PUBLIC HEALTH ASSESSMENT ADDENDUM
LETTERKENNY ARMY DEPOT
USA LETTERKENNY SOUTHEAST AREA
CHAMBERSBURG, FRANKLIN COUNTY, PENNSYLVANIA
AND
USA LETTERKENNY - PROPERTY DISPOSAL OFFICE AREA
CHAMBERSBURG, FRANKLIN COUNTY, PENNSYLVANIA
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
The contaminants discussed in subsequent sections of this public health assessment will be evaluated to determine whether exposure has occurred, and if so, whether that exposure has public health significance. ATSDR selects and discusses contaminants using the following information:
The listing of a contaminant in the contaminants-of-concern tables does not mean that it will cause adverse health effects if exposure occurs at the specified concentrations. Rather, the listing of a contaminant indicates that it will be discussed further in this public health assessment. The potential for adverse health effects resulting from exposure to contaminants of concern is discussed in the Public Health Implications section of this document.
Comparison values for ATSDR public health assessments are contaminant concentrations in specific media that are used to select contaminants for further evaluation. ATSDR and other agencies developed the values to provide guidelines for estimating the media concentrations of a contaminant that are unlikely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. See Appendix 5 for descriptions of the comparison values used in this public health assessment.
An overview of ongoing studies followed by contamination of groundwater, soils, surface water and other environmental media is presented to show how the SE and PDO Areas may be affecting the installation as a whole and the surrounding communities. The contamination in the SE and PDO Areas are discussed in subsequent paragraphs, by media-specific information.
Tables 4 and 5 (Appendix 3) list the contaminants of concern for the SE and PDO Areas. No information is available on air contaminant concentrations. Contaminant values are from studies conducted by Environmental Science and Engineering and published in separate Remedial Investigations for SE and PDO Areas and from data compiled by the U.S. Army Environmental Hygiene Agency for a water quality and biologic evaluation of Rocky Spring Lake (2, 3, 42).
Contaminants with the highest concentrations are volatile organic compounds (VOCs; e.g., trichloroethene, a solvent and its associated degradation product - dichloroethene), which were used in operations at Letterkenny.
1. Contamination at the Southeastern Area (SE Area)
Groundwater: Approximately 47 monitoring wells have been installed in the SE Area and have been periodically sampled for VOCs since 1981. The remedial investigation is based on data from eight of the monitoring wells, sampled in February 1987, and data from all 47 monitoring wells sampled in April and May 1987 (2). VOCs were not detected in six wells; the remaining 41 wells contained detectable concentrations of at least one VOC. Seven contaminants were detected in SE Area groundwater at concentrations exceeding ATSDR's comparison values (Table 4).
Groundwater contaminants at the SE Area are similar to those of the PDO Area, but maximum concentrations detected in 1987 were up to three orders of magnitude greater, e.g., trichloroethene- 95,000 µg/L, trans-1,2-dichloroethene- 110,000 µg/L (2). Those high contaminant concentrations originate from the IWTP lagoon, which was the disposal holding area for all liquid industrial wastewater (119) from possibly 1954 until 1987. Review of the chemical data indicate a decrease in concentration of VOCs in the groundwater with time and as the distance from the source increases (106).
Surface Water: Ten surface water samples were collected in or adjacent to the SE Area. Those samples were taken from outfalls of the Industrial Wastewater (IWW) system or at springs or creeks downstream of the installation boundary. Consequently, results of the surface water sampling are discussed in the following sections on IWW or off-site surface water.
Industrial Wastewater System: The industrial wastewater system in SE consists of the sewers and lift stations leading to the IWTP. Sixteen locations at lift stations, manholes, and surface water outfalls were sampled in March 1987 and analyzed for VOCs. Concentrations of 1,1,1-trichloroethane, methylene chloride, and 1,1,2,2-tetrachloroethane exceeded comparison values (Table 4). The maximum contaminant concentration measured was for methylene chloride at 176,000 µg/L. That concentration is approximately 100 times greater than other contaminant concentrations detected in SE Area wastewater. It is probable that this detection reflects sample contamination.
Toluene, xylene, ethylbenzene, and methyl isobutyl ketone were present in samples at concentrations below comparison values. High concentrations of some contaminants created elevated detection limits for all contaminants. All three lift stations were sampled. Seven of nine manholes sampled contained detectable concentrations of at least one analyte. Surface water samples at outfalls contained detectable concentrations of chloroform, methylene chloride, 1,1,1-trichloroethane, and 1,1,2,2-tetrachloroethane. Chemicals leaking from the sewer system into groundwater have not been documented; however, parts of the sewer system consist of 30-year-old, unreinforced clay pipe, indicating that such leaking is possible (2). During 1993, confirmed breaks in the industrial waste lines and storm sewer lines will be repaired (28, 106, 118).
Soil: Fifty-four surface and subsurface locations were sampled for VOCs and priority pollutant metals in February 1987. Sample locations were chosen on the basis of a soil-gas field survey. Five soil contaminants from the IWTP lagoon, which has already been remediated, showed concentrations above comparison values: methylene chloride, trichloroethene, 1,1-dichloroethene, lead, and beryllium (Table 4). Copper, chromium, lead, zinc, nickel, thallium, arsenic, mercury and beryllium were detected below comparison values in soils adjacent to the IWTP lagoon. Soils adjacent to the various trenches and landfills in the K Area show contaminant concentrations well below the comparison values with the exception of lead. Lead was detected at a maximum concentration of 3,620 mg/kg (Table 4). However, the soils in this area are scheduled for remediation during 1993. The background concentration range for lead measured in soils in the Letterkenny area are between 20 and 700 mg/kg. Xylene and trans-1,2-dichloroethene were also detected in soil at concentrations of 7,000 mg/kg and 2,000 mg/kg, respectively, which are below ATSDR's comparison values.
Air: No information is available on ambient air contaminant concentrations in the SE Area. Although VOCs volatilize rapidly from surface waters to air, contaminant concentrations are not likely to create adverse health effects because of atmospheric dispersion in the open, unconfined setting of the SE surface waters. Analyses of stack gases from a test incinerator designed to remove VOCs from contaminated soils indicated almost 100% oxidation of VOCs from discharge gases (4); the possibility of low temperature stripping of VOCs from SE Area soils was being considered. Stack concentrations of dichloroethene, trichloroethene, tetrachloroethane, and xylene were detected at concentrations lower than 0.0003 ppm which do not appear to be of public health concern.
2. Contamination at Property Disposal Office Area (PDO Area)
Groundwater: Well water from four PDO Area wells was sampled in February 1986, and well water from three additional wells was sampled in April and May 1987. Groundwater contaminants with concentrations above comparison values are the following: trichloroethene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, trans-1,2-dichloroethene, chloroform, and 1,1-dichloroethene, (Table 5). Carbon tetrachloride and 1,1-dichloroethane were also detected, but concentrations were below comparison values. Contaminated groundwater in the PDO Area discharges at Rocky Spring, situated about one-quarter mile upstream of Rocky Spring Lake (119). In general, groundwater contaminant concentrations decrease with increasing distance from PDO source areas. Insufficient samples were collected to evaluate contaminant concentrations over time.
Surface water: Seven locations were sampled for VOCs in Rocky Spring, Rocky Spring Lake, and Rocky Spring Creek in August and November 1984. Additional sampling was conducted downstream of Rocky Spring Lake Dam in January and May 1985. Detectable concentrations of trichloroethene, 1,1,1-trichloroethane, trans-1,2-dichloroethene, chloroform, 1,1-dichloroethene, 1,1-dichloroethane, methylene chloride, and tetrachloride were detected in surface waters of the PDO (Table 5). Contaminant concentrations are moderately to substantially greater than comparison values for trichloroethene, 1,1-dichloroethene, and 1,1-dichloroethane. Trans-1,2-dichloroethene, 1,1,1-trichloroethane, tetrachloroethene, and chlorobenzene are substantially lower than comparison values. Chloroform, methylene chloride, and 1,2-dichloroethane are essentially equal to comparison values. Chloroform is the only contaminant that has a downstream increase in concentration from the lake to the creek. The source of chloroform probably originates from the Letterkenny sewage treatment plant, which discharges into Rocky Spring Creek downstream of Rocky Spring Lake. Although there is insufficient sampling to document contaminant concentrations over time, VOC concentrations generally decrease downstream for each sampling period.
Soil: Thirty-two sites were sampled for VOCs and priority pollutant metals (mercury, arsenic, chromium, copper, lead, zinc, nickel and thallium). Sample locations were established on the basis of detectable soil gas field surveys. The soil at those areas with detectable levels of soil gas were then sampled for VOCs. Lead was measured at the Drum Storage Revetments (Table 5) at a maximum concentration of 50.1 µg/g which is within the broad range of soil-lead background concentrations measured in uncontaminated local soils (20 -700 mg/kg). Subsurface volatilization has caused elevated trichloroethene soil gas concentrations at several locations. Trichloroethene, 1,1,1-Trichloroethane, and 1,1-Dichloroethene were all detected in PDO soils (Table 5). Because of the relatively high solubility of those chemicals and overall rate of water movement in the area, it is not likely that VOCs will accumulate in the soils adjacent to or below the contaminant sources.
Food Chain: Rocky Spring Lake has been stocked primarily with rainbow trout. However, the lake is also inhabited by brown trout, brook trout, large-mouth bass, crappie, catfish, and bluegills. In May 1984, the Army sampled rainbow trout from the PDO Area trout-holding pond. The trout-holding pond is fed by Rocky Spring and located upstream of Rocky Spring Lake. Average concentrations of trichloroethene and trichloroethane in fish tissue (fillet) were 120 and 50 ppb, respectively (22). Fish tissue were collected and analyzed for pesticides in December 1986 and March 1987. That sampling was conducted in response to earlier fish kills in the trout rearing facilities at Rocky Spring Lake resulting, at least in part, from the application of the pesticide, endrin, by a nearby fruit grower. Although there were several pesticides detected in the fish tissue, the concentrations were well within the FDA action levels (42). Specifically, the following pesticides were detected: chlordane (0.007 ppm), dieldrin (0.013 ppm), endrin (0.05 ppm), metabolized chlordane (0.17 ppm), P,P'DDD (0.9 ppm), and P,P'DDE (0.14 ppm) (42). Thus far, pesticides and VOCs have been detected at levels below the U.S. Food and Drug Administration threshold levels for fish consumption (41) and the EPA's Acceptable Risk-Based Concentrations (TCE, 290 ppb; TCA, 55 ppb; and endrin, 410 ppb) (44).
The highest mercury concentration detected in surface water was 4.0 ppb in the summer of 1991 (41). That value is above the EPA's Maximum Contaminant Level (MCL) of 2 ppb. The source of mercury is reported to be from past mercury-containing munitions stored on the ground near Building 1467, upslope from the lake. Follow-up sampling of Rocky Spring Lake in November of 1991 did not detect mercury in lake waters, storm water runoff, or soil. However, mercury was detected in fish and duck tissue samples at levels within the background range for mercury in fish tissue and well below the U. S. Food and Drug Administration (FDA) action levels for fish consumption (41). Follow-up sampling of fish tissue, algae, and lake water from Rocky Spring Lake from April through September of 1992 detected mercury in fish tissues at levels within regional background levels and federal standards (118, 119). Those results have not yet been released. Additional sampling of fish tissue, algae, and surface water will be conducted from April through September 1993 (118).
Air: There is no sampling available on specific air contaminant concentrations in PDO. Although VOCs volatilize rapidly from surface waters to air, contaminant concentrations likely to create adverse health effects are not expected because of atmospheric dispersion in the open, unconfined setting of the PDO surface waters.
Concentrations of VOCs greater ATSDR comparison values were detected in well water of 41 off-site wells near the SE Area (2). Sampling results for 30 off-site wells (or springs) previously used for potable water supply are listed in Table 6. Locations of those wells and the respective contaminant concentrations for the April/May, 1987 sampling period are illustrated in Figure 4. Eight different VOCs were present at concentrations greater than comparison values (Table 6). Additionally, trans-1,2-dichloroethene, 1,1,2-trichloroethane, and carbon tetrachloride were detected at concentrations lower than comparison values. The VOC contamination extends to Rowe Run Spring, about one and one-half miles beyond the Letterkenny boundaries to the east and northeast of the SE Area (Figure 4).
People were exposed to VOCs at levels which may result in adverse health effects, if chronic exposure occurred at the maximum concentrations. However, the actual duration of exposure is unknown, and exposures stopped when residences with well water detected with VOCs greater than MCLs were supplied with bottled water in 1982. By 1987, those residences were connected to municipal water. Periodic monitoring of off-site wells/springs has indicated decreases in contaminant concentrations since VOCs were first detected in 1982 (106).
Sampling of other off-post residential wells in July of 1991 detected carbon tetrachloride, aluminum, and lead at concentrations above ATSDR's comparison values. Carbon tetrachloride was detected in one well (0.81 µg/L) near the SE Area. That well was connected to municipal water in May 1992, thereby eliminating exposure (92). Currently, there is no indication that aluminum and lead detections in those off-site wells are a result of contamination originating from Letterkenny Army Depot. Additional well sampling and hydrogeological studies will be performed to help identify the source of lead (106, 119). Aluminum was detected in three wells at concentrations of 2310, 405, and 187 µg/L. The majority of those were detected near the PDO Area, with the exception of 2,310 µg/L; it was detected near the SE Area. Lead was detected in six wells at levels of 54.4, 43.3, 31.9, 24, 17.2, and 15.8 µg/L (41). The majority of those were detected near the SE Area, with the exception of 54.4 and 24 µg/L which were detected near the PDO Area. Six private wells remain in service with lead contamination levels above 15 µg/L, the EPA action level. Those persons were referred to a health professional at the Pennsylvania Department of Health. Those past exposures are evaluated in the Toxicological Evaluation section.
In order to identify other facilities that could contribute to the release of contaminants into the environment near the Letterkenny, ATSDR searched the Toxic Chemical Release Inventory (TRI) for reports of documented spills/releases. EPA developed TRI from the chemical release (to air, water, and soil) information provided by specific industries. The TRI database indicated that there were three releases in 1987 and 1989, and five in 1988, reported by facilities with the same zip code as Letterkenny. In 1987, xylene (mixed isomers), ammonia, and sodium hydroxide (solution) were released from local businesses. In 1988, xylene, sodium hydroxide (solution--released twice), phosphoric acid, and ethylene glycol were released from local businesses. In 1989, three similar releases were reported: phosphoric acid, ethylene glycol, and xylene (mixed isomers). No other chemical releases that could contribute to environmental contamination have been reported in the TRI database for off-site industries/businesses near Letterkenny Army Depot.
D. Quality Assurance and Quality Control
In preparing this public health assessment, ATSDR relies on information from available documents. The validity of the analysis and conclusions drawn for this document are determined by the availability and reliability of the referenced information. The new environmental data obtained for this document indicates that appropriate QA/QC was performed.
The base is fenced and access to Letterkenny is restricted; it is unlikely that unauthorized nonemployees would have access to Letterkenny Army Depot. Overall, observations from the site visit did not indicate any physical hazards on the installation other than those normally associated with an industrial operation.
However, the limestone terrain in portions of the installation
presents the potential for sinkhole formation and substrate
collapse. Sinkholes formed as a result of limestone dissolution
and collapse may occur when subsurface dissolution weakens the
bearing strength of the substrate. The acidic waste generated at
Letterkenny increases the rate of limestone dissolution and has
created at least one known sinkhole under the IWTP lagoon. The
SE Area is composed of karst geology. In general, groundwater in
this area is dominated by fracture flow and any increase in the
rate of limestone dissolution will increase the movement of
pollutants.
An environmental exposure pathway consists of the following components: (1) a source of contamination, such as SE Area soils; (2) an environmental medium in which the contaminants may be present or may migrate, for example, soil and groundwater; (3) points of human exposure, such as private well water; (4) routes of exposure such as inhalation, ingestion, or dermal absorption; and (5) a receptor population, for example, people who drink contaminated water from private wells. Pathways are considered complete when all pathway components are present, or potentially present. Potentially complete, or potential pathways exist when one or more of the pathway components is not present. Past, present, and future exposure pathways that may represent a public health hazard are discussed in this section. Specific components of the pathways at Letterkenny are presented in Tables 7 and 8, Appendix 3.
Storing and disposing hazardous materials and wastes on and below the ground in landfills and unlined lagoons have contaminated the soil, surface water, and groundwater at Letterkenny Army Depot. Those practices have been discontinued. Seventeen contaminants have been identified at concentrations greater than ATSDR comparison values (Tables 4-6, Appendix 3); Most of those contaminants are VOCs. VOCs can volatilize from surface waters in a matter of hours or days and have an atmospheric half-life of approximately seven days (25). At Letterkenny, VOCs have migrated from surface soil to subsurface soil and, consequently, the groundwater because of downward infiltration of surface spills, or direct subsurface release from buried waste and IWTP lagoons. Because VOCs volatilize rapidly from surface waters to air, contaminant concentrations are likely to decrease because of atmospheric dispersion in the open, unconfined setting of the SE and PDO Area surface waters. Consequently, groundwater is the primary environmental pathway of VOC contamination.
If contaminated fish, game, food crops, and farm animals are consumed, they represent other points of exposure. Although food chain exposure originates with the initial contaminant source and media, those exposures are discussed independently. The pathways section includes a brief review of the hydrogeologic setting at Letterkenny and how it affects contaminant migration and exposure. The hydrogeologic overview is followed by a discussion of the specific contaminant pathways at Letterkenny with reference to contaminant migration and completed or potential human exposure.
Five geological formations occur in the Letterkenny vicinity: shales of the Martinsburg Formation and limestones and dolomites of the St. Paul Group, the Chambersburg Formation, the Rockdale Run Formation, and the Pinesburg Station Formation. Those limestone and dolomite formations have relatively low primary porosity, however, they are all highly fractured and faulted such that secondary porosity and permeability is high and collectively the units comprise the main aquifer for potable water (water used for drinking and other household purposes) in the Cumberland Valley. Because most flow is constrained by the fracture system, storage capacity or specific yield is generally low and largely determined by the thickness of overlying unconsolidated colluvium of clay, sand, pebbles and cobbles (2, 3).
Groundwater flow in the vicinity of Letterkenny follows the contours of the land. The hydraulically significant strata have been divided into three zones: the unconsolidated colluvium, an underlying zone of fractured and weathered bedrock, and the basal zone of unweathered bedrock. Groundwater flow is unconfined and restricted to the upper two zones. Below a depth of 150 feet (from ground surface), the fractures are dry and have not been enlarged by dissolution (2).
Because surface waters at and near Letterkenny may either emerge at springs or submerge at sinkholes, depending on local geologic and topographic characteristics, there is no distinction between surface water and groundwater flow. Consequently, the following pathway discussions will address combined surface/groundwater flow systems. A drainage divide separates the SE and PDO Areas such that both surface water and groundwater in the SE Area flows east and northeast away from the PDO Area, and the waterflow in PDO Area moves to the southeast away from SE Area (Figure 8) (26).
Groundwater containing VOCs from the SE Area emerges at two off-site springs: Rowe Run Spring and Pinola Spring. A maximum concentration of 110 µg/L of TCE has been detected at Rowe Run Spring. A maximum concentration of 5 µg/L of TCE has been detected at Pinola Spring (119).
Both subsurface and surface water flow from the PDO Area enter the Rocky Spring Lake system on the southern boundary of Letterkenny where most VOCs volatilize from lake and creek waters (3). Subsequently, contaminated groundwater in the PDO Area discharges at Rocky Spring, located approximately one-quarter mile upstream of Rocky Spring Lake. Atypical concentrations of chloroform in Rocky Spring Creek at the Letterkenny boundary may be a by-product of chlorination at the sewage treatment plant (2).
C. Southeastern Area - Surface Water/Groundwater Pathway
Primary release of contaminants from SE Area sources (the IWTP lagoon, K Area, and the IWTP sewer system) as well as the PDO Area sources, is by precipitation, wastewater infiltration, or seepage into the soil and groundwater (Table 7). VOCs are the primary contaminants. The lagoon area has undergone remediation and the K Area soils are slated for similar (low temperature) treatment.
Surface drainage from the SE Area is either southward through a storm drain outfall into Conococheaque Creek or northeastward into Rowe Run. In 1987, samples of a surface water outfall from the IWTP (SW-9), which discharges into Rowe Run, contained methylene chloride in concentrations of up to 1,080 µg/L in 1987. While at SW-10, approximately 300 meters downstream, at the installation boundary, the concentration of methylene chloride was reduced to 192 µg/L, apparently as a result of dilution and/or volatilization (2). Other VOCs were detected in surface water at concentrations either at or below the detection level, with the exception of 1,1,1-trichloroethane, which was detected at 7.1 µg/L.
Water flowing from Rowe Run Spring had a total VOC concentration of 192 µg/L. Dye injected into wells at the IWTP lagoon were also recovered from Rowe Run Spring, confirming that the lagoon was once a main source of contamination (5). Quantitative assessment of dye concentrations from the Groundwater Treatment Plant extraction wells and the spring over time indicate that the potential for pumping and treating the groundwater is limited because of the flow in numerous, restricted zones of the limestone fractures. In the absence of effective remediation of sources in the SE Area, downgradient well water may become contaminated in the future.
Primary exposure points for the SE Area surface water/groundwater pathway were off-site private wells and springs. Contaminated groundwater has migrated to off-site private wells east of the SE Area. Past exposure occurred via ingestion, inhalation, and dermal contact. The main contamination source has been identified as the previous industrial lagoon used to store sludges from the treatment plant and untreated industrial wastes from 1954 until a sinkhole that formed in the underlying karst was discovered in 1967 (119). Thirty-three years elapsed from the time disposal activities began at the lagoon area in 1954, until 1982, when VOCs exceeding MCLs were detected in off-site private wells. It is very unlikely that exposure could have occurred for this length of time, and it would be difficult to reasonably predict the length of time that exposure could have occurred. Data for those past exposures are limited; therefore, the actual concentrations and duration of exposure are unknown.
Those private wells near the SE Area were replaced in incremental fashion, first with bottled drinking-water, and then with connection to the Guilford Water Authority System (the municipal water system). Conversion to a centralized water-supply system began in October 1982 and was completed in 1987. Therefore, between 1982 and 1987, exposure to contaminated groundwater was possible through household activities such as showering and bathing, if private wells were used for those activities.
In the summer of 1991, sampling of other off-post residential wells near the SE Area detected carbon tetrachloride, aluminum, and lead (41). At this time, aluminum and lead detections have not been associated with Letterkenny. The concentrations detected are above ATSDR's comparison values. Carbon tetrachloride was detected in one well, and it was connected to municipal water by May 1992 (92). Exposure to carbon tetrachloride via ingestion, inhalation, and dermal contact has been eliminated. Previous concentrations are based on one sampling event, and those exposures represent a past, present, and future groundwater pathway for the residents using those wells. It is unknown how long aluminum and lead were present in off-site wells, but ingestion, inhalation, and dermal contact were possible.
Exposure is also possible as a result of accidental, occupational, or recreational use of the springs and creeks below the drainage outfalls or in areas where contaminated groundwater discharges and increases surface-water flow. Routes of exposure for the SE Area surface water/groundwater pathway are dermal contact, ingestion, and inhalation of volatilized VOCs. Possible receptor populations are remedial and maintenance workers and off-site residents. Restricting site access to nonessential personnel and ensuring that appropriate personal protective equipment is used along with proper procedures during sampling, remediation, or maintenance would diminish the possibility of exposures to workers. For off-site residents, the SE Area surface water/groundwater pathway is complete if accidental exposure to off-site groundwater or surface waters associated with SE Area occurs (Table 7). However, the pathway would be complete on an intermittent basis, and human exposure to those low levels is not likely to result in adverse health effects because of the limited duration of exposure.
D. Property Disposal Office Area - Surface Water/Groundwater Pathway
In the PDO Area, Rocky Spring Creek and Lake occupy a topographic low to which both surface and subsurface water flow. That conclusion is supported by the configuration of the surface of the water table as described by a groundwater contour map developed for this area (Figure 8, Appendix 2) (3). Thus, surface water or groundwater contaminants that have a source within the PDO Area are confined to a pathway which leads to Rocky Spring and then to Rocky Spring Lake and Creek. The RI concluded that no groundwater bypasses Rocky Spring or Rocky Spring Creek system (3). Consequently, all groundwater contamination from the PDO Area eventually merges with the surface waters of Rocky Spring Creek, which results in rapid volatilization of VOCs. The potential exposure point for the PDO Area surface water/groundwater pathway (Table 8) is the Rocky Spring Creek/Lake system. Downstream of the Rocky Spring Lake dam, VOC contaminant concentrations are below concentrations of concern as a result of volatilization. Waterflow in the PDO Area moves to the southwest away from the SE Area (106).
The Rocky Spring Creek/Lake system is not used as a water supply. Swimming in the lake is prohibited and thus the possible routes of exposure would be accidental ingestion, dermal contact, and inhalation of volatilized VOCs. The potential receptor population of the PDO Area surface water/groundwater pathway is limited to installation personnel, their dependents, and guests who use the Rocky Spring Lake/Creek system for recreational activities and maintenance/remedial workers who work with monitoring wells. As long as maintenance/remedial workers use personal protective equipment and follow appropriate procedures during maintenance and remedial activities, they will not be exposed to contaminants. However, if accidental exposure to groundwater or surface waters of the Rocky Spring Creek/Lake system does occur, the PDO Area surface water/groundwater pathway would be complete on an intermittent basis. Human exposure to those low levels is not of public health concern because of the limited duration of exposure.
Mercury has been detected in surface waters of Rocky Spring Lake and in fish tissues taken from fish in the lake. Mercury levels detected thus far in fish tissue were within regional levels and federal standards (119). The source of mercury is believed to be from past mercury-bearing munitions stored on the ground near Building 1456, a storage building in the AD/AS Area (48, 106, 118, 119). Sampling of surface water, fish tissue, and algae, as an indicator of contaminant uptake, is scheduled for April through September 1993 (118, 119).
Sampling of off-post residential wells near the PDO Area during July 1991 detected aluminum and lead (41). The concentrations detected are above ATSDR's comparison values and have not been associated with Letterkenny. Persons whose wells were tested were informed of the sampling results and referred by Letterkenny to a health professional at the Pennsylvania Department of Health. Previous concentrations are based on one sampling event, and those exposures represent a past, present, and future groundwater pathway for the residents using those wells. It is unknown how long those chemicals were present in off-site wells.
No contamination above detection limits has been measured in wells directly downstream of Rocky Spring Lake (Wells 84-1, 84-2 and 84-3) (3). However, sampling in October 1991 indicated the presence of low levels of total VOCs in a well outside of Gate 1 on Rocky Spring Road. The well is near the PDO Area boundary near Rocky Spring. During 1993, further assessment may determine if there is an association between the total VOCs detected in the well and Letterkenny's groundwater system. Also, a new OU was established for the PDO Area to address off-site PDO groundwater quality. Resampling of previous wells and a hydrogeological study are being planned for 1993.
E. SE, PDO, AD/AS Areas - Soils
Soil contamination has occurred at several locations as a result of land treatment, storage, and disposal activities at Letterkenny. Contaminants that characterize surface-soil contamination are primarily VOCs (Tables 4 and 5).
Lead (greater than 5 mg/kg) has been detected in soils of the K Area. Extensive sampling of K Area soils took place in September of 1992 to determine the extent of metals contamination to determine the feasibility of conducting thermal treatment and stabilization and/or solidification on the K Area soils. That study detected high levels of lead, cadmium, and chromium in the K Area soils (119). Treatment of those soils is planned in 1993.
In the PDO Area, VOCs and lead were detected at concentrations above comparison values at the Drums Storage Revetments and the Former Oil Burning Pit (Table 5), but further studies since then indicate that no action is warranted at those areas.
A Site Investigation at the AD/AS Area detected some chemicals above environmental comparison values, and additional soil sampling of some SWMUs are scheduled for 1993. Site access to the sites under investigation would be limited to contractors and Letterkenny personnel conducting further studies in those areas.
Because contaminated soil at the SE, PDO, and AD/AS Areas are either undergoing remediation or characterization, only remedial and maintenance workers would be exposed to contaminants. Potential exposure routes would be limited to dermal contact and accidental ingestion or inhalation of wind-blown dust. If personal protection equipment and appropriate procedures are followed during sampling, remediation, and maintenance, exposure to contaminated soil will be minimized. Since site access to Letterkenny Army Depot is restricted by fences and guarded gates, exposure to contaminated soils and surface waters at Letterkenny is unlikely for off-site persons.
F. SE, PDO, and AD/AS Areas - Food Chain
East of the SE Area boundary, farm animals drink from springs and creeks that are contaminated with VOCs. However, it is not known whether contamination is present in those animals or their by-products. Future studies are planned in the spring and summer of 1993 to evaluate possible uptake of contaminants from off-site springs (30). When results are available in the summer or fall of 1993, ATSDR will evaluate those potential food chain pathways.
Food crops east of the SE Area boundary may also be irrigated with off-site wells and springs. Those wells were replaced for drinking purposes, but may still be used for irrigation of gardens, crops, and other household uses (1). Consumption of those food crops represent another potential route of exposure (Table 7).
Mercury has been detected in surface waters of Rocky Spring Lake and in fish tissues taken from fish in the lake. Mercury levels detected thus far in fish tissue were within regional levels and federal standards (119). Fish consumed from Rocky Spring Lake represent a point of exposure to contaminants in the PDO Area surface water/groundwater pathway (Table 8). Receptor populations who may consume those fish include installation personnel, their dependents, and guests who have recreational access to the area. The source of mercury is believed to be from past mercury-bearing munitions stored on the ground near Building 1456, a storage building in the AD/AS Area (48, 106, 118, 119). Sampling of surface water, fish tissue, and algae, as an indicator of contaminant uptake, is scheduled for April through September 1993 (118, 119).
A population of deer resides in the AD/AS Area where they are hunted. Although environmental contamination of that area has been initiated, additional characterization is scheduled for 1993. Contaminant concentrations in deer flesh (venison), if present, are unknown. Thus, consumption of venison by installation personnel, their dependents and guests, and the public represents a potential pathway of human exposure to contaminants in the soil until environmental sampling is completed for this area.
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