OGDEN DEFENSE DEPOT
OGDEN, WEBER COUNTY, UTAH
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
The contaminants discussed in subsequent sections of this public health assessment will be evaluated to determine whether exposure to them has public health significance. ATSDR selects and discusses contaminants based on several factors: sample design, field and laboratory data quality, and comparison of chemical concentrations to levels that could cause cancer or other health effects. In addition, community health concerns are considered.
Evaluating the sample design may involve reviewing the installations' approach to locating contamination. Spacial distribution of sampling locations, sampling frequency, concentration changes over time, medium-to-medium differences, and correlation between the selected list of analytic parameters and suspected environmental contaminants are factors considered by ATSDR when determining the contaminants to which humans could be exposed.
Review of sampling field quality control procedures may include interpreting data on background (or regional) concentrations of chemicals. Additionally, the adequacy and number of replicate, spiked, and blank samples may be checked to verify detection of contaminants. To assess laboratory quality control, procedures used to verify instrument reliability may be reviewed.
Contaminant concentrations detected on and off site are compared to values developed by environmental (e.g., EPA) and health agencies (e.g., ATSDR) to provide an estimate of concentrations present in each environmental medium that should be evaluated for possible health effects if exposure to a contaminant occurs. Those values, in many cases, have been derived from animal studies. Health effects are not only related to the exposure dose, but to the route of entry into the body and the amount of chemical absorbed by the body. For those reasons, comparison values used in ATSDR public health assessments are contaminant concentrations in specific media and for specific exposure routes. The potential for adverse health effects from contaminants of health concern will be discussed in the Public Health Implications Section of this document.
Listing a contaminant in the data tables that follow does not mean that it will cause adverse health effects after exposure. Rather, the list indicates which contaminants will be further evaluated. The maximum media concentration is compared to an appropriate health assessment comparison value. The potential carcinogenicity of contaminants is also evaluated. When selected as a contaminant of concern in one medium, that contaminant will be reported in all media in which it is found.
These terms will be used in the information to follow:
| LTHA | Lifetime Health Advisory. LTHAs represent contaminant concentrations that EPA deems protective of public health over a lifetime (70 years) at an exposure of two liters of water per day. LTHAs are not enforceable through EPA regulations. |
| MCL | Maximum Contaminant Level. MCLs represent contaminant concentrations that EPA deems protective of public health over a lifetime (70 years) at an exposure rate of two liters of water per day. While MCLs are regulatory concentrations, PMCLGs and MCLGs are not. |
| MCLG | Maximum Contaminant Level Goal |
| ppb | parts per billion |
| ppm | parts per million |
| PMCL | Proposed Maximum Contaminant Level |
A. On-Site Contamination
In the past, both liquid and solid wastes were disposed at DDOU in burning and burial pits. Contaminants have been detected in soil, surface water, sediment, groundwater, and indoor air samples.
Soil
Surface Soils (<3" in depth)
Surface soil analyses were not listed for any of the OUs in the available documents. Because, wastes were principally buried, or burned in pits, then covered, surface soil contamination is unlikely. Soil gas surveys were conducted at most of the OUs. Soil gas results identify the location of volatile contaminant zones and can be used to simplify surface and subsurface sampling plans. Volatile contaminants can leach into groundwater or migrate through the soil to collect in confined spaces such as buildings. Based on the soil gas survey, and the location of several buildings, DDOU chose OUs 2 and 4 for confined space sampling. Those results will be discussed in the discussion on air contamination.
OUs - Soil Gas
OU 1 - Soil gas concentrations were low. Concentrations of 1,1 dichloroethene (1,1-DCE) were slightly above the detection limit in a soil gas survey of the area near Burial Site 1. The detection limit was 1 ppb (1).
OU 2 - Soil gas concentrations were low to moderate. Trichloroethene (TCE) concentrations were detected in the Parade Ground area; the highest concentration was 10 ppb. The highest 1,1-DCE concentrations detected were less than 1 ppb and were in the French Drain area. TCE concentrations in the Parade Ground area were between 0.6 to 10.2 ppb (1)(2).
OU 3 - No soil gas survey was conducted.
OU 4 - Soil gas concentrations were low. Elevated levels of 1,1-DCE (0.1 - 0.3 ppb) and TCE (0.2 - 1.6 ppb) were detected near Burial Site 4. The maximum concentrations of TCE were observed west and north of the burning pits and in areas 4-E and 4-B.
CSS Sites - surface sampling
PCB field-screening kits were used to detect soil contamination. The kit detection limit for PCBs was >50 ppm. Field screening detected PCBs in 21 samples. Those samples were further analyzed in the laboratory to quantify the PCB concentrations. PCB Study Area 1, where a power pole was reported to have a leaking transformer, showed surface soil levels of PCBs as high as 83 ppm within a three-foot radius. The second area, a vaulted transformer area, had wipe sample concentrations ranging from 8,800 - 58,000 ppm. Wipe samples are collected by wiping or scraping an area, then analyzing the wipe or scrape. The wipe samples were taken from concrete pads adjacent to the vaulted transformers inside the buildings. Oily deposits were visible in the sample areas, and the reported values reflect the PCB concentration in the oil collected on the wipe (1).
PCB transformer oil has contaminated soil in the storage area used during the decommissioning of the installation's PCB transformers. The PCB transformers were stored outdoors in the facility engineering section. PCB contamination as high as 23 ppm was measured in surface soil near the transformer storage area. During the initial site visit, ATSDR recommended sampling surface soil in the adjacent playground area because runoff from the transformer storage area drains to the playground area. Surface soil samples were collected from the playground and adjacent drainage areas in April 1992 (24 samples). PCBs were detected in five samples at concentrations ranging from 0.17-2.13 ppm. PCBs are not considered a contaminant of concern at those levels (6). The highest concentrations were detected in the drainage ditch adjacent to the fenceline. DDOU plans to excavate soil from areas on the playground where PCBs were detected above 0.5 ppm (6). Additionally, the IRP manager has asked the facility engineers' to move the transformers to an impervious concrete pad in a bermed area (6).
Soil and wipe samples were taken from concrete surfaces in storage buildings at the DDT/pesticide screening sites. A surface area was marked, wetted, then scraped onto a filter for analysis. Low concentrations of contaminants were detected. Wipe samples in Building 4A were the highest for p, p' dichlorodiphenyl dichloroethylene (DDE) and DDT (100 and 150 ppm, respectively) (1).
A lead contaminant screening study was conducted at the Pistol Range Target Area. Total lead analysis concentrations were low (<150 ppm).
Figure 2 shows the location of CSS sites.
Subsurface Soils (>3" depth)
Borehole and test pits were excavated in suspected burial areas at all of the OUs. The burial areas were identified by historical information or interpretation of past aerial photographs. The average test pit was eight feet deep, 15 feet long, and three feet wide. Most of the test pit soil analyses did not show elevated contaminant concentrations. The soil data could indicate that the contaminant source has dissipated, or they could indicate that the source was not found.
OUs- subsurface sampling
OU 1 - (Figure 6) Thirty-nine subsurface soil samples were collected at OU 1 during the four phases of the Remedial Investigation and Feasibility Study (RI/FS). Borehole sample analyses were low for VOCs (<1 ppm). No base neutral or acid extractable (BNAEs) compounds, pesticides, metals, or PCBs were detected in any of the samples at levels above ATSDR comparison values. One test pit (TP-1) and one borehole sample (SB-27) were collected from the Ogden Nature Center near Burial Site 1. The soil in the test pit appeared to be previously undisturbed possibly indicating that this area was not used as a burial site. The sample was analyzed for BNAEs, pesticides/PCBs, and metals; no soil contamination was detected to a sampling depth of 6.5 feet.
The Plain City Canal test pit, TP-2, had elevated levels of cadmium (9.8 ppm), lead (9,580 ppm), and zinc (11,000 ppm). Phase III (July-August 1990) and Phase IV (April 1991) sampling analyses included dioxins/furans and high-boiling-point hydrocarbons. Dioxins and furans were detected in several subsurface soil samples, and, according to the RI/FS, are most likely the result of combustion of wood and paper products, plastics, and plastic insulation on electrical wiring disposed at Burial Site 4-A (7).
OU 2 - (Figure 7) Borehole sample analyses were low (<1 ppm). The samples were analyzed for BNAEs, VOCs, pesticides/PCBs and metals. The test pit (TP-3) was excavated near the French Drain Area. A composite sample from 0-6" showed elevated levels of bromacil (3,700 ppm) and chlordane (450 ppm).
OU 3 - (Figure 7) Contaminants were detected in subsurface soil samples (2 to 6 feet deep) in the chemical agent materials area (Burial Site 3-A). Soil samples confirmed chloroacetophenone (2.5 ppm), adamsite (134 ppm), mustard gas (2,750 ppm), and thiodiglycol (1,200 ppm) at three locations (1). Thiodiglycol is a degradation product of mustard gas.
OU 4 - (Figure 7) Sixty-five subsurface soil samples have been collected from soil borings, monitoring well borings, and test pits at OU 4. Low levels of BNAEs, VOCs, pesticides, PCBs, and metals were detected in most of the test pits. Test pits TP-4 and TP-5 were excavated in the two burn pits that make up Burial Site 4-A. Elevated concentrations of mercury (2.0 ppm) and lead (308 ppm) were detected at sample depths of eight feet.
Surface Water
DDOU is traversed by two surface-water systems, Four-Mile Creek on the north and Mill Creek on the south; each flows generally east to west (8)(9). Figure 8 shows the flow and direction of site surface waters. The streams are primarily shallow irrigation canals, for which easements have been granted to cross the depot. Except for approximately 300 yards just west of Burial Site 4, and the final 100 yards on the depot, Four-Mile Creek is completely enclosed in a cast-iron pipe as it traverses the northern boundary. The industrial area's storm sewers discharge into the encased portion of Four-Mile Creek. Surface runoff from areas adjacent to Mill Creek flow into the creek. DDOU has conducted two surface stream studies; one in May 1985 during high-water conditions and the other in January 1990 during low-water conditions. Surface-water samples were analyzed for VOCs, BNAEs, pesticides/PCBs, metals, and physical characteristics.
OU 1 - Mill Creek branches flow east to west adjacent to OU 1 (Figure 9). Low (<0.3 ppb) concentrations of VOCs (primarily benzene and xylenes) were found in samples collected from points M1 and M2 during the 1990 sampling. M1 is upstream from DDOU. The metals detected (and their highest concentrations) included cadmium (4 ppb at M4 in 1985), chromium (160 ppb at M1 in 1985), lead (8 ppb at M2 in 1990), and mercury (0.3 ppb at M2 in 1990). All were below comparison values. There are few differences in concentrations between upstream and downstream samples. DDOU will conduct further stream analysis.
Sediment
Sediment samples were analyzed for VOCs, BNAEs, pesticides/PCBs, and metals. Metals were detected in the 1985 sediment samples at concentrations ranging from 0.6 to 1.4 ppm (cadmium), 6.9 to 14 ppm (chromium), 14 to 96 ppm (lead), 0.7 to 0.14 ppm (mercury), 7.1 to 18 ppm (nickel), 34 to 179 ppm zinc, 20 to 29 ppm (antimony) and 2.2 to 6.4 ppm (arsenic). Cadmium, chromium, antimony, and arsenic were above comparison values. Metals detected in the 1990 sediment samples include barium (37 to 57 ppm), chromium (5.6 to 9.0 ppm), lead (32 to 53 ppm), nickel (4.4 to 5.2 ppm), and zinc (57 to 120 ppm). As with surface waters, the sediment studies do not identify sources of contamination; there are few differences in concentration between upstream and downstream samples. DDOU will conduct further sediment analysis. ATSDR will review the information as it becomes available.
Groundwater
Shallow Aquifer (<50 feet)
Lenses of silty sand and clay and coarse-grained sand and gravel, underlain by dark brown silty clay, make up the shallow aquifer (1). The water-bearing zone is between 6 and 40 feet. Groundwater has been monitored by the Army since 1981; contaminants are at low concentrations. The most widespread VOCs detected were cis-1,2-DCE, TCE, and vinyl chloride. Groundwater flow is generally west at a rate between 6 and 50 feet per year.
Shallow Groundwater - VOCs
Cis-1,2-DCE shallow groundwater contamination is centered near OUs 1, 2, and 4. Although cis-1,2-DCE is the most widely dispersed contaminant in OU 1, it was not detected at concentrations exceeding EPA's Maximum Contaminant Level (MCL) promulgated under the National Safe Drinking Water Act. The highest concentration detected at OU 1 was 26 ppb (April 1991); the MCL for cis-1,2-DCE is 70 ppb. The highest concentration of cis-1,2-DCE at 84,000 ppb was detected at OU 4 (August 1990). Figures 10, 11, and 12 show the concentrations and locations of the cis-1,2-DCE groundwater plumes.
TCE contamination is centered around OUs 2 and 4. TCE concentrations were as high as 17 ppb (April 1991) in OU 4. Figure 13 shows the concentrations and locations of the TCE groundwater plumes.
Vinyl chloride contamination is centered near OUs 1 and 4. Vinyl chloride concentrations in OU 1 were as high as 7.8 ppb (April 1991). The MCL for vinyl chloride is 2 ppb. OU 4 had concentrations as high as 440 ppb during the April 1991 sampling. Figures 14 and 15 show the concentrations and locations of the vinyl chloride groundwater plumes.
Other VOCs detected in groundwater during 1991 sampling at OU 4 include ethylbenzene at levels as high as 150 ppb, toluene (34 ppb), trans-1,2-DCE (0.7 ppb), 1,2-dichlorobenzene (45 ppb), 1,4-dichlorobenzene (32 ppb), and benzene (30 ppb).
Fluctuating VOC concentrations in the shallow groundwater make it difficult to determine whether the contaminant concentrations are increasing or decreasing (7). DDOU has recently changed its monitoring well sampling technique and attributes some of the increase in contaminant concentrations to the new procedure. The new procedure should capture more VOCs; the previous technique might have purged VOCs from the sample before it could be collected. The most recent samples probably represent more accurate concentrations, but they are not significantly different in most cases.
Groundwater - Metals
Groundwater samples have been analyzed for VOCs, BNAEs, pesticides/PCBs, and metals. In addition, OU 3 wells have been monitored for the degradation products of mustard. Since the 1986 Environmental Science and Engineering (ESE) analyses, groundwater samples have been field-filtered, a procedure which removes particulate-sorbed metals. Thus, metal results are for dissolved metal only, resulting in low metal concentrations. ATSDR does not consider the filtered samples adequate for comparison to EPA drinking water standards (MCLs), which are based on unfiltered samples.
The 1986 samples were not field-filtered and showed concentrations of metals that were more than four times the drinking water standard (10). Regional soils are naturally high in metals (Table 2). DDOU attributes the elevated metals concentrations to suspended soil particulates rich in naturally occurring metals, rather than dissolved metals in groundwater resulting from a source of contamination (1). EPA and the state agree with DDOU that the source of metals contamination in groundwater cannot be attributed to DDOU (11)(12). However, if the leaching assumption is correct, then arsenic and chromium would likely have been present at levels above comparison values in OUs 1 and 4 as well, but this was not the case. Since the groundwater samples have been filtered after 1986, no trends could be determined. Based on this limited information, a source can not be determined.
DDOU has collected at least 156 soil samples and considers 60 of those samples to represent background concentrations based on their location outside contaminated areas affected by human activities (7). Table 2 is a summary of the background mean calculated from those 60 samples. The background mean concentrations fall within the concentrations detected regionally (7). Based on this soils data, it seems likely that the metals contamination detected in the unfiltered groundwater samples could be attributed, at least partially, to leaching from naturally high concentrations of metals in soil. Because groundwater may be used for potable purposes west of the DDOU boundary, and because the drinking water is probably not filtered before use, the metals could be ingested.
DDOU disregarded metals as contaminants of concern in the baseline risk assessment (1). Table 3 lists risk assessment contaminants of concern that DDOU has chosen for inclusion in future analyses and metals will not be included.
OU 1 - Cis-1,2-DCE is the most widespread VOC. The major source of VOC contamination is backfill in the Plain City Canal. Other potential, low-level sources of VOCs include unidentified areas in the Ogden Nature Center and Burial Sites 1, 3-B, and 3-C. VOCs and metals have been detected in groundwater samples taken from Ogden Nature Center and south. That property, which was previously owned by DDOU, and was the site of the Smoke and Incendiary Grenade Burning Ground. Contaminants have not been detected in monitoring wells placed at the Ogden Nature Center south of Mill Creek (Figure 10). Suspected disposal areas are east of those wells. Groundwater flow in this area is generally east to west.
OU 2 - TCE and cis-1,2-DCE are the most widespread contaminants. TCE (25 ppb), cis-1,2-DCE (200 ppb), tetrachloroethene (PCE) (7.8 ppb), methylene chloride (6.1 ppb), benzene hexachloride (delta BHC) (6.7 ppb) and chlordane (4.6 ppb) exceeded their respective MCLs. Historical data indicate that concentrations have not changed consistently over time. Arsenic (0.23 ppm) and chromium (0.25 ppm) also exceeded their respective MCLs.
OU 3 - Using the available data, there appears to be no groundwater contamination associated with the chemicals buried at OU 3 (1). No contaminants exceeding the MCL were detected in three downgradient monitoring wells.
OU 4 - Cis-1,2-DCE (360 ppb), trans-1,2-DCE (594 ppb), 1,2-dichloropropane (300 ppb), TCE (5.1 ppb), and vinyl chloride (330 ppb) were detected in concentrations above the MCLs during the October 1988 sampling. Benzene (26 ppb), cis-1,2-DCE (210 ppb), vinyl chloride (220 ppb) were all detected at levels above their respective MCLs in samples collected in December 1989 and January 1990. In the August 1990 sampling, the vinyl chloride detection limit was high at 10,000 ppb and was not exceeded and TCE was not detected above the 5,000 ppb laboratory detection limit. The MCLs for vinyl chloride and TCE are 2 ppb and 5 ppb respectively. The August 1990 detection limits were set too high to compare the concentrations with other standards. Cis-1,2-DCE was detected at levels as high as 84,000 ppb during the August 1990 sampling. The high detection limits may mask the presence of other halogenated hydrocarbons in the samples. The detection limits were high because cis-1,2-DCE was found in high concentrations (84,000 ppb) and sample dilution was required to permit analysis. The zone of vinyl chloride contamination probably originates beneath Burial Site 4-E and extends downgradient south and southwest in the direction of groundwater flow (7).
Table 2. DDOU Background Metals Concentrations in Soil
| METAL | BACKGROUND MEAN (ppm) | TYPICAL REGIONAL RANGE (ppm) |
| Arsenic | 5.1 | <0.1-97 |
| Barium | 47 | 0.7-50,000 |
| Cadmium | 0.22 | 0.01-0.7 |
| Chromium | 7.9 | 0.3-2,000 |
| Lead | 6.3 | <10-700 |
| Mercury | 0.02 | <0.01-4.6 |
| Nickel | 6.6 | 5.0-700 |
| Selenium | 1.8 | <0.1-4.3 |
| Silver | 0.45 | 0.01-5.0 |
| Zinc | 26 | 10-2,100 |
Table 3. DDOU Risk Assessment* Contaminants of Concern For All Media
| CONTAMINANT | OU 1 | OU 2 | OU 3 | OU 4 |
| Benzene | X | X | X | |
| Bromacil | X | |||
| Chlordane | X | X | ||
| Chloroform | X | |||
| Delta-BHC | X | |||
| 1,1-Dichloroethane | X | |||
| 1,1-Dichloroethene | X | |||
| cis-1,2-Dichloroethene | X | X | X | |
| trans-1,2-Dichloroethene | X | X | ||
| 1,4-Dichlorobenzene | X | |||
| Tetrachloroethene | X | |||
| Trichloroethene | X | X | X | |
| Vinyl Chloride | X | X |
BNAE compounds detected at levels above their comparison values during the August 1990 sampling included dibenzofuran (12 ppb), naphthalene (76 ppb), pentachlorophenol (40 ppb), 1,2,4 trichlorobenzene (26 ppb), and PCBs (Arochlor 1260, 130 ppb). Table 4 lists the groundwater contaminants that exceeded an MCL or other comparison values. Some listed contaminants are different from those DDOU chose for future analyses (Table 3). Because all of the contaminants exceeding comparison values will not be included in future analyses, the groundwater contamination plume movement may not be adequately tracked.
Deep Aquifer (110 to 125 feet)
Three monitoring wells were installed in the deep aquifer, one near OU 2 and two near OU 4. Low levels of barium (as high as 1.5 ppm) and arsenic (as high as 0.039 ppm) were detected in all of the wells. The January 1990 sample from OU 2 exceeded the MCL (1 ppm) for barium. Lead (at 0.002 ppm) was also present in the sample. During the August 1990 sampling of OU 4, arsenic was detected at 0.049 ppm. The MCL for arsenic is 0.05 ppm. Barium was detected at 0.69 ppm.
Air
Air contaminants may have been released during past burning. Waste solvents, oils, and other debris were burned at OU 4 from the 1940s to the mid-1960s. During that period, particulates from the burning were likely carried downwind. Air was not sampled during the burning.
DDOU investigated whether air contamination was resulting from VOCs (detected in soil and groundwater samples) volatilizing and collecting in nearby buildings. DDOU conducted indoor air monitoring in building were the groundwater below had high concentrations of contaminants. High concentrations of vinyl chloride in groundwater at OU 4 prompted DDOU to monitor indoor air in Building 326. No contaminants were detected (3). Likewise, DDOU conducted air sampling in one house in the depot housing area (immediately west of the Parade Ground and near OU 2). Some VOCs were detected at low levels: TCE (10.8 ppb), 1,1,1 trichloroethane (TCA) (9.40 ppb), and PCE (6.34 ppb) (13). DCE, however, was not detected in indoor air samples although it was detected in groundwater at concentrations as much as 25 times any other groundwater contaminant. The VOC levels detected in indoor air samples were below the Occupational Safety and Health Administration (OSHA) air exposure limits. The OSHA permissible exposure limits (PELs) for airborne contaminants are concentrations of chemicals that are protective of health in the workplace. PELs are usually listed as 8-hour time-weighted averages and apply to healthy adult employees working 40-hour weeks (14). The PELs for these contaminants are much higher than the values detected in the indoor air samples: TCE (PEL=50,000 ppb), 1,1,1 trichloroethane (350,000 ppb), and PCE (25,000 ppm).
Table 4. DDOU Shallow Groundwater Contaminants Exceeding the Comparison Value and their Highest Detected Concentration
| CONTAMINANT | CONCENTRATION (ppb) and SAMPLE DATE | COMPARISON VALUE | |||
| OU 1 | OU 2 | OU 4 | CONCENTRATION (ppb) | REF. | |
| VOCs | |||||
| Benzene | 28 (04/25/91) | 5 | MCL | ||
| Cis-1,2-DCE | 200 (12/13/89) | 84,000 (8/15/90) | 70 | MCL | |
| 1,2-Dichloropropane | 300 (10/88) | 5 | MCL | ||
| Methylene Chloride | 6.1 (12/04/89) | <5,000(08/15/90) | 5 | PMCL | |
| Tetrachloroethene (PCE) | 7.8 (12/14/89) | 5 | MCL | ||
| Trans-1,2-DCE | 594 (10/88) | 100 | MCL | ||
| Trichloroethene (TCE) | 25 (12/13/89) | 17 (04/23/91) | 5 | MCL | |
| Vinyl Chloride | 7.8 (04/10/91) | 360 (04/19/91) | 2 | MCL | |
| BNAEs | |||||
| Dibenzofuran | 12 (08/16/90) | NA | NA | ||
| Naphthalene | 76 (08/16/90) | 20 | LTHA | ||
| Pentachlorophenol | 40 (08/15/90) | 1 | PMCL | ||
| 1,2,4 Trichlorobenzene | 26 (08/16/90) | 9 | PMCL | ||
| PCB (Arochlor 1260) | 130 (08/16/90) | 0.5 | PMCL | ||
| METALS (ppm) | |||||
| Arsenic | 0.23 (01/10/90) | 0.05 ppm | MCL | ||
| Chromium | 0.25 (01/10/90) | 0.1 ppm | MCL | ||
| PESTICIDES | |||||
| Chlordane | 4.6 (01/10/90) | 2 | MCL | ||
| Delta benzene hexachloride (BHC) | 6.7 | NA | NA | ||
TCE, TCA, and PCE have been identified in urban, rural, and indoor air throughout the United States. These chemicals are present in many household items. All are solvents and used in adhesives, degreasers, textile processing, and pesticides to name a few uses. They may be emitted from such household items as carpets, carpet glue, wallpaper glue, and spray and solid insecticides. Their ambient air background values are generally in the low-ppb range in urban areas. Studies have shown that median values for TCE indoor air samples range from 0.2 to 4.8 ppb, with maximum values ranging from 0.2 to 12.2 ppb (15 - 17).
DCE was detected in groundwater at higher concentrations, and more frequently, than any other compound at DDOU. The groundwater concentrations of cis-1,2-DCE detected in OU 2 (the closest OU to the depot housing) were as much as 25 times higher than any the other VOC-groundwater contaminant. The DDOU investigation stated that DCE would be expected to be detected in air quality samples more frequently than TCE or PCE because it is in groundwater at higher concentrations than those compounds and is more volatile (13). DDOU speculated that the presence of TCE and PCE in indoor samples could be associated with dry-cleaned clothes and/or carpet cleaners. A contributing factor in this conclusion is the fact that the houses do not have basements or crawl spaces; therefore accumulation of volatile compounds is somewhat inhibited. DDOU concluded that there was no definitive evidence that contaminants found in the air inside the house are a result of contaminant migration from OU 2 groundwater (13). DDOU does not plan to conduct any additional indoor air monitoring.
Because the chemicals detected are found at similar concentrations in indoor air samples throughout the United States and they are common components in many household items, their origin may be associated with products found in the house. Based on the available analytical information, the concentrations of TCE, TCA, and PCE are not at levels of public health concern.
Food Chain
No fishing or hunting takes place at DDOU. Land is leased to local farmers for pasture or crops. None of the leases are in contaminated areas, and water is not used for irrigation.
Soil
Burial Sites 1 and 5 have been deeded to the City of Ogden and to Weber County, respectively. Burial Site 1 is on the Ogden Nature Center property. In 1985, a series of magnetic surveys (by electromagnetometer) were used to locate buried ferrous materials. Two burial areas have been identified: the first was near the backfilled trench, the second along the western margin of the site (Figure 3). Drum remnants are visible on the surface. The property was the site of the Smoke and Incendiary Grenade Burning Ground. No surface sampling data were provided. Although access is not restricted, the burial areas are seldom used.
An area of stressed vegetation on the southeastern corner of the Ogden Nature Center (referred to as the "dead zone") has not been characterized. DDOU officials have no documentation that the area was ever used as a landfill. An electromagnetometer survey of another part of the nature center (Burial Site 1) showed subsurface anomalies; indicating the presence of buried materials or some other ground disturbance. During an ATSDR site visit in March 1992, DDOU agreed to share those data with nature center employees in order to avoid future excavation in suspected contaminated areas.
Burial Site 5 is currently used by the Weber County fairgrounds. Soil sampling found no contamination at levels above comparison values.
Groundwater
The DDOU monitoring wells in the upper aquifer have successfully defined the groundwater contamination plume. During the RI/FS, DDOU surveyed well use on the western boundary. Seven private wells are used near the western boundary; DDOU believes they are used for irrigation and not human consumption. City water is available to residents in the area. DDOU will gather additional information on well use, including whether crops are irrigated, in late 1992.
The state has installed three shallow groundwater monitoring wells at the Ogden Nature Center; groundwater contamination has not been detected.
Other Potential Sources
In order to identify other facilities that could contribute to contamination near DDOU, ATSDR conducted a search of the Toxic Chemical Release Inventory (TRI) for the Weber County area. The TRI database was developed by EPA using chemical release information provided by certain industries. The database compiles annually quantities of toxic chemicals entering each environmental medium from manufacturing facilities that employ more than 10 people. DDOU is not a manufacturing facility and therefore not subject to this reporting requirement. Data have been compiled for the years 1987-1989. No local releases were listed for the contaminants detected above comparison values.
C. Quality Assurance And Quality Control
The findings of this public health assessment are based largely upon data developed by DDOU and reviewed by EPA and the state. When descriptions were provided, the QA/QC measures appeared consistent with measures normally taken during environmental sampling and analysis. The data are assumed to be accurate within the limits of the QA/QC procedures employed.
D. Physical and Other Hazards
The source of contamination from the operable units is reported to be buried. Operable units on the installation are not fenced, except for Burial Site 3-A, which contains chemical warfare identification and detection kits, empty 55-gallon drums, and compressed gas cylinders. Because access is restricted, 3-A is not a physical hazard at this time. Burial Site 4-D is reported to contain methyl bromide cylinders. Burial Site 1, which reportedly contains riot control agent (chloroacetophenone) and white smoke (hexachloroethane) containers, is partially on property now owned by the Ogden Nature Center. Empty drum remnants are visible on the surface in some areas. Because the Center has not fenced those areas, they are a physical hazard. The extent of the buried drum contamination or debris is not known. A physical hazard also exists for workers if ponds are constructed in past disposal areas at the Ogden Nature Center. Thus far, none of the ponds have been constructed in known or suspected disposal areas.
E. Environmental Contamination Summary
DDOU collected surface soil samples in the housing unit playground area in April 1992. PCBs were detected in five samples at concentrations ranging from 0.17-2.13 ppm. Those concentrations are not at levels of public health concern.
Subsurface soils on post are contaminated with VOCs, metals, and pesticides and could be sources of groundwater contamination.
Surface water and sediment studies showed insignificant differences in contaminant concentrations taken from sample points entering (upstream) and leaving (downstream) DDOU. Some of the contaminants detected in sediment samples were above comparison values. DDOU will conduct further surface water and sediment sampling. ATSDR will review the information as it becomes available.
Groundwater on post is contaminated with VOCs, BNAEs, pesticides, and metals. Groundwater off post (beyond the DDOU boundaries) is not contaminated at levels above MCLs, although the plume could migrate. Some of the contaminants exceeding comparison values in Table 4 are not listed scheduled for inclusion future analyses (Table 3). If the groundwater contamination plumes move off post toward private wells (used for crop irrigation or drinking water), those analytes should be considered because the groundwater contamination plume movement may not be adequately tracked. The groundwater contamination plume in the upper aquifer has been defined, and DDOU will remediate the shallow aquifer once the treatment-system design is complete.
Water samples analyzed for metals have been field-filtered. A 1986 unfiltered metals analysis showed concentrations more than four times the drinking water standard. EPA and the state agree with DDOU that the source of metals contamination in groundwater is not attributed to DDOU (11)(12). Soils in the region contain naturally occurring metals at high concentrations that may leach into the groundwater.
Contaminants have not been detected in monitoring wells on the Ogden Nature Center south of Mill Creek (Figure 10). Suspected disposal areas are east of those wells. The general groundwater flow in the area is east to west. The inability to detect contaminants may indicate that the suspected disposal areas are not sources of contamination.
Analyses of indoor air samples for VOCs revealed no contamination at levels above comparison values in buildings on DDOU. The buildings are in areas where subsurface soil contamination was detected, and the groundwater table was closest to the surface. None of the buildings have basements or crawl spaces where contaminants could collect. DDOU concluded from the indoor air monitoring that there was no definitive evidence that contaminants in air in homes are a result of contaminant migration from OU 2; this conclusion seems reasonable. Based on the available analytical information, the concentrations of TCE, TCA, and PCE are not at levels of public health concern
Waste solvents, oils, and other debris were burned at OU 4 from the 1940s to the mid-1960s. Air was not sampled during the period when burning took place.
Drum remnants are visible on the surface in areas of the Ogden Nature Center. Burial Site 1 and the dead zone are not used much by the nature center, but because the areas are not fenced, they could be a physical hazard. The extent of the buried drum contamination or debris is not known. Several areas at the nature center have been excavated to create ponds. None of the ponds were constructed in known or suspected disposal areas.
Analysis of the historical use of chemicals, their disposal, coupled with sampling results, establishes that contaminants exist and are moving through the environment. This section has documented that contaminants have been found in all of the sampled media. The next section will evaluate the mechanism for human exposure to those contaminants. Exposure points (e.g., potable water supplies) and routes (e.g., ingestion) and receptor populations will be examined in the Pathways Analyses Section.
Rainwater percolating through on-post soils and the past storage and disposal of wastes has contaminated the groundwater underlying the installation. Similarly, in the past, rainfall running off the study areas could have contaminated nearby surface water streams and sediments. Past contaminant releases associated with fugitive organic vapor emissions from waste handling, chemical agent disposal, and blowing soils and dusts are examples of possible on-post air contamination.
To determine whether people are exposed to contaminants migrating from a site, ATSDR evaluates the environmental and human components leading to human exposure. This pathways analysis consists of five elements: A source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure, and an exposed population.
A. Completed Exposure Pathways
No completed exposure pathway are evident in the areas with sufficient sampling information. In general, the first two components (a source of contamination and transport through an environmental medium) of a completed pathway are present at DDOU. Usually, one or more of the remaining components are missing. Because of the isolated location and the access restrictions surrounding the DDOU, little contact of humans with contamination through appropriate routes is present.
B. Potential Exposure Pathways
An exposure pathway is defined as potential if at least one of the components of a completed pathway is missing, or if information is not available for evaluating the pathway. The pathways discussed here, however, are listed as potential, primarily because of documented contamination, but they have no confirmed points of exposure, routes of exposure, or exposed populations. If exposures occurred, they primarily would be through incidental exposure to various contaminated media unless drinking water supplies become contaminated.
Three potential exposure pathways at DDOU were identified: 1) contact with or ingestion of surface soil contamination by humans; 2) migration of contaminated groundwater to drinking water wells downgradient from DDOU; and 3) past migration of contaminated dust and vapors in air to people.
SURFACE SOIL PATHWAYS
A trench near the center of Burial Site 1 was reported to be used for disposal of riot control agent and white smoke containers in 1945. Two burial areas have been identified: the first near the backfilled trench, the second along the western margin of the site. Field observations revealed 55-gallon drum remnants and smaller canisters on the ground and partially buried. An electromagnetometer survey conducted on Burial Site 1 and the study found subsurface anomalies. During the ATSDR site visits, a second possible disposal area was pointed out by nature center employees. Drum remnants, concrete blocks, and other debris were visible on the western margin of the nature center (called the dead zone by employees there). Although Burial Site 1 and the dead zone are not used much by the nature center, several other areas on the nature center have been excavated to create ponds. None of the ponds were constructed in known or suspected disposal areas. During an ATSDR site visit in March 1992, DDOU agreed to share those data with nature center employees so that areas of suspected contamination would not be excavated. Contaminants have not been detected in monitoring wells at the Ogden Nature Center south of Mill Creek (Figure 10). Suspected disposal areas are east of those wells. Groundwater in the area generally flows east to west. The inability to detect contaminants in those wells could indicate that the suspected disposal areas are not sources of contamination. Table 5 describes this pathway.
PRIVATE WELL PATHWAY
Contaminant releases to groundwater from buried waste have occurred and continue to occur as indicated by the sampling data. The contaminated groundwater plumes (exceeding the MCLs) are still within the installation boundaries. Monitoring wells have been installed on the western boundary and are sampled quarterly to track the plume migration. Since 1947, DDOU's drinking water has been supplied by two water districts, the City of Ogden and the Bona Vista Water District. Both of the districts draw water from the deeper groundwater aquifer and are outside the shallow groundwater contamination plume from DDOU. The monitoring well sampling data have satisfactorily defined the plume for the shallow aquifer. Concentrations of contaminants near the DDOU boundary are below the MCLs, although large groundwater contamination plumes of cis-1,2-DCE and TCE on post exceed the MCL. The state engineers' office has identified 11 families drinking water drawn from the shallow aquifer less than one mile downgradient from the plume area. DDOU has conducted a well usage survey and identified seven private wells are used near the western boundary. DDOU believes they are used for irrigation, not human consumption. City water is available to residents in the area. Only one well has been designated for domestic use (1). DDOU will gather additional information on the specific water usage and whether crops are irrigated when they sample the wells in late 1992. There has been a five-year drought in the area; groundwater may be drawn to areas that it generally would not influence. The Bona Vista Water District has one public well within a fourth of a mile of DDOU. The well is upgradient and in a deeper aquifer.
Since the 1986 ESE analyses, groundwater samples have been field- filtered. Metals analyses during the 1986 sampling showed concentrations more than four times the drinking water standard. Low metals concentrations have been detected in monitoring wells since that time. Soils in the region contain naturally occurring metals at high concentrations that may leach into the groundwater. Because groundwater may be used for potable purposes west of the DDOU boundary, and drinking water is probably not filtered before use, those metals could be ingested. Table 6 describes this potential pathway.
AIR PATHWAY
Air releases likely occurred from the 1940s until the mid 1960s during open burning of waste solvents, oils and various other debris. Large volumes of solvents and oils were not reported to have been burned. Although burning was likely infrequent, the particulate and vapors associated with that burning are a past potential pathway. Wind rose information from 1967 to 1976 indicates that winds are predominantly from the east southeast. Approximately 30% of the time, winds exceeded 12 knots (2). The closest housing area is approximately 1,500 feet west of the burning areas. If contaminants travelled to that area, the residential population potentially exposed during the burning periods was estimated at 158 (2). Ogden's population has not changed significantly since the 1960s. DDOU employed 8,000 workers during that period. No air sampling data are available from that period, however, based on the available information, it is likely this pathway would have represented only incidental, short-term exposure. Table 7 describes the air pathway.
Table 5. Pathway Analysis of Soil and Drum Remnant Contamination Associated With Burial Site 1 on The Ogden Nature Center
| SOURCE | MEDIA & TRANSPORT | POINT OF EXPOSURE | ROUTE OF EXPOSURE | POTENTIALLY EXPOSED POPULATION(S) | FACTORS THAT INFLUENCE EXPOSURE |
| Unknown
(Burial Site 1
was used for
riot control
agent and
white smoke
disposal. A
few 55-
gallon drum
remnants and
canisters are
on the ground
surface)
No data is available for some areas. |
ST-Surface Soil <3"
SS- Subsurface Soil SH- Drums on the surface at the Ogden Nature Center |
Soil at the Ogden Nature Center and drum parts | D-Dermal
O-Oral Children may touch the drums and accidentally ingest soil |
soil GP-Children playing and other visitors to the Ogden Nature Center. The center had 17,000
visitors; 10,000 were children.
WK-Workers during the construction of new ponds in known or suspected disposal areas |
An electromagnetometer survey conducted in Burial Site 1 showed subsurface anomalies, possibly indicating buried materials. During an ATSDR site visit in March 1992, DDOU agreed to share those data with nature center employees so that areas of suspected contamination would not be excavated. A test pit was excavated near Burial Site 1. Soil samples taken from the pit showed no contamination. This soil data may indicate that the contaminant source has dissipated or was not located. No surface soil sampling has been conducted in the suspect disposal areas and is not planned. Drum remnants are visible, but the areas (Burial Site 1 and the dead zone) are not used much by the Nature Center. |
Table 6. Pathway Analysis of Groundwater Contamination Associated with OUs 1-4
| SOURCE | MEDIA & TRANSPORT | POINT OF EXPOSURE | ROUTE OF EXPOSURE | POTENTIALLY EXPOSED POPULATION(S) | FACTORS THAT INFLUENCE EXPOSURE |
| OUs 1-4
(groundwater monitoring wells reveal contamination of the surficial aquifer. Contaminant concentrations beyond the DDOU boundaries are below the MCLs. |
Groundwater | Groundwater used for drinking water or crop irrigation near the western boundary of the installation | O-Oral
D-Dermal |
Citizens may be drinking from private wells downgradient from the contamination plume (state engineers' water rights records show at least 11 families within one mile west of the boundary, DDOU will confirm water use) | No drinking water monitoring program is in effect. DDOU has conducted a well survey and identified seven private wells near the western boundary. According to the IRP manager, DDOU will sample those wells and determine their use if requested by the residents. The groundwater contamination plume in the upper aquifer has been defined. No contamination (attributable to DDOU) has been detected in three deep monitoring wells on post. Groundwater flow may be influenced by the area's five-year drought. |
Table 7. Pathway Analysis of Potential Air Contamination Associated with Burial Site 4
| SOURCE | MEDIA & TRANSPORT | POINT OF EXPOSURE | ROUTE OF EXPOSURE | POTENTIALLY EXPOSED POPULATION(S) | FACTORS THAT INFLUENCE EXPOSURE |
| Burial Site 4
(Oil burn pits and burn pits) (No data available for the period of burning) |
MA-Air aerosolization and deposition from the open burning. | Air
outdoors On and off site |
I-Inhalation of fumes and particulates | Workers conducting the burning; 8,000 workers were at DDOU during 1940s-1960s. Residents downwind to the W-NW; closest housing population estimated at 158 | From the 1967-1976 windrose data, the winds were blowing from the E-SE > 12 knots 30% of the time. Based on the available information, it is likely this pathway would have represented only incidental, short-term exposure. |
A. Toxicologic Evaluation
Using the pathways analysis and available data, no completed exposure pathways have been identified at DDOU. A potential pathway is associated with Burial Site 1 on the grounds of the Ogden Nature Center. People who could be exposed to contaminants through incidental ingestion of and dermal contact with surface soil include children, other visitors to the nature center, and workers. Those incidental exposures would not be sufficient to cause adverse health effects. However, sampling was not conducted at all of the potential burial areas at that site. From a review of at the map of groundwater contamination plume at OU 1, contamination does not appear to be centered near Burial Site 1. No contamination has been detected in monitoring wells placed by the state south of Burial Site 1.
Contamination of groundwater in the shallow aquifer on post has been confirmed (primarily low levels of VOCs and metals). No adverse health effects would be expected from exposure to contaminants at the levels detected at the DDOU boundaries even if contamination migrated off post.
A past pathway was the open burning of waste in pits at Burial Site 4. Waste solvents, oils, and other debris were burned at the site from the 1940s to the mid-1960s. During that period, particulates from the burning could have potentially been carried downwind to a housing area some 1,500 feet west-northwest; approximately 158 residents live in that area. On-site workers were also potentially exposed. Air was not sampled during the burning period; therefore potential human exposures to contaminants in air cannot be evaluated, however, based on the available information, it is likely this pathway would have represented only incidental, short-term exposure.
B. Health Outcome Data Evaluation
Health data for the area surrounding DDOU were not reviewed because there were no completed exposure pathways identified, and no specific community health concerns were identified for which health outcome databases are available.
C. Community Health Concerns Evaluation
ATSDR has addressed each of the community concerns about health:
Are there potential health effects that might be caused from environmental problems at the Depot? Could Depot activities cause children living nearby to experience an increase in colds and allergies?
Currently, no exposures are occurring unless a well survey shows drinking water is contaminated off the post; this is not likely. Incidental exposures may be occurring at Burial Site 1 on the grounds of the Ogden Nature Center, however those incidental exposures would not be sufficient to cause adverse health effects. Waste solvents, oils, and other debris were burned at the site from the 1940s to the mid-1960s. Air was not sampled during the burning period, however, if exposures occurred, they would have been incidental, and short-term.
Allergy is a term originally used in 1906 to describe a "changed reaction" in an individual in response to an agent (allergen) on a subsequent exposure to the agent. Allergic reactions can include the range from asthma, eczema, hayfever, and urticaria. A genetic component to allergies has been demonstrated with early studies suggesting that with two allergic parents, there is a 50% chance of the children having allergies. A variety of non-genetic factors, such as quantity of exposure, nutritional status of the individual, viral illnesses, or chronic underlying infections, also play a role in the development of allergies. It has been suggested that 15% of the population may respond at some time to the stimulus of an allergen (18 - 19). Without any exposure, it is unlikely that the site contamination has caused any increase in the occurrence of these very common conditions.
There are no community-specific health outcome databases available to evaluate the concern about increased colds and allergies.
Is water from the Plain City Canal safe to use for watering lawns and gardens?
DDOU is drained by Mill and Four-Mile creeks, both of which traverse the installation east to west. The Plain City Canal was once connected to the two forks of Mill Creek, but was backfilled in 1972. Four-Mile Creek, the northern-most of the two creeks, flows north along the eastern border of DDOU before turning abruptly to the west where it flows across the depot. It is enclosed in a cast-iron pipe most of that distance. Mill Creek, approximately 1.5 miles to the south, also flows westward across DDOU, where it splits into two branches. A feeder runs into the south branch at the Nature Center property, where a small spring-fed pond is located. Both Mill and Four-Mile creeks are irrigation ditches fed by mountain runoff and springs (2) (Figure 8). Surface water and sediment studies showed insignificant differences in contaminant concentrations taken from sample points entering (upstream) and leaving (downstream) DDOU. Industrial areas are upstream of DDOU. Although limited, the current surface water data indicate that contamination does not exist at levels of concern and the water could be used for watering crops, lawns, or livestock. DDOU will conduct further surface water and sediment sampling. ATSDR will review the information as it becomes available.
Will drums be removed from the Ogden Nature Center, and what actions are planned for the "dead zone"?
Drum remnants are visible in several areas of the Ogden Nature Center. Burial Site 1 and the dead zone are not used much by the nature center, but because the areas are not fenced, they may be a physical hazard. The extent of the buried drum contamination or debris has not been established. The area of stressed vegetation on the southeastern corner of the Ogden Nature Center has not been characterized. DDOU officials have no documentation that the area was ever used as a landfill. An electromagnetometer survey done in another part of the nature center (Burial Site 1) showed subsurface anomalies; indicating the presence of buried materials or some other ground disturbance.
During the initial site visit, ATSDR recommended further investigation to determine the extent of physical and chemical contamination at the Ogden Nature Center. During the March 1992 site visit, ATSDR discovered that several areas at the nature center had been excavated to create ponds. None of the ponds were constructed in known or suspected disposal areas. ATSDR recommends that the location of subsurface anomalies be identified throughout the nature center, and that the information be shared with the center so that those areas are not excavated in the future. There are no plans at this time to remove debris from the Ogden Nature Center.
Is dirt removed from DDOU used for fill in surrounding neighborhoods contaminated?
According to DDOU officials, all contaminated soils removed from DDOU are taken to state or
federally permitted disposal sites. All shipments are documented. Since fill taken from DDOU
should be taken from uncontaminated areas, it is unlikely that dirt removed from DDOU for use
as fill would be contaminated with hazardous wastes.
