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PUBLIC HEALTH ASSESSMENT

NAVAL AIR WARFARE CENTER
[a/k/a NAVAL AIR DEVELOPMENT CENTER (8 WASTE AREAS)]
WARMINSTER TOWNSHIP, BUCKS COUNTY, PENNSYLVANIA


EVALUATION OF ENVIRONMENTAL CONTAMINATION AND POTENTIAL EXPOSURE PATHWAYS

What is exposure? and When do health effects occur?In this section, ATSDR evaluates whether community members have been (past), are (current), or will be (future) exposed to harmful levels of chemicals. Figure 4 describes the conservative exposure evaluation process used by ATSDR.

If exposure was or is possible, ATSDR then considers whether chemicals were or are present at concentrations that might be harmful to people. ATSDR does this by screening the concentrations of contaminants in environmental media (e.g., groundwater or soil) against health-based comparison values (CVs). CVs are chemical concentrations that health scientists have determined are not likely to cause adverse effects, even when assuming very conservative/worst case 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 examines potential exposure variables and the contaminant toxicology. ATSDR emphasizes that regardless of contaminant concentrations, a public health hazard exists only if people come in contact with, or are otherwise exposed to, harmful levels of contaminated media for sufficient frequency and duration.

After initial review of potential health hazards at NAWC, ATSDR identified the groundwater, surface soil, and surface water/sediment exposure pathways as requiring further evaluation. Following the strategy outlined above, ATSDR examined whether human exposure to harmful levels of contaminants via these pathways existed in the past, exists now, or could potentially exist in the future. ATSDR summarizes the evaluation of potential exposure pathways in Table 2 and 3 and describes it in more detail in the discussion that follows. To acquaint readers with terminology and methods used in this report, Appendix B provides a list of CVs, Appendices C and D summarize the methods and assumptions used to estimate exposures and support some of the report's conclusions, and Appendix E provides a glossary of terms.

Evaluation of Groundwater Exposure Pathway

Groundwater from local municipal wells and private wells is a primary source of drinking water for more than 100,000 people in the vicinity of NAWC. When chlorinated solvent-contaminated groundwater was discovered in 1979, area industries and NAWC were targeted as potential sources of contamination. Therefore, the Navy began investigations of NAWC wells and surrounding areas located proximate to the base. These investigations found that NAWC was a source of contamination in on-base wells, one municipal well, and private wells proximate to the base. During the course of these investigations, the Navy also identified other off-base sources of groundwater contamination that also could have potentially impacted municipal water supply systems and private wells proximate to the base.

What is a ppm or a ppb?The following sections describe the regional hydrogeology and an evaluation of potential exposures to drinking water contaminated by NAWC sources. Because the Navy conducted investigations of off-base areas, the following sections also discuss water supply systems that were initially evaluated by the Navy, but later determined by the Navy to be affected by off-base sources.

For wells affected by NAWC, including NAWC wells, a WMWA well, and private wells in the Ivyland/Kirk Road neighborhood, ATSDR examined potential exposures considering contaminant concentrations and well use, such as how often and for how long a well has been used. Based on a review of potential exposures and toxicological data, ATSDR concluded that past, current, and potential future exposures to contaminants from use of wells potentially affected by NAWC sources are below levels shown to result in illness or other adverse health effects.

For wells the Navy determined to be affected by off-base sources, including Upper Southampton Municipal Water Authority (SMWA) wells, Hatboro Water Authority (HWA) wells, Warminster Heights Development Corporation Wells (WHDC) wells, and private wells in the Flying Heels, Speedway, and Casey Village neighborhoods, ATSDR has included information about past Navy investigations, ongoing investigations, and completed remedial actions. Based on a review of available toxicologic and environmental data, ATSDR has concluded that current and future use of private wells in neighborhoods surrounding NAWC will not to result in illness or other adverse health effects. As a prudent public health measure, ATSDR recommends that private well users periodically (every 1 to 2 years) test their wells because groundwater conditions can change over time and unidentified sources may exist in the area. Regular maintenance and testing of private wells with treatment systems is especially important to ensure proper operation of these systems. As a general health consideration, private wells users should also regularly sample their wells for bacteria content, particularly at the point of use.

In addition, the Navy plans to organize and map available groundwater data, including chemical contamination locations and pressures and levels of ground and surface water. This information, combined with information from other potentially responsible parties, will be shared with area stakeholders, such as PADEP, PADOH, EPA, water suppliers, and residential well owners, to support wellhead protection programs, to increase the understanding of groundwater contamination, and to ensure continued protection of public health.

Hydrogeology

Hydrogeology is the study of the occurrence, distribution, and movement of groundwater in underground soil and rock formations. During investigations of NAWC, several interpretations of the hydrgeology at NAWC have been presented. This PHA provides a simplified description of the complex hydrogeologic systems present at NAWC, as described by the Navy. In the area around NAWC, investigators have identified three underground layers of water or aquifers: overburden, shallow bedrock, and deep bedrock. The overburden aquifer, located within the surface soil and weathered bedrock, extends from approximately 5 to 30 feet below ground surface (bgs). The shallow bedrock aquifer underlies the overburden aquifer and extends from approximately 30 to 100 feet bgs. Groundwater flow in the overburden and shallow bedrock is influenced by surface topography, as well as areas of high recharge, such as grassy areas near runways or leaking storm water pipes. The overburden and shallow bedrock aquifers have very low groundwater yields and are likely only used as a water supply by a small number of private wells. The deep bedrock aquifer occurs at depths greater than 100 feet bgs. Groundwater flow in the deep bedrock aquifer is influenced by fractures in the bedrock. This deep bedrock aquifer is a productive groundwater supply and is accessed by many of the municipal and private water supply wells in the region. When groundwater is pumped from the deep bedrock aquifer, groundwater from the overlying aquifers serves as a source of recharge (NUS Corporation 1985; Halliburton NUS 1992).

The direction of groundwater flow is influenced by surface and bedrock geology. Groundwater in the overburden aquifer flows northerly in areas of NAWC north of a topographic high in the central portion of the base and southerly in areas of NAWC south of the topographic high. In the shallow and deep bedrock aquifers, the preferred flow direction is horizontally along north-south oriented fractures, joints, and bedding planes (Figure 5) (NUS Corporation 1985; Halliburton NUS 1992).

On-Base NAWC Water Supply Wells

As many as ten on-site water supply wells pumping from the deep bedrock aquifer have provided NAWC with drinking water. Of these ten wells, five actively serve as water supply wells for NAWC and two are inactive, but could be used as a water supply if needed. None of these seven wells (3, 4, 6, 7, 8, 9, and 10) have been closed due to contamination. VOC contamination, primarily TCE and PCE, has been detected in the remaining three wells (1, 2, and 5), which no longer serve as water supply wells. Each of the ten NAWC wells are described in Table 4.

The Navy began sampling on-base water supply wells in 1979 when groundwater contamination in the area was first discovered. Based on the 1979 sampling results, the Navy closed Wells 1, 2, and 5 due to VOC contamination. The Navy continued to sample on-base wells between 1979 and 1981. TCE (273 parts per billion [ppb]) and PCE (33 ppb) were detected in Wells 1 and 2, located in Area D, when water supply well sampling began. Initial sampling of Well 5, located west of Area C, detected PCE (36 ppb) (Halliburton NUS 1992; Department of the Navy 1997b). Detected concentrations of TCE and PCE exceeded CVs in Wells 1, 2, and 5. Early investigations at NAWC also found various heavy metals (beryllium, copper, lead, nickel, and zinc) in groundwater monitoring wells; however, sampling results from these investigations are unavailable. NAWC has not closed any wells due to elevated metal concentrations and water supply wells have not contained metals above EPA's Maximum Contaminant Level (MCLs). Table 5 presents the maximum detected concentrations and associated CVs for TCE and PCE detected in NAWC wells.

TCE (to a maximum concentration of 293 ppb) and PCE (to a maximum concentration of 36 ppb) were detected in NAWC water supply wells when sampling first began in 1979. These are concentrations found at the wellhead, not at the tap or faucet where people would be drinking water. The Navy blended or mixed water from the different wells in the water distribution line, as described in Table 4, so that no person used water from a single well and no person would have contacted the maximum concentrations of TCE or PCE. Nonetheless, past on-base workers and residents may have been exposed to these contaminants in their drinking water supply prior to 1979, when the wells were closed.

To evaluate whether health hazards are associated with past exposures, ATSDR estimated the potential doses for on-base workers and residents (adults and children). To estimate doses, ATSDR cautiously evaluated contact with the maximum concentration measured at the wells to ensure that any public health conclusion about the past safety of the drinking water supply considered the worst-case scenario. ATSDR also cautiously assumed that workers were exposed for 30 years, which accounts for the period from the commencement of on-base disposal in approximately 1950 until closure of the contaminated water supply wells in 1979. On-base residents were conservatively assumed to be exposed daily for a period of 6 years although the average time military employees reside on base is only 2 to 3 years (Szamborski 1999). Moreover, it is unlikely that workers and residents obtained their drinking water supply from a single well at the maximum detected TCE and PCE concentrations over the entire exposure period assumed by ATSDR. These assumptions, ATSDR's methods, and the estimated doses are further described in Appendix C. The estimated doses indicated that in no case were TCE and PCE concentrations in NAWC water supply wells high enough to present a reasonable likelihood for harmful exposures to have occurred. ATSDR, therefore, concludes, based on available toxicologic and environmental data, that past exposures were below levels that result in illness or other adverse health effects.

To prevent current and future exposures, the Navy closed Wells 1, 2 and 5 when contamination was first discovered. These wells remain separate from the NAWC drinking water supply. The Navy has implemented institutional controls at the base to prevent supply well use and installation without proper treatment systems and approval by state and local authorities. In addition, the Navy regularly samples active water supply wells in compliance with local and state regulations to ensure the safety of the water supply. To ensure the continued safety of this water supply, regular sampling of Well 10 will continue after it is incorporated in the Warminster municipal water supply. The Navy also monitors groundwater to track contaminant movement and prevent contaminants from entering water supplies. Treatment systems, which address VOCs and other contaminants, are located and operated at the source areas at NAWC (Department of the Navy 1993, 1995, 1997b). Because the Navy has implemented measures to prevent exposures and protect active water supply wells, ATSDR concludes that current and future use of the NAWC water supply wells poses no public health hazards.

Off-Base Municipal Supply Wells

The WMWA pumps groundwater from the deep bedrock aquifer to supply a population of approximately 40,000 area residents. The WMWA water supply system is composed of 19 wells. During the summer months, WMWA buys water from the Philadelphia Suburban Water Co. to supplement their groundwater supply. This water is from a surface water source and comprises less than 1 percent of the WMWA water supply. Approximately 0.3 miles north of Area A (Sites 1, 2, and 3), WMWA supply system Well 26 is the closest well to NAWC (Smith 1998, 1999; EPA 1999).

When WMWA began sampling its water supply wells in 1979, they found elevated concentrations of TCE (67.8 ppb) and PCE (17 ppb) in Well 26 and, as a result, closed this well. Releases at NAWC were identified as the source of the TCE and PCE, as well as other VOCs later detected in Well 26. In order to reactivate Well 26, WMWA installed an air stripper to remove TCE, PCE, and any other VOCs from the water flowing into the distribution system. Operation of this well resumed in 1986. In 1992, the Navy sampled untreated water from Well 26 as part of their ongoing investigations at NAWC. TCE, PCE, and 1,1-dichloroethene (1,1-DCE) were detected above MCLs in untreated water. Analysis of the treated water indicated that the air stripper installed in 1986 removed VOCs, including TCE, PCE, and 1,1-DCE. Additional analysis of untreated water from Well 26 in January 1997 also detected TCE, PCE, and 1,1-DCE above MCLs. Again, analysis of treated water from Well 26 found no contaminants, indicating that the air stripper successfully removed VOCs from the water supply. In 1992, arsenic (3.7 ppb) was detected in untreated water below its MCL, but above its CV. ATSDR uses a CV below the MCL to ensure that arsenic is considered in health evaluations. Table 5 presents the maximum detected concentrations and associated CVs for contaminants detected above CVs in drinking water wells prior to closure (Ambler Laboratories 1979; Halliburton NUS 1993a; Analytical Laboratories, Inc. 1997; Smith 1998).

Past off-base residents may have been exposed to TCE and PCE between 1974, when the well first began supplying water until closure in 1979. Past, current, and future off-base residents may be exposed to arsenic, which was detected in Well 26 in 1992, in their drinking water supply from 1974 through 1979, and after 1986 when the well was reactivated. To evaluate whether health hazards are associated with these past exposures, ATSDR estimated the potential doses for residents living off base (adults and children). To estimate doses, ATSDR used conservative assumptions to ensure that any public health conclusion about the past safety of the drinking water supply considered the worst-case scenario. Residents were assumed to drink water containing the maximum detected concentration of TCE, PCE, and arsenic found during active use of the well. In addition, residents were assumed to be exposed daily when the well was active. Childhood exposures were assumed to occur daily for 6 years. Exposure as a teenager was considered an adult exposure. It is unlikely that residents obtained their entire drinking water supply from this well over the entire exposure period assumed by ATSDR. These assumptions, ATSDR's methods, and the estimated doses are further described in Appendix C. The estimated doses indicated that in no case were TCE, PCE, and arsenic concentrations in Well 26 high enough to present a reasonable likelihood for harmful exposures to have occurred. ATSDR, therefore, concludes that past exposures were below levels that cause illness or other adverse health effects.

To ensure the safety of the water supply, WMWA regularly samples active water supply wells, including treated water from Well 26, in compliance with state and local regulations. In addition, the Navy also monitors and treats shallow groundwater contamination on base to prevent further movement off base (Department of the Navy 1993, 1995, 1997b). Because the WMWA has implemented measures to prevent exposures and protect active water supply wells and the Navy has implemented measures to treat groundwater contamination, ATSDR concludes that current and future use of the WMWA water supply wells poses no public health hazards.

Off-Base Private Wells

Nearby industries, commercial businesses, and private residences operate private supply wells for drinking water. Depending on required yields, these private wells may obtain groundwater from the overburden, shallow bedrock, or deep bedrock aquifers. Private wells that may have been affected by NAWC activities are located in the Ivyland/Kirk Road neighborhood (Halliburton NUS 1992). This neighborhood is shown on Figure 2.

Ivyland/Kirk Road Neighborhood
The Ivyland/Kirk Road neighborhood (also referred to as Area 1, North) is located along the northwest boundary of NAWC adjacent to Area C. This neighborhood encompasses portions of Warminster and Ivyland. During investigations at NAWC in 1992, the Navy sampled two commercial wells (one at Wagner & Sons and one at Aztec Corporation) and one residential well in this neighborhood. Samples were analyzed for VOCs and metals. TCE (720 ppb), arsenic (4.4 ppb), lead (468 ppb), and manganese (52.5 ppb) were detected above CVs in the Wagner & Sons well. This well, however, is used only for the company's production process and not as a drinking water supply. Nonetheless, the Navy connected this facility to a potable water supply to prevent exposure to contaminants in the production well. Only arsenic (4.6 ppb) was detected in the Aztec Corporation well (use unknown) below its MCL, but slightly above its CV. No VOCs or metals were detected in the residential well above CVs.

In 1993, the Navy identified 52 private residential, 3 private commercial, and 2 WMWA water supply wells in this neighborhood. At this time, the Navy sampled 51 of the 57 wells for VOCs, which were the contaminants of concern based on NAWC groundwater monitoring. Some wells were not sampled because of denied property access. PCE (31 ppb) was the only VOC detected above its CV and EPA's MCL. The report summarizing the sampling and analysis results does not identify if the maximum detected concentration was found in a residential, commercial, or municipal well (Halliburton NUS 1993a, 1993b). Table 5 summarizes the maximum detected contaminant concentrations.

ATSDR evaluated exposures to workers or residents who may have contacted arsenic and PCE in their drinking water supply prior to 1993. ATSDR did not evaluate exposure to TCE in the Wagner & Sons well because this well was used as a production well, rather than a drinking water supply, and water undergoes treatment before use to remove VOCs. To evaluate whether health hazards are associated with these past exposures to workers and residents, ATSDR estimated the potential doses for residents (adults and children), who are assumed to have greater exposure than workers. To estimate doses, ATSDR used conservative assumptions to ensure that any public health conclusion about the past safety of the drinking water supply considered the worst-case scenario. Residents were assumed to drink water containing the maximum detected concentrations of PCE and arsenic daily from 1950, when on-base disposal commenced, until 1993, when alternate water supplies were provided. It is unlikely, however, that residents drank water from their well every day over the entire 43-year period assumed by ATSDR. In addition, it is unlikely that this well contained the maximum detected PCE and arsenic concentrations for the entire 43 years. Childhood exposures were assumed to occurred daily for 6 years. Exposure as a teenager was considered an adult exposure. These assumptions, ATSDR's methods, and the estimated doses are further described in Appendix C. The estimated doses indicated that in no case were PCE or arsenic concentrations in private wells high enough to present a reasonable likelihood for harmful exposures to have occurred. ATSDR, therefore, concludes that past exposures were below levels that cause illness or other adverse health effects.

The Navy eliminated low-dose exposures, as estimated by ATSDR, through a series of actions. Based on 1993 sampling results, the Navy immediately supplied bottled water to homes with PCE above EPA's MCL. Homes were then provided with groundwater treatment systems until they were connected to the municipal water supply in 1995. The Navy also connected the Wagner & Sons facility to a potable water supply to prevent exposure to TCE in the production well even though no one was expected to use this well for drinking water. To further prevent current and future exposures, the Navy monitors on- and off-base groundwater to track contaminant movement. The Navy has also installed water treatment systems to treat groundwater contamination on base and prevent further movement off base (Department of the Navy 1993, 1995, 1997b). Because the Navy connected homes to municipal water supplies and has implemented measures to monitor and treat groundwater contamination, ATSDR concludes that current and future exposures are not occurring in the Ivyland/Kirk Road neighborhood and groundwater poses no public health hazards.

Off-Base Municipal and Private Wells Affected by Off-Base Sources

When EPA first identified groundwater contamination in Bucks County, NAWC and industries were thought to be likely sources. To address potential sources at NAWC, the Navy conducted investigations not only within the base boundaries but also within adjacent neighborhoods to assess potential contaminant movement. As a result of Navy investigations, as well as investigations completed by EPA and the USGS, the water supplies discussed below were found to be affected by sources other than NAWC. Although this PHA was prepared to address only NAWC and areas impacted by NAWC contamination, ATSDR has included information regarding these water supplies because the Navy was initially identified as a potential source of contamination and the community has expressed concern about exposure to contaminants in their water supply. The following discussion includes descriptions of past Navy investigations, ongoing investigations, and completed remedial actions. Where appropriate, ATSDR has also included an assessment of potential exposures.

Upper Southampton Municipal Water Authority (SMWA)
SMWA supplies drinking water to a population of approximately 13,000 with a water supply system composed of three active wells. The closest well to NAWC is approximately 0.75 miles to the south. In addition, SMWA purchases approximately 70 to 80 percent of their water supply from the Bucks County Water Authority. SMWA blends purchased water and water from supply wells prior to distribution such that no one residence receives all its water from a single source (Pursel 1998; EPA 1999; Pursel 1999). In 1979, SMWA closed three supply wells due to TCE contamination (to 44 ppb). The TCE levels found in the SMWA wells were lower than the levels found in the WMWA supply well previously discussed. The source of TCE in the SMWA wells is unknown, but is not likely attributable to sources at NAWC (Ames 1998; Pursel 1998). ATSDR concluded that past exposure to TCE in the SMWA water supply were below levels that result in illness or other adverse health effects for the following reasons: 1) water was blended prior to distribution so that people were actually exposed to TCE concentrations much lower than the maximum detected concentration in a single well and 2) the maximum detected TCE concentration was lower than levels detected in the WMWA water supply (discussed previously) and found to be below levels that result in adverse health effects. In 1979, SMWA closed the contaminated wells to prevent further exposure. In addition, SMWA regularly samples active water supply wells under state and local regulations to ensure the safety of the water supply.

Hatboro Water Authority (HWA)
HWA serves a population of 18,900 with a water supply system composed of eight wells. The closest well in this system to NAWC is approximately 1.75 miles to the west. In 1979, HWA closed six water supply wells because of VOC contamination; information regarding specific contaminants and concentrations is unavailable (Halliburton NUS 1993a; EPA 1999).

Initially, the Fischer & Porter manufacturing plant, an NPL site located 1 mile southwest of NAWC (Figure 1), was believed to be the source of HWA well contamination. Therefore, Fischer & Porter provided HWA funds to install a water treatment system as required by a 1984 consent decree with EPA. However, later investigations found that the Fischer & Porter manufacturing plant was probably not the source of VOC contamination in HWA wells. The actual source of HWA well contamination has not been identified (Fischer & Porter no date). ATSDR was unable to evaluate exposures prior to 1979 because necessary information was unavailable. To prevent past (after 1979), current, and future exposures, HWA closed the contaminated wells and regularly samples active water supply wells under state and local regulations to ensure the safety of the water supply.

Warminster Heights Development Corporation (WHDC)
WHDC supplies drinking water to a population of 3,100 with a water supply system composed of two wells. The closest well in this system to NAWC is approximately 0.5 miles to the southwest. In 1979, WHDC closed both water supply wells because of VOC contamination. Information regarding specific contaminants and concentrations at the time of well closure is unavailable, however TCE and PCE concentrations have been reported in the well at levels rarely exceeding 100 ppb. Sampling from 1986, found TCE at approximately 150 ppb and tetrachloroethylene (PCE) at highs of 70 ppb (Halliburton NUS 1993a; EPA 1999; Fischer & Porter Company no date; Feeney 2000). Investigations found that the Fischer & Porter manufacturing plant, an NPL site located 1 mile southwest of NAWC (Figure 1), and not NAWC, was the likely source of contamination in WHDC wells. Therefore, Fischer & Porter provided WHDC funds to install a water treatment system as required by a 1984 consent decree with EPA. A ROD, completed in 1998, proposed ongoing operation of the water treatment system at the Fischer & Porter manufacturing plant to prevent ongoing well contamination (Halliburton NUS 1992; Ames 1998; Fischer & Porter no date).

In March 1999, PADOH, under a cooperative agreement with ATSDR, completed a health consultation addressing community concerns about past exposure to VOCs in WHDC supply wells, specifically increased cancer risk. To complete this health consultation, PADOH evaluated potential exposures and reviewed the toxicology literature. PADOH concluded that while there were past exposures to contaminants in groundwater, the wells no longer present a public health hazard because WHDC wells are treated and monitored under state and local regulations. In addition, PADOH concluded that no apparent increase in risk for cancer exists due to exposure to VOCs in the contaminated water supply (PADOH 1999).

Speedway Neighborhood
Speedway (Area 1, South) is located along the western boundary of NAWC proximate to Area D. This neighborhood is located within Warminster. The Navy identified 43 private residential water supply wells in Speedway during 1993 investigations. In 1993, the Navy sampled 37 of the 43 residential wells identified for VOCs, which were the contaminants of concern based on NAWC groundwater monitoring. Some wells were not sampled because of denied property access. PCE and TCE were both detected above CVs and MCLs in one private well (see Table 6). Subsequent investigations were unable to replicate these results and concluded that no extensive groundwater contamination problem was present in this neighborhood. The Navy provided a groundwater treatment system to the one home where contaminant concentrations exceeded MCLs. After the Navy installed this treatment system, a technical review of additional data collected by the Navy found that well contamination in the Speedway neighborhood was likely the result of releases at locations other than NAWC. EPA, however, has made no formal determination identifying a source of groundwater contamination in this neighborhood. Based on the technical review results, the Navy conducted maintenance activities on this water treatment system through November 1998 and then transferred responsibility for future operations and maintenance to the home owner (Halliburton NUS 1993b; Ames 1998; Ostrauskas 1999).

PCE (6 ppb) and/or TCE (46 ppb) were detected in 3 of the 37 wells, with only one well containing concentrations above EPA's MCL, when the wells were first sampled in 1993. As a result, residents served by these three wells may have been exposed to these contaminants in their drinking water supply prior to 1993. To evaluate whether health hazards are associated with these past exposures, ATSDR estimated the potential doses for residents (adults and children). To estimate doses, ATSDR used conservative assumptions to ensure that any public health conclusion about the past safety of the drinking water supply considered the worst-case scenario. Residents were assumed to drink water containing the maximum detected concentrations of PCE and TCE daily from 1950 when on-base disposal commenced until 1993 when treatment systems were installed. It is unlikely that a resident only drinks water from their well every day over the entire 43-year period assumed by ATSDR. In addition, it is unlikely that this well contained the maximum detected PCE and TCE concentrations for the entire 43 years. Childhood exposures were assumed to occur daily for 6 years. Exposure as a teenager was considered an adult exposure. These assumptions, ATSDR's methods, and the estimated doses are further described in Appendix C. The estimated doses indicated that in no case were PCE and TCE concentrations in private wells high enough to present a reasonable likelihood for harmful exposures to have occurred. ATSDR, therefore, concludes, based on available toxicologic and environmental data, that past exposures were below levels that result in illness or other adverse health effects.

Based on sampling results, the Navy supplied a groundwater treatment system to the home with water containing contaminants above MCLs. The Navy also monitors on-and off-base groundwater to track contaminant movement and installed groundwater treatment systems to prevent future impacts (Department of the Navy 1993, 1995, 1997b). Because the treatment system removes contamination from the water supply and prevents exposure, ATSDR concludes that current and future exposures are not occurring and will not occur in the Speedway neighborhood and groundwater poses no public health hazards. As a prudent public health measure; however, ATSDR recommends that private well users periodically (every 1 to 2 years) test their wells because groundwater conditions can change over time and unidentified sources may exist in the area. Regular maintenance and testing of private wells with treatment systems is especially important to ensure proper operation of these systems. As a general health consideration, private wells users should also regularly sample their wells for bacteria content, particularly at the point of use.

Flying Heels Neighborhood
The Flying Heels neighborhood (Area 2, West) is located south of NAWC within portions of Warminster. In 1993, the Navy identified 79 residential water supply wells in this neighborhood (Halliburton NUS 1993b). At this time, the Navy sampled 73 of the 79 wells for VOCs ,which were the contaminants of concern based on NAWC groundwater monitoring. Some wells were not sampled because of denied property access. The Derewal site, which is a former metallurgical facility located within the Flying Heels Neighborhood, may be a potential source of groundwater contamination in this neighborhood (Ostrauskas 1999).

TCE (6 ppb) was detected in 3 of the 73 wells, with only one well containing concentrations above EPA's MCL of 5 ppb, when the wells were first sampled in 1993 (see Table 6). Resampling by the Navy was unable to duplicate these results; therefore, the TCE detections may have been the result of sampling or analysis error versus actual groundwater contamination (Halliburton NUS 1993; Ostrauskas 1999). Nonetheless, ATSDR conservatively assumed that residents served by these three wells may have been exposed to TCE in their drinking water supply and evaluated whether health hazards are associated with past exposures. ATSDR evaluated potential health hazards by estimating the potential doses for residents (adults and children) using very conservative assumptions to ensure that any public health conclusion about the past safety of the drinking water supply considered the worst-case scenario. Residents were assumed to drink water containing the maximum detected concentration of TCE daily from 1950 when on-base disposal commenced until 1993 when treatment systems were installed. This assumption overestimates exposure because it is unlikely that residents only drink water from their well every day over the entire 43-year period assumed by ATSDR. Moreover, it is unlikely that this well contained the maximum detected TCE concentration for the entire 43 years, in fact, subsequent well sampling after the initial detection found no TCE. Childhood exposures were assumed to occur daily for 6 years. Exposure as a teenager was considered an adult exposure. These assumptions, ATSDR's methods, and the estimated doses are further described in Appendix C. The estimated doses indicated that in no case were TCE concentrations in private wells high enough to present a reasonable likelihood for harmful exposures to have occurred. ATSDR, therefore, concludes, based on available toxicologic and environmental data, that past exposures were below levels that result in illness or other adverse health effects.

The Navy was initially identified as a potential source of TCE in this neighborhood; therefore, the Navy supplied a groundwater treatment system to the home with TCE found above its MCL. Other private wells in this neighborhood are still being used for drinking water. Current investigation data suggest that sources other than the Navy are contributing TCE to groundwater in this neighborhood. However, to further prevent current and future exposures, the Navy currently monitors on-base groundwater to track contaminant movement at NAWC. The Navy has also installed water treatment systems to treat groundwater contamination on base and prevent off-base movement to this neighborhood (Department of the Navy 1993, 1995, 1997b). Because the Navy has implemented measures to monitor and treat groundwater contamination, ATSDR concludes that current and future exposures are not occurring in the Flying Heels neighborhood; therefore no public health hazards are present. As a prudent public health measure; however, ATSDR recommends that private well users periodically (every 1 to 2 years) test their wells because groundwater conditions can change over time and unidentified sources may exist in the area. Regular maintenance and testing of private wells with treatment systems is especially important to ensure proper operation of these systems. As a general health consideration, private wells users should also regularly sample their wells for bacteria content, particularly at the point of use (e.g. tap water).

Casey Village Neighborhood
Casey Village (Area 2, East) is located along the eastern boundary of NAWC within portions of Warminster and Upper Southampton. In 1993, the Navy identified and sampled 71 residential wells in this neighborhood. These wells were sampled for VOCs, which were the contaminants of concern based on NAWC groundwater monitoring. The VOCs carbon tetrachloride (to 8.7 ppb), 1,1-DCE (to 19 ppb), cis-1,2-dichloroethene (cis-1,2-DCE) (to 530 ppb), PCE (to 480 ppb), and TCE (to 1,200 ppb) were detected at concentrations above CVs and MCLs (see Table 6). These contaminants are found in two distinct plumes—a TCE plume in the eastern part of the neighborhood and a PCE plume in the southwestern part of the neighborhood. Because these VOC concentrations are an order of magnitude higher than VOC concentrations found in other neighborhoods and water supplies, ATSDR evaluated exposures to VOCs in drinking water supplies in Casey Village separately. This evaluation is described briefly in the following text and in detail in Appendix D.

As a result of their investigations, the Navy, EPA, and USGS believe that VOC contamination is likely from sources other than NAWC. One potential source of the TCE plume is a former underground septic system and drain field serving a single home in Casey Village. Reportedly, the owner of this home operated a grease trap cleaning business on the property. TCE was a solvent commonly used for degreasing (USGS 1998). The potential source of the PCE plume has not been identified, but is probably located within the Casey Village neighborhood. Surface and subsurface soil contamination are not the suspected sources of the PCE groundwater contamination. EPA and PADEP are conducting ongoing investigations in this neighborhood and may be contacted for additional information (Halliburton NUS 1994b; Department of the Navy 1994; Ames 1998; USGS 1998; Gold 1999; Ostrauskas 2000).

Regardless of the source of contamination, the Navy immediately provided bottled water to the homes where elevated VOC concentrations were detected in 1993. By 1995, the Navy and EPA connected all homes in Casey Village to the municipal water supply and abandoned all wells except a small number that were retained as monitoring wells. As a result of these actions, exposure to VOCs in private well water in Casey Village ceased.

To assess potential exposures to VOCs in private well water in Casey Village prior to 1993, ATSDR estimated the potential doses for residents (adults and children). To estimate doses, ATSDR used conservative assumptions to ensure that any public health conclusion about the past safety of the drinking water supply considered the worst-case scenario. Exposures were assumed to occur through drinking the water or other household uses, such as showering. Adults living in Casey Village were assumed to be exposed to VOC-contaminated well water every day for 43 years, from 1950 when on-base disposal started and most homes in Casey Village were built until 1993 when homes were provided with bottled water. The actual exposure duration is expected to be much shorter because the business suspected of causing the TCE plume commenced in the 1960s. Although, the source of the PCE plume is unknown, it is not expected that the plume existed before the neighborhood was developed or that private wells were contaminated with PCE when they first were used. Childhood exposures were assumed to occur daily for 6 years. Exposure as a teenager was considered an adult exposure. ATSDR also overestimated that adults and children were exposed every day for the entire 43 or 6 year period, respectively. The actual exposure frequency is expected to be much lower because people would drink water from other sources (e.g., work and school or pre-packaged drinks) and would travel away from their homes for vacations or other purposes.

In addition to using conservative assumptions about how long and how often people were exposed to VOC in their private wells, ATSDR also used conservative assumptions about the VOC concentrations in the private well water. Contaminants were detected in 34 of the 71 wells when they were first sampled in 1993. ATSDR assumed that a single well contained the maximum detected concentration of all the VOCs found and that a neighborhood resident would be exposed to these highest levels of VOCs over the entire exposure period (43 or 6 years for adults and children, respectively). The maximum detected VOCs concentrations, however, were found in different wells so that no resident could have been exposed to the highest levels of all of the VOCs found. Also, exposure to the maximum detected VOC concentrations over the entire exposure duration is not expected based on the groundwater movement and transport of contaminants from sources to the private wells. In addition, the well containing the highest concentrations of TCE (1,200 ppb) and cis-1,2-DCE (530 ppb) was not used as a drinking water supply after 1987 when the home was connected to the public water supply. This well served the home where the degreasing business was operated in the 1960s and 1970s. Wells in neighboring homes contained TCE and cis-1,2-DCE to a maximum of only 120 ppb and 36 ppb, respectively.

In addition to assessing exposure through drinking water, ATSDR also assessed exposures to TCE moving from the water to air during showering. To overestimate likely exposures, ATSDR used conservative assumptions about the concentration of TCE in the water, duration of showering, and transfer of TCE from the water to the air to estimate a TCE air concentration during showering. ATSDR's assumptions, methods, and the estimated doses are further described in Appendix D. The estimated VOC doses in water and TCE concentrations in air indicated that in no case were contaminant concentrations in private wells high enough to present a reasonable likelihood for harmful exposures to have occurred. ATSDR, therefore, concludes, based on available toxicologic and environmental data, that past exposures were below levels that result in illness or other adverse health effects.

Based on sampling results, the Navy and EPA connected homes in Casey Village to the municipal water supply; this was completed in 1995. Although no adverse effects are expected from past exposures, ATSDR supports EPA's decision to connect homes to public water supplies and prevent current and future exposures. This measure provides insurance against current and future health impacts. Because homes are connected to municipal water supplies, ATSDR concludes that current and future exposures are not occurring and will not occur in the Casey Village neighborhood and groundwater poses no public health hazards.

Evaluation of Surface Soil Exposure Pathway

During site investigations, the Navy identified eleven areas of potential soil contamination. Of these, ten areas are located proximate to research and industrial facilities or the airfield, where access was and is restricted by security guards and fences. Only one area is located in a portion of an on-base housing complex where access is unrestricted. ATSDR only evaluated exposure to surface soil because members of the public are not expected to contact subsurface soil on a regular basis.

The following sections provide a description of land uses at NAWC, an evaluation of potential exposures at areas located in restricted portions of the base, and an evaluation of potential exposures at the area located within on-base housing. Based on a review of contaminant concentrations, how often and how long exposures may occur, and completed or proposed remedial actions, ATSDR concludes that past, current, and potential future exposures to contaminated surface soil are not expected to cause illness or other adverse health effects.

Land Use

Approximately 484 acres of the total 734 acres comprising NAWC is occupied by runways. The primary runway has an east-west orientation and is located in the central portion of NAWC. A second, smaller runway with a north-south orientation is located in the western portion of NAWC. Research and industrial facilities are mainly located in the western and northwestern portion of NAWC. Individual research and operations buildings are located around the perimeter of the runways as well. On-base military housing is located in the northwestern and southeastern portions of NAWC. Since closure under the BRAC program, activities in the research, industrial, and operations areas have been minimal. Housing is still occupied by military personnel stationed at a nearby facility.

Soil Contamination Sites Located in Restricted Areas

Ten of the eleven potential areas of contamination identified during site investigations are located proximate to the research and industrial facilities or the airfield, where access was restricted by security guards and fences. The Navy divided these areas in three groups, based on location (Figure 2). Sites 1, 2, 3, and the Impoundment Area comprise Area A and are located in the northwest portion of NAWC northwest of Jacksonville Road and within a former research and industrial area. Sites 6 and 7 are included in Area B and are located in the south central portion of NAWC south of the runways. Sites 4, 8, the Maintenance Area, and Tile Field comprise Area C and are located in the north-central portion of NAWC north of the runways. Each of these sites, except Site 8, the Maintenance Area, and the Tile Field, were used for disposal of NAWC wastes. Site 8 served as a fire-fighting training area and the Maintenance Area was used for vehicle maintenance activities. The Tile Field is an area with several drainage lines, which may serve a preferred pathways for contaminant movement (Brown & Root 1996c). Details regarding activities and operations performed at each site are provided in Appendix A, Table A-1.

The Navy collected surface-soil samples at seven potential areas of contamination during a Phase III RI completed in November 1996. Sites 4 and 6 were evaluated during removal actions conducted in 1997 and 1998, respectively. The Navy did not collect surface-soil samples at the Impoundment Area because the majority of this area is occupied by concrete-lined impoundments and a sewage treatment plant. Sampling detected surface soil contaminated with polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dioxins, and/or metals above CVs at Sites 2, 3, 4, 6, and 8. Sampling at Site 1 and the Maintenance Area detected contamination below CVs and background. Sampling at Site 7 and the Tile Field found no contamination in surface soil (Halliburton NUS 1995; Brown & Root 1996a, 1996c; Department of the Navy 1997b). Contaminants detected in surface soil above CVs are presented in Table 7.

ATSDR evaluated potential past, current, and future public health hazards at soil contamination sites with limited access by first examining potential exposures. When the base was active, access to NAWC was limited to military and civilian personnel by perimeter fences, warning signs, security patrols, and gate guards. Base fences also prevented military families living in on-base housing from accessing sites close to the research and industrial facilities and the airfield. Military and civilian personnel that may have had access to areas with contamination above CVs included workers at Sites 2, 3, 4, and 6 (former disposal areas) and Site 8 (fire-fighting training area). However, these workers are expected to have worn long pants, work gloves, and work boots that would have further prevented exposure to site contaminants. Currently, access to NAWC is restricted by perimeter fences, warning signs, and security patrols to prevent exposure to soil contaminants above CVs. In addition, the Navy has completed removal actions at Sites 2, 3, 4, and 6 to prevent future exposures. The Navy is also planning to conduct additional remedial actions, as needed, prior to redevelopment to prevent future exposures (Brown & Root 1996a, 1996c; Department of the Navy 1997c; Ames 1998). Based on potential past exposures, limited site access, and remediation activities ATSDR concludes that past, current, and potential future site uses in areas of soil contamination in the research, industrial, and airfield portions of NAWC were below levels that result in illness or other adverse health effects.

Soil Contamination Sites Located in the Shenandoah Woods Housing Complex

Two of the 40 housing units (Units 401 and 402) in the Shenandoah Woods housing complex were partially built on a closed landfill (Site 5). The Navy placed a 2 foot layer of soil over the landfill and seeded the area when the landfill was closed. Site 5 and Units 401 and 402 are located in the southern portion of NAWC designated Area B (Figure 2). Between 450 and 550 residents live in the Shenandoah Woods housing complex. Access to Site 5 by military families living in on-base housing is unrestricted (Brown & Root 1996c; Ames 1999). Details regarding years of operation and site activities at the landfill are provided in Appendix A, Table A-1.

The Navy collected surface-soil samples at Site 5 during a Phase III RI completed in November 1996 and supplemental sampling conducted in December 1999. Surface-soil sampling detected benzo(a)pyrene (to 0.27 parts per million [ppm]), Aroclor-1254 (a PCB) (to 24 ppm), cadmium (to 10.5 ppm), and lead (to 1,020 ppm) at concentrations above CVs (see Table 7). (Brown & Root 1996c; Department of the Navy 2000e). Based on investigation results, a ROD was prepared and signed in August 2000.

Past, current, and future Shenandoah Woods residents may be exposed to surface-soil contaminants at Site 5 during outdoor activities. To evaluate whether health hazards are associated with exposures to these contaminants, ATSDR estimated the potential exposure doses for past, current, and future on-base residents (adults and children). To estimate doses, ATSDR used conservative assumptions to ensure that any public health conclusion about residence in Shenandoah Woods and contact with soil considered the worst-case scenario. Residents were assumed to contact soil containing the maximum detected contaminant concentrations daily for 6 years, although the average time military families reside in on-base housing is 2 to 3 years (Szamborski 1999). Contaminants were detected above CVs in only a small number of the total samples collected, for example, lead and benzo(a)pyrene were detected above CVs in only 1 of 16 samples. Therefore, it is unlikely that residents would have daily contact with contaminants above CVs. In addition, samples collected from the fenced yards for each of the apartments within Units 401 and 402 detected no contaminants above CVs. The samples containing contaminants above CVs were collected near the housing complex roadway. These assumptions, ATSDR's methods, and the estimated doses are further described in Appendix C. Although contaminants were detected slightly above CVs at several locations, in no cases were levels high enough to present a reasonable likelihood for harmful exposures to have occurred. ATSDR, therefore, concludes that past, current, and future exposures to contaminated surface soil were below levels that result in illness or other adverse health effects.

Evaluation of Surface Water and Sediment Exposure Pathway

Soil contaminants in Areas A, B, and C, as described in the previous section, may enter drainage channels and streams in surface water runoff from these areas. After entering drainage channels and streams, contaminants could be transported downstream in solution, suspension, or along the stream bottom. Downstream areas include depositional environments (e.g., point bars or overbank deposits or streams). Clean eroded soil or sediment, however, can dilute contaminated materials to background concentrations.

The following sections provide a description of NAWC hydrology and an evaluation of potential exposures associated with drainage channels and streams originating in Areas A, B, and C. These sections also describe the results from past investigations used in the evaluation of potential exposures. Based on a review of available data, how often and how long exposures may occur, and completed or proposed remedial actions, ATSDR concludes that past, current, and potential future exposures to contaminants in surface water and sediment during recreational use are below levels that cause illness or other adverse health effects. If data from stream monitoring identifies increased chemical concentrations or new chemicals, ATSDR requests that the Navy, EPA, and PADEP notify ATSDR and PADOH. If, after evaluation, the information changes the current PHA findings, ATSDR will then make appropriate public health recommendations.

Hydrology

NAWC is located on a ridge between two drainage basins. Natural surface water flow directions have been altered by surface grading, site paving, and a storm water drainage system composed of ditches, culverts, and storm sewers. The northern portion of the base (65%) drains into small tributaries or streams discharging to Little Neshaminy Creek located along the northern property boundary. The southern portion of the base (35%) drains into drainage channels and streams that comprise the headwaters of Southampton Creek, which is located along the southern property boundary and is a tributary to Pennypack Creek. Little Neshaminy Creek and Southampton Creek eventually drain into the Delaware River. The drainage channel and streams associated with Areas A, B, and C are intermittent. There are no lakes or ponds located within NAWC boundaries (Halliburton NUS 1992; Brown & Root 1996c).

Area A

Surface water within and adjacent to Area A, including Sites 1, 2, 3, and the Impoundment Area, consists of a tributary to Little Neshaminy Creek that originates at a storm water culvert under Jacksonville Road. This tributary flows northeasterly along the NAWC property boundary adjacent to Area A. During site investigations, the Navy collected surface water and sediment samples from the channels and streams on base and in downstream locations off base. Surface water and sediment sampling results were compared to drinking water and surface soil CVs, respectively, because no CVs have been developed for these media. Surface water sampling from this stream detected two VOCs, two PAHs, and four metals above drinking water CVs. Sediment sampling detected seven PAHs, two PCBs, one pesticide, and five metals above soil CVs (see Tables 8 and 9) (Brown & Root 1996c). To prevent movement of additional contaminants to the streams, the Navy completed removal actions at Sites 1, 2, and 3. The majority of the surface soil in the Impoundment Area is covered with concrete-lined impoundments and a sewage treatment plant (Ames 1998). In June 2000, a ROD was signed selecting regular stream monitoring as the most appropriate remedial action for Area A (Department of the Navy 2000d).

Drainage channels and streams originating from Area A flow through a residential neighborhood after leaving the base. Off-base residents (adults and children) in this area may use the streams for recreation. The most likely recreational use is walking, wading, or playing because the streams are small and flow is intermittent (surface water is present for only parts of the year). The lack of year-round surface water also prevents boating, swimming, and fishing as the stream does not support a fish population viable as a food source. During recreational use, adults and children are expected to contact sediment and surface water, when present.

To evaluate whether health hazards are associated with past or current exposures to contaminants in surface water and sediment, ATSDR assessed contaminants detected above drinking water and surface soil CVs. However, the drinking water and soil CVs may be considered overly conservative for use with surface water and sediment data. For example, the drinking water CVs are developed assuming that an adult resident drinks 2 liters of water everyday from a single source containing a contaminant. Within streams flowing from Area A, surface water is present for only a portion for the year, making daily exposure impossible. In addition, surface water is not used as a drinking water supply. It is extremely unlikely that a recreational user would ingest as much as 2 liters of water from the stream while wading or playing. The soil CVs also assume daily exposure. Weather constraints, such as rain, snow, and cold temperatures typical of the area, make it extremely unlikely that a resident would use the streams for daily recreation.

Nonetheless, ATSDR estimated potential exposure doses to contaminants in surface water and sediment. This estimate used very conservative assumptions to ensure that any public health conclusion about recreational use of streams considered the worst-case scenario. Residents were assumed to contact surface water and sediment containing the maximum detected contaminant concentrations 5 days per week, 26 weeks per year, for 50 years, from when on-base disposal commenced until remedial actions were identified. It is unlikely that a resident would use the streams for recreation at this frequency over the entire 50-year period assumed by ATSDR. In addition, it is unlikely that the surface water and sediment contained the maximum detected contaminant concentrations for the entire 50 years. Childhood exposures were assumed to occur daily for 6 years. Exposure as a teenager was considered an adult exposure. The assumptions about exposures, ATSDR's methods, and the estimated doses are further described in Appendix C. Although low levels of contamination were detected in surface water and sediment collected from streams draining Area A, in no cases were levels high enough to pose a reasonable likelihood for harmful exposures to occur. Based on available toxicologic and environmental data, estimated exposure doses, and remedial actions, ATSDR concludes that past, current, and potential future exposures to contaminants in surface water and sediment are below levels that result in illness or other adverse health effects.

Area B

Drainage channels in Area B, including Sites 5, 6, and 7, direct surface water flow to outfalls located along the southern NAWC property boundary. These outfalls feed a concrete drainage channel that flows southerly through an adjacent residential neighborhood. This drainage system comprises the headwaters to Southampton Creek. During site investigations, the Navy collected surface water and sediment samples from the channels and streams on base and in downstream locations off base. Surface water sampling detected thallium above its drinking water CV. Sediment sampling detected five PAHs and Aroclor-1260 (a PCB) above soil CVs (see Tables 8 and 9) (Brown & Root 1996c). To prevent additional contaminant movement to the streams, the Navy completed a removal action at Site 6. No surface-soil contamination was detected at Site 7 and (Brown & Root 1996a,1996c; Ames 1999). A ROD, selecting regular monitoring of the streams as the most appropriate remedial action, was signed in August 2000 (Department of the Navy 2000e).

Potential exposures to surface water and sediment in streams draining Area B are similar to exposures that would occur in streams draining Area A, as discussed above. Streams draining Area B flow through an on-base housing complex (Shenandoah Woods) and into a residential neighborhood abutting NAWC. These streams are also intermittent; therefore, the most likely recreational uses are walking, wading, or playing in the stream. Surface-water exposure would also only occur for a portion of the year. To evaluate whether health hazards are associated with exposure to contaminated surface water and sediment in streams draining Area B, ATSDR estimated potential exposure doses to contaminants detected above CVs using conservative assumptions, as described for Area A. These assumptions result in estimated doses that overestimate the levels of actual exposure. These assumptions, ATSDR's methods, and the estimated doses are further described in Appendix C. Although low levels of contamination were detected in surface water and sediment collected from streams draining Area B, in no cases were levels high enough to pose a reasonable likelihood for harmful exposures to occur. Based on available toxicologic and environmental data, the estimated exposure doses and remedial actions, ATSDR concludes that past, current, and potential future exposures to contaminants in surface water and sediment are below levels that result in illness or other adverse health effects.

Area C

Drainage channels in Area C (Sites 4, 8, Maintenance Area, and Tile Field) direct surface-water flow to outfalls located along the northern NAWC property boundary. These outfalls feed tributaries to Little Neshaminy Creek that flow northerly away from NAWC and through a residential neighborhood. During site investigations, the Navy collected surface water and sediment samples from on-base channels and streams and in downstream off-base locations. Surface water sampling detected lead and manganese above drinking water CVs and sediment sampling detected PAHs, arsenic, and iron above soil CVs (see Tables 8 and 9) (Brown & Root 1996c). To prevent additional contaminant movement to the stream, the Navy completed a removal action at Site 4. No contaminants above CVs were detected at the Maintenance Area or Tile Field. If necessary, remedial actions may be completed at Site 8 during redevelopment (Brown & Root 1996c; Department of the Navy 1997c). No further action was deemed necessary to address the Area C streams in a ROD released in April 2000 (Department of the Navy 2000a).

Potential exposures to surface water and sediment in streams draining Area C are similar to exposures that would occur in streams draining Area A, as discussed above. Streams draining Area C flow into a residential neighborhood abutting NAWC. These streams are also intermittent; therefore, the most likely recreational uses are walking, wading, or playing in the stream. Surface-water exposure would also only occur for a portion of the year. To evaluate whether health hazards are associated with exposure to contaminated surface water and sediment leaving NAWC, ATSDR estimated potential exposure doses for contaminants detected above CVs using conservative assumptions, as described for Area A. These assumptions result in estimated doses that overestimate the levels of actual exposure. These assumptions, ATSDR's methods, and the estimated doses are further described in Appendix C. Although low levels of contamination were detected in surface water and sediment collected from streams draining Area C, in no cases were levels high enough to pose a reasonable likelihood for harmful exposures to occur. Based on available toxicologic and environmental data, estimated exposure doses and remedial actions, ATSDR concludes that past, current, and potential future exposures to contaminants in surface water and sediment are below levels that cause illness or other adverse health effects.

Evaluation of Lead Paint Exposure Pathway

Based on ATSDR's detailed evaluation of possible adverse health effects from past, current, and future exposures to lead in on-base housing, ATSDR concluded that past exposure to lead was not expected to result in adverse health effects in all homes except one. In one home, lead exposures could have resulted in increased blood lead levels, however, possible adverse health effects are indeterminate because it is unknown if children and pregnant women lived in this home when lead was accessible. To prevent current and future exposures, the Navy completed removal and abatement actions at the officer housing area, Quarters A, and Quarters B. Lead paint was either removed or encapsulated, lead paint chips found at the foundation of residences were removed, and areas where lead concentrations in soil exceeded standards were remediated (Foster Wheeler 1998).

In 1996, the Navy conducted a lead study of residential housing areas to assess if lead paint was present at levels that may affect residents' health. Paint, dust, and soil samples from the Shenandoah Wood housing complex, the officer housing area, Quarters A, and Quarters B were sampled for lead. Lead was not detected in paint, dust, or soil at levels of concern in the Shenandoah Woods housing complex (Szamborski 1998).

Inspections of the officer housing area (six single-family homes), Quarters A (one single-family home), and Quarters B (one single-family home) identified lead paint at all eight residences in these housing areas. The inspections discovered, however, that less than 10 percent of the areas examined in each home contained cracked or peeling lead paint that was accessible for residents to contact. Dust sampling found lead above Housing and Urban Development (HUD) Guidelines in 2 of 8 samples collected at Quarters A. The HUD guideline for lead in floor dust is 100 micrograms per square foot (ug/f2); lead was found in one floor dust sample from Quarters A at 105 ug/f2. The HUD guideline for lead in window sill dust is 500 ug/f2; lead was found in one window sill dust sample from Quarters A at 658 ug/f2. Lead was also detected above its CV (400 ppm) in 2 of 5 samples (884 ppm and 8,734 ppm) collected adjacent to the foundation of this home (Quarters A), as well as in one background sample (422 ppm) collected near the officer housing area (Department of the Navy 1997a). Based on these results, lead abatement was conducted at each of the eight homes to prevent any current or future exposure (Foster Wheeler 1998).

Unborn children and preschool-age children are considered the most vulnerable population to lead poisoning. Unborn children are vulnerable because their developing nervous systems are susceptible to lead toxicity. Preschool children are vulnerable because of their hand-to-mouth behavior during play and efficient absorption of lead from ingestion. Nutritional deficiencies in iron and calcium can also increase susceptibility to lead poisoning.

ATSDR evaluated exposures to assess possible health effects from lead exposure to children. In the officer housing area and Quarters B, lead paint was found in less than 10 percent of the samples collected in each home. Therefore, exposure to lead paint in these homes may have occurred, but would have been infrequent and not expected to result in adverse health effects for children or pregnant women living in these homes. In Quarters A, lead paint was found in damaged condition in the basement, garage, a storage area, and on the home exterior. Lead was also found in dust slightly above HUD guidelines and in surface soil substantially above its CV at a this home. As such, ATSDR assessed possible impacts to blood lead levels from contact with the maximum detected soil concentration (8,734 ppm) even though it is highly unlikely that a child would contact lead at this level on a regular basis. Research has shown that blood lead levels in children increase approximately 1 to 7 micrograms per deciliter (ug/dL) for every 1,000 ppm increase in soil concentrations (ATSDR 1999b). Regular contact with 8,734 ppm of lead in soil, therefore, may result in an increase in blood lead levels of 8.7 to 61 ug/dL, which could raise a child's blood lead levels to above the Center for Disease Controls's level of concern (10 ug/dL)(1). Based on this assessment, ATSDR concluded that exposure to the maximum detected lead levels in soil could result in increased blood levels. However, it is unknown if children or pregnant women lived in this home when lead was accessible to the occupants. ATSDR, therefore, concluded that possible past adverse health effects from exposure to lead in Quarters A were indeterminate. All homes were abated for lead to prevent any current or future exposures.


COMMUNITY HEALTH CONCERNS

The communities near NAWC have expressed an interest in the environmental condition and/or reuse of the facility. The following communities are represented on the NAWC RAB that provides input to the Navy through the various steps in the environmental remediation process: Warminster Township, Northampton Township, and Ivyland Borough. The RAB meets monthly to discuss Navy activities and community concerns.

In 1994, NAWC prepared a Superfund community relations plan that summarized the results of community interviews with a total of 40 members of the surrounding communities (19 residents and 21 public representatives). Public representatives included officials from Warminster Township, Northampton Township, Upper Southampton Township, Ivyland Borough, and Warminster Heights. Representatives from the Bucks County Department of Health, the Chamber of Commerce, the Bucks County NAWC Economic Adjustment Committee, the Bucks County Planning Commission, the state House and Senate, the federal House and Senate, and PADEP were also interviewed. The community members interviewed expressed the following concerns:

  • Well Testing. Interviewees requested further information on the process used to determine which private wells are sampled and the interpretation of these testing results (Halliburton NUS 1994a).
  • The Navy conducted testing of private wells near NAWC and provided residents with the sampling results from their well. When the results were sent, the Navy included an explanation of testing results and a list of drinking water standards (Ames 1998).

  • Public Water Supply. Interviewees requested further information about the process used to determine which residents receive a water treatment system and which residents will be connected to a public water system (Halliburton NUS 1994a).
  • The Navy produced a series of fact sheets and disseminated these fact sheets to the community and local officials to address these concerns (Ames 1998).

  • Information. Over half of the residents interviewed for the community relations plan indicated that they felt that they were receiving insufficient information from the Navy, EPA, and local officials about environmental activities associated with NAWC. When information was received, it was too technical to understand (Halliburton NUS 1994a).
  • In addition to fact sheets, RAB meetings are held monthly. The RAB advertises the dates and times of their meetings and encourages community attendance (Ames 1998).

In addition to concerns identified in the Community Relations Plan, ATSDR also identified a number of other concerns based on communications with personnel at NAWC and discussions with the Buck County Health Department. These concerns are as follows:

  • There are localized groundwater contamination plumes in the area and some of the sources of this contamination have not been identified. Based on these facts, are community members exposed to groundwater contamination in drinking water and what is being done to identify sources and address the regional problem?
  • In 1979, EPA and PADEP identified groundwater contamination, primarily chlorinated solvents in Bucks County, Pennsylvania. This contamination has impacted several municipal water supply wells proximate to NAWC. Municipal water suppliers, however, are required under federal and state Safe Drinking Water Acts to regularly test their water supply to ensure that there are no contaminants present above EPA's MCLs or PADEP's MCLs. This regular testing ensures that the community is not exposed to harmful levels of contaminants in their drinking water and also identifies if the water supplies are being impacted by groundwater contamination. The regional EPA office and PADEP have been involved, and continue to be involved, in efforts to investigate and remediate potential source areas, including NAWC and other NPL sites (Figure 1). Based on drinking water monitoring requirements and ongoing investigations in the region, community members are not expected to be exposed to contaminants in municipal water supplies.

  • If the Northampton, Bucks County Municipal Water Authority installs a new groundwater supply well as proposed, will this well be impacted by contamination at NAWC?
  • The Northampton, Bucks County Municipal Water Authority is planning to install a new groundwater supply well north of NAWC. This well is proposed to be located in a drainage basin that has been impacted by groundwater contamination. For this reason, the Northampton, Bucks County Municipal Water Authority is concerned that the new well may be impacted by contamination at NAWC and has requested that the Navy install a test well between NAWC contamination and the drinking water supply wells. Sampling of the test well could provide an early warning that contamination is migrating toward the supply well. To date, this test well has not been installed. Currently, the Navy operates three groundwater extraction well networks and a treatment system to remove contamination from groundwater in the overburden aquifer in Areas A, C, and D. Investigations of groundwater in this area by the Navy are complete. Contamination within the shallow and deep bedrock aquifers, however, has not been fully characterized and contamination that may be present in these aquifers could impact the new groundwater supply well. Public health, however, will be protected regardless of potential impacts to the new groundwater supply well. Under state and federal regulations, public water supplies must be regularly tested to ensure that contaminants are absent or below EPA's MCLs and ensure the safety of the water supply. In addition, EPA, PADEP, and the Northampton, Bucks County Municipal Water Authority are aware of the groundwater contamination problems in the area and can closely monitor water supplies to prevent exposures.

  • The Shenandoah Woods housing complex was partially built on a closed landfill. Are residents exposed to harmful levels of contamination from the landfill?
  • No. ATSDR looked at the possible exposures from contaminants in groundwater and soil gas entering indoor air and surface-soil contact, as discussed in the following text, and determined the exposures would not be harmful. ATSDR, however, requests that the Navy, EPA, and PADEP notify ATSDR and PADOH if information regarding contamination at Shenandoah Woods changes. If after evaluation the information changes the current PHA findings, ATSDR will then make appropriate public health recommendations.

    Two multifamily housing units, Units 401 and 402, of the Shenandoah Woods housing complex were partially built on a former landfill (Site 5). Groundwater underlying Site 5 is contaminated with VOCs. Detections were generally low and only TCE and 1,2-DCE appeared to be within an identifiable plume. Based on plume dimensions, only TCE at concentrations between 1 ppb and 5 ppb was estimated to underlie Unit 401. Neither TCE nor 1,2-DCE were found underlying Unit 402. The WMWA water supply system provides drinking water to the Shenandoah Woods housing complex; therefore, residents are not exposed to contaminated groundwater associated with the landfill. VOCs in groundwater, however, may migrate to soil gas and indoor air. Four of six soil gas samples collected at Site 5 contained BTEX (benzene, toluene, ethylbenzene, and xylenes) to a maximum concentration of 3.6 ppb. PCE (0.3 ppb) and TCE (0.09 ppb) were each detected in only one soil gas sample. Indoor air sampling at Unit 401 detected only toluene (9 ppb) at a concentration below its CV. This low level of toluene could be present from household materials rather than from groundwater migrating from Site 5. TCE and 1,2-DCE were not detected in indoor at Unit 401 (Halliburton NUS 1992). Because only low levels of VOCs were found in groundwater, there were limited detections of VOCs in soil gas, and only toluene was detected in indoor air. Residents of Units 401 and 402 are not expected to be exposed to contaminants in indoor air from groundwater or soil gas at levels of health concern.

    As discussed in the previous section, surface soil-sampling detected Aroclor-1254, benzo(a)pyrene, cadmium, and lead above background levels and CVs. However, these contaminants were detected in only a small number of the total samples collected. For example, lead was detected above its CV in only 1 of 16 samples (Brown & Root 1996c). In order to evaluate the potential for adverse health effects from contact with these contaminants, ATSDR examined potential exposures, reviewed sampling data, and estimated doses for residents (adults and children) exposed to the maximum detected concentrations of these contaminants (details are provided in the previous section and Appendix C). Although low levels of contamination were detected in surface-soil samples, in no cases were the levels high enough to pose a reasonable likelihood for illness or other harmful exposures to occur.

    No further actions were deemed necessary to address groundwater and soil contamination in RODs released in September 2000. To address surface water and sediment contamination, regular monitoring of streams was selected as the appropriate remedial action (Department of the Navy 2000e). If new data from stream monitoring identify increased chemical concentrations or new chemicals, ATSDR requests that the Navy, EPA, and PADEP notify ATSDR and PADOH. If information changes the current PHA findings, ATSDR will then make appropriate public health recommendations.

  • Are off-site residents exposed to contaminants at harmful levels in streams fed by NAWC drainage and fish from these streams?
  • No. Although people who wade or play in the creek may contact some contamination, the levels would not be harmful.

    To assess potential health hazards from contaminants detected in surface water and sediment from streams draining NAWC, ATSDR first evaluated how people may be exposed to these contaminants. Streams leaving NAWC flow through residential neighborhoods. Therefore, off-base residents may contact contaminants in surface water and sediment during recreational use. However, streams leaving the base are intermittent (surface water flow is only present part of the year), and activities such as swimming, boating, and fishing are not feasible. Therefore, residents may be exposed to contaminants in surface water, when present, and sediment when using the streams for recreational activities such as walking, wading, or playing.

    To assess whether these recreational exposures may lead to adverse health effects, ATSDR estimated the potential exposure doses for past, current, and future recreational users. Details regarding the assumptions used in estimating exposure doses are presented in the previous section and in Appendix C. Although contaminants were detected above CVs for drinking water and soil, in no cases were levels high enough to present a reasonable likelihood for harmful exposures to have occurred. In addition, the Navy has completed or is conducting remedial actions at NAWC that will prevent additional contamination from migrating off-base in streams. Based on a review of exposure doses and remedial actions, ATSDR concluded that no public health hazards are associated with past, current, and future recreational use of streams fed by NAWC drainage. If new data from stream monitoring identifies increased chemical concentrations or new chemicals, ATSDR requests that the Navy, EPA, and PADEP notify ATSDR and PADOH. If, after evaluation, the information changes the current PHA findings, ATSDR will then make appropriate public health recommendations.

  • Could mercury, used at Building 70 (Centrifuge) and the former trickling filters for the wastewater treatment plant, have been released to the environment and affected drinking water supplies?
  • Based on past sampling data, ongoing groundwater monitoring programs, and mercury monitoring within Building 70, ATSDR concluded that it is unlikely that potential past mercury releases have affected or will affect drinking water supplies.

    Building 70 (Centrifuge) is located in the western portion of NAWC near Sites 1, 2, and 3. The Centrifuge began operation in 1954 and is still used to test flight personnel. The Centrifuge uses 50 pounds of mercury for electrical grounding. There are no records of past mercury spills or leaks. The Navy reports that mercury is only lost through volatilization during maintenance operations. A mercury detector is present within the building to detect releases (EA Engineering, 1995). In addition, the Navy installed and tested monitoring wells near Building 70 in efforts to identify contamination associated with Sites 1, 2, and 3 and contamination potentially migrating off base. Mercury was detected in only 3 of 24 groundwater samples collected and the detected concentrations were below EPA's MCL (Halliburton NUS 1993a).

    The wastewater treatment plant, located in the western portion of NAWC, included several trickling filters. Water treated in the plant flowed through these trickling filters before discharging to a nearby stream. Use of the trickling filters ceased in 1998. There is concern about mercury releases from these filters because a seal used in the trickling filter was made of mercury. Visual inspection of the tanks containing the trickling filters identified mercury proximate to the seal. Investigations in the stream that received discharges from the trickling filters found no mercury in surface water and mercury was found in sediment below its CV. WMWA will likely remove these filters under their plans to build a new sewage treatment plant at NAWC (Ames 2000).

  • What security measures will be taken to ensure that trespassers will not be exposed to physical and chemical hazards during remediation and redevelopment?
  • Until September 1999, access to NAWC was limited by perimeter fences, gate guards, and roving patrols. Currently, Navy personnel overseeing the base redevelopment conduct daily inspections and work with the local police departments to prevent unauthorized use of the base (Ames 1999, 2000).

  • Does the chromium hot spot identified at Site 6 pose a health concern to past, current, and future site users?
  • Investigations conducted in association with the removal action at Site 6 did not detect chromium in surface soil at concentrations above background. No chromium hot spot was identified in surface soil. The Navy has conducted a removal action at Site 6 to prevent future exposures to other site contaminants (Brown & Root 1996b; Ames 2000).

  • Are workers, residents, and future site users at risk of injury from physical hazards, such as open pits or scrap metal debris, located at NAWC?
  • To prevent injury, the Navy restricts site access and discourages trespassers with perimeter fences, warning signs, and regular security patrols. Construction workers on base during redevelopment will follow Occupational Safety and Health Act (OSHA) regulations to prevent personal injury. The Navy is maintaining security and access restrictions and removing physical hazards during redevelopment to prevent future injury.


ATSDR CHILD HEALTH INITIATIVE

ATSDR recognizes that infants and children may be more sensitive to exposures than adults in communities with contamination in water, soil, air, or food. This sensitivity is a result of a number of factors. They are more likely to be exposed because they play outdoors and they often bring food into contaminated areas. Children are shorter than adults, which means they breathe dust, soil, and heavy vapors close to the ground. Children are also smaller, resulting in higher doses of chemical exposure per body weight. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Most importantly, children depend completely on adults for risk identification and management decisions, housing decisions, and access to medical care. Therefore, ATSDR is committed to evaluating their special interests at sites such as NAWC, as part of the ATSDR Child Health Initiative.

ATSDR has attempted to identify populations of children in the vicinity of NAWC. Seven schools are located within one mile of NAWC. Roughly 2,439 children under the age of 6 years are estimated to live within 1 mile of NAWC. Within the military families stationed at Willow Grove, but living in on-base housing units at NAWC, there are approximately 500 children under the age of 18 (1990 Census of Population and Housing 1991; Szamborski 1999).

Like other people living or working at or in the vicinity of NAWC, children may contact contamination in site media. Children may have been exposed to contaminants in NAWC, municipal, and private drinking water wells; surface soil at Site 5; and surface water and sediment in streams on and off base. Lead exposures present a unique concern for children, therefore, ATSDR also evaluated possible lead paint and dust exposures. To evaluate whether children may experience adverse health effects from these exposure, ATSDR estimated the potential doses for children either living on or near NAWC. ATSDR estimated doses using very conservative assumptions that overestimate the levels of actual exposure. These assumptions, ATSDR's methods, and the estimated doses are further described in Appendix C. ATSDR concluded that exposure to site contamination does not pose unique health hazards for children. In all homes except one, exposures to lead paint or dust was not expected. In one home, lead exposures could have resulted in increased blood lead levels, but it is unknown if children or pregnant women lived in this home when lead was accessible. Therefore, possible adverse effects from lead exposures were indeterminate. These conclusions are based on ATSDR's exposure evaluation and the following information:

  • To estimate exposures, ATSDR used extremely conservative assumptions that overestimate the potential risk. For example, ATSDR assumed that children were exposed to the maximum detected contaminant concentrations over the entire exposure period, which is unlikely to occur. ATSDR also overestimated how long or how often exposures would occur. Using these assumption, ATSDR's evaluation of doses indicated that there are no expected adverse health effects. More information about the evaluation of doses is provided in the "Evaluation of Environmental Contamination and Potential Exposure Pathways" section and Appendix C of this PHA.


  • NAWC, surrounding communities, and regulatory agencies are aware of the contamination issues stemming from activities at NAWC. The Navy has taken measures and conducted remedial activities to prevent future contaminant releases to the environment. NAWC also monitors groundwater to ensure the safety of the water supply and prevent future exposures. In addition, surrounding communities monitor their water supplies. Regulatory agencies oversee activities at NAWC to ensure that proper actions are taken to address existing contamination and prevent future contamination.


  • Lead paint was found in eight on-base residences. In seven of these homes, lead paint was found in only 10 percent or fewer of the samples collected from each home. As a result, lead exposures may have occurred, but lead poisoning would not have been expected because only limited lead paint was available for exposure. In one home, lead paint, as well as lead in dust and soil, was found. Exposures at this home could have resulted in increased blood lead levels, as discussed in the "Evaluation of Environmental Contamination and Potential Exposure Pathways section of this PHA. It is unknown, however, if children or pregnant women lived in this home when lead was accessible to the occupants. Therefore, possible adverse effects from lead exposures were indeterminate. All homes have been abated for lead to prevent current and future exposures.

1 Possible increased blood levels were calculated as follows:
1 ug/dL per 1,000 ppm x 8,834 ppm = 8.7 ug/dL
7 ug/dL per 1,000 ppm x 8,834 ppm = 61 ug/dL


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