leaks and spills occurred. Also, items containing hazardous materials were disposed onsite. With the exception of the early mustard agent disposal activity, DDMT has kept complete and detailed records of materials spilled or disposed, and their locations. For this reason, the sources and types of contamination at DDMT are generally well identified.
A review by the Army of installation records suggests that about 77 waste disposal sites, spill locations, and other sites of possible environmental concern exist at DDMT. These sites are called Installation Restoration Program (IRP) sites. Many of these IRP sites are located in Dunn Field (2) (See Figure 4).
In 1981, DLA began evaluating the management of hazardous waste materials at its facilities, including DDMT (3). In 1988, DDMT began to investigate soil and groundwater contamination. To aid in the study, DDMT was divided into four operable units (OUs)(4). These are shown in Figure 4. Based primarily on concern that the groundwater aquifer used to supply drinking water could be contaminated, the facility was proposed for placement on the National Priorities List (NPL) in August 1991, and placed on the NPL in October of 1992. The chemical contaminants of greatest concern are volatile organic compounds (VOCs), mainly cleaners and solvents, petroleum products, pesticides and metals.
According to the 1990 Census, a total of about 825,000 people live in Shelby County, where DDMT is located. In the two census tracts surrounding DDMT, totaling 6.84 square miles, there are about 25,000 residents (15). Figure 5 shows population density of the area around DDMT.
DDMT employs about 1,200 civilians and 16 military personnel. Base housing consists of 8 units with a population of about 24, including military personnel and family members (14). This housing is located in the southeastern corner of the site.
DDMT is located in the metropolitan Memphis area. The vicinity is an area of mixed residential, commercial, and industrial land use.
The facility is divided into two sections. The Main Installation, covering 578 acres, is heavily developed. The land area is graded, paved and built-up with warehouses, storage areas and administrative buildings. There are relatively small open, grassy areas throughout the main facility.
The small base housing areas are located in the extreme southeastern corner of DDMT. The largest grassed area is the golf course, located in the southeastern portion of the facility. The only significant onsite water bodies are the Golf Course Pond and Lake Danielson, both within the golf course area. Fishing and swimming are not allowed in either of these ponds.
The other portion of the facility, Dunn Field, covers 64 acres of level to gently rolling terrain. It is located next to the northwestern portion of the Main Installation. Dunn Field is an open storage area, with about half the land surface covered by grass. The remainder of the area is mostly graded, paved or covered in gravel or by large bauxite piles. A majority of the 77 listed waste disposal and spill areas are located in Dunn Field (2).
Surface water drainage from DDMT enters two neighboring creeks, Cane Creek, about ½ mile northwest of DDMT, and Nonconnah Creek, about one mile to the south. Cane Creek is a tributary of Nonconnah Creek. Nonconnah Creek is a tributary of the Mississippi River. The drainage channels from DDMT are often dry, depending on seasonal rainfall. The creeks are classified by the state of Tennessee for propagation and maintenance of fish and other aquatic species, livestock and wildlife watering and irrigation. Both creeks are also classified for recreation. Some fishing and other recreational use occur on both these creeks.
Bass, bluegill, and catfish are the predominant fish found in surface waters around DDMT. Recreational fishing does occur in Nonconnah Creek and to lesser extent in Cane Creek. Fishing would not occur in the drainage ditches from DDMT because they rarely contain appreciable amounts of water, and are often dry. Wildlife species such as squirrels, red fox, mourning dove and quails have been observed within DDMT and in the vicinity. Due to the extensive urban development in the area, hunting is not allowed within city limits and is therefore not a normal or frequent activity.
Soils at DDMT ranges in thickness from six to forty feet. Although not a primary water-bearing unit, following rainfall, the surface soils may briefly contain small, shallow water-bearing zones.
Sediments under the surface soils comprise the shallow watertable aquifer (An aquifer is a water-bearing zone). This aquifer ranges in thickness from 40 feet to about 131 feet. It is this aquifer that is believed to be contaminated by chemicals from DDMT. This aquifer is not believed to discharge to surface waters in the area of DDMT (2).
The groundwater flow in this shallow aquifer, in the DDMT area, is in two general directions. From Dunn Field, the flow is to the west. At the Main Installation, the general direction of groundwater flow is west to northwest. Recent information obtained in the northwest portion of the Main Installation and Dunn Field area suggests that, in places, there may be leakage from the shallow aquifer into deeper units (7).
Directly under the shallow aquifer is a layer of clay-like material that provides a barrier that limits (but does not necessarily eliminate) leakage between that aquifer and the deeper aquifer, called the Memphis Sand Aquifer. The Memphis Sand Aquifer is the primary source of water for the area, providing about 95 percent of the water supplies for the Memphis area. In accordance with EPA and state safe drinking water requirements, the Memphis water supply is monitored on a regular basis and is treated if necessary before the water is used (5). Most of the recharge (replenishment) of this aquifer occurs where the aquifer is at the surface several miles to the east of DDMT. 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 (6).
MLG&W has in place a monitoring and treatment program for the water supply, in order to protect the supply from the possibility of contamination from any possible source. MLG&W does monitor for the types of chemicals that are possible contaminants from DDMT. Additionally, MLG&W has in place plans to treat the water supply, if necessary, to keep these chemicals from reaching the public (5). Interim remedial plans for DDMT include a program of pumping the contamination for the shallow aquifer and treating the water to further limit the possibility that contamination reaches the water supply (4).