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PETITIONED HEALTH CONSULTATION

GROUNDWATER PATHWAY EVALUATION

BRUNSWICK WOOD PRESERVING
BRUNSWICK, GLYNN COUNTY, GEORGIA


DISCUSSION

Assessment Methodology

For each environmental medium at a site, ATSDR examines the type and concentrations of relevant contaminants. In this document, ATSDR used comparison values in selecting contaminants for further evaluation within an exposure pathway. Because public water systems are monitored for compliance with EPA's Maximum Contaminant Levels (MCLs), ATSDR selected MCLs as comparison values for this site. MCLs are enforceable drinking water standards. ATSDR also used the Reference Dose Media Guides (RMEGs) for contaminants without established MCLs. ATSDR then considers how people might come into contact with the contaminants. Because the level of exposure depends on the route of exposure and the concentration of contaminants, this exposure information is essential to determine if a public health hazard exist.

Potential exposure pathways for BWP include groundwater and on-site soil pathways. The evaluation of the groundwater pathway is included in this consultation. Information gathered and removal or remedial activities conducted since ATSDR's 1992 Health Consultation is considered. The purpose of this consultation is to evaluate whether contaminants in the groundwater could represent a potential health concern for the public. Contaminants found in on-site soil that could migrate to the groundwater include PCP, PAHs, dioxin, arsenic, and chromium. These chemicals have documented human health effects.

Groundwater Exposure Pathway

Groundwater refers to bodies of water, or aquifers, that lie under the earth's surface. Groundwater can become contaminated when chemicals migrate or leach from soils or contaminated areas (e.g., lagoons, surface and buried impoundments) into an underlying aquifer. Water typically flows at a slow rate through the aquifer lessening the chance of contaminant migration. Wells and springs are supplied by groundwater, and it is only through drinking or other domestic uses of well and spring water that people are directly exposed to potentially contaminated groundwater. Because the groundwater flows towards Burnett Creek, exposure may also occur indirectly via contact with surface water or via consumption of Burnett Creek fish. ATSDR assessed available site data in its evaluation of the groundwater contamination at the site. A summary of the site's hydrogeology, groundwater use, and groundwater quality data are presented in the following discussion.

    Hydrogeology

The aquifer beneath the site (local hydrogeology) has not been adequately characterized, making determination of groundwater flow and possible contaminant movement from the site difficult. Study of the regional hydrogeology suggests that the aquifer in the area of the site consists of three water-bearing layers: the surficial layer, the Miocene layer, and the deeper, Floridan layer (EPA, 1995). Groundwater beneath the site tends to flow primarily south-southwesterly and toward Burnett Creek; it may also be influenced by tidal fluctuations (Taylor, 1992). Recent observations also suggest that groundwater flow may have been strongly influenced by the drained surface impoundment, as the water- filled impoundment previously served to recharge the groundwater (EPA, 1996).

    Groundwater Use

The Brunswick area relies on groundwater for its potable water supply. Drinking water supplied by groundwater sources are described below.

  • Seven deep aquifer municipal wells service approximately 28,000 to 30,000 residents. This is the only source of water for Brunswick's municipal water supply (BWD, 1997). The municipal wells include the Glynco Wells 1 and 2, Brunswick Villa, Goodyear Park, Perry Park, Howard, and Coffin Park wells. These wells are located more than one-mile south of the site.
  • More than fifty private wells in the immediate area of the site were identified by EPA in 1991.

    Groundwater Quality Data

    On Site

During its 1991 preliminary site assessment, EPA collected eight on-site groundwater samples adjacent to the surface impoundment and in the CCA process areas. No samples were taken near the creosote/PCP process area in the southwestern portion of the site. The samples were analyzed for volatile organic compounds (VOCs), PAHs, PCP, and metals. Figure 3 shows the locations of monitoring wells and Table 1 presents the contaminant concentrations recorded at those monitoring wells (EPA, 1991c).

Several wells contained concentrations of VOCs, including benzene (2.3 ppb) and ethylbenzene (0.9 to 51 ppb) below the EPA MCLs. With the exception of chromium (220 ppb), beryllium (6.6 ppb), and lead (89 ppb) detected in Well 4 situated near the western edge of the Lagoon, metal concentrations were below EPA's MCLs or action level for lead. Chromium in the groundwater corresponds to levels (300 to 700 ppm) present in contaminated subsurface soils (3 to 8 feet below ground surface) and possible recharge from the buried impoundments (EPA, 1991a; EPA, 1991b; EPA, 1996). The presence of petroleum products was also noted in wells near the surface impoundment (Wells 2 and 4).

Analytical methods were not adequately sensitive to detect PCP and PAHs above the MCLs because the minimum quantitation limit (MQL) for these compounds exceeded the MCLs. The MQLs used for PCP (20 ppb or 400 ppb) and benzo(a)pyrene (10 ppb or 200 ppb) exceeded their MCLs of 1 ppb and 0.2 ppb, respectively. The MQL is the lowest concentration that is accurately detected by the analytical method.

EPA has installed approximately 12 additional groundwater monitoring wells as part of the remedial investigation (RI) and analyzed the samples for site-related contaminants. The forthcoming RI data will allow ATSDR to more fully evaluate potential exposure via the groundwater pathway. EPA will consider additional groundwater investigations if the RI data do not fully delineate the extent of groundwater contamination with a high degree of confidence (EPA, 1997a).

    Off Site: Municipal Drinking Water Wells

Brunswick's public water supply, by regulation, must meet EPA safe drinking water standards. The Southeast Region Office of the GADNR Environmental Protection Division (EPD), located in Brunswick, routinely monitors and ensures compliance of the Brunswick public water supply system with these standards. Because compliance is not required for some wood preserving compounds, routine monitoring may not discover the presence of some site-related contaminants. Therefore, to determine whether contaminants had migrated to off-site municipal wells, EPA's Environmental Services Division (ESD) sampled the Brunswick municipal wells in May 1995 and 1996 and analyzed the samples for the complete target compound list and target analyte list which includes site-related compounds. No site-related compounds were found in the municipal water supply wells at levels above their MCLs (EPA, 1997b).

    Off Site: Private Potable Water Wells

In 1991 and 1992, EPA identified and sampled over 50 private wells adjacent to the site and downstream of Burnett Creek to determine whether off-site migration of site-related contaminants had occurred (see Figure 4) (EPA, 1991a, 1992). The majority of the wells are within a 1-mile radius of the site. Some private wells are as close as 200 yards of the process area, the drained surface impoundment, or the buried impoundments. The water samples were analyzed for wood preserving compounds, VOCs, and metals. The results are presented in Table 2. Of the more than 50 private wells sampled, only one well had detectable levels of wood-preserving compounds, containing the PAHs phenanthrene and pyrene at 10 ppb each (EPA, 1991). Follow-up samples collected from this well failed to confirm the presence of contamination. No VOCs (including benzene) or metals were detected in the samples.

PCP and benzo(a)pyrene were not detected above their respective minimum quantitation limit (MQL) in off-site private wells or on-site monitoring wells (Tables 1 and 2). However, because the MQLs exceeded the health standards (MCLs) for these contaminants, the risk from potential exposure to these contaminants cannot be thoroughly evaluated. In a worsecase exposure scenario where contaminant concentrations at the exposure point are equivalent to the MQL, exposures would be considered a public health concern. However, to determine if potential exposure to these contaminants in private wells is a public health concern, the extent of the PCP and benzo(a)pyrene contamination should be determined using appropriate MQLs for PCP and benzo(a)pyrene.

Since the ATSDR 1992 Health Consultation, two additional private wells near the site have been sampled. One well located on Oak Bluff Road about 1.25 miles south of the site was sampled for PAHs and PCP in 1993, and the other well located on Marie Trace about 1 mile east of the site was sampled for VOCs, PAHs, PCP, and metals in 1995. Neither well contained site-related contamination (Lewis, 1993; Adams, 1995). In addition, the CBEP, a governmental, community, and business partnership created to assess environmental conditions in Brunswick, conducted a Brunswick area wide groundwater and a private well sampling effort in December 1996 (EPA, 1996). Four private wells within close proximity to the BWP were sampled. Two of the four wells had been previously sampled in 1991 for wood preserving compounds, but because they lie particularly close to the site or Burnett Creek, they were resampled. The analytical results were not available for review (EPA, 1997b).

Private wells in the immediate vicinity of the site have not been regularly monitored since 1991. EPA has conducted additional characterization of groundwater contamination in its recent RI. Forthcoming groundwater monitoring data from this effort should provide a clearer picture of the extent of groundwater contamination beneath the site and potential, present, and future groundwater pathways.


Potential Biota Exposure Pathway

Consumption of fish from Burnett Creek was identified as a potential exposure pathway. Contaminated groundwater from the site appears to be migrating toward and releasing into Burnett Creek. Certain toxic compounds identified at BWP can accumulate in fish, including PAHs, dioxins, and metals. Because Burnett Creek is potentially contaminated with chemicals that are know to bioaccumulate in fish and no fish samples have been collected from the creek, it is unknown if this pathway is of public health concern. ATSDR cannot fully evaluate this exposure pathway without Burnett Creek fish monitoring data.


COMMUNITY HEALTH CONCERNS

No community health concerns have been brought to ATSDR's attention by the Glynn County Health Department (GCHD, 1997). In 1993, ATSDR received a request from a Brunswick citizen to investigate potential exposures to site-related contaminants, including exposure through contaminated groundwater/drinking water supplies. Review of the current data concerning this concern is included in this health consultation. ATSDR will continue to monitor community concern (e.g., communicate with the Glynn County Health Department) as a continuation of the health consultation process.



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