PUBLIC HEALTH ASSESSMENT
CORNHUSKER ARMY AMMUNITION PLANT
GRAND ISLAND, HALL COUNTY, NEBRASKA
The Cornhusker Army Ammunition Plant (CAAP), an installation under the command of the U.S. Army
Armament, Munitions and Chemical Command (AMC-COM), U.S. Army, U.S. Department of Defense,
has been involved in munitions production since 1942. Although munitions have not been produced
since 1973, because of past disposal activities, CAAP was placed in 1987 on the Environmental
Protection Agency's (EPA) 
National Priorities List for hazardous waste sites. The Agency for Toxic
Substances and Disease Registry (ATSDR) prepared a preliminary public health assessment in 1988.
ATSDR has since reviewed currently available environmental data and has prepared this public health
assessment.
CAAP is three miles west of Grand Island in Hall County, Nebraska. Sampling of soil on the installation has shown contamination with metals, volatile organic compounds (VOCs), and explosives, including cyclotrimethylenetrinitramine (RDX), trinitrotoluene (2,4,6-TNT or TNT), and hexamethylenetetramine (HMX). Contaminated areas have been preliminarily evaluated, but assessment of the extent of contamination is not complete. Environmental evaluation is continuing in the ongoing Remedial Investigation/Feasibility Study (RI/FS). The isolation of and limited access to most on-post areas limits the likelihood of people coming into contact with any contamination. If land use patterns at CAAP change, however, further environmental study will be needed to ensure human health is protected.
Off-post contamination of groundwater with explosives, nitrates, and possibly VOCs and other unknown compounds has in the past and currently poses a public health hazard. The number of persons exposed in the past by ingesting contaminated groundwater cannot be accurately estimated. The majority of residents exposed to contaminated drinking water in the past now have access to an alternative water supply. Exposure may be possible, however, if residents consume vegetables grown in private gardens irrigated with contaminated water; recent laboratory studies indicate that plants may efficiently absorb RDX. ATSDR discussed this information with the U.S. Army Toxic and Hazardous Materials Agency (USATHAMA), EPA, Nebraska Department of Environmental Control (NDEC), and the Nebraska Department of Health (NDH) and recommended that residents stop using contaminated water to irrigate their vegetable gardens. On July 30, 1991, NDEC and NDH advised residents to stop eating vegetables grown in gardens irrigated with water from private wells. ATSDR attended a public meeting sponsored by NDEC and NDH on August 5, 1991, to discuss the new information with the public.
Discussions continued between ATSDR, USATHAMA, EPA, NDEC, and NDH concerning possible vegetable contamination, and, in August 1991, USATHAMA began sampling vegetables and soil from residential gardens, as well as soil from yards irrigated with contaminated water. Results from the vegetable sampling indicate that RDX was not detected above the 0.19 ppm health risk limit developed using EPA guidelines. A public meeting to discuss the results of this sampling was sponsored by USATHAMA on November 7, 1991. ATSDR attended that meeting. Additional soil and vegetable sampling is proposed during the RI/FS investigation.
To reduce human exposure to groundwater contaminants, ATSDR recommends continuing to monitor private drinking water wells for contaminants to ensure timely replacement of contaminated drinking water sources. In addition, water from contaminated private wells should not be used for swimming pools, gardens, or lawns. CAAP has made the city's water supply available to the cattle feedlot areas. Using city water to water livestock would eliminate the possibility of contaminants building up in cattle.
ATSDR considers contamination from CAAP a public health hazard because of long-term human exposures to hazardous substances. Evidence exists that exposures have occurred and are occurring. The estimated exposures are to a substance or substances at concentrations in the environment that, upon long-term exposure, could cause adverse health effects to any segment of the nearby population. Those adverse health effects might be the result of either carcinogenic or noncarcinogenic toxicity from a chemical exposure.
Because people might have been exposed to RDX or other contaminants in the past at levels that could cause illness, ATSDR's Health Activities Recommendation Panel determined that follow-up health activities are needed. ATSDR will carry out site-specific surveillance and disease- and symptom-prevalence studies as follow-up activities.
A. Site Description and History
The Cornhusker Army Ammunition Plant (CAAP) is a government-owned, contractor-operated (GOCO) facility. The installation is under the command of the U.S. Army Armament, Munitions and Chemical Command (AMC-COM), U.S. Army, U.S. Department of Defense. CAAP is located three miles west of Grand Island in Hall County, Nebraska (Fig. 1). The primary mission of the facility during World War II, and the Korean and Vietnam conflicts was production of artillery shells, bombs, and rockets. The plant was on standby status, except for production of munitions, from 1942-1945, 1950-1957, and 1965-1973. A portion of the facility was used from 1945-1948 for production of fertilizer. Currently, 16.1 square miles of the 18.7-square-mile facility are leased for agriculture, grazing, and/or wildlife management. Munitions activities have ceased.
In 1980, as part of the U.S. Army's Installation Restoration Program (IRP), the U.S. Army Toxic and Hazardous Materials Agency (USATHAMA) conducted an installation assessment of CAAP (1). This assessment determined that the potential existed for groundwater contamination and migration from munitions activities. In 1982, sampling and analysis of on-post monitoring wells indicated that the shallow groundwater aquifer was contaminated with RDX and TNT and the contamination had migrated to at least the installation boundary. Evaluation of groundwater contaminants in off-post areas began in 1983. Explosives contamination, especially RDX, was confirmed in on-post wells and found in five of 16 off-post wells used for supply of drinking water and irrigation. RDX contamination of the shallow groundwater aquifer had migrated approximately three miles northeast of CAAP.
In early 1984, 461 off-post, domestic drinking water wells were sampled, primarily in the Le Heights and Capital Heights residential areas (hereafter referred to as Capital Heights), which are approximately two miles from CAAP. Results of the analysis indicated that more than 200 drinking water wells in the off-post area were contaminated with RDX. Bottled water was supplied by the Army from January 1984 through June 1986 during construction of a permanent alternative water-supply system. To extend the City of Grand Island water system to the affected area, a system of dewatering wells was used to lower the water table sufficiently to allow installation of the water mains. During that time, water was discharged to Silver Creek north of the residential area. In December, 1986, 800 residences were given an opportunity to connect to the Northwest Grand Island Water Supply Extension.
In order to reduce the likelihood that explosives-contaminated soil would continue to contaminate groundwater, an on-site Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) removal action was performed. Incineration of soil surrounding 56 surface impoundments began in August, 1987, at a site north of load lines 2 and 3 and south of the northern magazine area. A total of 44,722 tons of soil were excavated and incinerated. Ash from the incineration was analyzed to ensure that no residual explosives or metals were buried at CAAP. Excavated areas were backfilled with natural fill taken from a site in the eastern area of the facility.
As a result of the documented contamination of soil and groundwater, CAAP was placed on the U.S. Environmental Protection Agency's (EPA) National Priorities List (NPL) for hazardous waste sites in July, 1987. A federal facilities Inter-Agency Agreement among the EPA, Nebraska Department of Environmental Control (NDEC), and the U.S. Army for the cleanup became effective in September, 1990. CAAP is developing a workplan for a Remedial Investigation/Feasibility Study (RI/FS). The RI/FS will characterize further the extent of contamination and evaluate alternatives for cleaning up the site.
The Agency for Toxic Substances and Disease Registry (ATSDR) is authorized by CERCLA to conduct public health assessments on NPL sites to evaluate the public health significance of those sites. ATSDR determines whether health effects are possible and recommends actions to reduce or prevent possible health effects. A preliminary health assessment addressing CAAP was prepared by ATSDR in 1988 (2).
To accomplish the goals of the IRP at CAAP, one off-post study area and 11 on-post study areas have been designated (see Table 1). The off-post groundwater study area was described previously. Descriptions of the on-post study areas and their histories are provided following Table 1.
TABLE 1. Designated Study Areas for the CAAP Institutional Restoration Program
OFF POST
1. Off-Post GroundwaterON POST
1. Load, Assemble, and Pack Facilities
2. Burning Grounds
3. Sanitary Landfill
4. Shop Area
5. Nitrate Area
6. Pesticide/Herbicide/Fertilizer Storage Area
7. Pistol Range
8. Gravel and Clay Pit Area
9. Magazine Areas
10. Drainage Ditches
11. Sewage Treatment Plant
Load, Assemble and Pack (LAP)
Facilities. Five separate sets of buildings, called Load Lines 1-5,
were used for munitions production (Fig. 2). Wastewater containing explosives
was produced from specific operations, including screening, melting and mixing,
rod and pellet manufacturing, remelt and refill, and washing and laundry. During
some operations, such as screening of TNT and RDX from a flake form into sifted
powder, explosive dust was generated and removed from the air with Schneible
units (wet scrubbers). Water from the units was recycled after explosive particles
were allowed to settle; however some excess wastewater was generated. After
completion of those processes, as well as others, such as melting and pouring
of munitions, operating procedures called for periodic washdown of machinery
and interior building surfaces.
Wastewater was removed through interior building open drains into a sack sump (a concrete pit equipped with a canvas-like filter bag). The bag was used to filter out solid explosive particles. The wastewater, which contained explosives not filtered out in the sack sump, then traveled through open concrete channels into a circular earthen impoundment. The masonry-walled pit was open to the sand and gravel bottom. An overflow channel from this impoundment connected with a leaching pit designed to handle any water that did not filter through the bottom of the impoundment.
Production records were used to estimate the amount of waste solution discharged to the ground during WWII and the Korean and Vietnam conflicts (1). During those operations, 26,410 kilograms (kg) of TNT and 7,300 kg of RDX were estimated to be discharged to the sump/leach pit collection system.
Burning Grounds. The
burning grounds in the northwestern corner of the installation cover approximately
960,000 square feet (Fig. 2). Early on in CAAP's operation, the area was used
for disposal by burning of a variety of materials, including TNT, RDX, tritonal,
aluminum powder, ammonium nitrate, and lead azide. The area is no longer used
and is covered by natural grassland vegetation. A portion of the area might
contain unexploded ordnance from past failed detonation attempts; it is fenced
with warning signs. Aerial photos and geophysical investigations indicate a
series of trenches (3). Historical records indicate that sludge
from a settling basin in the shop area, which received wastewater from the laundry
and other shop facilities, was burned and disposed of in the burning grounds
area (1). During excavation and incineration in 1986, construction
materials from the contaminated surface impoundments and materials used in the
incineration process were thermally treated at the burning grounds. Approximately
5,549 cubic yards of explosives-contaminated soil were excavated from the earthen
surfaces of the burning pads and incinerated when the area was closed following
thermal treatment operations (1).
Sanitary Landfill. The sanitary landfill in the northwestern part of the installation, immediately south and east of the burning grounds, opened in 1969 and has not been used for at least six years (Fig. 2). The 55-acre site was used for disposing trash, scrap wood, and inert construction materials. Approximately 2,400 cubic yards of those materials were buried annually in 6 to 10-ft deep trenches (1). Historical records indicate that hazardous wastes such as acetone, dimethylaniline, resin emulsifier, isopropyl and polyvinyl alcohol, aluminum trihydrate, ethanolamine, and contaminated metals may have been disposed in the landfill (1). Some of those records list a flammable liquids disposal area west of the landfill.
Shop Area. The shop area includes 28 buildings and sheds on a 1,500 ft x 2,000 ft site in the southeastern part of the facility (Fig. 2). Various support activities took place at the shop area, including laundry, vehicle storage and maintenance, open storage, rail loading and unloading, and filling of underground and aboveground storage tanks. The only building now in use is leased to a private contractor for equipment storage. During munitions operations, approximately 1,900 kg of TNT and RDX in laundry wastewater were discharged to the ground through a settling basin and surface ditch systems in the area.
Nitrate Area. This area consists of a main building, several small buildings, a rail loading yard, and several open storage areas (Fig. 2). The area was used for production of explosives during WWII and for production of fertilizer from 1945 through 1948. Since 1979, the area has been leased to a tenant for railroad car repair. During periods of munitions production before 1973, a lab in the area was used for chemical analysis of explosives. Nitrates and other chemicals associated with fertilizer production may have been released from 1945 through 1948. Wastewater containing hazardous substances could have been released to drainage ditches or leachfields. Activities of the current tenant (railroad operation) include welding, sandblasting, painting, and use of motor oil, hydraulic oil, solvents, diesel, gasoline, and oil- and water-based paints. The potential exists for hazardous substance release by way of spills into the drainage systems. The release of small quantities of hazardous waste at the site is currently regulated by a Resource Conservation and Recovery Act of 1980 (RCRA) permit (4).
Pesticide and Fertilizer Storage Areas. Various pesticides and fertilizers have been and are currently used at CAAP. Pesticides and fertilizers have been stored and mixed in five buildings in the southern part of CAAP (Fig. 2). Material has included malathion, chlordane, aldrin, Urox liquid, 2,4,-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), thiosperse, Boracil, Benzabor, Arsenal, Roundup, Pramitol 25E, and Dacthal 5-C (1).
Pistol Range. This area covers 30 acres near CAAP's western boundary (Fig. 2). The area was used for small arms fire and as an open burning area (5). It has since been under cultivation for several years.
Gravel and Clay Pit Area. This 600-ft by 1,800-ft area in the western part of CAAP is currently covered by grass (Fig. 2). Historically, the area was used for disposing construction material, crankcase oil, battery cables, and trash (1).
Magazine Areas. The north storage magazine area covers 400 acres and contains 102 aboveground magazines. The south magazine area covers 450 acres and has 117 aboveground magazines (Fig. 2). Past activities in the area indicate the potential for contamination of surface and subsurface soils and groundwater. Currently, 130 of these structures are leased to individuals for storage (1).
Drainage Ditches. Three man-made drainage ditches are at CAAP (Fig. 2). Surface water is in the ditches only during heavy precipitation and is discharged into Silver Creek. The West Channel is a north-to-south-oriented, man-made drainage ditch constructed in 1973. It receives runoff from Load Line 5, a portion of Load Line 4, the sanitary landfill, and the eastern half of the burning ground. The East Channel is a north-to-south-oriented, man-made drainage ditch constructed in 1973. It receives runoff from Load Lines 2 and 3 and the north and south magazine areas. The railroad ditch is a north-to-south-oriented, man-made drainage ditch constructed in 1942. It parallels the railroad tracks along the eastern boundary of the installation and receives runoff from the nitrate area, shop area, and Load Line 1.
Sewage Treatment Plants. Two sewage treatment plants are at CAAP (Fig. 2). One plant in the southeastern area served the administration area, staff housing area, and Fire and Guard headquarters from 1942 to 1974; the system was replaced in 1974. A sewage treatment plant north of Load Line 4 served during periods of production. The potential existed in the past for introduction of explosives and other potentially toxic substances, including cleaners and solvents, into the sewer systems and subsequently into surface and subsurface soils and groundwater.
ATSDR staff joined a representative of the Army Environmental Hygiene Agency on a site visit to
CAAP on April 11-12, 1991. Discussions were held with a representative of USATHAMA and with
the CAAP Commander's representative concerning the progress of the IRP. A site tour was taken of the
installation, including the study areas to be investigated in the during the IRP. Access to the fenced
installation was controlled by security guards; access was open to most areas inside the installation.
During a drive through the load lines, the ATSDR representatives observed asbestos siding on most of
the buildings. Areas that previously contained the cesspools and leachfields on the load lines were
visited. The areas had been excavated and filled; no soil contamination was obvious. During a drive
through the magazine areas, decontamination markings were seen on the magazines. ATSDR staff also
visited an area used for burial of ashes produced by soil incineration; no evidence of seepage from the
area was seen. The same was true for the sanitary landfill. During a drive through the shop area, some
stored equipment was observed; most facilities were empty. Drainage ditches were seen in the area.
The site visit also included a tour of the laundry facility, burning grounds area, and the burial area for
explosives. Approximately two acres of the burial site were fenced (two wire) and marked with a
hazardous explosives sign. The area was covered with grass and contained a crater about 40 ft in diameter. The trench area was pointed out.
Although not seen on the visit, deer are abundant on the installation. Hunting is permitted outside the installation boundaries. Most of the installation was under cultivation.
C. Demographics, Land Use, and Natural Resource Use
Cornhusker Army Ammunition Plant is in Hall County, Nebraska, approximately two miles west of the City of Grand Island. Grand Island is the third largest city in Nebraska, with an estimated 1990 population of 39,386. The population rose from 33,180 in 1980 to 39,386 in 1990. Hall County rose in population from 47,690 in 1980 to 48,925 in 1990 (6). A summary of the population's employment and income is presented in the Appendix. The economy includes industry, agriculture, retailing/wholesaling, and services. In 1980, the per capita income for individuals was $7,291. About 7% of the population was below poverty level.
The subdivisions of Le Heights and Capital Heights include approximately 450residences and are on the western side of Grand Island about two miles from CAAP's eastern boundary. Northwest High School and Engleman Elementary School are near the subdivision. The Nebraska Veteran's Home is also in the area. Demographic data for an area (including Capital and Le Heights subdivisions) bounded on the north by County Highway 37, on the east by U.S. Highway 281, on the south by U.S. Highway 30, and on the west by County Highway 20 is presented in the Appendix. Data for the city of Grand Island and Hall County are also included for comparison purposes.
That area had a 1990 population of 4,733. Nearly all persons were white. A slightly higher percentage of persons under age 10 lived in the selected area compared to Grand Island and Hall County. An average of over three persons per household occurred in the area. These figures indicate the presence of a large percentage of young families in their childbearing years relative to the city and county populations. A much lower percentage of persons were age 65 and older, again indicating that this area is populated predominantly by young families.
Just under 85 percent of all housing units were owner-occupied, which suggests a nontransient population (i.e., renters tend to not remain in that residence for an extended period of time); this percentage is much higher than those for the city and county. Median value of owner-occupied homes was higher in the selected area compared to the city and county in general.
Land use at CAAP includes the lease of 42 tracts (100-500 acres each) to 25 farmers. Crops planted on the land are primarily corn for cattle and alfalfa. Two tracts are used for grazing about 100 head of cattle. Several tenant industries lease buildings and land; 136 storage magazines are leased for private use. A railroad repair operation averages about 75 employees. A fiberglass operation has approximately 25 employees. In addition, some buildings are leased for storage by various companies. Water on post is provided by a 100 ft-deep drinking water well and by several irrigation wells.
Most of the land between CAAP and the city limits is used for crop production, including corn and alfalfa. Cattle feedlots and a gravel quarry operation are also present. Husker Harvest Days, an annual event, is a farm demonstration and display show that attracts hundreds of thousands of people to the southwestern corner of CAAP property.
Well water is used for drinking and agricultural purposes in the area between CAAP and Grand Island. The City of Grand Island receives water from the shallow aquifer; it is drawn from nine wells southeast of the city and a well field three miles south on an island in the Platte River. Water is pumped to a distribution system and treated by chlorination. Further discussion of the groundwater aquifer is in the Environmental Contamination and Other Hazards section of this document.
Health outcome data for the area surrounding CAAP were reviewed. The Nebraska State Health Department Vital Statistics Annual Report for 1989 included information on births, marriages, and deaths categorized to the county level (7). The Nebraska State Health Department Cancer Registry also contained information categorized to the county level (8).
ATSDR identified community health concerns using a variety of methods. Citizens, correspondence with elected officials (9) and citizens' interviews conducted during development of the USATHAMA CAAP Community Relations Plan (10) were reviewed. Discussions were held with Grand Island City officials during ATSDR's site visit April 11-12, 1991. Discussions also were held with citizens at public meetings convened by the Nebraska Department of Health, the Nebraska Department of Environmental Control (11), and the U.S. Army (12). The following concerns were identified:
What are the health effects of RDX, and what is a safe level of RDX in drinking water? What is the risk of getting cancer from drinking RDX-contaminated water?
What are the health effects of TNT and other contaminants found in the contaminated drinking water? What are safe levels for those contaminants in drinking water?
Does RDX accumulate in cattle that drink contaminated water?
Does RDX accumulate in crops irrigated with contaminated water?
Should private well water be used in swimming pools?
What is the extent and exact location of the contaminated water plume? Does more than one plume exist?
Is the drinking water at Northwest High School contaminated?
Have all residential drinking water wells been tested?
Was the incineration of soil at CAAP successful in removing all the contamination?
What is the extent of contamination of buildings and soil on the installation itself?
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
Introduction
In the past, both liquid and solid wastes have been disposed at CAAP in leaching and burning pits. Operational activities have generated wastes in the sanitary landfill, shop area, and the pesticide storage area. Contaminants have been detected in soil, sediment, surface water and groundwater. CAAP began collecting groundwater samples in August, 1982, and continues to collect samples to determine the extent of contamination. Other groups that have sampled groundwater include the U.S. Geological Survey (USGS), NDEC, and EPA. Groundwater contamination (primarily containing explosives) from the leach pits and, possibly, other sources was detected in the early 1980s and prompted immediate action. Previous remediation activities at CAAP included providing an alternative water supply to the Capital Heights subdivision and incinerating explosives-contaminated soil from the leaching pits. Sampling to define the extent of contamination continues for soil, sediment, and groundwater.
The contaminants discussed in subsequent sections of this public health assessment will be evaluated to determine whether exposure to them has public health significance. ATSDR selects and discusses contaminants based on several factors: sample design, field and laboratory data quality, and comparison of chemical concentrations to levels that could cause cancer or other health effects. In addition, community health concerns are considered.
Evaluating the sample design involves reviewing the installations' approach to locating contamination. Spacial distribution of sampling locations, sampling frequency, concentration changes over time, medium-to-medium differences, and correlation between the selected list of analytic parameters and suspected environmental contaminants are factors considered by ATSDR when determining the contaminants to which humans could be exposed.
Review of sampling field quality control procedures may include interpreting data on background (or regional) concentrations of chemicals. Additionally, the adequacy and number of replicate, spiked, and blank samples may be checked to verify detection of contaminants. To assess laboratory quality control, procedures used to verify instrument reliability may be reviewed.
Contaminant concentrations detected on and off site are compared to health comparison values which are concentrations of chemicals that are believed to be without adverse health effects. Those values are developed by agencies to provide estimates of levels at which health effects are not observed. Those values, in many cases, have been derived from animal studies. Health effects are not only related to the exposure dose, but to the route of entry into the body and the amount of chemical absorbed by the body. For those reasons, comparison values used in ATSDR public health assessments are contaminant concentrations in specific media and for specific exposure routes. The potential for adverse health effects from contaminants of health concern will be discussed in the Public Health Implications section of this document.
Listing a contaminant in the data tables that follow does not mean that it will cause adverse health effects. Rather, the list indicates which contaminants will be evaluated further. The concentration of a contaminant in a particular media is compared to an appropriate health assessment comparison value. The potential carcinogenicity of contaminants is also considered. When selected as a contaminant of concern in one medium, that contaminant will be reported in all media in which it is found.
These terms will be used in the information to follow:
| CREG | Cancer Risk Evaluation Guide. CREGs are estimated contaminant concentrations based on a one excess cancer in a million persons exposed over a lifetime. CREGs are calculated from EPA's cancer slope factors. |
| EMEG | Environmental Media Evaluation Guide. EMEGs are screening values used to select chemical contaminants of potential health concern. EMEG values are calculated by using ATSDR conservative exposure assumptions that would protect the most sensitive segment of the population. |
| LTHA | Lifetime Health Advisory. LTHAs represent contaminant concentrations that EPA deems protective of public health over a lifetime (70 years) at an exposure rate of two liters of water per day. LTHAs are not enforceable through EPA regulations. |
| MCL | Maximum Contaminant Level. MCLs represent contaminant concentrations that EPA deems protective of public health over a lifetime (70 years) at an exposure rate of two liters of water per day. |
| ppb | parts per billion |
| ppm | parts per million |
| RfD | Reference Dose. EPA's Reference Dose (RfD) is an estimate of the daily exposure dose to a contaminant that is unlikely to cause adverse health effects. |
Background on Explosives Production and Breakdown Products
Explosives were not manufactured at CAAP; explosive compounds were shipped from other facilities. In order for the reader of this public health assessment to understand the complexity of the contamination that may have resulted from past handling of explosives, the chemical manufacturing and breakdown processes are described here. As with any chemical manufacturing process, each step of the reaction is not always complete. When the final product is obtained, many chemical compounds may be present as contaminants or may have been produced as waste from previous production steps. Those compounds may include: 1) chemicals used in excess in each reaction step, and/or 2) intermediate by-products of a chemical or waste carried through as contaminants of the final product. In addition, once a final product is made, it is subject to chemical breakdown into other products. This takes place through reaction with chemicals in the environment or through breakdown by biological processes in the environment. RDX and TNT will be described here.
RDX is synthesized by the nitration of hexamethylenetetramine, which is obtained from the reaction of formaldehyde and ammonia (13). RDX is only slightly soluble in water; it does not degrade under aerobic conditions, but degrades somewhat anaerobically in the presence of organic nutrients. The rate of biotransformation is unknown (14). The biological degradation products of RDX are characterized by nitroso derivatives. By-products and breakdown products are listed in Table 2.
TNT can be manufactured by one-, two-, or three-stage nitration processes; toluene and mixed acids are the raw materials. The three-stage process has the advantages of maximum yield and greater product purity. Nitration is carried out by adding the nitrating acid to the toluene, mononitrotoluene, or dinitrotoluene solution. The unreacted nitrotoluenes and dinitrotoluenes result as mixture impurities. Other impurities are listed in Table 2.
The crude TNT is then purified by using the sellite process, which consists of washing it with a solution of sodium sulfite and sodium hydrogen sulfite. The sodium sulfite reacts only slightly with the desired TNT isomer, but reacts readily with the undesired isomers. The undesired isomers and the sulfite react to form water-soluble compounds that are readily removed from the desired TNT by washing with water. The sulfite also reacts with tetranitromethane (another undesired by-product from the TNT production) which is water soluble. The sodium sulfite does not react with dinitrotoluene or trinitrobenzoic acid so they remain as impurities.
The yield of purified TNT can be as high as 80% (13). Once TNT has reached the environment, it degrades under aerobic and anaerobic conditions. The breakdown products of 2,4,6 TNT form monoaminodinitrotoluenes and tetranitroazoxy-toluene. U.S. Army Corps of Engineers determined in the analysis of field-contaminated soils, that the sum of 2-amino-4,6-dinitrotoluene (2-A) and 4-amino-2,6-dinitrotoluene (4-A) actually exceeded the amount of TNT detected (14). The breakdown products are listed in Table 2.
Because of the number and variety of chemical compounds that may result from the handling and disposal of explosives, the discussion to follow will cover contaminants that were detected in the various media sampled, the list of chemicals that the laboratory looked for (list of analytes), and the list of contaminants potentially present, but not included in the list of analytes.
TABLE 2. Impurities and breakdown products of RDX and TNT
| RDX | TNT |
| Impurities | |
| hexamethylenetetramine (HMX) | 2,4,6-trinitrobenzoic acid |
| 2,4-dinitrotoluene (DNT) | |
| nitrotoluenes | |
| tetranitromethane | |
| dinitrocresol | |
| phenol | |
| cyanic acid | |
| ammonium salts | |
| (2,6),(3,4),(2,3)-DNT | |
| Biotransformation Products | |
| hexahydro-1-nitroso-3,5-dinitro-1,3,5- triazine (MNX) | 2-amino-4,6-dinitrotoluene (2-A) |
| hexahydro-1,3 dinitroso-5-nitro-1,3,5- triazine (DNX) | 4-amino-2,6-dinitrotoluene (4-A) |
| hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (TNX) | 1,3,5-trinitrobenzene (TNB) |
| 1,3-dinitrobenzene (DNB) | |
| hydrazine | 2,4,6-trinitrobenzaldehyde |
| 1,1 dimethylhydrazine | 3,5-dinitroaniline |
| 1,2 dimethylhydrazine | 4,6-dinitrobenzoic acid |
| 1,1 dimethylnitrosamine | tetranitroazoxytoluene |
| formaldehyde | |
| methanol | |
CAAP conducted a field sampling survey in 1982. Soil samples were collected from several cesspools and leach pits around each of the five load lines. Sampling depths ranged from 0-18 inches to 18-36 inches. The samples were analyzed for explosives, including TNT, 2,4-DNT, 2,6-DNT, TNB, DNB, NB, and RDX (see Table 2 for full chemical names). The highest concentrations were detected for TNT (67,000 mg/kg or parts per million [ppm]), RDX (12,000 ppm), and 2,4-DNT (4,400 ppm). Soils were excavated from the high-concentration areas for the incineration project. The target excavation levels were set at 5 ppm for TNT, 10 ppm for RDX, 15 ppm for 1,3,5-TNB, 0.5 ppm for 2,4-DNT, and 0.4 for 2,4-DNT (3). This excavation was an attempt to remove the major source of groundwater and soils contamination remaining at CAAP. A high water table prohibited the excavation to the target levels in 29 of the 58 impoundments. Instead, soils were excavated to five feet below the water table. No post excavation soil samples could be taken and the soil concentrations are assumed to be higher than the target levels (3). The impoundments were filled with clean fill. Pre-excavation concentrations in several of the high water table impoundments were high (examples are listed above) and concern exists that these soils may continue to act as a source of contamination (3).
In the Fall of 1990, surface soil samples (0-6 in or 0-1 ft) were collected in the LAP facilities area. Analysis showed high concentrations of TNT and elevated concentrations of lead, chromium, cadmium, and nitrobenzene. The highest concentrations of TNT and lead were detected near Load Line 4 near Buildings 4L-7 and 4L-5, respectively. The highest chromium concentration was detected in the northwestern corner of Load Line 5. Table 3 lists the highest concentrations of explosives detected in the fall 1990 sampling.
The soil sample collected near building C-3-4 in the North Magazine Area had lead contamination as high as 1,460 ppm. TNT contamination was 28.4 ppm in a soil sample collected at the southern edge of the magazine area. The sampling included 16 samples randomly collected from the North Magazine Area, which were analyzed for explosives and metals. Only two samples showed soil contamination. Additional sampling is planned for this area, however, the analysis will include only explosives and metals. Seventeen surface soil samples were collected from the South Magazine Area; no contamination was detected. Table 4 shows typical concentrations of explosives and metals found at the other study areas in the 1990 sampling.
Proposed Sampling During RI/FS
The stated purpose of previous sampling, including samples taken in Fall 1990, was not to define the extent of contamination, but to delineate areas requiring further study (1). Additional sampling, including a more complete list of analytes, is planned. For example, the previous sampling did not in most cases include VOCs, pesticides/polychlorinated biphenyls (PCBs), and other specific compounds associated with explosive breakdown products suspected to be a result of the activities at CAAP.
The soil sampling efforts carried out thus far are best categorized as grab sampling; that is, taking a sample from one location. This method gives little information on the areal distribution of the contamination and assumes the samplers know the exact location of the contamination. Grab sampling (or biased sampling) is appropriate when the source areas are known. That information can be used to develop a sampling plan designed to determine the extent of contamination. Areal composite sampling, samples composited from individual grab samples collected over an areal, grid, or cross-sectional basis, in conjunction with grab sampling provides better information for assessing public health concerns. Background samples for each media provide information for determination of chemical concentrations that may be present regionally. Chemicals found in background samples may be naturally occurring or from some other source.
CAAP will determine the extent of soil contamination from sampling conducted during the ongoing RI/FS. The RI/FS workplan proposes a phased approach to this sampling. Phase one will include additional biased samples from sites with historic activities similar to other sites from which contaminants have been detected (15, 16). All surface soil samples will be collected from depths to one foot; at this depth, evaluation of contaminants to which people might be exposed by dermal contact is less certain since the soil contaminants would be diluted. Additionally, phase one sampling includes systematic grid sampling at sites where biased sampling results have indicated explosives and metals in surface soils (15). The samples will be collected using field-screening techniques. The grid sample analyses will be used to prepare reliable maps to initially delineate the extent of contamination sampling to be conducted in phase two. Surface and subsurface samples will be collected during phase two in order to define the lateral and vertical extent of contamination.
TABLE 3. Soil Contamination Detected in LAP Area, Fall 1990
| Comparison Value in ppm for child/adult |
25/350
|
NONE
|
250/3,500*
|
10/140
|
25/350
|
| Reference |
Calculated from RfD
|
|
EMEG
|
EMEG
|
Calc. from RfD
|
| Load Line |
2,4,6-TNT
|
Lead
|
Chromium
|
Cadmium
|
Nitrobenzene
|
| 1 | 5,190 | 175 | 58.6 | ||
| 2 | 7,260 | 101 | 49.5 | 52.5 | |
| 3 | 963 | ||||
| 4 | 8,920 | 1,620 | 848 | ||
| 5 | 556 | 1,190 | 8.09 | ||
| Assumptions: * The data do not specify Cr+3 or Cr+6. The EMEG is for Cr+6. EMEG and RfD calculations use a child body weight = 10 kg and an ingestion rate of 200 kg/day. The adult is calculated using a body weight of 70 kg at an ingestion rate of 100 kg/day. |
|||||
TABLE 4. Examples of Soil Contamination
Detected in Study Areas, Fall 1990
| Comparison Value in ppm for child/adult | 25/350 | 2.5/35 | 150/ 2,100 |
2,500/ 35,000 |
100/ 1,400 |
3,500/ 49,000 |
N/A | 250/ 3,500* |
|
| Reference | Calc. from RfD | RfD | RfD | RfD | EMEG | NONE | RfD | RfD | EMEG |
| Study Area | 2,4,6-TNT | 1,3,5-TNB | RDX | HMX | 2,4-DNT | Lead | Barium | Mercury | Chromium |
| Burning Grounds | 0.5-5,060 | 0.5-14.9 | 2.5-10.9 | 2.5-28.2 | 5.6 | ||||
| Sanitary Landfill | 32.7-45.5 | 444 | |||||||
| Shop Area | 9.38 | ||||||||
| Gravel Pit Area | 848 | ||||||||
| North Magazine Area | 28.4 | 1,460 | |||||||
| * The data do not specify Cr+3 or Cr+6. The EMEG is for Cr+6. | |||||||||
Proposed Analytes During RI/FS
The phase one field-screening analysis will include 2,4,6 TNT, cadmium, chromium, and lead. Five percent of the total number of field-screening samples will be quantified for those same analytes using laboratory analysis. The list of proposed analytes for phase two in the RI/FS sampling plan is more inclusive than that for previous sampling. Table 5 lists the proposed RI/FS analytes for explosives and some of the impurities and biotransformation products of RDX and TNT. Some of the compounds not specifically analyzed for will be detected as tententatively identified compounds if their concentration is at least 10% higher than the equipment calibration standards. Addition of some of the other compounds to the analyte list would define the extent of contamination more fully. Compounds such as hydrazine and 1,1-dimethylnitrosamine have been studied with respect to health effects and might be considered for inclusion (17, 18).
Three primary surface runoff accumulation ditches on site include the eastern and western channels and the railroad ditch. When flowing, those ditches and channels discharge into Silver Creek. No surface water or sediment sampling has been conducted, although it is discussed in the RI/FS workplan.
The RDX contamination plume was first detected in 1982; CAAP continues to monitor the contamination. On-site monitoring wells have detected contamination with the explosives RDX (307 µg/L as parts per billion, ppb); TNT (5,290 ppb); 1,3,5-TNB (352 ppb); 1,3-DNB (6.77 ppb); 2,4-DNT (12.3 ppb); and 2,6-DNT (4.2 ppb). Lead and mercury were not detected at concentrations above their detection limits of 19 and 0.243 µg/L, respectively. Barium, cadmium, and chromium were not analyzed for, but are proposed analytes in the RI/FS workplan. The current workplan outlines plans to sample for other constituents not previously sampled. On-site drinking water wells are approximately 100 feet deep; they are monitored semi-annually for explosives and quarterly for VOCs. No contamination has been detected to date; the wells are used by tenants. On-site irrigation wells have some of the highest levels of explosives contamination found at CAAP (1). Those high levels may be caused by the increased pumping capacity of the irrigation wells and their ability to draw contaminants toward them. VOCs were also detected during the August, 1984, on-post irrigation and monitoring well sampling.
Several areas on site are leased to local farmers for growing corn and alfalfa and raising cattle. Several of the leased areas are in suspected or confirmed soil contamination areas. In addition to being grown or raised on potentially contaminated soil, those crops and animals may be watered with contaminated water. After 1989 Army research studies became available to CAAP that indicated plant uptake of TNT and RDX was plausible, CAAP reconsidered the leasing program. In the Fall of 1991, CAAP purchased all crops grown in confirmed contamination areas so they would not be used. CAAP plans to discontinue those leases. Crop sampling is planned in the RI/FS workplan, but has not been described at this time.
TABLE 5. Comparison of Proposed Analytes to RDX and TNT Impurities and Breakdown Products*
| RDX | TNT | Proposed Analytes For RI/FS |
| Impurities | HMX | |
| hexamethylenetetramine | 2,4,6-trinitrobenzoic acid | |
| 2,4-dinitrotoluene (DNT) | 2,4-DNT | |
| tetranitromethane | ||
| dinitrocresol | ||
| phenol | phenol | |
| cyanic acid | ||
| ammonium salts | ||
| (2,6),(3,4),(2,3) DNT | (2,6) DNT | |
| Biotransformation Products | ||
| hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) | 2-amino-4,6-dinitrotoluene (2-A) | 2-A |
| hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX) | 4-amino-2,6-dinitrotoluene (4-A) | |
| hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (TNX) | 1,3,5-trinitrobenzene (TNB) | 1,3,5-TNB |
| 1,3-dinitrobenzene (DNB) | 1,3-dinitrobenzene | |
| hydrazine | 2,4,6-trinitrobenzaldehyde | |
| 1,1-dimethylhydrazine | 3,5-dinitroaniline | |
| 1,2-dimethylhydrazine | 4,6-dinitrobenzoic acid | |
| 1,1-dimethylnitrosamine | tetranitroazoxytoluene | |
| formaldehyde | ||
| methanol | ||
| 2,4,6-TNT | ||
| RDX | ||
| nitrobenzene |
*Some of the compounds not proposed for specific analysis will be detected as tentatively identified compounds if their concentration is at least 10% higher than the equipment calibration standards.
Cattle grazing continues in areas away from probable sources of soil contamination. The extent of contamination, if any, of water sources used by those cattle is not known.
No information was available on sediment and surface water sampling off site. Additional information will be collected during the RI/FS.
In August, 1991, USATHAMA began sampling vegetables and soil from residential gardens, as well as soil from yards irrigated with RDX- and TNT- contaminated water. At least two vegetables (including corn, peppers, tomatoes, grapes, or carrots) from each of eight gardens in the Capital Heights and Le Heights subdivisions were tested for RDX. No RDX was found in concentrations greater than the detection limits of the assays, which were all below the health risk level of 0.19 ppm (19). The 0.19 ppm level in vegetables was developed using EPA guidelines (19).
Analyses for RDX, TNT, and HMX were also performed on 24 samples from yard and garden soils. Concentrations of RDX, TNT, and HMX were all below their respective detection limits of 0.323 ppm, 1.20 ppm, and 1.21 ppm (19). Additional soil and vegetable sampling is proposed during the RI/FS (15).
No sampling data are available on livestock, particularly, cattle watered with contaminated private well water. Calculations have been made, based on risk analysis assumptions, which suggest that general concentrations of RDX and TNT found in the area groundwater would not accumulate in meat of cattle (20).
To appreciate how groundwater contamination might disperse, an understanding of the area's geology is useful. Terrain in the area is nearly flat to slightly sloped. The ground surface at CAAP and the surrounding area slopes gently as elevations drop approximately 100 feet from the southwest to northeast. Soils are developed in quaternary windblown silts (Peorian loess) and range from silty to very sandy at depths to 5 to 40 feet below ground surface. Beneath the surficial loess deposits lie moderately to highly permeable, unconsolidated Pleistocene sands and gravels. Soils in the study area north and east of CAAP vary from silty to sandy loams and have a high permeability. Unconsolidated Pleistocene sands and gravels vary in thickness from 30 to 430 feet in southeastern Hall County. The primary source of groundwater in Hall County is the saturated Pleistocene sand, gravel, and associated unconsolidated sediments (the alluvial aquifer) which are near the current land surface. Those sand and gravels overlie unconsolidated Pleistocene silts and clays. The sand and clay interval varies in thickness from 45 to 100 feet. The silts and clays are underlain by the Tertiary Ogallala Formation (1). Figure 3 illustrates typical soil permeabilities for Hall County.
Most wells near CAAP are completed in the alluvial (shallow) aquifer, but some wells in the central and western parts of Hall County are completed in the underlying Ogallala Formation (a deeper aquifer). A groundwater model indicated that the Ogallala may be the primary source for recharge of the alluvial aquifer. In the vicinity of CAAP, groundwater is typically 15 to 25 feet below ground surface with seasonal fluctuations varying from four to six feet in the monitoring wells. Water levels in irrigation wells are reported to fluctuate 20 feet or more. Horizontal flow velocities in sandy parts of the alluvial aquifer are estimated to range from 75 to 394 ft/year, and from 404 to 827 ft/year in gravelly parts. Flow is southwest to northeast, approximately parallel to the Platte River (1). Groundwater contamination off site is extensive, with plumes as large as four miles long by one mile wide along the eastern boundary (21) (see Figure 4). The most frequently documented groundwater contaminants are RDX and TNT. Other documented, off-site groundwater explosives include nitrobenzene, 1,3-DNB, 1,3,5-TNB, and 2,4- and 2,6-DNT. Groundwater uses include drinking, commercial and residential irrigation, filling of private swimming pools, and commercial animal watering.
Based on field measurements, RDX was estimated to be migrating at roughly the same rate as groundwater flow in the shallow aquifer and has migrated approximately twice as far as the other tested contaminants (22). EPA representatives have surmised that the chemical transformations and/or adsorption onto the geologic medium of the nitroaromatic compounds may explain their limited migration compared to RDX (22).Several studies have shown that TNT is readily biotransformed in the environment, reportedly polymerizes, and becomes tightly bound to organic materials (14). Because the study area consists mainly of sand and gravel, the attraction to organic materials might not have been as prominent as that seen in other studies. Another explanation is that parent TNT has broken down and degradation products may be moving with the groundwater. RDX studies have shown that it degrades under anaerobic conditions in the presence of organic nutrients. Because discharges of TNT to groundwater began in 1941 and discharges of RDX to groundwater began in 1950, a substantial length of time has passed during which degradation could take place. Consequently, the breakdown products of TNT and RDX may be migrating along with the groundwater. Those products may or may not be detected with the analytical methods used for detection of TNT. Historically, analytic parameters have not included analysis for many of the explosives' breakdown products. Primary breakdown products of TNT (2-A and 4-A) have not been analyzed. HMX, a major breakdown product and by-product of RDX, has been detected in several on- and off-post groundwater samples. In comparison to RDX, however, the extent of contamination has not been fully characterized. RDX was the predominant contaminant used to track the plume movement, and most wells were analyzed for that constituent only. Table 5 lists some of the proposed analytic parameters for future sampling (3).
EPA reviewed available data from the on- and off-post groundwater sampling and determined that insufficient information is available to conclude that contaminant concentrations are decreasing over time (22). The available data do not adequately define the extent of contamination for several reasons:
1. Different sampling procedures, such as well purging and sample handling methods, influence the data.
2. Detection limits have changed during the study period, and quality assurance and quality control (QA/QC) procedures may have varied among different laboratories.
3. Only one contaminant was consistently analyzed for in a majority of wells and the sampling frequency was limited. The EPA review found that 32% of the wells were sampled only once, and 32% were sampled twice (22).
4. It is impossible to accurately define the water-bearing zones sampled because of the lack of well construction data, use of unpredictable binding materials, and long wellscreen lengths. The lack of depth-discrete information prevents determination of the actual vertical and, to some extent, the horizontal contamination concentrations. Because many of the wells are irrigation and drinking water wells not installed by the Army, well construction data is available for only 30% of the wells. Construction data for some wells indicates that well sections were joined using polyvinyl chloride (PVC) glue. PVC glue has been shown not to be an effective seal for such joints because it allows water infiltration from a zone other than the screened zone. The limited well construction information indicates that many of the irrigation and drinking water wells around CAAP are screened over long intervals, a characteristic which would also fail to give depth-discrete sampling information. Additionally, dilution from the long screen lengths makes it impossible to determine the maximum contaminant concentration or to accurately prepare concentration contour maps.
5. The aquifer recharge because of intense precipitation and/or drawdown from irrigation wells can play an influential role in the irregular rate or direction of plume movement.
Sampling Performed by CAAP
A preliminary assessment was conducted by CAAP in August, 1982. Groundwater monitoring wells were installed around the load lines, nitrate area, and the burning grounds to assess the water table configuration, estimate groundwater flow velocities, and provide a groundwater sampling network. Results of the study indicated that leaching of explosives had caused groundwater contamination that had at least reached the installation boundary.
In January, 1983, 46 wells were sampled, including 30 on-post and 16 off-post wells (11 were for potable water supply and five were for irrigation). Explosives contamination was detected in seven on-post as well as five off-post wells (2 irrigation and 3 drinking water wells). The RDX concentrations in the drinking water wells were 17.6, 18.2, and 59.7 ppb.
In November, 1983, samples were taken from 14 on-post and 41 off-post wells. RDX contamination was detected in 12 on-post irrigation or monitoring wells and eight off-post drinking water wells. The eight contaminated drinking water wells included the water source for the Baptist Temple (21.8 ppb RDX).
Two of the residential drinking water wells sampled in January were resampled in the November event. RDX concentrations in those wells were 59.7 and 17.6 ppb in January and 43.8 and 124 ppb in November, 1983. A public announcement about off-post contamination was issued by CAAP on April 20, 1983.
In February, 1984, 472 wells were sampled, including 461 off-post domestic drinking water supply wells. Results of the analysis indicated that more than 200 drinking water wells in the off-post residential area were contaminated with RDX. Residents were offered an alternative water supply on April 6, 1984. Residents from 860 homes accepted the offer. Between June, 1984, and March, 1986, quarterly groundwater sampling and monitoring of on- and off-post wells was conducted. On- and off-post samples were analyzed for RDX; selected on-post wells were analyzed for TNT and other explosive compounds (1). Contaminant maps depicting the extent and location of plumes relative to existing structures or roadways don't exist or are difficult to read. Additional sampling is planned to determine other potential contaminants of concern and possible source areas.
Other Agency or Group Sampling
(Public and Private Water Supply Sampling for VOCs - 1982 to 1987)
In March, 1984, USGS sampled wells in the Grand Island area. Samples were analyzed for VOCs. No contamination was detected in the Grand Island Municipal wells at that time. In April, 1984, NDEC selectively sampled six municipal and private wells in the Grand Island area. Contamination was found in one municipal and three private wells; the Lincoln Street Municipal well contained 6.6 µg/L tetrachloroethene (PCE). The three private wells (including the Baptist Temple) contained various VOCs (trichloroethylene 32 µg/L [TCE]), 1,1,1-trichloroethane 15.8 µg/L [TCA]), 1,1-dichloroethene 9.2 µg/L [DCE]), and 1,2 dichloroethane 8.7 µg/L [DCA]). All three exceeded EPA's maximum contaminant levels (MCLs). The other three private wells had nondetectable concentrations of contaminants, but the detection limit was 50 µg/L. That limit is above most of the MCLs. In July, 1985, NDEC again sampled four selected private wells in Capital Heights (different from the April, 1984, wells). TCA was detected at levels up to 6.3 µg/L in one well. In 1987, samples from three private wells showed levels of trihalomethanes up to 19 µg/L. In August, 1987, EPA sampled the Baptist Temple well and detected bromoform and dibromochloromethane at 7 µg/L and chloroform at 2 µg/L. A summary of the sampling conducted by CAAP, NDEC, and EPA from 1982 through 1987 is given in Table 6.
(Monitoring Well Sampling by the University of Nebraska - Fall 1984)
In the Fall of 1984, the Conservation and Survey Division of the University of Nebraska (CSDUN) installed 35 additional monitoring wells at 13 locations downgradient from CAAP. CSDUN used those wells and data from existing monitoring and residential wells in an attempt to define the horizontal and vertical extent of explosives and nitrates contamination. CSDUN determined that the source of the explosives contamination was CAAP (21). Analysis of the nitrogen isotope composition (15N) of the nitrate ranged from +4.6 % to +15.0 %; Hall County averaged +4.3 %. The 15N signature associated with the fertilizer manufactured at CAAP is equivalent to about +1.5 %. Cattle feedlots and their associated spraying activities east of CAAP overlie much of the groundwater where the RDX plume is located. Shallow wells near that area contained relatively high levels of chloride and nitrate with 15N>10 %. High chloride levels are normally found in groundwater containing animal and/or human waste (21). CSDUN concluded that the principal source of contamination east of CAAP was agricultural leachates derived from animal wastes and commercial N-fertilizers. That analysis portrays the nitrate contamination as a regional problem, supported by its presence in the city water supply. In addition, a five year summary (1979-1983) of nitrate levels in 589 Hall county wells showed that from 67-79% of the wells had nitrate concentrations >10 ppm (23). However, the interpretation of and conclusions about the explosives data are debatable. The well construction was questionable (PVC glue was used to join the casings), and the study used data from other wells. ATSDR classifies the findings on the extent of explosives contamination as inconclusive.
TABLE 6. Summary of groundwater sampling for RDX/TNT (1982-1984), VOCs (1984-1987)
| Sampling Date | Total # Wells Sampled | On Post | Off Post | ||
| Monitoring Well | Irrigation Well | Irrigation Well | Drinking Water Well | ||
| RDX/TNT (Data Source: CAAP) | |||||
| August 1982 | 33 | 33 | |||
| January 1983 | 46 | 12 (6) | 13 (1) | 5 (2) | 11 (3) |
| November 1983 | 55 | 14* (7) | (5) | 41** | 41** (8) |
| February 1984 | 472 | 11 | 461 | ||
| VOCs (Data Source: as noted) | |||||
| April 1984 (NDEC) | 6 | 3*** | |||
| August 1984 (CAAP) | 55 | 33 | 22 | ||
| July 1985 (NDEC) | 4 | 3*** | |||
| August 1987 (EPA) | 2 | 1*** | |||
(Grand Island Water Supply Nitrate Sampling)
The City of Grand Island water supply is provided by nine wells southeast of the city and by a well field three miles south of the city on an island in the Platte River. Water is pumped to a distribution system and treated by chlorination. Several of the city wells have elevated nitrate levels (between 1 and 10 ppm) and periodically exceed the MCL (10 ppm); several wells have been abandoned because of that high nitrate problem. The city expects that the nine remaining wells may be closed out over the next few years because of the high nitrate levels, and the Platte River well field will be the sole source of drinking water for the area.
Although residents near CAAP have been provided with an alternative water supply, CAAP will continue to monitor private wells in and near the plume area for signs of contaminant movement. Future analyses will include nitrates. Residents outside the plume area can, therefore, compare their drinking water well data with the MCL of 10 mg/L.
Table 7 lists the highest concentrations of contaminants detected in off-post private and public water supplies and the years sampled.
Other Potential Sources
In order to identify other facilities that could contribute to contamination near CAAP, ATSDR conducted a search of the Toxic Chemical Release Inventory (TRI) for the Hall County area. The TRI database was developed by EPA using chemical release information provided by certain industries. The database compiles annually quantities of toxic chemicals entering each environmental medium from manufacturing facilities that employ more than 10 people. CAAP is not a manufacturing facility and therefore not subject to this reporting requirement. Data have been compiled for the years 1987-1989. No local releases were listed for the contaminants of concern.
C. Quality Assurance And Quality Control
The findings of this public health assessment primarily are based upon data developed by CAAP and reviewed by EPA and the State of Nebraska. When descriptions were provided, the QA/QC measures appeared consistent with measures normally taken with environmental sampling and analysis. The data are assumed to be accurate within the QA/QC procedures employed.
Many on-site buildings contain asbestos, especially in siding used during construction. An asbestos survey of the buildings has been conducted. A lead paint survey revealed chipping lead-based paint in many of the on-site buildings.
TABLE 7. Highest Concentrations of Contaminants Detected in Off-Post Public and Private Water Supplies
| CONTAMINANT | CONCENTRATION µg/L | SAMPLING DATE AND SOURCE | COMPARISON VALUE µg/L | ||
| child | adult | REFERENCE | |||
| Explosives | |||||
| 2,4-DNT 1 | 7 | * (All explosives, CAAP) | 20 | 70 | EMEG |
| 2,6-DNT 1 | 6 | * | NA | 0.05 | CREG |
| HMX | 6.5 | 5/24/89 | NA | 400 | DWHA |
| 1,3,5-TNB | 114 | 12/2/84 | 0.5** | 1.8 | RfD |
| 2,4,6-TNT | 445 | 3/19/85 | 5 | 18 | RfD |
| RDX | 371 | 3/19/85 | NA | 2 | DWHA |
| VOCs | |||||
| Bromoform 1 *** | 7 | 8/25/87 (EPA) | 100 | 100 | MCL |
| Chloroform 1 *** | 2 | 8/25/87 (EPA) | 100 | 100 | MCL |
| 1,2-DCA 1 (Lincoln Street well) | 8.7 | 4/12/84 (NDEC) | 5 | 5 | MCL |
| 1,1-DCE (Lincoln Street well) | 9.2 | 4/12/84 (NDEC) | 7 | 7 | MCL |
| Dibromochloromethane | 7 | 8/25/87 (EPA) | NA | 20 | DWHA |
| 1,1,1-TCA | 19.2 | 7/23/84 (NDEC) | 200 | 200 | MCL |
| 1,1,2-TCA | 6.3 | 7/10/85 (NDEC) | 5 | 5 | MCL |
| Tetrachloroethene 1 | 6.6 | 4/12/84 (NDEC) | 5 | 5 | MCL |
| TCE (Lincoln Street well) | 32.1 | 4/12/84 (NDEC) | 5 | 5 | MCL |
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