PUBLIC HEALTH ASSESSMENT
SACRAMENTO ARMY DEPOT
SACRAMENTO, CALIFORNIA
EVALUATION OF ENVIRONMENTAL CONTAMINATION AND EXPOSURE PATHWAYS
In this section, exposure pathways are evaluated to determine whether people accessing or living near SADA could have been (past scenario), are (current scenario), or will be (future scenario) exposed to site-related contaminants. In evaluating exposure pathways, ATSDR identifies whether exposure to contaminated media has occurred, is occurring, or will occur through ingestion, dermal (skin) contact, or inhalation of vapors. When exposure to contaminated media occurs, the exposure pathway is regarded as "complete." To determine whether completed pathways pose a potential health hazard, ATSDR compares contaminant concentrations to health-based comparison values (ATSDR, 1997a). Comparison values are calculated from scientific literature available on exposure and health effects. These values, which are derived for each of the different media, reflect the estimated contaminant concentration for a given chemical that is not likely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. If contaminant concentrations are above comparison values, ATSDR further analyzes exposure variables (for example, duration and frequency) and the toxicology of the contaminant. This exposure evaluation process is summarized in Figure 7.
ATSDR analyzed all 55 sites at SADA to determine if there are past, current, or future public health hazards associated with them. ATSDR identified the SP groundwater plume as the only site with a potentially completed pathway and of community concern. No other community concerns were identified by ATSDR. Information on the SP groundwater plume is summarized in Table 1, the text following, and Appendix A. An analysis of available information for the other 54 sites, which is summarized in Appendix A, indicates that these sites are not associated with public health hazards. No site-related contaminants were detected at 30 sites. For the remaining 24 sites, ATSDR based its conclusions on one or more of the following scenarios: (1) contaminant levels detected in the area are too low to pose a health hazard, (2) past and current exposures have been prevented by strict security measures, or (3) affected areas have been or will be remediated.
The South Post Burn Pits are believed to be the source of contamination for the SP groundwater plume. Between the late 1950s and 1966, plating shop wastes, paints, sludges, oil and grease, batteries, and construction debris (scrap metal, concrete, wood, and glass) were incinerated in the South Post Burn Pits (EPA, 1993). Wastes that did not burn leaked into soils. The organic constituents of these wastes migrated through the soil and contaminated the underlying groundwater (EPA, 1994). A variety of volatile organic compounds (VOCs), including some at levels above ATSDR's drinking water comparison values, have been detected in the groundwater plume (Kleinfelder, 1995, 1996a, 1996b). Appendix A includes a list of these contaminants.
The plume has migrated in a southern direction and extends at least 1,900 feet beyond SADA's property boundaries (Figure 2). Recent sampling results indicate that the plume extends as far south as Berry Avenue (CVRWQCB, 1997a; Kleinfelder, 1997b). Investigations are ongoing to further delineate the extent of the plume (CVRWQCB, 1997a). The affected groundwater is predominantly in the shallow A/B zone (79 to 148 feet below ground surface) of the aquifer, although some contaminants have also migrated to zone C (156 to 188 feet below ground surface)(Kleinfelder, 1996a).
No on-site production wells draw water from the SP groundwater plume (SADA, 1997b). Municipal wells have supplied drinking water to SADA throughout its history (SADA, 1997b). A number of off-site production wells are near SADA; nine are in the general vicinity of the SP groundwater plume. These wells are at Eastman Products (8191 Elder Creek), Inline Hockey Arena (formerly known as Black Magic Products) (8137 Elder Creek Road), Ellis Company (8201 Elder Creek Road), Smog Tech (formerly known as Drake's Auto Wrecking) (8398 Elder Creek), 8188 Berry Avenue, and four residences (7501, 8128, 8140, and 8144 Elder Creek) (Figure 8). In the 1980s, CVRWQCB collected samples from eight of these off-site wells; site-related VOCs were detected in some (Kleinfelder, 1997a). A discussion of these contaminants is provided in the "SP Groundwater Plume--Past Exposure" section of this report.
In 1989, efforts to remediate the SP groundwater plume were initiated with the installation of seven on-site extraction wells. The wells draw the underlying groundwater to the surface and contaminants are degraded using a technology that uses ultraviolet (UV) light and hydrogen peroxide (Kleinfelder, 1989). In 1995, efforts to remediate the SP plume were expanded and intensified with the installation of an additional on-site vertical extraction well, two horizontal wells, and one off-site well (Kleinfelder, 1995). Since the remedial activities were initiated in 1989, groundwater contaminant levels have steadily decreased (Kleinfelder, 1995).
Current Exposure
Ingestion, Inhalation of Vapors, and Dermal Contact
The community surrounding SADA currently receives its water from municipal wells, which are not affected by the SP groundwater plume (CVRWQCB, 1997a, 1997b, 1997c). ATSDR assumes, therefore, that none of the private wells are currently used for drinking water purposes. To determine whether the wells are being used for non-drinking water purposes, the California Department of Health Services (CDHS) investigated the current usage of the nine off-site wells (CDHS, 1997) . The results of the investigation indicated:
The Ellis Company well is the only well confirmed to be in use for non-drinking water purposes. Data to assess current contaminant concentrations are unavailable. Because contaminant concentrations in the SP plume have been decreasing steadily since 1989, ATSDR assumes that the current concentrations are no greater than those of the past. As discussed below in the "Past Exposure" section, past contaminant concentrations were too low to pose a public health hazard via inhalation or dermal contact (the two non-drinking exposure routes).
Ingestion, Inhalation of Vapors, and Dermal Contact
Definitive evidence indicating whether the off-site private wells have permanently been decommissioned is unavailable (DWR, 1997). Assuming they have not been permanently decommissioned, these wells could be used in the future. Also, new production wells could be installed (Kleinfelder, 1997a). Even if groundwater from this area is used in the future, exposures of future populations will not pose a health hazard because remedial activities (described previously) should prevent further migration of the plume and remediate the groundwater to conditions that are acceptable for drinking (that is, all contaminants will be reduced to concentrations below federal maximum contaminant levels [MCLs] or more stringent California standards) (Kleinfelder, 1995). To ensure that the cleanup levels are achieved and maintained, groundwater monitoring will be conducted as part of a base-wide monitoring plan and a 5-year review. The Army, EPA, and the state of California agree that these clean-up levels are achievable. If this assumption proves incorrect, the system performance standards or the remedy, or both, will be re-evaluated (Kleinfelder, 1995).
Past Exposure
Ingestion
Eastman Products, Ellis Company, and at least two of the previously mentioned residential wells were used for drinking water in the past (ATSDR, 1991; CA EPA, 1997; Kleinfelder, 1997c; SADA, 1997a). The other five wells may also have been used for drinking water, but this has not been confirmed. The off-site wells were sampled in the 1980s (ATSDR, 1991; Kleinfelder, 1997a) and, with the exception of the Smog Tech well, contaminants were detected in all of them. ATSDR compared the maximum contaminant concentration (detected during sampling events conducted in the 1980s) with ATSDR's cancer and noncancer comparison values (Cancer Risk Evaluation Guide for 1 X 10-6 excess cancer risk [CREG] and Environmental Media Evaluation Guide [EMEG], and federal MCLs) (ATSDR, 1997a). ATSDR chose to evaluate maximum detected concentrations to be conservative. Contaminants detected at levels below these comparison values were not analyzed further. For the contaminants detected at levels above ATSDR's comparison values, exposure doses were calculated (based on conservative estimates of ingestion rates [2.0 liters per day] and exposure frequencies [exposure over a 70-year period]) and evaluated as follows:
ATSDR's evaluation determined that there was no apparent public health hazard associated with ingestion of groundwater in the past. Justification for this conclusion follows.
In addition to ingesting groundwater from contaminated wells, workers and residents could have inhaled vapors or directly contacted water while engaging in industrial activities, bathing, and rinsing food. Rather than evaluating inhalation and dermal contact hazards separately, ATSDR evaluated the total hazard associated with exposure to groundwater via ingestion, inhalation, and dermal contact because these hazards may be additive. To be conservative, ATSDR doubled maximum contaminant concentrations to account for all three exposure scenarios and then evaluated noncancer risks and cancer risks using the same methodology described in the "Past Exposure--Ingestion" section of this report. ATSDR concluded that no apparent health hazard was associated with ingesting, inhaling, or contacting the contaminants detected in private wells. (All exposure doses were at levels less than ATSDR's MRLs and the cancer risk calculated was less than 1.0 x 10-4.)
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