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PUBLIC HEALTH ASSESSMENT

TOOELE ARMY DEPOT (NORTH AREA)
TOOELE, TOOELE COUNTY, UTAH


ENVIRONMENTAL CONTAMINATION AND POTENTIAL EXPOSURE PATHWAYS

The primary goal of a PHA is to identify whether people living near a suspected or known hazardous waste site are being or have been exposed to site-related contaminants and evaluate the potential exposure to see if it could cause harmful effects. To accomplish this mission, ATSDR looks at both the type and amount of contaminants released by the site into the environment and how the community comes into contact with those contaminants.

Previous sections of this PHA describe what is known about the industrial and military activities that have occurred at TEAD. This section describes the type and amount of contaminants that have been measured in the environment, and how the community comes into contact with those contaminants. Some of the contaminants can occur naturally (e.g., arsenic, lead, and other metals) and may be detected as a result of natural processes not related to activities at TEAD. Other contaminants detected on site are likely the result of TEAD activities (i.e., industrial chemicals and explosives). All of these contaminants will be considered in this evaluation.

People may be exposed to chemicals by inhalation (breathing in contaminated air), ingestion (eating contaminated foods and/or drinking water), or by direct contact with skin (dermal). When people are exposed to chemicals, the exposure does not always result in adverse health effects. The type and severity of the health effects that may occur in an individual from contact with the contaminants depend on a variety of factors. The major factors include the toxicological properties of the contaminants, the amount of contaminant to which the individual is exposed, how often and for how long the exposure occurs, and the manner in which the contaminant enters the body (i.e., breathing, ingesting, or skin/eye contact). Other factors that can affect how a person's body reacts to a specific chemical exposure are the individual's age, sex, nutritional status, genetics, and health status. Many of these factors can influence how the individual absorbs, distributes, metabolizes, and excretes the contaminant, and may ultimately influence whether exposure to a contaminant results in harmful effects.

During this PHA, the bulk of our work was spent on identifying the ways in which people could come into contact with contaminants present at TEAD. ATSDR uses the term "exposure pathway" to describe the way that a chemical moves from its source (where it began) to where and how people can come into contact with (or get exposed to) it. An exposure pathway consists of five elements and if all five elements exist, the exposure pathway is considered to be completed. A completed exposure pathway represents the link between the environmental contamination that exists on the site and the community that lives near the site. The text box on the following page describes each of the exposure pathway elements and describes how they relate to TEAD and the surrounding communities.

ATSDR evaluated whether people have been (past), are (current), or could be (future) exposed to harmful levels of chemicals migrating from TEAD, based on the strength of all the available evidence to evaluate potential health effects. Figure 4 describes ATSDR's exposure evaluation process. This process is designed to provide a conservative estimate of exposure. As a result this estimated exposure will likely exceed the actual exposure to the nearby community. This is done to ensure that ATSDR's evaluations are health protective.

If exposure was or is possible, ATSDR then considers whether chemicals were or are present at levels that might be harmful to people. ATSDR does this by screening the concentrations of contaminants in an environmental medium against health-based comparison values (CVs) (Appendix A). CVs are chemical concentrations that health scientists have determined are not likely to cause adverse effects, even when assuming very conservative or safe exposure scenarios. Because CVs are not thresholds of toxicity, environmental levels that exceed CVs would not necessarily produce adverse health effects. If a chemical is found in the environment at levels exceeding its corresponding CV, ATSDR closely examines the potential exposure variables and the toxicology of the contaminant in order to identify the type of health effects that could be expected from the exposure. Regardless of the level of environmental contamination, a public health hazard exists only if people come in contact with, or are otherwise exposed to, harmful levels of contaminated media.

A summary of the evaluation of these exposure pathways is presented in Table 2 and described in more detail in the discussion that follows. To acquaint readers with terminology used in this report, a glossary is included in Appendix B. For most of the contaminated sites (SWMUs) identified at TEAD, a completed pathway is not evident.

Table 1, "Evaluation of the Public Health Hazards Associated With the Operable Units and Other Source Areas at TEAD," summarizes the site description and waste disposal history for each SWMU, presents results of environmental investigations, and describes what corrective actions have been taken. The column in Table 1 titled "Investigation Results/Environmental Monitoring Results" provides, when available, the chemical name and corresponding concentrations measured in the soil, groundwater, surface water, or sediment. Unless noted otherwise, the chemicals listed were detected at that site at least once with a concentration above ATSDR's CV. The concentration presented with the chemical is the highest concentration of that chemical, detected at that site, in that environmental medium (soil, groundwater, surface water, or sediment). Those contaminants reported may only represent a small sub-set of the contaminants that were considered in the chemical analysis.

The Five Elements of an Exposure Pathway
And Their Relevance to the TEAD Communities: Element 1: Contaminant Source or Release
Each site at TEAD that was known or suspected to be contaminated was evaluated to identify the types of contaminants that were released and how they were released. Examples include chemical spills or releases from leaking drums, historical disposal into lagoons, and releases during munitions disposal activities., Element 2: Environmental Fate and Transport
Once released into the environment, contaminants may move through and across environmental media (i.e., air, water, soil) and/or degrade into less hazardous chemicals. At TEAD, the majority of the releases were directly or indirectly to the soil; transport off-post is typically through the groundwater., Element 3: Exposure Point or Area
The location where people might come into contact with the contaminated environmental media. The main exposure points are 1) playing or working in the soil of a contaminated site and 2) drinking or bathing in contaminated water after it has left the site., Element 4: Exposure Route
This is the specific manner by which people physically come in contact with the contaminant(s). The main exposure routes are 1) ingestion of contaminants from groundwater, surface water, or soil; 2) dermal contact with contaminants in soil, groundwater, or surface water; and 3) inhalation of contaminants in air., Element 5: Potentially Exposed Populations
The characteristics of the populations that may come, or may have come, in contact with the contaminants. If a portion of TEAD is used for residential or recreational purposes, this may include some residents near TEAD who use a private groundwater well to supply their drinking water and children who may play in the soil.

ATSDR uses CVs to identify chemicals and sites which should be looked at a little more closely. If a site contains contaminants with concentrations all below the CVs, that site will not pose a public health hazard to the community. If a site does contain contaminants with concentrations above the CVs, then it is looked at more closely to see if a completed exposure pathway exists. If the contaminants are not transported off of the site and people do not have access to the site, the exposure pathway is not complete and this site does not pose a public health hazard to the community.

The final column in Table 1, "ATSDR's Evaluation of Public Health Hazards," describes whether contaminants identified at TEAD represent a completed exposure pathway for people living nearby or for members of the community who may have access to any portions of the contaminated site. The contaminants identified at the majority of the TEAD sites do not represent a completed exposure pathway and, therefore, do not pose a public health hazard. In those cases, the final column also provides a brief explanation as to why the site does not pose a public health hazard for the community. There are however, a couple of sites where the potential exposure pathway required a more detailed review; those evaluations will be described below.

ATSDR reviewed the environmental data generated from initial environmental assessments and remedial investigations (RIs) of the 57 SWMUs at TEAD to determine if there are any associated past, current, or future public health hazards. ATSDR also evaluated other environmental data such as drinking water and air monitoring data. From this review, ATSDR identified and evaluated five potential exposure pathways of concern. Table 2 summarizes the exposure elements and main findings for each of the following pathways.

Potential Exposure to Contaminated Groundwater

  1. Past and current use of on-site drinking water supply wells at TEAD.

  2. Past and current use of off-site private drinking water wells, municipal wells, and other private supply wells to the north and east of the northern boundary of the depot.

Potential Exposure to Air Contaminants

  1. Past and current exposure of Grantsville residents to air contaminants from OB/OD activities at TEAD.

Potential Exposure to Contaminated Surface Soil

  1. Past and current exposure to ordnance and explosive waste (OEW) on private farm land adjacent to TEAD OB/OD activities.

  2. Past and current exposure to lead-contaminated soil from trap and skeet range activities at SWMU 57.

Evaluation of Contaminated Groundwater

Sources and Extent of Groundwater Contamination at TEAD

The disposal of industrial wastes at TEAD has resulted in groundwater contamination underneath the depot. There are two primary contaminant plumes at TEAD: 1) the industrial waste lagoon, which has been designated the main plume, and 2) the northeastern area boundary plume. Although several contaminants have been detected, trichloroethylene (TCE) is the principal contaminant of concern because its extent and concentration in the two primary plumes is considerably greater than the extent and concentrations of other contaminants detected (e.g., 1,2-dichloroethane and carbon tetrachloride).

Industrial Waste Lagoon (Main) Plume

The main plume is the larger of the two groundwater plumes identified at TEAD and is approximately 1.9 miles at its widest point. This plume appears to originate in the southeastern portion of the TEAD industrial area. The most significant sources for this plume are the IWL and associated unlined wastewater ditches, the old IWL, the sanitary landfill, a trench near Building 609 (SWMU 49), and numerous buildings in the TEAD maintenance area, including Buildings 600, 604, 607, 611, 614, 615, 619, 620, and, 637 (Kleinfelder 1998a, 2000).

Results of groundwater monitoring conducted in 1988 showed that TCE concentrations ranged from 0.10 ppb to 250 ppb. In addition to TCE, other VOCs such as 1,1,1-trichloroethane and carbon tetrachloride were detected in monitoring wells. The major focus of this discussion is on TCE, because in addition to being found at levels exceeding its CV, TCE is detected in almost twice as many wells at TEAD as any other contaminant (USACE TEAD database, November 2002). TCE levels have been detected as high as 300 ppb in the main plume (Table 4). The highest concentrations were found in samples from monitoring wells adjacent to the wastewater ditches south of the IWL.

It is estimated that the downgradient end of the main plume is approximately 1,500 feet north of the northern TEAD boundary, at least 400 feet thick, and contains approximately 36 billion gallons of groundwater with TCE concentrations greater than 5 ppb. Natural movement of the contaminant plume is estimated to be between 700 and 1,200 feet per year (Kleinfelder 2000; Montgomery 1988). A pump-and-treat system has been installed in the north-central boundary of the depot to treat TCE-contaminated groundwater before it migrates off site. The treatment system currently handles approximately 5,000 gallons of groundwater per minute (Ageiss 1994).

Northeastern Boundary Plume

Sampling results from monitoring wells installed in 1996 and 1997 found concentrations of TCE above 100 ppb along a narrow plume, the abovementioned "northeast boundary plume." The plume extends northward approximately 7,500 feet from the northern end of the former maintenance area to beyond the northeastern TEAD boundary. The source(s) and extent of the northeastern boundary plume are in the process of being characterized. The primary contaminant associated with this plume is TCE. TCE has been detected at concentrations as high as 1,500 ppb near the suspected source, a sump located on the west side of Building 679, part of SWMU 58. The downgradient extent of the TCE plume is not known and additional monitoring wells have been installed to delineate the northeast extent of the plume where it has the potential to migrate off site (Kleinfelder 1998a, 2000). TCE was not detected in groundwater samples from upgradient monitoring wells along the eastern TEAD property boundary and from the Defense Reutilization and Marketing Office yard. The off-site extent of the TCE plume is in the process of being delineated and the most recent sampling efforts show that the TCE plume (5 ppb contour) extends nearly 1 mile from the northeast boundary of TEAD.

Past and Current Use of On-Site Drinking Water Supply Wells at TEAD

Summary

There are two active supply wells (wells #1 and #3) that are used to provide drinking water to TEAD. Both wells are located in the southern and central portion of the Maintenance Area (Figure 3). They are upgradient from the two primary groundwater plumes located at TEAD (Figure 3) and are not affected by site-related contaminants. TEAD well #2, located in the northeast portion of the BRAC parcel, was used as a drinking water source for TEAD until January 2000 (Monty Rashwan, TEAD Engineering, personal communication, September 6, 2001). A drinking water source protection plan has been developed for each well and all monitoring results have met both state and federal drinking water standards. ATSDR concludes that groundwater poses no past or current public health hazard for on-site drinking water.

Nature and Extent of Contamination

ATSDR reviewed recent drinking water monitoring data from TEAD. TEAD representatives are required to submit a Drinking Water Source Protection Plan for each of its drinking water supply wells. Available data were collected from 1994 (nitrate, nitrite, and VOCs), 1997 (lead and copper), 1998 (nitrate, pesticides, and VOCs), 1999 (lead and copper), and March 2001 (VOCs and pesticides). Results of all the monitoring tests met all state and federal safe drinking water standards. In February 1997, lead (90 ppb) was detected in one sample taken from the tap. However, according to a TEAD official, the contamination source was a new fire sprinkler system installed just days before sampling. Once the line was flushed and resampled the level dropped below the detection limit (<3.0 ppb) (TEAD 1994; Department of the Army 1997, 1998a, 1998b; Utah Division of Drinking Water 2000; Utah DOH 2001; Monty Rashwan, TEAD Engineering, personal communication, June 4, 2001).

Evaluation of Potential Public Health Hazards

Past Exposure

Based on reviews of past drinking water monitoring reports for TEAD, ATSDR did not identify any contaminants that would be of public health concern. A schedule for testing drinking water from supply wells # 1, #2 and # 3, which has been approved by the State of Utah's DEQ, Division of Drinking Water, has been in place at TEAD since the primary and secondary drinking water standards were promulgated. All drinking water wells have been monitored for bacteria monthly; nitrates every year; inorganics, volatile organic compounds (VOCs), and pesticides every 3 years; and radionuclides every 4 years. All past monitoring tests have met state and federal safe drinking water standards for VOCs, pesticides, and metals. ATSDR concludes that drinking water from all supply wells at TEAD did not pose a past public health hazard.

Current Exposures

ATSDR reviewed the most recent drinking water monitoring from March 2001 and did not identify any contaminants that would be of public health concern. TEAD drinking water continues to meet all state and federal safe drinking water standards. Based on recent monitoring results, ATSDR concludes that drinking water from the two supply wells at TEAD does not pose a public health hazard.

Past and Current Use of Off-Site Private Drinking Water Wells, Municipal Wells, and Other Private Supply Wells to the North and East of the Northern Boundary of the Depot

Summary

Two TCE plumes originate from the TEAD maintenance area; the northeast boundary plume is known to extend off-base. Municipal water systems for Tooele City and Grantsville have not been, and are not currently, affected by TEAD-related groundwater contamination. Continued monitoring of the plume's boundaries and municipal water supplies is expected to ensure the water quality will not be affected by the TCE plumes. The off-base migration of the northeast boundary TCE plume has affected a private well, located just beyond the northeastern boundary of TEAD. This well is used for industrial purposes only, not for drinking, and does not pose a hazard to the employees.

It is possible that other wells in the area are impacted by the TCE plume; however, the levels are not expected to pose a public health hazard for irrigation, stock watering, or industrial purposes. All residents within 1 mile of the northeast boundary of TEAD are expected to be connected to the Tooele City municipal water system for their domestic water supplies (e.g., drinking, cooking, showering).

Nature and Extent of Contamination

In the Tooele Valley only water rights for small domestic wells (i.e., less than 1.73 acre feet of water used per year) are available. Someone proposing any larger water use would need to obtain rights from an already existing water permit. During 1987, a TEAD contractor conducted an inventory of all water rights applications within a 5-kilometer radius of the TEAD boundary. The area included rangeland and irrigated cropland as well as the incorporated towns of Grantsville and Tooele. Water rights information was obtained from the Utah State Division of Water Rights. At that time, very few wells (fewer than five) were located within 1 mile of the northern border of TEAD (Montgomery 1987).

A September 2001 search of water rights identified 36 wells that are permitted to use groundwater for domestic purposes within 2 miles north of the northern boundary of the depot. Most of these private wells are either in the city of Grantsville or just to the east of Grantsville (UDWR 2001; USGS 1997; Montgomery 1989). Within 1 mile of the TEAD northern boundary, groundwater is primarily used for irrigation and to support cattle and other livestock.

A Grantsville municipal well is about one quarter mile north of the northwest corner of the depot. The well is 505 feet deep and is screened between 280 and 480 feet. The well has been providing drinking water to approximately 100 individuals since 1999. This municipal well is monitored routinely and meets all state and federal drinking water standards (Joel Kertamus, Public Works Director, Grantsville City, personal communication, September 6, 2001).

The closest off-site production well is the Bolinder well which is used by the Staker/JB Parsons asphalt manufacturing facility. This well was drilled in 1984 and registered with Utah's Division of Water Rights as a "non-potable" supply well. This well is located near highway 112, approximately 200 feet northeast of the TEAD boundary. The Bolinder well has been sampled at five different times between April 1997 and April 1998. The groundwater samples from the Bolinder well were only analyzed for TCE since this is the primary contaminant that has been detected in the TEAD northeastern boundary plume. The maximum TCE concentration (220 ppb) was detected during July and October 1997. The lowest TCE concentration (140 ppb) was detected in January 1998 (Dames & Moore 1998b). These concentrations are much higher than EPA's maximum contaminant level (5 ppb) for TCE in drinking water, but the water from the Bolinder well is only used for industrial purposes.

After TCE was detected in the Bolinder well just northeast of the TEAD boundary, eight new off-site monitoring wells were installed by TEAD to characterize the off-site migration of the plume. As of September 2001, samples have been collected and analyzed from the new monitoring wells. These wells range from 175 feet to 375 feet deep and are located mostly north of the Bolinder well. TCE was detected in all eight wells, at a maximum concentration of 141 ppb (Well A) and a minimum concentration of 0.61 ppb (Well C) (Tooele Army Depot 2001). Three additional wells are going to be installed and additional samples will be collected to further characterize the extent of the groundwater plume.

Evaluation of Potential Public Health Hazards

Past Exposure

The water rights inventory conducted in 1987 did not identify any significant groundwater use (i.e., fewer than five wells) within 1 mile of the northern boundary and very limited groundwater use within 3 miles of the northern boundary (Montgomery 1987). Based on all available information that has been collected, groundwater near the northeast and eastern groundwater plumes underneath TEAD is not routinely used as a source of drinking water. The Bolinder well was drilled in 1984 and, according to the water rights records available on the Utah DEQ Web site, the well was not permitted for domestic uses. Interviews with current employees indicate that bottled water is used for all drinking and cooking needs. Therefore, ATSDR concludes that private wells, north of the depot, were not used to supply drinking water. Their use for irrigation or industrial purposes did not pose a past public health hazard.

Current Exposures

Current exposures from the northeast boundary TCE plume are not expected because, according to Tooele City representatives, residents near the northeast boundary of TEAD are connected to the Tooele City municipal water supply; and all municipal wells meet state and federal safe drinking water standards. According to Grantsville City representatives, residents living near the northern boundary of TEAD are connected to a municipal well operated by the city of Grantsville; that well also meets state and federal safe water drinking standards. But if current or future residents within 1 mile of the northeast corner of the TEAD choose to use private groundwater wells to supply their domestic water needs (e.g., drinking, cooking, showering), they should contact the Tooele County Department of Health to obtain information, including fees and schedules, for appropriate groundwater testing. ATSDR concludes that current municipal drinking water sources are not affected by the TEAD TCE plume. The plume monitoring conducted by TEAD and municipal well monitoring conducted by Tooele City and Grantsville are expected to ensure continued water quality in the future. Private wells located within 1 mile of the northeast corner or north-central boundary of TEAD may be affected by the TCE plume; water quality is believed to be appropriate for irrigation, stock watering, and industrial uses.

Evaluation of Air Contamination

Past and Current Exposure to Air Contaminants From Open Burning/Open Detonation Activities at TEAD

Summary

ATSDR used a variety of data sources to evaluate the potential exposure of Grantsville residents to contaminants released during TEAD open burn/open detonation (OB/OD) operations. The bang-box tests identify the major contaminants released by OB/OD operations and roughly quantifies the mass released based on the net explosive weight of the munitions. Environmental sampling at TEAD and other sites confirms the identity of the major contaminants in the plume and that off-base soil contamination is not likely due to OB/OD activities. Air modeling simulations predict that OB/OD operations could affect the 24-hour ambient air quality for a few days each year; however, for the majority of the year OB/OD operations are not expected to lead to ambient air concentrations above the EPA's National Ambient Air Quality Standards (NAAQS). Finally, air monitoring results in Grantsville confirm that the air quality there is within the NAAQS standards and does not appear to be affected by OB/OD operations. ATSDR concludes that exposures to air contaminants from OB/OD activities at TEAD do not pose a current public health hazard for residents living in close proximity to the depot.

Nature and Extent of Contamination

The OB/OD Unit is located in the southwestern corner of TEAD, about 3,000 feet from the nearest western boundary and 4,000 feet from the nearest southern boundary. The northern base boundary is approximately 4 miles north of the OB/OD site and downtown Grantsville, the closest community, is about 6 miles north of the OB/OD unit. The OB/OD Unit consists of separate detonation and burn areas; it has been in operation since the 1940s, used for demilitarization activities including munitions detonation and propellant burning. The activities at the OB/OD unit continue today on a reduced schedule.

The TEAD air pathway assessment is based on data gathered from a variety of sources, including 1) tests performed under specifically controlled conditions (i.e., the Army's bang-box emission tests); 2) tests performed under normal operating conditions at TEAD and other OB/OD operations around the country; 3) air modeling performed for TEAD operations; and 4) air monitoring conducted in Grantsville. The following is a brief summary of ATSDR's evaluation. A question/answer section is included in the community concerns section of this document to provide specific information to local residents.

OB/OD Activities

Open burning activities at TEAD occur on 15 burn pads at the burn area within the TEAD demolition range. Open burning is conducted to destroy waste bulk propellants. A maximum of 12 burn pans are used per day, with a maximum of two burns conducted per pan per day. There are approximately 120 burn days per year and the maximum amount burned for any single event is currently 1,000 pounds net explosive weight per pan (TEAD 1998).

The open detonation process at TEAD is conducted in 19 subsurface pits. The depth of the pits are determined by the quantity of munitions to be treated. There are approximately 120 open detonation days per year and the maximum amount detonated for any single event is currently 750 pounds net explosive weight per pit. This maximum weight limit for explosive materials has been in place since 1996 (TEAD 1998). Between 1992 and 1996 the maximum amount detonated allowed for any single event was 1,500 pounds net explosive weight. Prior to 1992, TEAD allowed a maximum detonation limit of up to 3,000 pounds per pit. In addition, "static firing" is conducted in six silos, with a maximum of four firings of each silo per day and a maximum net explosive weight per silo of 755 pounds (Larry McFarland, TEAD, personal communication, January 17, 2001; William Ienatsch, TEAD, personal communication, September 19, 2001; Larry McFarland, TEAD, comments provided for the pre-decisional draft for data validation, January 2003).

TEAD does not conduct OB/OD activities all year round because of the frequent and long-lasting temperature inversions that occur in winter months. Typically OB/OD operations occur from April to November. TEAD has established meteorological criteria for conducting OB/OD activities that include a wind speed under 20 miles per hour (mph) for open burning and under 15 mph for open detonation operations, visibility at least 1 mile or greater, and less than a 75 percent chance of precipitation. Meteorological conditions are monitored by two 10-meter towers located near the OB/OD unit (TEAD 1998). The meteorological restrictions are designed to minimize the impact of noise propagation caused by inversion layers.

Emissions

All materials treated by OB/OD are solids. Potential emissions from the OB/OD activities primarily includes products of combustion (i.e., carbon monoxide, carbon dioxide, nitrogen and nitrogen oxides, water, sulfur dioxide, and methane). Other emissions may include products of incomplete combustion (i.e., energetic materials such as explosives and organic materials) (TEAD 1998).

Munitions to be destroyed are loaded onto pallets and buried in 7- to 10-foot-deep pits dug into the hillside. Each detonation generates a large plume of smoke and dust, from the actual combustion of the explosive material and the cover soil. Direct measurements of air emissions from OB/OD activities has not been conducted at TEAD. However, a variety of tests, have been conducted under controlled conditions or at other OB/OD sites. These test results have identified the major constituents released by the detonation and the amount of each constituent relative to the mass of material burned or detonated.

Tests conducted by the Army and EPA measured the emission of hundreds of chemicals which could potentially be released during OB/OD operations. These are frequently referred to as the 'bang box' tests because the burns and detonations were performed inside an enclosed test chamber specially designed to measure the concentration of all types of compounds that could be released by burning or detonating explosive materials. These tests identified the amount of each chemical released per pound of explosive used, for a wide variety of conventional munitions. Results indicate that while hundreds of compounds are potential combustion by-products, only a limited number of compounds are truly probable by-products, and even fewer are emitted at levels that would be detectable in the environment following an OB/OD operation in the field.

This research indicates that water vapor, carbon dioxide (CO2), particulate matter with an aerodynamic diameter of 10 microns or less (PM10), and carbon monoxide (CO) are the major by-products of OB/OD operations. Other chemicals are also released, but at much lower levels. This is consistent with other types of hydrocarbon combustion processes, such as those used in automobile engines, fireplaces, and boilers. For OB/OD events, carbon dioxide and PM10 are the two compounds emitted at the highest levels from either open burn or open detonation operations. The PM10 emissions are at least 10 times greater than any other compound emitted from OB/OD events. In addition, PM10 is often measured as a part of OB/OD emission studies and as a normal air quality indicator (EPA, 1998); therefore, PM10 is an easily measured indicator of potential downwind effects from OB/OD events.

The velocity of the explosion and the heat released by the explosion combine to create an open detonation plume that rises hundreds of feet into the air above the detonation pit. The contaminants in the plume then mix with the surrounding air as it moves with the wind, further reducing the contaminant concentration within the plume. Every time the radius of a spherical plume increases to twice its previous size, the concentration of each chemical in the plume is reduced to 1/8th (12.5%) of its previous value. Dilution calculations and atmospheric transport models indicate that the concentration of each contaminant in the plume is rapidly diluted as the plume moves downwind. From late morning through late afternoon, while the surface air over the land is warmer than the surface air over the Great Salt Lake, the predominant wind direction is from the north to the south, away from Grantsville, the nearest community. Even on days when the winds are towards the north, in the direction of Grantsville, the air transport model predicts the 24-hour PM10 concentration will not exceed the NAAQS for most open detonation days.

Air Monitoring

Most of Tooele County is in compliance with federal ambient air quality standards. The State of Utah's Division of Air Quality has designated portions of the Oquirrh Mountains at elevations above 5,600 feet as a sulfur dioxide non-attainment area. This non-attainment area, which includes portions of the upper areas of the Oquirrh mountains in the northeast portion of Tooele County, was established as a result of emissions from a copper smelter located approximately 25 miles northwest of Grantsville in Salt Lake County. TEAD is outside the boundaries of the designated non-attainment area. Sulfur dioxide (SO2) monitoring was conducted in Grantsville in 1997; SO2 concentrations did not exceed the NAAQS (TEAD 1998; Bruce Allen, Utah DEQ, Division of Air Quality, personal communication, September 11, 2001).

Local air monitoring data were obtained from the state of Utah's DEQ, Division of Air Quality, and EPA's Aerometric Information Retrieval System, commonly referred to as AIRS. The Division of Air Quality operates an air quality monitoring station located on South Park Street in Grantsville, approximately 2 miles north of the TEAD boundary and 6.8 miles north of the OB/OD unit. PM10, SO2, and hydrogen chloride (HCl) have been measured at this site from 1993 through 1997. In addition, chlorine gas (Cl2) has been sampled continually since December 1996. Since January 1999, the Division of Air Quality also has been measuring the criteria pollutants HCl and PM2.5 (particulate matter whose particles are smaller than 2.5 microns) at the Grantsville monitoring station.

Since the Grantsville monitoring station was established in April 1993, no sampling results have exceeded the Division of Air Quality's screening values for HCl and Cl2. Most all parameters were below EPA's NAAQS (Table 5). In 1993, one 24-hour average measurement for PM10 (186 micrograms per cubic meter, or µg/m3) exceeded EPA's standard of 150 µg/m3. This test result was waived by the EPA, however, because road paving activities were being conducted at the time. ATSDR has reviewed PM2.5 data from the Grantsville air monitoring station from January 1999 through December 31, 2000. The highest measurement recorded during this time was 34 µg/m3, well below EPA's regulatory standard of 65 µg/m3.

According to Army officials, ambient air monitoring stations have not been established in any locations within TEAD (Dave Woodworth, Environmental Engineer, TEAD, personal communication, January 18, 2000; Department of the Army 1984). Based on discussions with Utah's Division of Air Quality, there have been very few complaints in recent years concerning OB/OD activities at TEAD (Bruce Allen, Utah DEQ, Division of Air Quality, personal communication, September 11, 2001). However, in response to community concerns about possible adverse health effects from air pollutants, TEAD conducted limited monitoring during OB/OD activities conducted at the Deseret Chemical Depot (DCD).

An air monitoring station was located 1 mile downwind from an OB/OD site at DCD. Air sampling was conducted for a 4-hour period on open detonation days; 2 hours prior to detonation through 2 hours after detonation. The study focused on air monitoring data for those days when the winds blew over the OB/OD range and then towards the monitoring station. Monitoring was performed from Sep 13, 1991 to Sep 3, 1992. The net explosive weight ranged from 5 to 12,765 lbs, with an average of approximately 4,600 lbs. As a comparison, the maximum detonation limit at TEAD was 3,000 lbs per pit in 1992 and is currently 750 lbs per pit (TEAD 1993).

Monitoring results indicate the PM10 concentrations measured during these 4-hour periods was less than 53 µg/m3 and that the concentration varied little between OD and non-OD days. As a comparison, the NAAQS standard for 24-hr measurements is 150 µg/m3. The measured concentrations on both OD and non-OD days were well below regulatory limits.

The concentrations of various metals associated with the PM10 was also measured. Barium, cadmium, chromium, and lead were detected at concentrations well below ATSDR comparison values and below average values measured for other rural areas. These results indicate there is little difference in the air quality at locations of approximately 1 mile downwind of the OB/OD site on days when OD events occur compared to days when they do not occur.

Evaluation of Potential Public Health Hazards

Past Exposure

The maximum amount of ordnance and explosive materials allowed to be detonated in each pit was higher in the past. Before 1990, the permitted net explosive weight for detonations was as much as 7 times greater than it is currently. The extent of open burning has also been reduced in recent years due to less overall OB/OD activity. Air monitoring results for Grantsville are not available for the time period when the maximum net explosive weight was over 1,500 pounds.

ATSDR evaluated the Army's air measurements for the Deseret Chemical Depot (DCD) detonations using net explosive weights of 5,000 to 7,000 pounds. Air monitoring at DCD showed no impact at locations ¼ to 2 miles downwind of the open detonation site. Air concentrations for PM10 and the composition of the PM10 were within the range normally measured in rural areas, for both days with and days without OD operations. In addition, the concentrations were below levels of health concern. However, modeling results suggest these monitoring locations may have been too close to the OD operation to measure the maximum ground-level downwind concentration following the OD operation. Therefore the actual air concentrations in Grantsville for OD operations prior to 1990 are not known. Measured results indicate that since 1993, Grantsville residents have not been exposed to contaminants from the OB/OD operations that would be expected to cause adverse health effects.

Current Exposures

ATSDR used a variety of data sources to evaluate the potential exposure of the Grantsville community to contaminants released during open detonation operations. The bang-box tests identified the major contaminants released by OB/OD operations and roughly quantified the mass of each compound released, based on the net explosive weight of the munitions. Environmental sampling at TEAD and other sites confirms the identity of the major contaminants in the plume and that OB/OD operations are not likely to impact air quality or cause soil contamination off site. Air modeling simulations predicted that OB/OD operations could affect the 24-hour ambient air quality for a few days each year; however, for the majority of the year OB/OD operations are not expected to lead to ambient air concentrations above the NAAQS. Air monitoring results in Grantsville confirm that the air quality there is within the NAAQS standards and does not appear to be affected by OB/OD operations. Air monitoring in Grantsville also indicates there is no apparent difference in the PM10 concentration on OD days compared to non-OD days. Based on the results of the bang-box tests and the results of PM10 air monitoring for Grantsville, it is unlikely that the health of Grantsville residents would be affected by any of the compounds released during OD events. ATSDR concludes that air contaminants released during OB/OD operations at TEAD do not pose a public health hazard.

Evaluation of Soil Contamination

Past and Current Exposure to Ordnance and Explosive Wastes on Private Farm Land Adjacent to TEAD OB/OD Activities

Summary

During 1993, the Army Corps of Engineers identified ordnance and explosive wastes (OEW) on an active agricultural area just west of the southwestern TEAD boundary, adjacent to the OB/OD unit. The 483-acre parcel of land is currently owned by an individual who has farmed the property for over 17 years. The Army Corps of Engineers conducted removals from sections of this property in 1993 and 1994; however, some sections remain to be cleared. In 1999, ATSDR concluded that agricultural use of the field posed a public health hazard, based on the likely presence of OEW on uncleared land and the potential for OEW detonation, however remote, from the land use could possibly result in a health impact. This property has been included in the Military Munitions Response Program and the remaining uncleared land will be cleared using this program. ATSDR recommends that the uncleared portion of the land not be farmed until clearance actions are complete.

Nature and Extent of Contamination

During an initial site visit to TEAD in April 1998, ATSDR observed an active agricultural area just west of the southwestern TEAD boundary, in close proximity to the OB/OD unit. The property, which is approximately 483 acres, is owned by an individual who has farmed the property for over 17 years. During 1993, the Army Corps of Engineers identified OEW on this property. In 1993, Army contractors cleared approximately 180 acres of land containing OEW from the surface to 3 feet bgs. In 1994, another 112 acres in total were cleared. Additional sweeps to identify OEW and remove it from the property were conducted in 1995. In August 1995, the depot sent a letter to the property owner suggesting that the land not be farmed due to the continued presence of OEW. However, according to TEAD officials, the land continues to be used for agriculture. TEAD has requested, but not yet received, additional funding from the Army to remove the remaining OEW. According to TEAD representatives, the off-site farmland containing OEW was recently included the Military Munitions Response Program, making the site eligible for future funding cleanup activities (Larry McFarland, TEAD, May 2003).

Evaluation of Potential Public Health Hazards

Past Exposure

Based on a previous review of information regarding OEW on private farm land adjacent to the OB/OD unit, ATSDR concludes that agricultural use of the field posed a public health hazard. Although past uses of the land for farming have not resulted in any accidents, the risk of explosion was unknown. Because OEW was likely still present on uncleared land, there was the potential that accidental detonation could result in harm.

Current Exposures

ATSDR has reevaluated the hazard potential from OEW on private farm land adjacent to the OB/OD unit since the initial health consultation was released in February 1999. ATSDR concludes that current and future uses of the agricultural area immediately adjacent to the OB/OD unit at TEAD pose a public health hazard. The land continues to be used for farming and all the property has not been completely cleared of OEW. According to TEAD officials, the procedures regarding maximum detonation are in place to prevent additional OEW materials from entering any portion of the property. However, any areas of this property that have not yet been cleared does represent a potential for detonation, and could possibly result in a health impact. ATSDR recommends that the uncleared portion of the land not be farmed until clearance actions are complete.

Past and Current Exposure to Lead-Contaminated Soil From Trap and Skeet Range Activities at SWMU 57

Summary

The skeet and trap shooting range (i.e., the skeet range) encompasses approximately 10 acres near the northwest corner of the main entrance of TEAD. This area is part of the BRAC parcel which has been transferred to a private developer. The soil within the skeet range was contaminated with lead as a result of skeet shooting activities. A proposed redevelopment plan at the skeet range includes a residential area. According to TEAD representatives, the skeet range was cleaned to residential standards in October 2002.

ATSDR concludes that lead-contaminated soil at the skeet range did not pose a past and does not pose a current public health hazard. Access to the skeet range has always been restricted to authorized personnel. Opportunities for exposure were generally very limited, since the frequency and duration of time spent at the range was very brief. A soil removal action was conducted during the fall of 2002. Following DEQ approval of conformational soil sampling, this area will be available for residential use.

Nature and Extent of Contamination

The skeet and trap shooting range is located within SWMU 57. The area potentially impacted by the skeet range encompasses approximately 10 acres. Samples were collected and tested for inorganic and organic contaminants at SWMU 57 in December 1995 and December 1996 as part of the Phase II field investigation. Eight soil samples from the surface (i.e., 0 to 6 inches bgs) and six subsurface samples were collected during the initial Phase II sampling. Lead was detected in surface soil above EPA's screening level of 400 ppm in two of the eight sampling locations. The maximum lead concentration detected was 160,000 ppm in surface soil and 79,000 ppm in subsurface soil. The extent of the highest lead concentrations was limited to approximately 2 acres. Other contaminants detected above ATSDR's CVs in surface soil include antimony (3,040 ppm), arsenic (1,700 ppm), and benzo(a)pyrene (200 ppm) (SAIC 1998).

Evaluation of Potential Public health Hazards

Past Exposure

Lead shot has been used in the past during skeet shooting activities. Access to the skeet range had been limited to TEAD personnel and children were not allowed to play or be present in this area. Any exposure to contaminated soil from dermal contact or ingestion would be very minimal, since individuals would not be spending much time at the skeet range. Since the potential for exposure to adults is very low and access to the skeet range was restricted to TEAD personnel, ATSDR concludes that exposures to lead-contaminated soil did not pose a past public health hazard.

Current Exposures

The skeet range is on land that is expected to be developed for residential use. In October 2002, the lead-contaminated soil was removed from the skeet range (Larry McFarland, TEAD, comments provided for the pre-decisional draft for data validation, January 2003). Currently, this area is restricted to TEAD personnel and no unauthorized individuals are allowed on the property. It is anticipated that approval of the cleanup based on state residential cleanup standards for soil will be obtained from the Utah DEQ in the spring of 2003, at which time the property will be released for development by the new property owner. The development of a residential area is dependent on obtaining approval from Utah DEQ. ATSDR concludes that the skeet range does not pose a current public health hazard. As long as residential soil standards for lead are met, the skeet range will not pose a public health hazard for future residential uses. ATSDR concludes that if the confirmation soil sampling results indicate that the soil meets residential standards and is approved for residential use by DEQ there will be no public health hazard for this site.


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