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PUBLIC HEALTH ASSESSMENT

OGDEN DEFENSE DEPOT
OGDEN, WEBER COUNTY, UTAH


ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

The contaminants discussed in subsequent sections of this public health assessment will beevaluated to determine whether exposure to them has public health significance. ATSDR selectsand discusses contaminants based on several factors: sample design, field and laboratory dataquality, and comparison of chemical concentrations to levels that could cause cancer or otherhealth effects. In addition, community health concerns are considered.

Evaluating the sample design may involve reviewing the installations' approach to locatingcontamination. Spacial distribution of sampling locations, sampling frequency, concentrationchanges over time, medium-to-medium differences, and correlation between the selected list ofanalytic parameters and suspected environmental contaminants are factors considered by ATSDRwhen 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 assesslaboratory quality control, procedures used to verify instrument reliability may be reviewed.

Contaminant concentrations detected on and off site are compared to values developed byenvironmental (e.g., EPA) and health agencies (e.g., ATSDR) to provide an estimate ofconcentrations present in each environmental medium that should be evaluated for possiblehealth effects if exposure to a contaminant occurs. Those values, in many cases, have beenderived from animal studies. Health effects are not only related to the exposure dose, but to theroute 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 inspecific media and for specific exposure routes. The potential for adverse health effects fromcontaminants of health concern will be discussed in the Public Health Implications Section ofthis document.

Listing a contaminant in the data tables that follow does not mean that it will cause adversehealth effects after exposure. Rather, the list indicates which contaminants will be furtherevaluated. The maximum media concentration is compared to an appropriate health assessmentcomparison value. The potential carcinogenicity of contaminants is also evaluated. Whenselected as a contaminant of concern in one medium, that contaminant will be reported in allmedia in which it is found.

These terms will be used in the information to follow:
LTHA Lifetime Health Advisory. LTHAs represent contaminant concentrations that EPAdeems protective of public health over a lifetime (70 years) at an exposure of two liters of waterper day. LTHAs are not enforceable through EPA regulations.
MCL Maximum Contaminant Level. MCLs represent contaminant concentrations that EPAdeems protective of public health over a lifetime (70 years) at an exposure rate of two liters ofwater 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 airsamples.

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 isunlikely. Soil gas surveys were conducted at most of the OUs. Soil gas results identify thelocation of volatile contaminant zones and can be used to simplify surface and subsurfacesampling plans. Volatile contaminants can leach into groundwater or migrate through the soil tocollect in confined spaces such as buildings. Based on the soil gas survey, and the location ofseveral buildings, DDOU chose OUs 2 and 4 for confined space sampling. Those results will bediscussed in the discussion on air contamination.

OUs - Soil Gas

OU 1 - Soil gas concentrations were low. Concentrations of 1,1 dichloroethene (1,1-DCE) wereslightly above the detection limit in a soil gas survey of the area near Burial Site 1. The detectionlimit was 1 ppb (1).

OU 2 - Soil gas concentrations were low to moderate. Trichloroethene (TCE) concentrationswere 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. TCEconcentrations 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 wereobserved 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 forPCBs was >50 ppm. Field screening detected PCBs in 21 samples. Those samples were furtheranalyzed in the laboratory to quantify the PCB concentrations. PCB Study Area 1, where apower pole was reported to have a leaking transformer, showed surface soil levels of PCBs ashigh as 83 ppm within a three-foot radius. The second area, a vaulted transformer area, had wipesample concentrations ranging from 8,800 - 58,000 ppm. Wipe samples are collected by wipingor scraping an area, then analyzing the wipe or scrape. The wipe samples were taken fromconcrete pads adjacent to the vaulted transformers inside the buildings. Oily deposits werevisible in the sample areas, and the reported values reflect the PCB concentration in the oilcollected on the wipe (1).

PCB transformer oil has contaminated soil in the storage area used during the decommissioningof the installation's PCB transformers. The PCB transformers were stored outdoors in the facilityengineering section. PCB contamination as high as 23 ppm was measured in surface soil near thetransformer storage area. During the initial site visit, ATSDR recommended sampling surfacesoil in the adjacent playground area because runoff from the transformer storage area drains tothe playground area. Surface soil samples were collected from the playground and adjacentdrainage areas in April 1992 (24 samples). PCBs were detected in five samples at concentrationsranging 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 0.5ppm (6). Additionally, the IRP manager has asked the facility engineers' to move thetransformers to an impervious concrete pad in a bermed area (6).

Soil and wipe samples were taken from concrete surfaces in storage buildings at theDDT/pesticide screening sites. A surface area was marked, wetted, then scraped onto a filter foranalysis. Low concentrations of contaminants were detected. Wipe samples in Building 4Awere 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 leadanalysis 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 burialareas were identified by historical information or interpretation of past aerial photographs. Theaverage test pit was eight feet deep, 15 feet long, and three feet wide. Most of the test pit soilanalyses did not show elevated contaminant concentrations. The soil data could indicate that thecontaminant 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 fourphases of the Remedial Investigation and Feasibility Study (RI/FS). Borehole sample analyseswere 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 ATSDRcomparison values. One test pit (TP-1) and one borehole sample (SB-27) were collected fromthe Ogden Nature Center near Burial Site 1. The soil in the test pit appeared to be previouslyundisturbed possibly indicating that this area was not used as a burial site. The sample wasanalyzed for BNAEs, pesticides/PCBs, and metals; no soil contamination was detected to asampling 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) samplinganalyses included dioxins/furans and high-boiling-point hydrocarbons. Dioxins and furans weredetected in several subsurface soil samples, and, according to the RI/FS, are most likely the resultof combustion of wood and paper products, plastics, and plastic insulation on electrical wiringdisposed at Burial Site 4-A (7).

OU 2 - (Figure 7) Borehole sample analyses were low (<1 ppm). The samples were analyzed forBNAEs, VOCs, pesticides/PCBs and metals. The test pit (TP-3) was excavated near the FrenchDrain Area. A composite sample from 0-6" showed elevated levels of bromacil (3,700 ppm) andchlordane (450 ppm).

OU 3 - (Figure 7) Contaminants were detected in subsurface soil samples (2 to 6 feet deep) in thechemical 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 threelocations (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 thetwo burn pits that make up Burial Site 4-A. Elevated concentrations of mercury (2.0 ppm) andlead (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 Creekon the south; each flows generally east to west (8)(9). Figure 8 shows the flow and direction ofsite surface waters. The streams are primarily shallow irrigation canals, for which easementshave been granted to cross the depot. Except for approximately 300 yards just west of Burial Site4, and the final 100 yards on the depot, Four-Mile Creek is completely enclosed in a cast-ironpipe as it traverses the northern boundary. The industrial area's storm sewers discharge into theencased portion of Four-Mile Creek. Surface runoff from areas adjacent to Mill Creek flow intothe creek. DDOU has conducted two surface stream studies; one in May 1985 during high-waterconditions and the other in January 1990 during low-water conditions. Surface-water sampleswere 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 frompoints 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 ppbat M1 in 1985), lead (8 ppb at M2 in 1990), and mercury (0.3 ppb at M2 in 1990). All werebelow comparison values. There are few differences in concentrations between upstream anddownstream samples. DDOU will conduct further stream analysis.

Sediment

Sediment samples were analyzed for VOCs, BNAEs, pesticides/PCBs, and metals. Metals weredetected 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 1990sediment samples include barium (37 to 57 ppm), chromium (5.6 to 9.0 ppm), lead (32 to 53ppm), nickel (4.4 to 5.2 ppm), and zinc (57 to 120 ppm). As with surface waters, the sedimentstudies do not identify sources of contamination; there are few differences in concentrationbetween 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 siltyclay, 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 lowconcentrations. The most widespread VOCs detected were cis-1,2-DCE, TCE, and vinylchloride. 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. Althoughcis-1,2-DCE is the most widely dispersed contaminant in OU 1, it was not detected atconcentrations exceeding EPA's Maximum Contaminant Level (MCL) promulgated under theNational 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 at84,000 ppb was detected at OU 4 (August 1990). Figures 10, 11, and 12 show the concentrationsand 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 groundwaterplumes.

Vinyl chloride contamination is centered near OUs 1 and 4. Vinyl chloride concentrations inOU 1 were as high as 7.8 ppb (April 1991). The MCL for vinyl chloride is 2 ppb. OU 4 hadconcentrations as high as 440 ppb during the April 1991 sampling. Figures 14 and 15 show theconcentrations and locations of the vinyl chloride groundwater plumes.

Other VOCs detected in groundwater during 1991 sampling at OU 4 include ethylbenzene atlevels 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 determinewhether the contaminant concentrations are increasing or decreasing (7). DDOU has recentlychanged its monitoring well sampling technique and attributes some of the increase incontaminant concentrations to the new procedure. The new procedure should capture moreVOCs; the previous technique might have purged VOCs from the sample before it could becollected. The most recent samples probably represent more accurate concentrations, but theyare not significantly different in most cases.

Groundwater - Metals

Groundwater samples have been analyzed for VOCs, BNAEs, pesticides/PCBs, and metals. Inaddition, OU 3 wells have been monitored for the degradation products of mustard. Since the1986 Environmental Science and Engineering (ESE) analyses, groundwater samples have beenfield-filtered, a procedure which removes particulate-sorbed metals. Thus, metal results are fordissolved metal only, resulting in low metal concentrations. ATSDR does not consider thefiltered samples adequate for comparison to EPA drinking water standards (MCLs), which arebased on unfiltered samples.

The 1986 samples were not field-filtered and showed concentrations of metals that were morethan 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 particulatesrich in naturally occurring metals, rather than dissolved metals in groundwater resulting from asource of contamination (1). EPA and the state agree with DDOU that the source of metalscontamination in groundwater cannot be attributed to DDOU (11)(12). However, if the leachingassumption is correct, then arsenic and chromium would likely have been present at levels abovecomparison values in OUs 1 and 4 as well, but this was not the case. Since the groundwatersamples have been filtered after 1986, no trends could be determined. Based on this limitedinformation, a source can not be determined.

DDOU has collected at least 156 soil samples and considers 60 of those samples to representbackground concentrations based on their location outside contaminated areas affected by humanactivities (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 unfilteredgroundwater samples could be attributed, at least partially, to leaching from naturally highconcentrations of metals in soil. Because groundwater may be used for potable purposes west ofthe DDOU boundary, and because the drinking water is probably not filtered before use, themetals 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 futureanalyses and metals will not be included.

OU 1 - Cis-1,2-DCE is the most widespread VOC. The major source of VOC contamination isbackfill in the Plain City Canal. Other potential, low-level sources of VOCs include unidentifiedareas in the Ogden Nature Center and Burial Sites 1, 3-B, and 3-C. VOCs and metals have beendetected 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 GrenadeBurning Ground. Contaminants have not been detected in monitoring wells placed at the OgdenNature 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), benzenehexachloride (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 associatedwith the chemicals buried at OU 3 (1). No contaminants exceeding the MCL were detected inthree 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 duringthe 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 1989and January 1990. In the August 1990 sampling, the vinyl chloride detection limit was high at10,000 ppb and was not exceeded and TCE was not detected above the 5,000 ppb laboratorydetection limit. The MCLs for vinyl chloride and TCE are 2 ppb and 5 ppb respectively. TheAugust 1990 detection limits were set too high to compare the concentrations with otherstandards. Cis-1,2-DCE was detected at levels as high as 84,000 ppb during the August 1990sampling. The high detection limits may mask the presence of other halogenated hydrocarbonsin the samples. The detection limits were high because cis-1,2-DCE was found in highconcentrations (84,000 ppb) and sample dilution was required to permit analysis. The zone of vinyl chloridecontamination probably originates beneath Burial Site 4-E and extends downgradient south andsouthwest in the direction of groundwater flow (7).

Table 2.

DDOU Background Metals Concentrations in Soil
METALBACKGROUND MEAN (ppm)TYPICAL REGIONAL RANGE (ppm)
Arsenic5.1<0.1-97
Barium470.7-50,000
Cadmium0.220.01-0.7
Chromium7.90.3-2,000
Lead6.3<10-700
Mercury0.02<0.01-4.6
Nickel6.65.0-700
Selenium1.8<0.1-4.3
Silver0.450.01-5.0
Zinc2610-2,100
Adapted from Reference 7

Table 3.

DDOU Risk Assessment* Contaminants of Concern For All Media
CONTAMINANT OU 1OU 2OU 3OU 4
BenzeneXX
X
Bromacil
X

ChlordaneXX

Chloroform
X

Delta-BHC
X

1,1-DichloroethaneX


1,1-DichloroetheneX


cis-1,2-DichloroetheneXX
X
trans-1,2-DichloroetheneX

X
1,4-Dichlorobenzene


X
Tetrachloroethene
X

TrichloroetheneXX
X
Vinyl ChlorideX

X
Adapted from Reference 1
* These chemicals will be included in future analyses of all media sampled by DDOU.

BNAE compounds detected at levels above their comparison values during the August 1990sampling 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 thegroundwater contaminants that exceeded an MCL or other comparison values. Some listedcontaminants are different from those DDOU chose for future analyses (Table 3). Because all ofthe contaminants exceeding comparison values will not be included in future analyses, thegroundwater 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 inall 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 at0.69 ppm.

Air

Air contaminants may have been released during past burning. Waste solvents, oils, and otherdebris were burned at OU 4 from the 1940s to the mid-1960s. During that period, particulatesfrom 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 andgroundwater samples) volatilizing and collecting in nearby buildings. DDOU conducted indoorair 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 monitorindoor air in Building 326. No contaminants were detected (3). Likewise, DDOU conducted airsampling in one house in the depot housing area (immediately west of the Parade Ground andnear 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 airsamples although it was detected in groundwater at concentrations as much as 25 times any othergroundwater contaminant. The VOC levels detected in indoor air samples were below theOccupational Safety and Health Administration (OSHA) air exposure limits. The OSHApermissible exposure limits (PELs) for airborne contaminants are concentrations of chemicalsthat are protective of health in the workplace. PELs are usually listed as 8-hour time-weightedaverages 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 Valueand their Highest Detected Concentration
CONTAMINANTCONCENTRATION (ppb) and SAMPLE DATECOMPARISON VALUE
OU 1OU 2OU 4CONCENTRATION (ppb)REF.
VOCs
Benzene

28(04/25/91)5MCL
Cis-1,2-DCE
200(12/13/89) 84,000(8/15/90)70MCL
1,2-Dichloropropane

300 (10/88)5MCL
MethyleneChloride
6.1(12/04/89)<5,000(08/15/90)5PMCL
Tetrachloroethene(PCE)
7.8(12/14/89)
5MCL
Trans-1,2-DCE

594 (10/88)100MCL
Trichloroethene(TCE)
25 (12/13/89) 17(04/23/91)5MCL
Vinyl Chloride 7.8 (04/10/91)
360 (04/19/91)2MCL
BNAEs
Dibenzofuran

12(08/16/90)NANA
Naphthalene

76(08/16/90)20LTHA
Pentachlorophenol

40(08/15/90)1PMCL
1,2,4Trichlorobenzene

26(08/16/90)9PMCL
PCB (Arochlor1260)

130(08/16/90)0.5PMCL
METALS (ppm)
Arsenic
0.23(01/10/90)
0.05 ppmMCL
Chromium
0.25(01/10/90)
0.1 ppmMCL
PESTICIDES
Chlordane
4.6(01/10/90)
2MCL
Delta benzenehexachloride(BHC)
6.7
NANA
Adapted from references (1), (2), (3), (7)
MCL = Maximum Contaminant Levels represent contaminant concentrations that EPA deemsprotective of public health (considering the availability and economics of water treatmenttechnology) over a lifetime (70 years) at a consumption rate of two liters per day. PMCL =Proposed MCL
LTHA = Drinking Water Health Advisory for a lifetime (70 years). Published by EPA.
NA = None Available

TCE, TCA, and PCE have been identified in urban, rural, and indoor air throughout the UnitedStates. These chemicals are present in many household items. All are solvents and used inadhesives, degreasers, textile processing, and pesticides to name a few uses. They may beemitted from such household items as carpets, carpet glue, wallpaper glue, and spray and solidinsecticides. Their ambient air background values are generally in the low-ppb range in urbanareas. Studies have shown that median values for TCE indoor air samples range from 0.2 to 4.8ppb, 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 othercompound at DDOU. The groundwater concentrations of cis-1,2-DCE detected in OU 2 (theclosest 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 bedetected in air quality samples more frequently than TCE or PCE because it is in groundwater athigher concentrations than those compounds and is more volatile (13). DDOU speculated thatthe presence of TCE and PCE in indoor samples could be associated with dry-cleaned clothesand/or carpet cleaners. A contributing factor in this conclusion is the fact that the houses do nothave basements or crawl spaces; therefore accumulation of volatile compounds is somewhatinhibited. DDOU concluded that there was no definitive evidence that contaminants found in theair inside the house are a result of contaminant migration from OU 2 groundwater (13). DDOUdoes not plan to conduct any additional indoor air monitoring.

Because the chemicals detected are found at similar concentrations in indoor air samplesthroughout the United States and they are common components in many household items, theirorigin may be associated with products found in the house. Based on the available analyticalinformation, 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.

B. Off-Site Contamination

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 (byelectromagnetometer) were used to locate buried ferrous materials. Two burial areas have beenidentified: the first was near the backfilled trench, the second along the western margin of thesite (Figure 3). Drum remnants are visible on the surface. The property was the site of theSmoke 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 toas the "dead zone") has not been characterized. DDOU officials have no documentation that thearea was ever used as a landfill. An electromagnetometer survey of another part of the naturecenter (Burial Site 1) showed subsurface anomalies; indicating the presence of buried materialsor some other ground disturbance. During an ATSDR site visit in March 1992, DDOU agreed toshare those data with nature center employees in order to avoid future excavation in suspectedcontaminated areas.

Burial Site 5 is currently used by the Weber County fairgrounds. Soil sampling found nocontamination at levels above comparison values.

Groundwater

The DDOU monitoring wells in the upper aquifer have successfully defined the groundwatercontamination 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 forirrigation and not human consumption. City water is available to residents in the area. DDOUwill 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, ATSDRconducted 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 certainindustries. The database compiles annually quantities of toxic chemicals entering eachenvironmental medium from manufacturing facilities that employ more than 10 people. DDOUis 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 contaminantsdetected above comparison values.

C. Quality Assurance And Quality Control

The findings of this public health assessment are based largely upon data developed by DDOUand reviewed by EPA and the state. When descriptions were provided, the QA/QC measuresappeared 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 onthe installation are not fenced, except for Burial Site 3-A, which contains chemical warfareidentification and detection kits, empty 55-gallon drums, and compressed gas cylinders. Becauseaccess is restricted, 3-A is not a physical hazard at this time. Burial Site 4-D is reported tocontain methyl bromide cylinders. Burial Site 1, which reportedly contains riot control agent(chloroacetophenone) and white smoke (hexachloroethane) containers, is partially on propertynow owned by the Ogden Nature Center. Empty drum remnants are visible on the surface insome areas. Because the Center has not fenced those areas, they are a physical hazard. Theextent of the buried drum contamination or debris is not known. A physical hazard also existsfor 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. PCBswere detected in five samples at concentrations ranging from 0.17-2.13 ppm. Thoseconcentrations are not at levels of public health concern.

Subsurface soils on post are contaminated with VOCs, metals, and pesticides and could besources of groundwater contamination.

Surface water and sediment studies showed insignificant differences in contaminantconcentrations taken from sample points entering (upstream) and leaving (downstream) DDOU. Some of the contaminants detected in sediment samples were above comparison values. DDOUwill conduct further surface water and sediment sampling. ATSDR will review the informationas 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 inTable 4 are not listed scheduled for inclusion future analyses (Table 3). If the groundwatercontamination plumes move off post toward private wells (used for crop irrigation or drinkingwater), those analytes should be considered because the groundwater contamination plumemovement may not be adequately tracked. The groundwater contamination plume in the upperaquifer 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 analysisshowed concentrations more than four times the drinking water standard. EPA and the stateagree with DDOU that the source of metals contamination in groundwater is not attributed toDDOU (11)(12). Soils in the region contain naturally occurring metals at high concentrationsthat may leach into the groundwater.

Contaminants have not been detected in monitoring wells on the Ogden Nature Center south ofMill Creek (Figure 10). Suspected disposal areas are east of those wells. The generalgroundwater flow in the area is east to west. The inability to detect contaminants may indicatethat the suspected disposal areas are not sources of contamination.

Analyses of indoor air samples for VOCs revealed no contamination at levels above comparisonvalues in buildings on DDOU. The buildings are in areas where subsurface soil contaminationwas detected, and the groundwater table was closest to the surface. None of the buildings havebasements or crawl spaces where contaminants could collect. DDOU concluded from the indoorair monitoring that there was no definitive evidence that contaminants in air in homes are a resultof contaminant migration from OU 2; this conclusion seems reasonable. Based on the availableanalytical information, the concentrations of TCE, TCA, and PCE are not at levels of publichealth 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 andthe dead zone are not used much by the nature center, but because the areas are not fenced, theycould be a physical hazard. The extent of the buried drum contamination or debris is notknown. Several areas at the nature center have been excavated to create ponds. None of theponds 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 hasdocumented that contaminants have been found in all of the sampled media. The next sectionwill 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 inthe Pathways Analyses Section.

PATHWAYS ANALYSES

Rainwater percolating through on-post soils and the past storage and disposal of wastes hascontaminated the groundwater underlying the installation. Similarly, in the past, rainfall runningoff the study areas could have contaminated nearby surface water streams and sediments. Pastcontaminant releases associated with fugitive organic vapor emissions from waste handling,chemical agent disposal, and blowing soils and dusts are examples of possible on-post aircontamination.

To determine whether people are exposed to contaminants migrating from a site, ATSDRevaluates the environmental and human components leading to human exposure. This pathwaysanalysis consists of five elements: A source of contamination, transport through anenvironmental medium, a point of exposure, a route of human exposure, and an exposedpopulation.

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 anenvironmental medium) of a completed pathway are present at DDOU. Usually, one or more ofthe remaining components are missing. Because of the isolated location and the accessrestrictions surrounding the DDOU, little contact of humans with contamination throughappropriate routes is present.

B. Potential Exposure Pathways

An exposure pathway is defined as potential if at least one of the components of a completedpathway is missing, or if information is not available for evaluating the pathway. The pathwaysdiscussed 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. Ifexposures occurred, they primarily would be through incidental exposure to variouscontaminated media unless drinking water supplies become contaminated.

Three potential exposure pathways at DDOU were identified: 1) contact with or ingestion ofsurface soil contamination by humans; 2) migration of contaminated groundwater to drinkingwater wells downgradient from DDOU; and 3) past migration of contaminated dust and vapors inair to people.

SURFACE SOIL PATHWAYS

A trench near the center of Burial Site 1 was reported to be used for disposal of riot control agentand white smoke containers in 1945. Two burial areas have been identified: the first near thebackfilled trench, the second along the western margin of the site. Field observations revealed55-gallon drum remnants and smaller canisters on the ground and partially buried. Anelectromagnetometer survey conducted on Burial Site 1 and the study found subsurfaceanomalies. During the ATSDR site visits, a second possible disposal area was pointed out bynature center employees. Drum remnants, concrete blocks, and other debris were visible on thewestern margin of the nature center (called the dead zone by employees there). Although BurialSite 1 and the dead zone are not used much by the nature center, several other areas on the naturecenter have been excavated to create ponds. None of the ponds were constructed in known orsuspected disposal areas. During an ATSDR site visit in March 1992, DDOU agreed to sharethose data with nature center employees so that areas of suspected contamination would not beexcavated. Contaminants have not been detected in monitoring wells at the Ogden Nature Centersouth of Mill Creek (Figure 10). Suspected disposal areas are east of those wells. Groundwaterin the area generally flows east to west. The inability to detect contaminants in those wells couldindicate that the suspected disposal areas are not sources of contamination. Table 5 describesthis pathway.

PRIVATE WELL PATHWAY

Contaminant releases to groundwater from buried waste have occurred and continue to occur asindicated by the sampling data. The contaminated groundwater plumes (exceeding the MCLs)are still within the installation boundaries. Monitoring wells have been installed on the westernboundary and are sampled quarterly to track the plume migration. Since 1947, DDOU's drinkingwater has been supplied by two water districts, the City of Ogden and the Bona Vista WaterDistrict. Both of the districts draw water from the deeper groundwater aquifer and are outsidethe shallow groundwater contamination plume from DDOU. The monitoring well sampling datahave satisfactorily defined the plume for the shallow aquifer. Concentrations of contaminantsnear the DDOU boundary are below the MCLs, although large groundwater contaminationplumes of cis-1,2-DCE and TCE on post exceed the MCL. The state engineers' office hasidentified 11 families drinking water drawn from the shallow aquifer less than one miledowngradient from the plume area. DDOU has conducted a well usage survey and identifiedseven private wells are used near the western boundary. DDOU believes they are used forirrigation, not human consumption. City water is available to residents in the area. Only one wellhas been designated for domestic use (1). DDOU will gather additional information on thespecific 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 itgenerally 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 analysesduring the 1986 sampling showed concentrations more than four times the drinking waterstandard. 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 intothe groundwater. Because groundwater may be used for potable purposes west of the DDOUboundary, 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 wastesolvents, oils and various other debris. Large volumes of solvents and oils were not reported tohave been burned. Although burning was likely infrequent, the particulate and vapors associatedwith that burning are a past potential pathway. Wind rose information from 1967 to 1976indicates 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 theburning areas. If contaminants travelled to that area, the residential population potentiallyexposed during the burning periods was estimated at 158 (2). Ogden's population has notchanged significantly since the 1960s. DDOU employed 8,000 workers during that period. Noair sampling data are available from that period, however, based on the available information, itis likely this pathway would have represented only incidental, short-term exposure. Table 7describes the air pathway.

Table 1.

Pathway Analysis of Soil and Drum Remnant Contamination Associated With Burial Site 1 on The Ogden Nature Center
SOURCEMEDIA & TRANSPORTPOINT OF EXPOSUREROUTE OF EXPOSUREPOTENTIALLY EXPOSED POPULATION(S)FACTORS THAT INFLUENCE EXPOSURE
Unknown(Burial Site 1was used forriot controlagent andwhite smokedisposal. Afew 55-gallon drumremnants andcanisters areon the groundsurface)
No data isavailable forsome areas.
ST-Surface Soil <3"
SS- Subsurface Soil
SH- Drums onthe surface atthe OgdenNature Center
Soil at theOgdenNatureCenter anddrum partsD-Dermal
O-Oral
Children maytouch thedrums andaccidentallyingest soil
soil GP-Children playing and other visitors to the Ogden Nature Center. The center had 17,000visitors; 10,000 were children.
WK-Workers duringthe construction ofnew ponds in knownor suspected disposalareas
An electromagnetometer survey conducted inBurial Site 1 showed subsurface anomalies,possibly indicating buried materials. Duringan ATSDR site visit in March 1992, DDOUagreed to share those data with nature centeremployees so that areas of suspectedcontamination would not be excavated. A testpit was excavated near Burial Site 1. Soilsamples taken from the pit showed nocontamination. This soil data may indicatethat the contaminant source has dissipated orwas not located. No surface soil sampling hasbeen conducted in the suspect disposal areasand is not planned. Drum remnants arevisible, but the areas (Burial Site 1 and thedead zone) are not used much by the NatureCenter.


Table 6.

Pathway Analysis of Groundwater Contamination Associated with OUs 1-4
SOURCEMEDIA & TRANSPORTPOINT OF EXPOSUREROUTE OF EXPOSUREPOTENTIALLY EXPOSED POPULATION(S)FACTORS THAT INFLUENCE EXPOSURE
OUs 1-4
(groundwatermonitoring wellsrevealcontamination ofthe surficialaquifer. Contaminantconcentrationsbeyond theDDOUboundaries arebelow theMCLs.
Groundwater Groundwaterused fordrinking wateror cropirrigation nearthe westernboundary of the installationO-Oral
D-Dermal
Citizens may bedrinking from privatewells downgradientfrom the contaminationplume (state engineers'water rights recordsshow at least 11families within one milewest of the boundary,DDOU will confirmwater use)No drinking watermonitoring program is ineffect. DDOU has conducteda well survey and identifiedseven private wells near thewestern boundary. According to the IRPmanager, DDOU will samplethose wells and determinetheir use if requested by theresidents. The groundwatercontamination plume in theupper aquifer has beendefined. No contamination(attributable to DDOU) hasbeen detected in three deepmonitoring wells on post. Groundwater flow may beinfluenced by the area'sfive-year drought.


Table 7.

Pathway Analysis of Potential Air Contamination Associated with Burial Site 4
SOURCEMEDIA & TRANSPORTPOINT OF EXPOSUREROUTE OF EXPOSUREPOTENTIALLY EXPOSED POPULATION(S)FACTORS THAT INFLUENCE EXPOSURE
Burial Site 4
(Oil burn pits andburn pits)

(No data availablefor the period ofburning)

MA-Airaerosolization anddeposition fromthe open burning.Air
outdoors
On and off site
I-Inhalation offumes andparticulatesWorkers conducting theburning; 8,000 workerswere at DDOU during1940s-1960s. Residentsdownwind to the W-NW; closest housingpopulation estimated at158From the 1967-1976windrose data, thewinds were blowingfrom the E-SE > 12knots 30% of thetime. Based on theavailable information,it is likely thispathway would haverepresented onlyincidental, short-termexposure.


PUBLIC HEALTH IMPLICATIONS

A. Toxicologic Evaluation

Using the pathways analysis and available data, no completed exposure pathways have beenidentified at DDOU. A potential pathway is associated with Burial Site 1 on the grounds of theOgden Nature Center. People who could be exposed to contaminants through incidentalingestion of and dermal contact with surface soil include children, other visitors to the naturecenter, and workers. Those incidental exposures would not be sufficient to cause adverse healtheffects. 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 doesnot appear to be centered near Burial Site 1. No contamination has been detected in monitoringwells placed by the state south of Burial Site 1.

Contamination of groundwater in the shallow aquifer on post has been confirmed (primarily lowlevels of VOCs and metals). No adverse health effects would be expected from exposure tocontaminants at the levels detected at the DDOU boundaries even if contamination migrated offpost.

A past pathway was the open burning of waste in pits at Burial Site 4. Waste solvents, oils, andother 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 areasome 1,500 feet west-northwest; approximately 158 residents live in that area. On-site workerswere also potentially exposed. Air was not sampled during the burning period; thereforepotential human exposures to contaminants in air cannot be evaluated, however, based on theavailable information, it is likely this pathway would have represented only incidental, short-termexposure.

B. Health Outcome Data Evaluation

Health data for the area surrounding DDOU were not reviewed because there were no completedexposure pathways identified, and no specific community health concerns were identified forwhich 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 theDepot? Could Depot activities cause children living nearby to experience an increase incolds and allergies?

Currently, no exposures are occurring unless a well survey shows drinking water is contaminatedoff the post; this is not likely. Incidental exposures may be occurring at Burial Site 1 on thegrounds of the Ogden Nature Center, however those incidental exposures would not be sufficientto cause adverse health effects. Waste solvents, oils, and other debris were burned at the sitefrom the 1940s to the mid-1960s. Air was not sampled during the burning period, however, ifexposures 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 inresponse to an agent (allergen) on a subsequent exposure to the agent. Allergic reactions caninclude the range from asthma, eczema, hayfever, and urticaria. A genetic component toallergies has been demonstrated with early studies suggesting that with two allergic parents, thereis a 50% chance of the children having allergies. A variety of non-genetic factors, such asquantity of exposure, nutritional status of the individual, viral illnesses, or chronic underlyinginfections, also play a role in the development of allergies. It has been suggested that 15% of thepopulation may respond at some time to the stimulus of an allergen (18 - 19). Without anyexposure, it is unlikely that the site contamination has caused any increase in the occurrence ofthese very common conditions.

There are no community-specific health outcome databases available to evaluate the concernabout 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 towest. The Plain City Canal was once connected to the two forks of Mill Creek, but wasbackfilled in 1972. Four-Mile Creek, the northern-most of the two creeks, flows north along theeastern border of DDOU before turning abruptly to the west where it flows across the depot. It isenclosed in a cast-iron pipe most of that distance. Mill Creek, approximately 1.5 miles to thesouth, also flows westward across DDOU, where it splits into two branches. A feeder runs intothe south branch at the Nature Center property, where a small spring-fed pond is located. BothMill 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 contaminantconcentrations taken from sample points entering (upstream) and leaving (downstream) DDOU. Industrial areas are upstream of DDOU. Although limited, the current surface water data indicatethat 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 sedimentsampling. ATSDR will review the information as it becomes available.

Will drums be removed from the Ogden Nature Center, and what actions are planned forthe "dead zone"?

Drum remnants are visible in several areas of the Ogden Nature Center. Burial Site 1 and thedead zone are not used much by the nature center, but because the areas are not fenced, they maybe a physical hazard. The extent of the buried drum contamination or debris has not beenestablished. The area of stressed vegetation on the southeastern corner of the Ogden NatureCenter has not been characterized. DDOU officials have no documentation that the area wasever 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 orsome other ground disturbance.

During the initial site visit, ATSDR recommended further investigation to determine the extentof physical and chemical contamination at the Ogden Nature Center. During the March 1992 sitevisit, ATSDR discovered that several areas at the nature center had been excavated to createponds. None of the ponds were constructed in known or suspected disposal areas. ATSDRrecommends 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 thefuture. 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 orfederally permitted disposal sites. All shipments are documented. Since fill taken from DDOUshould be taken from uncontaminated areas, it is unlikely that dirt removed from DDOU for useas fill would be contaminated with hazardous wastes.


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