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PUBLIC HEALTH ASSESSMENT

ROCKY MOUNTAIN ARSENAL
ADAMS COUNTY, COLORADO




Table 9.

Contaminants of Potential Concern: Surface Soil - RMAED run of 10/15/93
Analyte Groups/Analyte
** Inclusion of analytes in this scoping table does NOTmean exposure to listed analytes will necessarily causeadverse health effects.**
On-/Off-
Post
Maximum
Detect (ppm)
Average
Detect (ppm)
FrequencyComparison
Value (ppm) &
Source
EPA Cancer
Class
Organosulfur Compounds -
Herbicide Related (OSCHs)

Chlorophenylmethyl sulfide (CPMS)On400.082.1115/2002None
Chlorophenylmethyl sulfone (CPMSO2)On300.026.58434/2002None
Chlorophenylmethyl sulfoxide (CPMSO)On70.019.32510/1999None
Organochlorine Pesticides (OCPs)
Aldrin (ALDRN)On14,000.030.1621,044/31270.04 CREGB2
Chlordane (CLDAN)On710.019.38183/29910.5 CREGB2
Off7.81.257/111




Table 9.

Contaminants of Potential Concern: Surface Soil - RMAED run of 10/15/93
Analyte Groups/Analyte
** Inclusion of analytes in this scoping table does NOTmean exposure to listed analytes will necessarily causeadverse health effects.**
On-/Off-
Post
Maximum
Detect (ppm)
Average
Detect (ppm)
FrequencyComparison
Value (ppm) &
Source
EPA Cancer
Class
Organochlorine Pesticides (OCPs)
Dieldrin (DLDRN)On2,500.011.0641,464/3,12420 EMEG-adult
0.04 CREG
B2
Off0.270.0369/111
Anions & Cations
Arsenic (AS)On1,080.026.247694/2,259200 EMEG-
adult
0.4 CREG
A
Off4.633.3914/65
ICP Metals
Copper (CU)On2,34020.2461,710/1,892None
Lead (PB)On3,44043.158712/1,981500 EPAAction Level
Off41.222.1517/17




Table 10.

Contaminants of Potential Concern: Sediment - RMAED run of 9/8/93
Analyte Groups/Analyte
** Inclusion of analytes in this scoping table doesNOT mean exposure to listed analytes willnecessarily cause adverse health effects.**
On-/Off-
Post
Maximum
Detect (ppm)
Average
Detect (ppm)
FrequencyComparison
Value (ppm) &
Source
EPA Cancer
Class
Triazines
Atrazine (ATZ)On9,700.02,262.7810/2720,000 RMEG-
adult

Organochlorine Pesticides (OCPs)
Aldrin (ALDRN)On1,000.012.65122/18320 EMEG-adult
0.04 CREG
B2
Dieldrin (DLDRN)On240.06.101112/18240 EMEG-adult
0.04 CREG
B2
Off0.370.03714/58
Anions & Cations
Arsenic (AS)On16.58.3399/127200 EMEG-adult
0.4 CREG
A
Beryllium (BE)On3.371.32756/1094000 RMEG-
adult
0.2 CREG
B2




Table 11.

Contaminants of Potential Concern: Air - RMAED run of 8/10/93
Analyte Groups/Analyte
** Inclusion of analytes in this scoping table doesNOT mean exposure to listed analytes willnecessarily cause adverse health effects.**
On-/Off-
Post
Maximum
Detect
(µg/m3)
AverageDetect(µg/m3)FrequencyComparison
Value (µg/m3) &
Source
EPA Cancer
Class
Volatile Halogenated Organics
(VHOs)

1,2-Dichloroethane (12DCLE)On20.0 0.21513/23830.04 CREGB2
Off0.3550.199811/45
Carbon tetrachloride (CCL4)On20.00.94762,141/2,37310 EMEG
0.07 CREG
B2
Chlorobenzene (CLC6H5)On20.00.5023 50/2,383None
Off0.06140.0454/45
Chloroform (CHCL3)On29.50.57681,714/2,3740.04 CREGB2
Off0.3470.11540/45
Methylene chloride (CD2CL2/
CH2CL2)
On74.42.4351,526/2,05930 EMEG
2 CREG
B2
Off0.4520.320742/45
Tetrachloroethylene (TCLEE or PCE)On20.01.5521,390/2,377600 EMEG
2 CREG
B2-C
Off0.490.31623/45




Table 1.

Contaminants of Potential Concern: Air - RMAED run of 8/10/93
Analyte Groups/Analyte
** Inclusion of analytes in this scoping table doesNOT mean exposure to listed analytes willnecessarily cause adverse health effects.**
On-/Off-
Post
Maximum
Detect
(µg/m3)
Average
Detect
(µg/m3)
FrequencyComparison
Value (µg/m3) &
Source
EPA Cancer
Class
Volatile Aromatic Organics (VAOs)
Benzene (C6H6)On20.01.9912,085/2,3732 EMEG
0.1 CREG
A
Off0.3610.306645/45
Organosulfur Compounds -
Herbicide Related (OSCHs)

Chlorophenylmethyl sulfone (CPMSO2)On1.940.342925/448None
Chlorophenylmethyl sulfoxide (CPMSO)On1.740.362112/448None
Organochlorine Pesticides (OCPs)
Aldrin (ALDRN)On0.20.00945175/1,6490.0002 CREGB2
Chlordane (CLDAN)On1.70.1728431/2,0640.003 CREGB2
Dieldrin (DLDRN)On1.730.015957/1,9980.0002 CREGB2




Table 11.

Contaminants of Potential Concern: Air - RMAED run of 8/10/93
Analyte Groups/Analyte
** Inclusion of analytes in this scoping list doesNOT mean exposure to listed analytes willnecessarily cause adverse effects.**
On-/Off-
Post
Maximum
Detect
(µg/m3)
Average
Detect
(µg/m3)
FrequencyComparison
Value (µg/m3)
& Source
EPA Cancer
Class
ICP Metals / Anions & Cations
Arsenic (AS)On0.01390.00114517/1,6330.0002 CREGA
Off0.003420.001019/24
Mercury (HG)On2.741.1337/8900.06 EMEG
Cadmium (CD)On0.0280.00265252/1,6410.2 EMEG
0.0006 CREG
B2
Off0.003220.0012712/24




Table 12A.

Historical Range of Contaminants Detected in On- and Offpost Biota.
Contaminant Species Sample Type On-/Off-
Post
Location
Contaminant
Level
(ppm) (a)
Comparison
Value
(ppm)
Source (b)
Arsenic
(AS)
Largemouth bassTissueOn2.0-2.20.5-2.0
FDA
Allowable
Level
BRI
Pheasant"On<0.25-1.82IEARC
Mercury
(HG)
Largemouth
bass
"On0.55 ave.1.0
FDA
Action
Level
A
Carp"Off0.052-0.155A
Pike"On 0.405 ave.IEARC
Mallard
duck
"On<0.050-0.066
(21.8)
IEARC/
(BRI)
Pheasants"On0.106-0.32IEARC/
BRI
Mourning
dove
"On0.05-0.40IEARC/
BRI
Aldrin
(ALDRN)
Mallard
duck
"On0.005-0.200.3
FDA
Action

Level

BRI
Mourning
dove
"On0.0227-1.3IEARC
Dieldrin
(DLDRN)
Channel
catfish
"On0.0301-0.6180.3
FDA
Action
Level
IEARC
"Off0.251A
Carp"Off0.235A
Northern
pike
"On0.202--0.470IEARC
Bluegill"On0.0194-0.515IEARC
Largemouth
bass
"On0.0199-0.860IEARC
A
Mallard"On0.01-4.53
(81.6)
IEARC
(BRI)
PheasantTissueOn0.02-5.95IEARC
BRI
PheasantLiverOff0.380A
DeerLiverOn0.101-0.281IEARC
OOURI
Mourning
dove
TissueOn7.80-32.0
(56.0)
IEARC
(IEARC)
ChickenTissueOff0.23A
LiverOff0.23A
EggOff0.0179A
CowTissueOff0.053-0.078A
Endrin
(ENDRN)
Channel
catfish
TissueOn0.1010.3
FDA
Action
Level
IEARC
Bluegill"On0.0976IEARC
Largemouth
bass
"On0.0478-0.0518IEARC
Mallard"On0.02-0.104IEARC
BRI
Mourning
dove
"On0.14-1.30IEARC
BRI
DDTLargemouth
bass
"On0.144-0.2995.0
FDA
Allowable
Level
for fish
(additive with DDE)
IEARC
Pheasant"On0.03BRI
Mourning
dove
"On0.04-0.308IEARC
BRI
DDEChannel
catfish
"On0.0661-0.376IEARC
Northern
pike
"On0.118-0.602IEARC
Largemouth
bass
"On0.0718-0.613IEARC
MallardTissueOn0.101-0.408IEARC
MallardLiverOn0.101-0.638IEARC
PheasantTissueOn0.0701-0.430IEARC
LiverOn0.109-0.810IEARC
Mourning
dove
TissueOn0.04-0.942IEARC
BRI
ChickenTissueOff0.106OOURI
Chlorophenylmethyl
- sulfide
(CPMS)
Mourning
dove
"On0.3-1.46NoneBRI
Mallard"On0.04
BRI
- sulfone
(CPMSO2)
Pheasant"On0.36-14.5NoneBRI
Mourning
dove
"On0.22-2.53
BRI
- sulfoxide
(CPMSO)
Mallard"On0.25-0.26NoneBRI
Dibromochloropropane
(DBCP)
Pheasant"On0.03NoneBRI

(a) The contaminant levels recorded in this column are from samples collected for or recorded in the listed "source" documents. The time interval represented by thesamples is indicated by the dates in "[]s" listed with the following source report.

(b) The sources used to compile this profile of RMA and nearby areas biota contaminants:
............OOURI - Offpost Operating Unit Remedial Investigation (ESE, 1988); [1985-86].
............A - Offpost Operating Unit Remedial Investigation, Final Addendum (HLA, 1992a); [1988-89].
............BRI - Biota Remedial Investigation (ESE, 1989b); [1973-84].
............IEARC - Integrated Endangered Assessment/Risk Characterization, Proposed Final (EBASCO, 1994); [1988-90].

NOTE: Contaminant levels given in parentheses "( )" are isolated detections above the usually observed values. The report which documents the listed value is alsolisted in "( )".



Table 12B.

Onpost contaminant accumulation: 1994 Biomonitoring Program (USFWS, 1995).
SpeciesSample TypeDieldrin (a)
(ppm)
DDE (b)
(ppm)
HG (c)
(ppm)
CootsLiver0.038 - 0.2260.017 - 0.0230.155 - 0.137
Brain0.052----
Muscle0.017 - 0.0650.051--
GI Contents0.018 - 0.038----
Carcass0.0800.025--
Redhead ducksLiver0.090 - 0.3730.0170.812 - 1.58
Brain0.027 - 0.071----
Muscle0.027 - 0.0680.0190.375
GI Contents0.046 - 0.062----
Eggs1.20.159--
Canada geeseLiver0.029 - 0.039----
Brain------
GI Contents______
Mallard ducksLiver0.023 - 0.0530.017 - 0.0250.111 - 0.256
Brain------
Muscle----0.082 - 0.095
GI Contents0.054----
Mourning dovesLiver0.104 - 0.533----
Muscle0.021 - 0.0260.018--
      (a) FDA Action Level: Dieldrin = 0.3 ppm
      (b) FDA Allowable Level: DDE + DDT = 5.0 ppm
      (c) FDA Action Level: Mercury = 1.0 ppm


Offpost Contamination

Nature and Extent of Contamination

This section discusses the nature and extent of contamination north of RMA in the Offpost StudyArea and in the "EPA Study Area" west of RMA in Commerce City. The Offpost RI, RIAddendum reports, and the Chemical Sales Company Interim Public Health Assessment(CDPHE, 1992a) were the primary sources of information for these media. Other sources ofinformation include the CMP annual groundwater and air quality monitoring reports (eg. Stollar,1991a, 1992b). ATSDR also made numerous queries of the environmental data recorded in theRMAED to evaluate contaminant concentrations, locations, and changes over time.

Groundwater

Semivolatile Organic Compounds

This section provides a summary of the nature and extent of contamination in groundwater in theOffpost Study Area. The groundwater contaminant data incorporated in the Offpost RI (ESE,1988), the RI Addendum (HLA, 1992a), and the Endangerment Assessment/FeasibilityAssessment (HLA, 1992b) represent data collected from 1985 to 1991. This "historical" dataserves to describe the character and extent of Offpost contamination which, depending on thesampling locations, is the character of that contamination before, during and/or after theimplementation of interim remedial actions (IRAs) and the construction and operation ofgroundwater intercept and treatment facilities (BCSs).

In general, the combined effect of those IRAs and BCSs has been to minimize, or in some cases,to eliminate certain contaminants in the Offpost Study Area. The mitigative effects of thoseIRAs/BCSs were ongoing during collection of the 1985-1993 data-set for Offpost domesticdrinking water wells. Thus, that data-set (see Table 5A & B) provides a historical perspective ofOffpost groundwater quality in the Alluvial and Arapahoe Aquifers during that interval. The"maximum detection" value given often records the maximum contaminant-levels early in theclean-up process and the "average detection" values given reflects a generalized, cumulative,sliding-average measuring both the area-wide levels of contamination in the groundwaterplumes, and in many cases, the progressive effects of the IRAs/BCSs.

To assess the current levels of Offpost groundwater contamination, Tables 5A & B alsoincorporates data extracted from the RMAED on the detections recorded between October 1990and December 1993 from those Offpost Study Area domestic water wells. The detectionsrecorded for that period were a more recent set of sampling data from the ongoing DomesticWell Sampling Program conducted by the Tri-County Health Department and recorded in theRMA database. Because of the large number of wells sampled, a rotating schedule for wellsampling is used. Thus, when the database was queried in April 1994, the "most recent" samplecollected from any given Off Post Study Area domestic or drinking water well was a samplecollected sometime during the interval from September 1990 through December 1993.

The results of a subsequent cycle of sampling of 103 wells during April 1994 are incorporatedlater in the Assessment in Tables 13, 14, and 17 when examining pathways of human exposureand provide an even better perspective on the changes in Offpost contamination with time.

The historical (1985-1993) data is discussed below to describe the extent to contamination in thearea and is contrasted with the contaminant levels described by the more recent sampling data(10/90 - 12/93) recorded in the RMAED database. This comparison is made to illustrate thetrends in contamination and the effects of the remedial activities undertaken so far.

Historically, diisopropyl methylphosphonate (DIMP); dicyclopentadiene (DCPD); dieldrin, andendrin, have been the most widespread and consistently detected semivolatile organiccompounds (SVOCs) in groundwater of the Offpost Study Area. Of those chemicals, DIMP isthe most widespread of all the groundwater contaminants in the Offpost Study Area (HLA,1992b, p. I-12).

DIMP: The issue of a safe drinking water level

DIMP is a very uncommon groundwater contaminant, and because of it's unique association withRMA, DIMP has received considerable attention from state and federal authorities. Due to it'smobility in groundwater, DIMP has served as a good indicator for the extent of RMA-relatedgroundwater contamination. The EPA has evaluated the available toxicological studiesperformed to assess the potential health effects to humans from DIMP exposure, and, in 1989,established a Lifetime Health Advisory (LTHA) of 600 ppb and a chronic Reference Dose (RfD)of 0.08 mg/kg/day for DIMP in drinking water. In 1994, the state of Colorado adopted a state-wide interim groundwater standard of 8 ppb. In making this policy decision, the Water QualityControl Commission, recognized the scientific disagreement among competent scientific expertsin this matter and thus adopted an "interim" groundwater standard. The Commission alsorecognizes the potential for future modification should additional relevant information becomeavailable.

ATSDR has reviewed the principal toxicological studies regarding DIMP, particularly Aulerich,Hart, and Bucci, and has determined that the Aulerich study, conducted in 1979 and used by thestate of Colorado to derive it's interim groundwater standard, is not appropriate for assessingpotential risks to humans exposed to DIMP in drinking water. Until a subsequent study provesotherwise, the Bucci study appears to be the best study on which to assess the potential forhuman health effects from DIMP exposure, and the Lifetime Health Advisory and RfD,established by the EPA, appears to be protective of public health.

ATSDR agrees with the National Academy of Science in their review of the Aulerich study: it isinconclusive because of apparent reporting problems in the Aulerich report, the inadequacy ofthe pathologic examinations of the animals, uncertainty about the experimental conditions, andlack of original laboratory data (Doull, 1990). There are several methodological flaws that makethe Aulerich study inappropriate for determining potential health risks to people exposed toDIMP in drinking water, but the most significant is that necropsies were not performed in theAulerich study, and the cause of death was not determined. The reason for mortality observed in female mink will never be known, because appropriate pathological findings were notundertaken, and thus, Aulerich is not an appropriate study upon which to base a drinking waterstandard. Please refer to Appendix B for more information about DIMP.

The ATSDR Division of Toxicology is currently preparing a Toxicological Profile on DIMP thatwill in greater detail examine all DIMP studies conducted to date and, if sufficient data exists,determine an acceptable level of human exposure to DIMP in drinking water that is protective ofpublic health. The ATSDR toxicological profile is intended to succinctly characterize thetoxicological and adverse health effects information for the specific chemical being described, inthis case, DIMP. Each profile identifies and reviews the key literature (that has been peer-reviewed) that describes a chemical's toxicological properties. If sufficient toxicologicalinformation exists, the profile will provide the following: 1) An examination, summary, andinterpretation of available toxicological information and epidemiological evaluations on achemical to determine the levels of significant human exposure for the chemical and theassociated acute, subacute, and chronic health effects; 2) A determination of whether adequateinformation on the health effects of each substance is available or in the process of developmentto determine levels of exposure that present a significant risk to human health of acute, subacute,and chronic health effects; and 3) Where appropriate, identification of toxicological testingneeded to identify the types or levels of exposure that may present significant risk of adversehealth effects in humans. A draft of that toxicological profile is targeted for release late in 1996. That draft will be available for public comment for a 90-day period before the finalToxicological Profile is prepared.

DIMP: The Effect of the Conceptual Agreement

The Conceptual Agreement of June 13, 1995 (Colorado, 1995) includes components that ensurecontinued operation of all Boundary Containment Systems (BCSs) including the Offpost Systemand the Onpost RMA pump and treat systems (Component #15); acquisition, by Shell and theArmy, of an additional 4,000 acre-feet of water for the South Adams County Water andSanitation District water supply system (Component #16); and the requirement that RMA andShell Oil Company pay for and construct a water distribution system to provide municipal waterto all existing well owners within the DIMP plume north of the Arsenal. The plume will bedefined by the extent of DIMP detected above the detection limit of 0.392 ppb (for anapproximation see Fig. 6). Thus, municipal water or an alternative water source will be suppliedto residents with levels of DIMP in their wells at levels well below the 8 ppb level state standard. The groundwater remedy specified in the Conceptual Agreement was incorporated in theROD for the RMA Offpost Operable Unit (HLA, 1995). The remedy adopted willeliminate human exposure to DIMP in the Offpost area north of the Arsenal.

Distribution of SVOCs

Figure 6 illustrates that, in 1990, DIMP was distributed in a continuous plume extending fromthe RMA north and northwest boundaries to the South Platte River. In 71 of 89 samplescollected from monitoring wells in the Offpost Study Area, DIMP was above the CertifiedReporting Limit of 0.392 ppb (HLA, 1992a, Table 2.5). In general, the highest concentrationsof DIMP offpost occur between the RMA northern boundary and the O'Brian Canal. Thehighest observed concentrations were 5800 ppb in the First Creek paleochannel and 860 ppb inthe northwest paleochannel (HLA, 1992b, p. I-12, I-13).

The more recent DIMP concentrations in domestic drinking water wells through December 1993are shown to range from 950 to 0.392 ppb (see Table 5A). The maximum detection of 950 ppbDIMP was detected in a March 1993 sample from well 1178B. The users of that private well,which had previously contained DIMP in the 200-400 ppb range, had previously been suppliedwith bottled water. That well is now used as an irrigation well and as a monitoring well. Basedupon sampling completed in April 1994, the concentration range of DIMP in both Alluvialand Arapahoe Aquifer drinking water wells then ranged from 28.5 to 2.1 ppb.

The distribution of dieldrin in 1990 is shown in Figure 7. Dieldrin occurs in the Offpost StudyArea north of both the northern and northwestern RMA boundaries. The highest concentrationsof dieldrin have been found in wells located in the First Creek paleochannel, ranging from 0.6 to0.87 ppb. Dieldrin plumes have also been interpreted in limited areas in the northernpaleochannel and in two areas north of the northwestern RMA boundary. Detectableconcentrations of dieldrin in the northern paleochannel and northwestern paleochannel rangedfrom 0.05 to 0.14 ppb (HLA, 1992b, p. I-13). Dieldrin was detected at 0.06 ppb in only onegarden irrigation well (1189A) sample collected in the 1990 - 1993 round of samples collected(RMAED query of 04/26/94; see Table 17).

The highest concentrations of endrin ranged from approximately 0.25 to 0.75 ppb for wellsimmediately north of the northern RMA boundary. The maximum concentration of endrin was0.748 ppb from monitoring well 37309, located approximately 1500 feet north of RMA. Endrinwas also detected in groundwater samples collected from wells in the central portion of thenorthern paleochannel (HLA, 1992b, p. I-13). The 1990 - 1993 sampling of drinking waterwells did not detect endrin at levels exceeding the 2.0 ppb Lifetime Health Advisory (LTHA)established by EPA (see Table 5A).

Other SVOCs were detected in groundwater samples from the Offpost Study Area. The otherSVOCs detected include the pesticides atrazine, malathion, and parathion; the organosulfurcompounds 4-chlorophenylmethyl sulfone (CPMSO2) and 4-chlorophenylmethyl sulfoxide(CPMSO); and the organochlorine pesticides aldrin, isodrin, chlordane, 2-2-bis (para-chlorophenyl)-1,1-dichloroethene (DDE), and 2-2-bis (para-chlorophenyl)-1,1,1-trichloroethane(DDT; HLA, 1992b, p. I-13).

The distribution of atrazine in the Offpost Study Area is similar to that of the organochlorinepesticides (OCPs). Atrazine was detected in 21 Offpost Study Area wells, with the maximumconcentrations occurring in the First Creek (46.0 µg/l) and northern (72.9 µg/l) paleochannels. Atrazine was generally not detected in groundwater samples collected from the Offpost Study Area off the northwestern RMA boundary, except for two isolated occurrences(HLA, 1992b, p. I-13, I-14). In the 1990 - 1993 samples collected from drinking water wells,the concentration atrazine ranged from 5.81 to 4.63 ppb (see Table 5A).

Although CPMSO2 and CPMSO are both organosulfur compounds (OSCHs), their distributionsin offpost groundwater differ. CPMSO was generally only found in samples collected fromwells installed in the northern paleochannel, whereas CPMSO2 was generally only found insamples collected from wells located in the First Creek paleochannel. CPMSO was generallyfound at levels higher than those reported for CPMSO2. CPMSO was detected at concentrationsup to 82.2 ppb in the northern paleochannel. CPMSO2 was also detected in the First creekpaleochannel at concentrations up to 21.0 ppb (HLA, 1992b, p. I-14). CPMSO and CPMSO2were not detected in the Offpost Study Area drinking water wells samples collected during the1990 -1993 sampling round (see Table 5A).

The distribution of the additional OCPs (aldrin, isodrin, chlordane, DDE, and DDT) is similar tothe previously discussed distribution of the OCPs dieldrin and endrin. The maximumconcentrations of these compounds generally occur in the First Creek paleochannel, usually inthe area 500 to 1000 feet north of the NBCS. Generally, only sporadic, isolated occurrences ofthese compounds were observed in the Offpost Study Area north of the RMA northwesternboundary (HLA, 1992b, p.I-14).

Volatile Organic Compounds

The volatile organic compounds (VOCs) most frequently detected in the Offpost Study Areagroundwater include chloroform, chlorobenzene, dibromochloropropane, tetrachloroethene,trichloroethene, 1,2-dichloroethene, carbon tetrachloride, and benzene (HLA, 1992b, p. I-14).

Historically, the most frequently detected VOC has been chloroform. Chloroform has beenfound primarily downgradient of the NWBCS and in the northern paleochannel. Chloroformwas generally not found in the First Creek paleochannel. Concentrations of chloroformemanating from the northern RMA boundary are higher than concentrations in the Offpost StudyArea north of the northwestern RMA boundary. The highest concentrations of chloroformmeasured in monitoring wells were at the north end of the northern paleochannel (200 to 400ppb). The highest concentration of chloroform detected in the northwestern paleochannel was19.8 ppb (HLA, 1992b, p. I-14). The range of chloroform detected in the 1990 - 1993 samplingof drinking water wells was from 25.0 to 0.73 ppb (see Table 5A).

The only other VOCs detected during the 1990 - 1993 sampling episode were 1,2-dichloroethane(4.85-1.57 ppb) and tetrachloroethylene (14.7-0.95 ppb; see Table 5A).

Surface Water

Dicyclopentadiene (DCPD), chloromethyl sulfone and sulfoxide (CPMSO2 & CPMSO), atrazine(ATZ), arsenic, and lead have been detected in Offpost surface waters a levels of potentialconcern (see Table 8). Those detections were largely limited to First Creek immediately northof the Arsenal and upgradient of the Burlington Ditch/O'Brian Canal, with a few, low-level(below comparison-value) detections of DIMP further downgradient in BurlingtonCanal/O'Brian Canal (HLA, 1992b, p. I-19). Distribution of the contaminants is very limited inextent and may be related to discharges from the RMA sewage treatment plant. As discussed inthe pathways section of this Assessment, that plant was closed in 1994.

Surface Soil

Aldrin, endrin, dieldrin, and isodrin have been detected in Offpost Study Area soils (HLA,1992b, p. I-7). Those compounds have been used as insecticides in areas similar to the OffpostStudy Area from the 1940s to the mid-1970s. Aldrin was used in the early 1950s to protectcotton against boll weevils and in the 1970s for soil application in grain crops and termitecontrol. In Colorado, dieldrin was used to control insects in field vegetables, grain, and fruitcrops and against termites and locusts. Endrin was also used to control a wide range of pests. These insecticides were banned for general uses in 1974 by the EPA. Aldrin and dieldrin maystill be used for certain restricted uses such as subsurface insertion for termite control anddipping non-food roots (HLA, 1992b, p. I-7).

ATSDR has reviewed the Offpost surface soil data incorporated in the RMAED database and hasdetermined that chlordane (CLDAN), dieldrin (DLDRN), and arsenic (AS) occur inconcentrations high enough to be considered contaminants of potential concern in the OffpostStudy Area (see Table 9). However, the occurrence of those contaminants is relativelyinfrequent and concentrations average tens to hundreds of times lower than Onpostconcentrations for those chemicals. Permissive evidence is presented in the OffpostEndangerment Assessment that suggests that eolian deposition of RMA-derived OCPs may beresponsible for the slightly elevated levels of those pesticides detected immediately north ofRMA (HLA, 1992b, p. I-18, Figs. 16-17). The highest levels of chlordane and dieldrin detectedin the Offpost area seem to reflect a pattern more consistent with documented off site use ofthose pesticides (HLA, 1992a, p. 91-94). The arsenic detections may reflect natural soilvariations and other non-RMA influences.

Sediment

ATSDR reviewed the Offpost sediment data recorded in RMAED (see Table 10) and did notnote sediment contamination at levels of potential concern. The OCPs and DBCP were the mostfrequently detected, at levels below appropriate comparison values, and those detections werelocalized along First Creek. Scattered detections along the canal/ditch system were recorded butmay reflect local sources of contamination ( HLA, 1992b, p. I-20).

Air

As documented in the Offpost Operable Unit RI (ESE, 1988, p. 2 -24-28 and 6-1), the state ofColorado and the EPA have conducted off-site monitoring and Offpost Study Area air qualityconditions have been simulated from Onpost data. The data amassed on Offpost air quality isincorporated in the RMAED database. ATSDR reviewed the data generated from a data basequery of August 10, 1993 and determined, from that data, that 1,2-dichloroethane (12DCLE),chlorobenzene (CLC6H5), chloroform (CHCL3), benzene (C6H6), arsenic (AS), and cadmium(CD) potentially are the contaminants of potential concern in the Offpost Study Area (see Table11).

The air quality data amassed Onpost and that incorporated in the EPA Toxic Chemical ReleaseInventory database (TRI, 1994) strongly suggest that the occurrence of most of the aircontaminants listed here for the Offpost Study Area can be derived from non-RMA sources. TRI (1994) data collected only from the Zip Code areas immediately adjacent to the Arsenalindicates a possible Offpost source for all air-borne contaminants except 1,2-dichloroethane(12DCLE) and chlorobenzene (CLC6H5). Contamination sources for those chemicals in off-sitelocations beyond the Zip Codes queried in TRI or synthesis of those chemicals within the mix ofambient air contaminants recorded by the TRI queries can not be excluded.

Biota and Vegetable Produce

Onpost wildlife

Because some wildlife species that reside or visit the Onpost area can be hunted (and consumed)in the nearby off post areas, an examination of the accumulation of contaminants in those Onpostwildlife species provides valuable information on potential levels of contamination in off postbiota. A record of contaminant accumulation in Onpost biota for the interval from 1973 to 1984was compiled in the Biota Remedial Investigation (ESE, 1989b). That record was supplementedwith data collected for 1988 to 1990 for the Onpost Integrated Endangerment Assessment andRisk Characterization (EBASCO, 1990). Those historical data are incorporated in Figure 12A.

Inspection of that data reveals that, of those Onpost samples collected from species that may ordo travel to off-post locations, mallard ducks (mercury and dieldrin), pheasants (dieldrin), andmourning doves (aldrin, dieldrin, and endrin) have been found to contain levels of hazardoussubstances greater that FDA Action Levels. Some, but not all, of the higher levels ofcontaminant accumulation in those species are found in the earlier samples collected.

In 1993, the USFWS initiated the Biomonitoring Program (BMP) for the Rocky MountainNational Wildlife Refuge. Among the many objectives of that program, data is being gatheredto ascertain in waterfowl using Onpost lakes and wetlands contain significant concentrations ofcontaminants. Because mourning doves use the Refuge but may be hunted and consumed off ofthe Refuge data has also been collected by USFWS to assist in the evaluation of the potentialhuman health risk that may arise from consumption of these birds.

Table 12B gives the Onpost waterfowl and mourning dove contaminant accumulation datacompiled by the USFWS for the 1994 BMP (see USFWS, 1995). Although not all data hadbeen received when this assessment was prepared, the data indicate detectable dieldrinaccumulation in 12 of 15 waterfowl samples of liver tissue analyzed and 3 of 8 mourning doveliver samples. Of those liver tissue detections only one waterfowl sample (0.373 ppm) and onemourning dove sample (0.533 ppm) exceeded the 0.3 ppm FDA Action Level. The maximumconcentration of dieldrin detected in this suite of samples was 1.2 ppm dieldrin found in 4redhead duck eggs. This same duck had the highest overall liver, brain, and muscleconcentrations of dieldrin. The eggs also had the only detection of DDT (0.02 ppm) and thehighest concentration of DDE (0.159 ppm). The highest liver concentration of DDE (0.035ppm) was also found in this redhead duck. The male redhead collected with this female had thehighest concentration of dieldrin in GI contents.

The two juvenile Canada geese were collected for the 1994 BMP because most geese on theRMA Refuge are resident and may indicate whether contaminant accumulation occurs on theRefuge. The dieldrin levels measured in those geese liver samples range from 0.029 to 0.039ppb. which is in the low end of the range of the other waterfowl liver dieldrin values (0.023 to0.373 ppm). These data indicate that waterfowl may be accumulating contaminants from theRefuge aquatic habitats (USFWS, 1995). However, the dieldrin, DDE, and HG levels detectedin the edible tissue of the redhead ducks(18) was below the FDA Action Level for all contaminants. In other words, human consumption of the ordinarily edible portions of these duckscollected in 1994 would not represent a human health threat.

Examination of the historical data compiled in Table 12A shows that, in the past, analyses ofmourning doves have exhibited high concentrations of organochlorine pesticides (OCPs). Because mourning doves that use the Refuge may be hunted in off post areas the level ofcontaminants in the edible tissue portions of those doves is of potential human health concern.

To further evaluate this potential risk and to better understand the health of doves in thisecosystem the USFWS collected additional contaminant accumulation data on this speciesduring 1994. A total of 12 birds were collected and samples of brain, liver, and muscle tissueanalyzed for OCPs, chlordane, DDE, AS, and HG. There were no detections of aldrin, endrin,isodrin, chlordanes, or arsenic. The results of these additional tests are summarized in Table12B.

Dieldrin was detected in 6 of 12 doves tested, but of those positive contaminant detections onlyone sample of liver tissue at 0.533 ppm dieldrin was above the FDA Action levels. Ediblemuscle tissue of those dove tested did not contain contaminant concentration above FDA ActionLevels and the indication is, based on the 1994 data, that human consumption of mourningdoves taken in the off post areas is not likely to pose a health risk.

Offpost wildlife

Offpost biota sampling was conducted following an ecological characterization of terrestrialenvironments. Sampling for the Offpost RI was initiated in the spring of 1985 and was resumedin 1988-89 for the RI Addendum. Although contamination of resident game species on RMAwas previously established, information on the possible movement of wildlife from RMA toOffpost areas was lacking. Species such as pheasants and cottontail rabbits that could transportOnpost contaminants to Offpost locations were emphasized in the investigations and werestudied to delineate the size of the home ranges occupied by those species.

Absence of sufficient water in streams crossing RMA boundaries precludes movement ofpotentially contaminated fish, but the terrestrial species are not thus limited. Investigation of migratory waterfowl and mourning doves was not conducted Offpost because it was concludedthat those species appear to present a lesser potential hazard to humans due to the large rangemovements associated with migration and the potential dispersal of individual birds that spendsome portion of a year at RMA with other birds that never or rarely visit the RMA environs.

The target analytes for biota in the Offpost Study Area were arsenic, mercury, and theorganochlorine pesticides (OCPs) aldrin, dieldrin, endrin, DDE, and DDT (see Table 12A). Thebiota samples collected included wildlife species commonly considered suitable for humanconsumption: bluegill, carp, channel catfish, and ring-necked pheasant. Agricultural biotasamples of cow milk and fat, brain, muscle, liver, and kidney tissue and chicken egg, fat/skin,muscle, and liver were collected from a farm located immediately north of 96th Avenue, about300 ft north of RMA in section 14 (T2S, R67W) and just north of the NBCS. The OCP dieldrinwas the contaminant found most often in biota of the Offpost Study Area. Cow fat, chickentissue, fish and pheasants all had detectable concentrations of dieldrin. Aldrin, endrin, and DDTwere not detected in any biological samples taken in the Offpost Study Area. Mercury wasdetected in tissue samples of carp collected from the Maul Reservoir along First Creek (Sec. 14,T2S, R67W). Concerns expressed by Offpost residents about the possibility of DBCPcontamination in cattle, led to testing of cow's milk produced in the Offpost area. DBCP wasnot detected in the milk samples analyzed (HLA, 1992a, p.106).

Inspection of the biota sampling data compiled in Table 12A reveals that, of the samplescollected Offpost, only the level of dieldrin detected in pheasant liver tissue (0.380 ppm) exceedsthe corresponding FDA Action level of 0.30 ppm for that pesticide.

Based upon the limited number and low-levels of detections of target analyte contaminants in theOffpost biota samples collected, ATSDR concludes that the only contaminant of potentialconcern suggested by the available data is the organochlorine pesticide (OCP) dieldrin. Dieldrinhas been detected in Offpost surface soils and has also been detected in the control samples(background samples) of juvenile pheasant tissue analyzed (<0.031-18.6 ppm dieldrin, wetweight basis; EBASCO, 1993, Appendix C). It follows that, in addition to potential Onpostexposure to dieldrin, off post agricultural use of dieldrin is one of the possible sources of thedieldrin detected in pheasant tissue and liver analyzed in the Offpost Study Area. Regardless ofthe source, dieldrin is a potential contaminant of concern in off post pheasants, even thoughthe detections have been infrequent (< 20%; EBASCO, 1993, Appendix C). Because of the low-level or infrequent detections of OCPs, DDE, DDT, arsenic, and mercury in waterfowl andmourning doves, particularly given the apparent declining trend over time, those contaminantsand species are not considered to be of human health concern (ingestion) in the off post areas.

Offpost vegetable produce

Because concerns had been expressed by other federal agencies and the state about DIMP uptakein Offpost vegetables, the Army developed a vegetable testing method to develop data toevaluate this concern. The Army asked Tri-County health Department to obtain samples ofgarden vegetables from Offpost sites to determine what concentrations of DIMP, if any, are inOffpost vegetables. The samples were collected from the garden of private residence north ofRMA on October 12, 1995 and from two large vegetable farms on November 10, 1995. Theprivate garden was selected by the Army because it is irrigated only with water from well 1178Bwhich has higher concentrations of DIMP remaining than any other Offpost area well. Theconcentration of DIMP in that well have ranged from about 150 to 950 ppb. The commercialfarms were selected because they utilize a combination of groundwater (DIMP <20 ppb) andsurface water (uncontaminated by DIMP).

The concentration of DIMP in vegetables irrigated with well 1178B ranged from nondetect to920 ppb. The vegetable samples taken from the larger Offpost farms had no detections of DIMP(RMA, 1995). The actual concentrations of DIMP found in these vegetable samples is less thanpredicted in the evaluation performed for the Offpost endangerment assessment (HLA, 1992b). That endangerment assessment had reported a hazard quotient of 0.3 (the threshold level ofconcern is 1.0) associated with consumption of vegetables. The actual concentrations measuredwould suggest an even lower hazard quotient. Thus, based upon the available data, there appearsvery little, if any, risk associated with the consumption of garden vegetables irrigated with wellwater containing as much as 950 ppb DIMP. As provided by the Conceptual Agreement(Colorado, 1995) and the Offpost ROD (HLA, 1995), the replacement of individual drinkingwater wells with a municipal water supply system throughout the Offpost area of DIMPdetection in groundwater (>0.392 ppb) may largely eliminate the use of small irrigation wellsand, thereby, further eliminate any residual risk that may be associated with the consumption ofgarden vegetables grown in this area.

Quality Assurance and Quality Control

We have reviewed the Quality Assurance/Quality Control (QA/QC) summary informationassociated with the many RI-related documents. Acceptable practices and standards have beenincorporated in those studies. Some samples from RMA were sent to the Eureka Lab inCalifornia. Subsequently that laboratory has been removed from EPA's list of acceptablelaboratories and data produced by that laboratory has not been used in the evaluation ofcontaminants at RMA. Otherwise, the data used in this Assessment appears to meet establishedQA/QC standards.

Physical and Other Hazards

The existence of chemical warfare agents and unexploded ordnance (UXO) is and will, untilfinal site cleanup is completed, continue to represent a hazard at RMA. IRAs have beendesigned and implemented to eliminate or reduce the potential hazard from agent and munitionsremaining at RMA. Component 14 of the Conceptual Agreement (Colorado, 1995) and theOnpost ROD (Foster Wheeler, 1996) specifies that munitions and munitions wastes will belocated, excavated, and, if necessary, destroyed. Disposal of the UXO and associated wasteand soils will be in the Onpost hazardous waste landfill. After final site cleanupundiscovered chemical warfare agents and UXO may represent a very small ongoing hazard forfuture land uses and users at RMA. However, because of the nature of the final remedy selectedfor Onpost soils and structures (e.g. Foster Wheeler, 1996, Table 5.4-11), the remaininglocations of any potential munitions wastes or UXO in surface or shallow subsoils will be knownand be very few in number.

The potential for occurrence of agent and UXO prior to final site cleanup was summarized in the RISR (EBASCO, 1992, p. 2-23 - 2-27) and that summary follows.

To a great extent, the handling of chemical warfare agents has been strictly monitoredthroughout RMA history and agent compounds have been the focus of specific actions designedto mitigate the potential for their release to the environment. Furthermore, agents generally haveshort half-lives when exposed to the natural elements and, with the exception of mustard thatmay have been trapped in voids beneath buildings, are generally not persistent in soils. Agentsoccur within some buildings, containment vessels, piping, and other structures within which theywere manufactured, handled, demilitarized, or stored.

Figure 2.2-1 given in the RISR (EBASCO, 1992) is a map of areas at RMA that are consideredto have potential for the occurrence of agents. The map was drawn conservatively as a "worst-case" scenario representing the maximum possible geographic extent of potential agentoccurrences. Areas on the map were delineated on the basis of a review of the RMA database,pertinent historical information and RI reports. Specifically, the SARs were surveyed and allreferences to agent occurrences noted. Individual CARs for those areas where agent presence atsome time was referenced were reviewed by identifying on a map all locations and samplecollection points where agent occurrence was suspected, recounted, or analytically examined. An audit of the RDMED database consisting of a query and plot of the resulting data points forall agent detections was accomplished and compared and combined with the results of theliterature review. Finally, a second review in the literature and by interview with knowledgeableindividuals was accomplished to cross-check for all reported detections in the database only.

With the exception of mustard under certain conditions where it is protected from weatheringeffects (e.g., in soils beneath a concrete pad), chemical warfare agents are highly unstable andvery rapidly degrade to breakdown products which, though still considered contaminants, do notconstitute the immediate threat to life or health posed by the chemical warfare agents (EBASCO,1992). Detections of Lewisite and mustard are recorded in the South Plants area and in Basin A(RMA, 1994). Historical accounts of agents are presented in the CARs and SARs, and byhistorical documentation and individual deposition in the administrative record; an account ofsample collection and handling protocols for potential agent occurrence is presented in AppendixA2 of the RISR (EBASCO, 1992).

RMA has also been used historically to manufacture, store, test, demilitarize, and dispose avariety of conventional munitions. RISR Figure 2.2-2 (EBASCO, 1992, p.2-26) is a map ofareas of RMA that are considered to have potential for the occurrence of unexploded ordnance(UXO). Those areas were delineated based on a review of pertinent historical formation and RIreports. The map was drawn conservatively as a "worst-case" scenario representing themaximum possible geographic extent of potential UXO occurrences. It is emphasized that thelikelihood of actual UXO occurrence in most of the areas indicated in RISR Figure 2.2-2 is low(EBASCO, 1992). The majority of areas considered to have potential for UXO are formermunitions testing and disposal areas.


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