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PUBLIC HEALTH ASSESSMENT

CORNHUSKER ARMY AMMUNITION PLANT
GRAND ISLAND, HALL COUNTY, NEBRASKA


SUMMARY

The Cornhusker Army Ammunition Plant (CAAP), an installation under the command of the U.S. ArmyArmament, 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 producedsince 1973, because of past disposal activities, CAAP was placed in 1987 on the EnvironmentalProtection Agency's (EPA) National Priorities List for hazardous waste sites. The Agency for ToxicSubstances 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 healthassessment.

CAAP is three miles west of Grand Island in Hall County, Nebraska. Sampling of soil on theinstallation has shown contamination with metals, volatile organic compounds (VOCs), and explosives,including cyclotrimethylenetrinitramine (RDX), trinitrotoluene (2,4,6-TNT or TNT), andhexamethylenetetramine (HMX). Contaminated areas have been preliminarily evaluated, butassessment of the extent of contamination is not complete. Environmental evaluation is continuing inthe ongoing Remedial Investigation/Feasibility Study (RI/FS). The isolation of and limited access tomost on-post areas limits the likelihood of people coming into contact with any contamination. If landuse patterns at CAAP change, however, further environmental study will be needed to ensure humanhealth is protected.

Off-post contamination of groundwater with explosives, nitrates, and possibly VOCs and other unknowncompounds has in the past and currently poses a public health hazard. The number of persons exposedin the past by ingesting contaminated groundwater cannot be accurately estimated. The majority ofresidents exposed to contaminated drinking water in the past now have access to an alternative watersupply. Exposure may be possible, however, if residents consume vegetables grown in private gardensirrigated with contaminated water; recent laboratory studies indicate that plants may efficiently absorbRDX. ATSDR discussed this information with the U.S. Army Toxic and Hazardous Materials Agency(USATHAMA), EPA, Nebraska Department of Environmental Control (NDEC), and the NebraskaDepartment of Health (NDH) and recommended that residents stop using contaminated water to irrigatetheir vegetable gardens. On July 30, 1991, NDEC and NDH advised residents to stop eating vegetablesgrown in gardens irrigated with water from private wells. ATSDR attended a public meeting sponsoredby 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 possiblevegetable contamination, and, in August 1991, USATHAMA began sampling vegetables and soil fromresidential gardens, as well as soil from yards irrigated with contaminated water. Results from thevegetable sampling indicate that RDX was not detected above the 0.19 ppm health risk limit developedusing EPA guidelines. A public meeting to discuss the results of this sampling was sponsored byUSATHAMA on November 7, 1991. ATSDR attended that meeting. Additional soil and vegetablesampling is proposed during the RI/FS investigation.

To reduce human exposure to groundwater contaminants, ATSDR recommends continuing to monitorprivate drinking water wells for contaminants to ensure timely replacement of contaminated drinkingwater sources. In addition, water from contaminated private wells should not be used for swimmingpools, 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, uponlong-term exposure, could cause adverse health effects to any segment of the nearby population. Thoseadverse health effects might be the result of either carcinogenic or noncarcinogenic toxicity from achemical exposure.

Because people might have been exposed to RDX or other contaminants in the past at levels that couldcause illness, ATSDR's Health Activities Recommendation Panel determined that follow-up healthactivities are needed. ATSDR will carry out site-specific surveillance and disease- and symptom-prevalence studies as follow-up activities.


BACKGROUND

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 andChemical Command (AMC-COM), U.S. Army, U.S. Department of Defense. CAAP is located threemiles west of Grand Island in Hall County, Nebraska (Fig. 1). The primary mission of the facilityduring 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 offertilizer. 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 andHazardous Materials Agency (USATHAMA) conducted an installation assessment of CAAP (1). Thisassessment determined that the potential existed for groundwater contamination and migration frommunitions activities. In 1982, sampling and analysis of on-post monitoring wells indicated that theshallow groundwater aquifer was contaminated with RDX and TNT and the contamination hadmigrated to at least the installation boundary. Evaluation of groundwater contaminants in off-post areasbegan in 1983. Explosives contamination, especially RDX, was confirmed in on-post wells and foundin five of 16 off-post wells used for supply of drinking water and irrigation. RDX contamination of theshallow 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 Heightsand Capital Heights residential areas (hereafter referred to as Capital Heights), which are approximatelytwo miles from CAAP. Results of the analysis indicated that more than 200 drinking water wells in theoff-post area were contaminated with RDX. Bottled water was supplied by the Army from January1984 through June 1986 during construction of a permanent alternative water-supply system. Toextend the City of Grand Island water system to the affected area, a system of dewatering wells was usedto lower the water table sufficiently to allow installation of the water mains. During that time, waterwas discharged to Silver Creek north of the residential area. In December, 1986, 800 residences weregiven 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 contaminategroundwater, an on-site Comprehensive Environmental Response, Compensation, and Liability Act of1980 (CERCLA) removal action was performed. Incineration of soil surrounding 56 surfaceimpoundments began in August, 1987, at a site north of load lines 2 and 3 and south of the northernmagazine area. A total of 44,722 tons of soil were excavated and incinerated. Ash from theincineration 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 inJuly, 1987. A federal facilities Inter-Agency Agreement among the EPA, Nebraska Department ofEnvironmental 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). TheRI/FS will characterize further the extent of contamination and evaluate alternatives for cleaning up thesite.

The Agency for Toxic Substances and Disease Registry (ATSDR) is authorized by CERCLA to conductpublic health assessments on NPL sites to evaluate the public health significance of those sites. ATSDRdetermines whether health effects are possible and recommends actions to reduce or prevent possiblehealth 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 havebeen 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 Groundwater

ON 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 pitequipped with a canvas-like filter bag). The bag was used to filter out solid explosive particles. Thewastewater, which contained explosives not filtered out in the sack sump, then traveled through openconcrete channels into a circular earthen impoundment. The masonry-walled pit was open to the sandand gravel bottom. An overflow channel from this impoundment connected with a leaching pit designedto 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 duringWWII and the Korean and Vietnam conflicts (1). During those operations, 26,410 kilograms (kg) ofTNT 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.

B. Site Visit

ATSDR staff joined a representative of the Army Environmental Hygiene Agency on a site visit toCAAP on April 11-12, 1991. Discussions were held with a representative of USATHAMA and withthe CAAP Commander's representative concerning the progress of the IRP. A site tour was taken of theinstallation, including the study areas to be investigated in the during the IRP. Access to the fencedinstallation 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 ofthe buildings. Areas that previously contained the cesspools and leachfields on the load lines werevisited. The areas had been excavated and filled; no soil contamination was obvious. During a drivethrough the magazine areas, decontamination markings were seen on the magazines. ATSDR staff alsovisited an area used for burial of ashes produced by soil incineration; no evidence of seepage from thearea was seen. The same was true for the sanitary landfill. During a drive through the shop area, somestored 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 forexplosives. Approximately two acres of the burial site were fenced (two wire) and marked with ahazardous 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 theinstallation 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 theCity of Grand Island. Grand Island is the third largest city in Nebraska, with an estimated 1990population of 39,386. The population rose from 33,180 in 1980 to 39,386 in 1990. Hall County rosein population from 47,690 in 1980 to 48,925 in 1990 (6). A summary of the population's employmentand 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. About7% of the population was below poverty level.

The subdivisions of Le Heights and Capital Heights include approximately 450residences and are onthe western side of Grand Island about two miles from CAAP's eastern boundary. Northwest HighSchool and Engleman Elementary School are near the subdivision. The Nebraska Veteran's Home isalso 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 cityof 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 percentageof persons under age 10 lived in the selected area compared to Grand Island and Hall County. Anaverage of over three persons per household occurred in the area. These figures indicate the presenceof a large percentage of young families in their childbearing years relative to the city and countypopulations. A much lower percentage of persons were age 65 and older, again indicating that this areais populated predominantly by young families.

Just under 85 percent of all housing units were owner-occupied, which suggests a nontransientpopulation (i.e., renters tend to not remain in that residence for an extended period of time); thispercentage is much higher than those for the city and county. Median value of owner-occupied homeswas 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 plantedon the land are primarily corn for cattle and alfalfa. Two tracts are used for grazing about 100 head ofcattle. Several tenant industries lease buildings and land; 136 storage magazines are leased for privateuse. A railroad repair operation averages about 75 employees. A fiberglass operation hasapproximately 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 andalfalfa. Cattle feedlots and a gravel quarry operation are also present. Husker Harvest Days, an annualevent, is a farm demonstration and display show that attracts hundreds of thousands of people to thesouthwestern 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 southeastof the city and a well field three miles south on an island in the Platte River. Water is pumped to adistribution system and treated by chlorination. Further discussion of the groundwater aquifer is in theEnvironmental Contamination and Other Hazards section of this document.

D. Health Outcome Data

Health outcome data for the area surrounding CAAP were reviewed. The Nebraska State HealthDepartment Vital Statistics Annual Report for 1989 included information on births, marriages, anddeaths categorized to the county level (7). The Nebraska State Health Department Cancer Registry alsocontained information categorized to the county level (8).


COMMUNITY HEALTH CONCERNS

ATSDR identified community health concerns using a variety of methods. Citizens, correspondencewith elected officials (9) and citizens' interviews conducted during development of the USATHAMACAAP Community Relations Plan (10) were reviewed. Discussions were held with Grand Island Cityofficials during ATSDR's site visit April 11-12, 1991. Discussions also were held with citizens atpublic meetings convened by the Nebraska Department of Health, the Nebraska Department ofEnvironmental 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 oneplume 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 storagearea. Contaminants have been detected in soil, sediment, surface water and groundwater. CAAP begancollecting groundwater samples in August, 1982, and continues to collect samples to determine theextent of contamination. Other groups that have sampled groundwater include the U.S. GeologicalSurvey (USGS), NDEC, and EPA. Groundwater contamination (primarily containing explosives) fromthe leach pits and, possibly, other sources was detected in the early 1980s and prompted immediateaction. Previous remediation activities at CAAP included providing an alternative water supply to theCapital 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 evaluatedto determine whether exposure to them has public health significance. ATSDR selects and discussescontaminants based on several factors: sample design, field and laboratory data quality, and comparisonof 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 andsuspected environmental contaminants are factors considered by ATSDR when determining thecontaminants to which humans could be exposed.

Review of sampling field quality control procedures may include interpreting data on background (orregional) concentrations of chemicals. Additionally, the adequacy and number of replicate, spiked, andblank samples may be checked to verify detection of contaminants. To assess laboratory qualitycontrol, procedures used to verify instrument reliability may be reviewed.

Contaminant concentrations detected on and off site are compared to health comparison values whichare concentrations of chemicals that are believed to be without adverse health effects. Those values aredeveloped by agencies to provide estimates of levels at which health effects are not observed. Thosevalues, in many cases, have been derived from animal studies. Health effects are not only related to theexposure 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 contaminantconcentrations in specific media and for specific exposure routes. The potential for adverse healtheffects 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 healtheffects. Rather, the list indicates which contaminants will be evaluated further. The concentration ofa 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 ofconcern 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 thecontamination that may have resulted from past handling of explosives, the chemical manufacturing andbreakdown processes are described here. As with any chemical manufacturing process, each step of thereaction is not always complete. When the final product is obtained, many chemical compounds maybe present as contaminants or may have been produced as waste from previous production steps. Thosecompounds 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, oncea final product is made, it is subject to chemical breakdown into other products. This takes placethrough reaction with chemicals in the environment or through breakdown by biological processes inthe environment. RDX and TNT will be described here.

RDX is synthesized by the nitration of hexamethylenetetramine, which is obtained from the reaction offormaldehyde and ammonia (13). RDX is only slightly soluble in water; it does not degrade underaerobic conditions, but degrades somewhat anaerobically in the presence of organic nutrients. The rateof biotransformation is unknown (14). The biological degradation products of RDX are characterizedby 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 arethe raw materials. The three-stage process has the advantages of maximum yield and greater productpurity. Nitration is carried out by adding the nitrating acid to the toluene, mononitrotoluene, ordinitrotoluene 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 solutionof sodium sulfite and sodium hydrogen sulfite. The sodium sulfite reacts only slightly with the desiredTNT isomer, but reacts readily with the undesired isomers. The undesired isomers and the sulfite reactto form water-soluble compounds that are readily removed from the desired TNT by washing withwater. The sulfite also reacts with tetranitromethane (another undesired by-product from the TNTproduction) which is water soluble. The sodium sulfite does not react with dinitrotoluene ortrinitrobenzoic acid so they remain as impurities.

The yield of purified TNT can be as high as 80% (13). Once TNT has reached the environment, itdegrades under aerobic and anaerobic conditions. The breakdown products of 2,4,6 TNT formmonoaminodinitrotoluenes and tetranitroazoxy-toluene. U.S. Army Corps of Engineers determined inthe 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 anddisposal of explosives, the discussion to follow will cover contaminants that were detected in the variousmedia sampled, the list of chemicals that the laboratory looked for (list of analytes), and the list ofcontaminants 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  
Adapted from Reference 14

A. On-Site Contamination

Soil

CAAP conducted a field sampling survey in 1982. Soil samples were collected from several cesspoolsand leach pits around each of the five load lines. Sampling depths ranged from 0-18 inches to 18-36inches. 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 wereexcavated from the high-concentration areas for the incineration project. The target excavation levelswere 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 0.4for 2,4-DNT (3). This excavation was an attempt to remove the major source of groundwater and soilscontamination remaining at CAAP. A high water table prohibited the excavation to the target levels in29 of the 58 impoundments. Instead, soils were excavated to five feet below the water table. No postexcavation soil samples could be taken and the soil concentrations are assumed to be higher than thetarget levels (3). The impoundments were filled with clean fill. Pre-excavation concentrations inseveral of the high water table impoundments were high (examples are listed above) and concern existsthat 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 nearBuildings 4L-7 and 4L-5, respectively. The highest chromium concentration was detected in thenorthwestern corner of Load Line 5. Table 3 lists the highest concentrations of explosives detected inthe fall 1990 sampling.

The soil sample collected near building C-3-4 in the North Magazine Area had lead contamination ashigh as 1,460 ppm. TNT contamination was 28.4 ppm in a soil sample collected at the southern edgeof the magazine area. The sampling included 16 samples randomly collected from the North MagazineArea, 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 andmetals. Seventeen surface soil samples were collected from the South Magazine Area; no contaminationwas detected. Table 4 shows typical concentrations of explosives and metals found at the other studyareas 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 theextent 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 inmost cases include VOCs, pesticides/polychlorinated biphenyls (PCBs), and other specific compoundsassociated 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 asample from one location. This method gives little information on the areal distribution of thecontamination 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 todevelop 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 concentrationsthat may be present regionally. Chemicals found in background samples may be naturally occurringor from some other source.

CAAP will determine the extent of soil contamination from sampling conducted during the ongoingRI/FS. The RI/FS workplan proposes a phased approach to this sampling. Phase one will includeadditional biased samples from sites with historic activities similar to other sites from whichcontaminants have been detected (15, 16). All surface soil samples will be collected from depths to onefoot; at this depth, evaluation of contaminants to which people might be exposed by dermal contact isless certain since the soil contaminants would be diluted. Additionally, phase one sampling includessystematic grid sampling at sites where biased sampling results have indicated explosives and metalsin surface soils (15). The samples will be collected using field-screening techniques. The grid sampleanalyses will be used to prepare reliable maps to initially delineate the extent of contamination samplingto 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.
Adapted from Reference 3


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.
Adapted from Reference 3
Note: No data were available for the Nitrate, Pesticide Storage, Pistol Range, Drainage Ditch, and Sewage Treatment Plant Areas. The available data only reported analysis for explosives and metals.

Proposed Analytes During RI/FS

The phase one field-screening analysis will include 2,4,6 TNT, cadmium, chromium, and lead. Fivepercent of the total number of field-screening samples will be quantified for those same analytes usinglaboratory analysis. The list of proposed analytes for phase two in the RI/FS sampling plan is moreinclusive than that for previous sampling. Table 5 lists the proposed RI/FS analytes for explosives andsome of the impurities and biotransformation products of RDX and TNT. Some of the compounds notspecifically analyzed for will be detected as tententatively identified compounds if their concentrationis at least 10% higher than the equipment calibration standards. Addition of some of the othercompounds to the analyte list would define the extent of contamination more fully. Compounds suchas hydrazine and 1,1-dimethylnitrosamine have been studied with respect to health effects and mightbe considered for inclusion (17, 18).

Sediment

Three primary surface runoff accumulation ditches on site include the eastern and western channels andthe railroad ditch. When flowing, those ditches and channels discharge into Silver Creek. No surfacewater or sediment sampling has been conducted, although it is discussed in the RI/FS workplan.

Groundwater

The RDX contamination plume was first detected in 1982; CAAP continues to monitor thecontamination. On-site monitoring wells have detected contamination with the explosives RDX (307µg/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 abovetheir detection limits of 19 and 0.243 µg/L, respectively. Barium, cadmium, and chromium were notanalyzed for, but are proposed analytes in the RI/FS workplan. The current workplan outlines plansto sample for other constituents not previously sampled. On-site drinking water wells are approximately100 feet deep; they are monitored semi-annually for explosives and quarterly for VOCs. Nocontamination has been detected to date; the wells are used by tenants. On-site irrigation wells havesome of the highest levels of explosives contamination found at CAAP (1). Those high levels may becaused by the increased pumping capacity of the irrigation wells and their ability to draw contaminantstoward them. VOCs were also detected during the August, 1984, on-post irrigation and monitoring wellsampling.

Food Chain

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
Adapted from Reference 3, and 14

*Some of the compounds not proposed for specific analysis will be detected as tentatively identifiedcompounds 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.

B. Off-Site Contamination

Sediment/Surface Water

No information was available on sediment and surface water sampling off site. Additional informationwill be collected during the RI/FS.

Soil/Food Chain

In August, 1991, USATHAMA began sampling vegetables and soil from residential gardens, as wellas 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 Heightsand Le Heights subdivisions were tested for RDX. No RDX was found in concentrations greater thanthe detection limits of the assays, which were all below the health risk level of 0.19 ppm (19). The 0.19ppm 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 wellwater. Calculations have been made, based on risk analysis assumptions, which suggest that generalconcentrations of RDX and TNT found in the area groundwater would not accumulate in meat of cattle(20).

Groundwater

To appreciate how groundwater contamination might disperse, an understanding of the area's geologyis useful. Terrain in the area is nearly flat to slightly sloped. The ground surface at CAAP and thesurrounding area slopes gently as elevations drop approximately 100 feet from the southwest tonortheast. Soils are developed in quaternary windblown silts (Peorian loess) and range from silty tovery sandy at depths to 5 to 40 feet below ground surface. Beneath the surficial loess deposits liemoderately to highly permeable, unconsolidated Pleistocene sands and gravels. Soils in the study areanorth and east of CAAP vary from silty to sandy loams and have a high permeability. UnconsolidatedPleistocene sands and gravels vary in thickness from 30 to 430 feet in southeastern Hall County. Theprimary source of groundwater in Hall County is the saturated Pleistocene sand, gravel, and associatedunconsolidated sediments (the alluvial aquifer) which are near the current land surface. Those sand andgravels overlie unconsolidated Pleistocene silts and clays. The sand and clay interval varies in thicknessfrom 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 andwestern 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 alluvialaquifer. In the vicinity of CAAP, groundwater is typically 15 to 25 feet below ground surface withseasonal fluctuations varying from four to six feet in the monitoring wells. Water levels in irrigationwells are reported to fluctuate 20 feet or more. Horizontal flow velocities in sandy parts of the alluvialaquifer 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). Groundwatercontamination off site is extensive, with plumes as large as four miles long by one mile wide along theeastern boundary (21) (see Figure 4). The most frequently documented groundwater contaminants areRDX 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 residentialirrigation, filling of private swimming pools, and commercial animal watering.

Based on field measurements, RDX was estimated to be migrating at roughly the same rate asgroundwater flow in the shallow aquifer and has migrated approximately twice as far as the other testedcontaminants (22). EPA representatives have surmised that the chemical transformations and/oradsorption onto the geologic medium of the nitroaromatic compounds may explain their limitedmigration compared to RDX (22).Several studies have shown that TNT is readily biotransformed inthe environment, reportedly polymerizes, and becomes tightly bound to organic materials (14). Becausethe study area consists mainly of sand and gravel, the attraction to organic materials might not havebeen as prominent as that seen in other studies. Another explanation is that parent TNT has brokendown and degradation products may be moving with the groundwater. RDX studies have shown thatit degrades under anaerobic conditions in the presence of organic nutrients. Because discharges of TNTto groundwater began in 1941 and discharges of RDX to groundwater began in 1950, a substantiallength of time has passed during which degradation could take place. Consequently, the breakdownproducts of TNT and RDX may be migrating along with the groundwater. Those products may or maynot be detected with the analytical methods used for detection of TNT. Historically, analytic parametershave not included analysis for many of the explosives' breakdown products. Primary breakdownproducts 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 toRDX, however, the extent of contamination has not been fully characterized. RDX was the predominantcontaminant 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 thatinsufficient information is available to conclude that contaminant concentrations are decreasing overtime (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 ofwell construction data, use of unpredictable binding materials, and long wellscreen lengths. Thelack of depth-discrete information prevents determination of the actual vertical and, to someextent, the horizontal contamination concentrations. Because many of the wells are irrigationand drinking water wells not installed by the Army, well construction data is available for only30% of the wells. Construction data for some wells indicates that well sections were joinedusing polyvinyl chloride (PVC) glue. PVC glue has been shown not to be an effective seal forsuch joints because it allows water infiltration from a zone other than the screened zone. Thelimited well construction information indicates that many of the irrigation and drinking waterwells around CAAP are screened over long intervals, a characteristic which would also fail togive depth-discrete sampling information. Additionally, dilution from the long screen lengthsmakes it impossible to determine the maximum contaminant concentration or to accuratelyprepare 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 wellswere installed around the load lines, nitrate area, and the burning grounds to assess the water tableconfiguration, estimate groundwater flow velocities, and provide a groundwater sampling network. Results of the study indicated that leaching of explosives had caused groundwater contamination thathad at least reached the installation boundary.

In January, 1983, 46 wells were sampled, including 30 on-post and 16 off-post wells (11 were forpotable 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 concentrationsin 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 contaminationwas detected in 12 on-post irrigation or monitoring wells and eight off-post drinking water wells. Theeight contaminated drinking water wells included the water source for the Baptist Temple (21.8 ppbRDX).

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 inNovember, 1983. A public announcement about off-post contamination was issued by CAAP on April20, 1983.

In February, 1984, 472 wells were sampled, including 461 off-post domestic drinking water supplywells. Results of the analysis indicated that more than 200 drinking water wells in the off-postresidential area were contaminated with RDX. Residents were offered an alternative water supply onApril 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 explosivecompounds (1). Contaminant maps depicting the extent and location of plumes relative to existingstructures or roadways don't exist or are difficult to read. Additional sampling is planned to determineother 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 thosewells and data from existing monitoring and residential wells in an attempt to define the horizontal andvertical extent of explosives and nitrates contamination. CSDUN determined that the source of theexplosives contamination was CAAP (21). Analysis of the nitrogen isotope composition (15N) of thenitrate ranged from +4.6 % to +15.0 %; Hall County averaged +4.3 %. The 15N signature associatedwith the fertilizer manufactured at CAAP is equivalent to about +1.5 %. Cattle feedlots and their associated spraying activities east of CAAPoverlie much of the groundwater where the RDX plume is located. Shallow wells near that areacontained relatively high levels of chloride and nitrate with 15N>10 %. High chloride levels arenormally found in groundwater containing animal and/or human waste (21). CSDUN concluded thatthe principal source of contamination east of CAAP was agricultural leachates derived from animalwastes and commercial N-fertilizers. That analysis portrays the nitrate contamination as a regionalproblem, 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 nitrateconcentrations >10 ppm (23). However, the interpretation of and conclusions about the explosives dataare debatable. The well construction was questionable (PVC glue was used to join the casings), and thestudy 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***
Adapted from Reference 1, 24
( ) Indicates the number of wells in which explosives were detected.
* 14 wells were sampled. Information on the distribution was not available.
** 41 wells were sampled. Information on the distribution was not available.
An alternative water supply was offered to residents on 4/6/84.
*** An unknown number of wells was sampled; an estimate is given. The estimate is the number of samples cotaminated with detectable levels of VOCs.

(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 fieldthree miles south of the city on an island in the Platte River. Water is pumped to a distribution systemand treated by chlorination. Several of the city wells have elevated nitrate levels (between 1 and 10ppm) and periodically exceed the MCL (10 ppm); several wells have been abandoned because of thathigh nitrate problem. The city expects that the nine remaining wells may be closed out over the nextfew years because of the high nitrate levels, and the Platte River well field will be the sole source ofdrinking water for the area.

Although residents near CAAP have been provided with an alternative water supply, CAAP willcontinue 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 theirdrinking 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 watersupplies and the years sampled.

Other Potential Sources

In order to identify other facilities that could contribute to contamination near CAAP, ATSDRconducted a search of the Toxic Chemical Release Inventory (TRI) for the Hall County area. The TRIdatabase was developed by EPA using chemical release information provided by certain industries. Thedatabase compiles annually quantities of toxic chemicals entering each environmental medium frommanufacturing facilities that employ more than 10 people. CAAP is not a manufacturing facility andtherefore 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 andreviewed by EPA and the State of Nebraska. When descriptions were provided, the QA/QC measuresappeared consistent with measures normally taken with environmental sampling and analysis. The dataare assumed to be accurate within the QA/QC procedures employed.

D. Physical And Other Hazards

Many on-site buildings contain asbestos, especially in siding used during construction. An asbestossurvey 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
Adapted from References 19, 24
* Sampling date unknown (22).
** RfD for TNB was derived from studies based on m-dinitrobenzene because of a lack of data on TNB. An extremely high uncertainty factor was used to derive this RfD.
*** These compounds are classified as trihalomethanes and could originate from chlorination of the water supply.
1 - These compounds are classified as B2 carcinogens (probable human carcinogens).
DWHA = Drinking Water Health Advisory for a lifetime. Published by EPA.


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