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In this section, ATSDR evaluates environmental data to determine whether contamination poses hazards to people having access to or living near the ALAAP site. For each environmental medium found to be contaminated, ATSDR examines the types and concentrations of contaminants. ATSDR uses comparison values for screening contaminant concentrations in an environmental medium and to select contaminants for further evaluation. Contaminant concentrations at or below comparison values may reasonably be regarded as harmless. Because comparison values do not represent thresholds of toxicity, however, exposure to contaminant concentrations above comparison values will not necessarily produce health effects. In fact, ATSDR comparison values are designed to be many times lower than levels at which no adverse health effects were observed in experimental animal or epidemiological studies.

Comparison values used in this document include ATSDR's health-based environmental media evaluation guides (EMEGs) and cancer risk evaluation guides (CREGs) and EPA's action level for lead. CREGs are estimated contaminant concentrations that may theoretically result in one excess cancer in a million persons exposed over a lifetime, and EMEGs provide estimates of human exposure to a contaminant that is likely to be without appreciable risk of noncarcinogenic health effects. EPA's action level is a health-based value enforceable for drinking water.

ATSDR then considers how people might come into contact with or incur exposure to contaminated media. ATSDR determines whether exposure occurs through ingestion, dermal contact with contaminated media, or inhalation of vapors or fugitive dust. The potential for health effects from an exposure is also related to contaminant concentration, exposure variables (e.g., duration and frequency), and the toxicology of the contaminant. ATSDR considers these factors together to determine whether the site poses any health hazards. This exposure evaluation process is further explained in Figure 6.

After the initial review of potential health hazards at the site in 1987, and as a continuation of the public health process, ATSDR gathered and reviewed additional site-related information. ATSDR determined that potential pathways requiring further evaluation included exposure to on-site surface soil, drinking water supplies, and area surface water and sediment. Because hunting, and perhaps fishing, occurs near ALAAP, ATSDR also evaluated exposures occurring through consumption of game or fish. Environmental samples collected since that initial public health assessment indicate that the principal site-wide contaminants include nitroaromatic compounds and lead. Other site-related contaminants include asbestos and polychlorinated biphenyls (PCBs) found primarily in site buildings/demolition debris and former transformer sites, respectively.

The following sections present an evaluation of potential pathways by media. A summary of the potential exposure pathways is provided in Table 3.

Evaluation of Soil Exposure Pathways

Past site operations and waste disposal practices have resulted in the contamination of on-site soil. A series of environmental studies and investigations have been conducted at ALAAP to characterize the nature and extent of soil contamination in Areas A and B. Soil samples were analyzed for nitroaromatic compounds, metals, volatile organic compounds (VOCs), and semivolatile organic compounds (SVOCs), and selected samples also were analyzed for PCBs and pesticides. ATSDR used these environmental data to evaluate whether soil contaminants exist at levels that may pose potential public health hazards to hunters, loggers, and trespassers.

Area A

Surface soil samples (0 to 1 foot below ground surface) collected from Area A primarily contained nitroaromatic compounds and metals at low levels typical of background concentrations. Lead, which was detected in two study areas of Area A, was the only contaminant detected at significant levels. During the 1979 exploratory survey, elevated lead concentrations (up to 1,580 milligrams per kilogram [mg/kg]) were detected in surface soil at the Old Burning Ground; the lead-contaminated soil was removed during 1986 and 1987 remedial activities. Additional explosive and lead contaminated soil was detected in the Old Burning Ground and the New Trench during a supplemental investigation, but it was excavated in 1994 under the Interim Record of Decision. Surface soil samples currently show lead concentrations less than 100 mg/kg.

In addition, during its 1995 Area A RI activities, the Army detected additional lead in soil at concentrations reaching 13,500 mg/kg in the Cannon Range (Figure 4), where ammunition debris is buried; however, most lead concentrations detected were below 100 mg/kg. The Army also detected low concentrations of PAHs related to controlled burning of building debris in the Small Arms Ballistics Range (ESE, 1995a). Because Area A has been sold without restrictions on use of the property, the remaining contaminated soil will be remediated to criteria suitable for residential use (lead-contaminated soil to 400 mg/kg and PAH-contaminated soil to a level based on EPA's target exposure level of acceptable risk) (ESE, 1996).

Area B

Results of the environmental monitoring efforts indicate that soil in Area B is contaminated with elevated concentrations of nitroaromatic compounds and lead, and with an isolated hot spot of PCBs. During the 1985 and 1986 RI activities, TNT levels as high as 22,000 mg/kg and 1,100 times greater than ATSDR's CREG were found in the Red Water Ditch (ESE, 1986; ATSDR, 1993b). Elevated TNT concentrations were also found in the Southern and Northern TNT Manufacturing Areas (7,660 mg/kg), but with much less frequency. Most of the nitroaromatic contamination was limited to the surface soil (SAIC, 1996b). Soil containing these elevated TNT concentrations was remediated in 1994 to 100 mg/kg. During 1996 RI/FS activities, elevated concentrations of TNT (up to 26,100 mg/kg) were infrequently detected in the Smokeless Powder Facility, the Flashing Ground, and the Propellant Area; however, most TNT concentrations in these study areas were below 100 mg/kg.

Lead associated with the lead ingot pouring process was widespread in surface soil of the Lead Remelt Facility, where levels reached 24,000 mg/kg. In addition, lead from waste disposal practices and contaminated building debris was found in the Sanitary Landfill/Lead Facility and the Demolition Area, but with much less frequency and at lower concentrations (1,538 mg/kg to 11,000 mg/kg) than in the Lead Remelt Facility. Lead contamination in these study areas was confined to the top 7 feet of soil. The FS proposes removal of the lead-contaminated soil from these areas. Other metals, including arsenic and beryllium, were detected at levels slightly above ATSDR's comparison values and at levels above background concentrations; however, these metals are not believed to be related to manufacturing or process activities that occurred during the active period of the installation (SAIC, 1996a).

An isolated hot spot of PCBs was found in the Smokeless Powder Facility. Concentrations in soil (1 to 10 feet below ground surface) ranged from 17 mg/kg to 102 mg/kg, greatly exceeding ATSDR's CREG of 0.4 mg/kg (SAIC, 1996a).

As discussed above, TNT-contaminated soil has been removed from several of the waste areas, and additional measures are proposed in the 1996 RI/FS for the TNT-, lead-, and PCB-contaminated soil. These remedial actions are summarized in Table 2.

Exposure to Area A and Area B Soil

Although soil in certain portions of the site is contaminated with TNT, lead, and PCBs, on-site soil is unlikely to pose a health hazard to the general public. A perimeter fence restricts access to the site and, therefore, direct contact with contaminated on-site soil. Trespassers who may have entered the site in the past through breaches in the fence probably did so intermittently, and such brief and infrequent exposure is not likely to pose a health hazard. The breaches in the fence have since been secured.

Hunting has occurred in portions of the site. Although there were no designated hunting sections in Areas A and B, most people probably hunted in the nonindustrial, wooded areas of the site. Hunters who gained access to these portions of Area A or Area B are unlikely to have incurred significant exposure to site-related contaminants. The time spent walking through the site was likely minimal (a few hours per hunt on a few weekends per year) and involved little direct contact with soil in the most contaminated areas. Hunting is no longer allowed in Area B, and the limited hunting in Area A is not expected to pose a health hazard because relatively low concentrations of site-related contaminants are presently in this area.

Loggers currently clear-cut in portions of Area B that need to be remediated, and they may have logged near these areas in the past. It is unlikely, however, that any single logger is in frequent and long-term contact with the TNT-, lead-, or PCB- contaminated soil in localized areas of the site. Very few areas of exposed soil, or points of contact, exist because the site is overgrown with vegetation. Even if loggers work in Area B, they are unlikely to incur excessive exposure because the personal protective equipment required for logging activities is expected to minimize direct contact with soil contaminants.

ATSDR expects future exposure opportunities to continue to diminish because the Army continues taking actions to reduce on-site soil contamination to levels acceptable for industrial or residential use. ATSDR concludes that exposure to on-site soil in Areas A and B is unlikely to pose a public health hazard.

Evaluation of Groundwater Exposure Pathways

Numerous groundwater samples were collected from Area A and Area B and analyzed for nitroaromatic compounds, metals, VOCs, SVOCs, PCBs, and pesticides. ATSDR evaluated the nature and extent of groundwater contamination in the shallow and deep aquifers beneath the site and whether contamination appears to be migrating in the direction of drinking water wells.

Groundwater Contamination

Area A

VOCs, SVOCs, pesticides, and PCBs were not detected in any samples collected from groundwater beneath Area A (ESE, 1995a). Low levels of nitroaromatic compounds below the ATSDR comparison values (maximum concentrations: 2,4-DNT, 0.473 microgram per liter (µg/L); 2,6-DNT, 0.54 µg/L; nitrobenzene, 1.73 µg/L) were present in the shallow aquifer in several locations, including the Old Burning Ground, the Small Arms Ballistics Range, and the Rubble Pile and decreased with distance from the suspected source areas (ESE, 1995a). Even lower levels of nitroaromatic compounds had migrated to the deeper bedrock aquifer. None of the contamination has migrated beyond Area A's boundaries.

Recent sampling suggests that on-site nitroaromatic groundwater contamination beneath Area A has decreased. Contaminant levels are expected to continue to decrease with time because suspected source areas (i.e., the Old Burning Ground and the Old Well Area) have been remediated.

Metals were found widespread in the groundwater across Area A during 1994 and 1995 sampling events. Of the metals detected, only beryllium (28.7 µg/L), cadmium (456 µg/L), and manganese (72.2 µg/L) were found at concentrations exceeding ATSDR comparison values at the Old Burning Ground. The source of metals is not known with certainty. None of the activities in Areas A used metals in production or produced these metals as by-products of production (ESE, 1995b). Although their presence in groundwater at great depths may suggest that they are naturally occurring, neither beryllium nor cadmium were present in background samples collected from undeveloped government-owned land located north and east of the site boundary (ESE, 1995a).

Area B

A groundwater divide runs beneath Area B. The portion to the east of the divide generally lacks a shallow aquifer and only low concentrations of site-related contaminants (e.g., nitroaromatic compounds and metals [including lead]) have been detected in the deep aquifer (SAIC, 1996a).

The area west of the divide contains the majority of the ALAAP's industrial activities and is where two zones of contamination have been identified in the shallow aquifer. The first zone consists of a broad expanse of elevated concentrations of nitroaromatic compounds (2,4-DNT up to 49,400 µg/L and 2,4,6-TNT as high as 230 µg/L) spanning across the southern portion of Area B between the Propellant Shipping Area and the Blending Tower Area, and extending toward the Southern TNT Manufacturing Area (SAIC, 1996a).

The second zone of groundwater contamination west of the divide contains lower nitroaromatic compound concentrations extending from the southwestern corner of Area B that underlies the Kimberly-Clark facility and advancing to the Smokeless Powder facility. Other isolated areas of contamination include the Northern Manufacturing Area, the Acid/Organic Manufacturing Area, and the Tetryl Manufacturing Area (SAIC, 1996a). These localized areas of contamination may reflect areas of higher contaminant concentrations moving through fissures in the underlying bedrock. Contaminants were also detected in deep bedrock wells advanced in Area B, although the concentrations were generally lower than those in the shallow aquifer. Nitroaromatic compounds present in the deep bedrock aquifer included 2,4-DNT (up to 14,600 µg/L) and TNT (up to 22.9 µg/L), which were found near the Southern TNT Manufacturing Area.

Lead was found at levels as high as 64,400 µg/L in the shallow aquifer and in excess of EPA's action level for lead of 15 µg/L. The area of lead contamination extends from the southern portion of the ALAAP site to the Propellant Shipping Area, the Blending Towers, and the Southern TNT Manufacturing Area. Lead (94.2 µg/L) and arsenic (202 µg/L) also were found in deep bedrock wells located in the Northern TNT Manufacturing Area at concentrations exceeding comparison values for drinking water (SAIC, 1996a).

Groundwater monitoring efforts indicate that contaminants have not migrated beyond the northeast boundary of the site (SAIC, 1996a). Several isolated contaminated groundwater locations are near groundwater discharge points on the Coosa River; however, this pathway does not appear to contribute significant amounts of site-related material to the river. A forthcoming RI should provide more information on whether contamination, if any, exists on the Kimberly Clark and GSA property located south of the current installation boundary. Corrective actions outlined in the 1996 Supplemental Remedial Investigation and Feasibility Study for Area B call for removing contaminated soils--the suspected source of groundwater contamination--and allowing natural attenuation to achieve levels below EPA's maximum contaminant levels established by the Safe Water Drinking Act (SAIC, 1996b). These proposed clean-up measures should prevent any future migration of the plume to off-site areas. The Army will conduct groundwater monitoring every year for the first 5 years, and then every 5 years for a total of 30 years to ensure that clean-up levels are achieved (SAIC, 1996b). If the levels are not achieved, the Army will pursue other corrective actions.

Exposure via On-Site Drinking Water Supplies

Past Exposure

Groundwater under Area B has been contaminated with nitroaromatic compounds and lead, although this groundwater is not suitable for human consumption, no groundwater supplied drinking water wells ever existed in either Areas A or B. Between approximately 1942 and 1945 Area B acquired drinking water from the on-site Army operated water plant, which received water from surface water sources. After the Army stopped using the on-site water plant, they obtained water from the Kimberly Clark water facility. Both obtained water from the Coosa River, consequently, exposure to contaminated groundwater beneath the site has probably not occurred in the past.

Current and Future Exposures

Currently, no manufacturing operations or groundwater-supplied wells are known to exist on site. Future groundwater use in Area B will be controlled by groundwater use restrictions proposed to accompany any Area B land transaction. Thus, no exposure to contaminated groundwater beneath the site is likely to occur, either now or in the future.

Exposure via Off-Site Drinking Water Supplies

Small Public Supply/Private Wells: Past, Current, and Future Exposures

Site-related contaminants have not affected small public supply or private wells located near the installation. The nearest wells to the site are located away from the direction of groundwater flow from Area B, where the highest levels of contaminants were detected (ADPH, 1996). In 1990, tap water samples were collected by the Talladega County Water Department from four public supply and private wells located either north, east, or southeast of the installation. Water samples were analyzed for nitroaromatic compounds, tetryl, and lead (ESE, 1991). Nitroaromatic compounds and tetryl concentrations were below detection in the samples; one public supply well contained lead at 1.4 µg/L, which is below EPA's action level of 15 µg/L. In addition, three private bedrock wells (well depths exceed 150 feet) at a farm north of Area A were sampled at the request of the farm owner. Samples were collected from flowing taps after a 15-minute purge cycle. The results indicate that the wells were not affected by site-related nitroaromatic compounds (ESE, 1995a). Additional private wells are located downgradient from the flow of groundwater from the site, and at a distance greater than 2 miles from the current site boundary. These wells will not likely be affected by elevated levels of contaminants.

Proposed on-site corrective actions (source removal and natural attenuation) should reduce contaminant concentrations in the groundwater to levels below the Safe Drinking Water Act's maximum contaminant levels and prevent off-site migration. The Army will periodically monitor the groundwater quality beneath the site to ensure clean-up goals are being achieved.

Municipal Wells: Past, Current, and Future Exposures

The city of Childersburg's municipal water supply draws water from two deep aquifer wells, the closest of which is situated approximately 2 miles south of the current site boundary and away from the predominant direction of groundwater flow from the site. These two wells were sampled in the 1990 sampling program described above and no site-related compounds were detected. For this reason, ATSDR determined that past, current, and future uses of Childersburg's municipal well water are unlikely to result in adverse health effects associated with site-related contaminants.

Evaluation of Surface Water and Sediment Exposure Pathways

Exposure to On-Site Surface Water and Sediment

A 1995 sampling event characterized the water quality in each of the major surface drainage ways and tributaries in Area B, including the Red Water Storage Basin, the Aniline Sludge Basin, the Flashing Ground, the Red Water Ditch, the Crossover Ditch, and Beaver Pond Drainage System. Several of these on-site water bodies drain into the Coosa River or Talladega Creek. No significant surface water bodies exist in Area A, where surface runoff predominantly drains into Area B's ditches and drainage systems and the Talladega Creek.

The Army collected and analyzed surface water and sediment samples for VOCs, SVOCs, metals, PCBs/pesticides, and nitroaromatic compounds and their by-products. ATSDR reviewed the sampling data and found that only low levels of nitroaromatic compounds were found in surface water samples collected from on-site surface water drainage systems. The highest nitroaromatic contamination was found in the Beaver Pond Drainage System (TNT, 0.318 µg/L), where the source of the nitroaromatic compounds is believed to be the nearby TNT Manufacturing Areas (SAIC, 1996a). Metals were frequently detected in sediment. The highest metal concentrations were found in the Red Water Ditch and the Crossover Ditch (arsenic, 52.9 mg/kg; chromium, 294 mg/kg; mercury, 1 mg/kg). With the exception of arsenic concentrations that exceed the CREG of 0.6 mg/kg, contaminant concentrations were below ATSDR's comparison values for soil.

The public's exposure to surface water and sediment in on-site basins, ditches, and drainages is restricted by the fence that surrounds ALAAP. Even if exposures were to occur, contaminants are not present at levels that would pose a public health hazard. Nitroaromatic compounds and metals are not readily absorbed through the skin, and exposure to the low levels found in the surface water and sediment would have to occur frequently over a long period of time to cause adverse health effects. Therefore, this pathway does not represent a hazard to public health.

Exposure to Off-Site Surface Water and Sediment

Because several on-site ditches and drainages empty off site, the Army collected off-site sediment samples from the nearby Coosa River and the Talladega Creek. Surface water samples were not collected; however, contaminant concentrations are typically higher in sediment than in surface water because sediments serve as contaminant reservoirs. Coosa River samples contained low concentrations of nitroaromatic compounds, PAHs, VOCs, and metals. Although the highest contaminant concentrations, particularly certain metals (e.g., barium, 509 mg/kg; mercury, 1.2 mg/kg), were detected immediately downstream of the Red Water Ditch outfall, no significant differences in concentrations were noted between upstream and downstream reaches (SAIC, 1996a).

The Army also collected 100 sediment samples from various locations along the Talladega Creek, including the mouth of the creek near Coosa River, near the outfall of a tributary draining the Flashing Ground and Lead Remelt Facility, and at transects along the Flashing Ground, the Lead Facility, and the Demolition Landfill. Low levels of nitroaromatic compounds and VOCs were present in the samples, and metals were frequently detected near the Flashing Ground. Mercury concentrations ranged from 0.104 mg/kg to 0.134 mg/kg, but below ATSDR's EMEG of 1,000 mg/kg (SAIC, 1996a). Contaminant concentrations decreased with distance from source areas, and the lowest contaminant concentrations were found downstream and near the Coosa River.

Exposures to the low levels of contaminants in sediment and assumed lower levels in surface water are expected to be minimal. ATSDR learned that the Talladega Creek is not used for recreational activity and the Coosa River (in the area of the site) is used for boating and, perhaps, fishing, but not for swimming (ADPH, 1996). ATSDR determined that dermal contact with low levels of site contaminants during recreational activities is likely to be infrequent and brief, and should not result in adverse health effects. Contaminant levels in the Talladega Creek and the Coosa River should continue to decrease as remediation efforts remove on-site contaminant sources. For these reasons, ATSDR concludes that past, current, and future recreational use of Coosa River is unlikely to result in adverse health effects.

Evaluation of Food Chain Exposure Pathways

Some people hunt deer and small game in Area A and the abutting woodland, and fish in water bodies near the site. ATSDR evaluated whether hunters, anglers, and their families are exposed to site-related contaminants when they consume game or recreationally caught fish.

Consumption of Game

To determine whether area game are affected by site contaminants, the Army conducted several bioaccumulation studies that investigated whether deer grazing near ALAAP accumulate nitroaromatic compounds or their metabolites. No nitroaromatics were found in the tissues of 12 deer (ATSDR, 1996b; Shugart et al., 1990). Results of bioaccumulation studies conducted near other ammunition plants where nitroaromatics were used indicate limited, if any, uptake by deer (US AHEA, 1994; US ACHPPM, 1994). Together these results suggest that deer demonstrate limited ability to bioaccumulate nitroaromatic compounds. Therefore, ATSDR concludes that consumption of venison caught near the site is not likely to result in adverse health effects.

People also hunt small game animals, including rabbits, possum, quail and squirrel. Consequently, the Army investigated bioaccumulation of site-related contaminants (i.e., nitroaromatic compounds, metals, SVOCs, and PCB/pesticides) in rabbits collected from some of the most contaminated areas of the site (i.e., Acid/Organic Manufacturing Area, the Tetryl Manufacturing Area, the Flashing Ground, and the Propellant Shipping Area.) Nitroaromatic compounds were not detected, and SVOCs and most metals were detected in low concentrations in the samples. Arsenic, however, was measured at a maximum concentration of 0.25 mg/kg, which is slightly higher than the typical dietary level found in meats (up to 0.14 mg/kg) (SAIC, 1996a; ATSDR, 1993a). To conservatively evaluate potential health hazards, ATSDR estimated exposure doses to this amount of arsenic in small game and determined that hunters and their family members would have to consume large quantities of rabbit (more than 1 pound per week) over a 70-year lifetime to exceed levels considered protective of public health.

Consumption of Fish

The Army collected 52 fish samples from a tributary of the Talladega Creek and several ditches and drainages that convey water from the site to the Coosa River, including the Red Water Ditch, the Crossover Ditch, the Beaver Pond Drainage System. Samples were analyzed for nitroaromatic compounds, metals, SVOCs, and PCBs/pesticides (SAIC, 1996a). (The species of the sampled fish were not identified in available documentation.)

ATSDR determined that nitroaromatic compounds and pesticides were not present and that PCBs and SVOCs were detected both infrequently and at low levels in the fish samples. In contrast, metals, especially mercury, were frequently detected in fish tissue samples. The highest levels of mercury (0.37 mg/kg and 0.89 mg/kg) were detected in fish collected from a tributary of the Crossover Ditch. The mercury levels, however, are below the Food and Drug Administration (FDA) action level for mercury in fish of 1 mg/kg supported by the Alabama Department of Public Health (EPA, 1995).

Area anglers are not likely to consume fish containing site-related contaminants at levels of health hazards. Although anglers may fish along the Coosa River near the site, muddy water and thick vegetation create less than favorable fishing conditions (US AEC, 1997). The unfavorable conditions are likely to reduce the fishing activity and, therefore, potential health hazards associated with consumption of large quantities of potentially contaminated fish.

On the basis of the results of bioaccumulation studies and a review of scientific literature, ATSDR concludes that consumption of game or fish poses no apparent public health hazard to hunters, anglers, or their families.

Evaluation of Physical Hazards

Exposure to Asbestos Fragments

Site buildings containing Transite® siding have been burned and the resulting rubble, which has been scattered and mixed into site soil at many waste areas, has been a source of friable asbestos (easily crumbled asbestos). Friable asbestos can migrate through airborne dispersion, potentially posing health hazards to people who inhale its fibers. Clean-up actions instituted in 1986 and 1987 have removed most of the asbestos fragments. Although scattered fragments of asbestos may remain in soil in portions of the site, opportunities for exposure are limited. The perimeter fence restricts public access to the site, and significant airborne dispersion of asbestos fragments is likely to be limited by the heavy natural vegetative ground cover.

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