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 NOT mean exposure to listed analytes will necessarily cause adverse health effects.** |
On-/Off- Post |
Maximum Detect (ppm) |
Average Detect (ppm) |
Frequency | Comparison Value (ppm) & Source |
EPA Cancer Class |
| Organosulfur Compounds - Herbicide Related (OSCHs) |
||||||
| Chlorophenylmethyl sulfide (CPMS) | On | 400.0 | 82.11 | 15/2002 | None | |
| Chlorophenylmethyl sulfone (CPMSO2) | On | 300.0 | 26.584 | 34/2002 | None | |
| Chlorophenylmethyl sulfoxide (CPMSO) | On | 70.0 | 19.325 | 10/1999 | None | |
| Organochlorine Pesticides (OCPs) | ||||||
| Aldrin (ALDRN) | On | 14,000.0 | 30.162 | 1,044/3127 | 0.04 CREG | B2 |
| Chlordane (CLDAN) | On | 710.0 | 19.38 | 183/2991 | 0.5 CREG | B2 |
| Off | 7.8 | 1.25 | 7/111 | |||
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 NOT mean exposure to listed analytes will necessarily cause adverse health effects.** |
On-/Off- Post |
Maximum Detect (ppm) |
Average Detect (ppm) |
Frequency | Comparison Value (ppm) & Source |
EPA Cancer Class |
| Organochlorine Pesticides (OCPs) | ||||||
| Dieldrin (DLDRN) | On | 2,500.0 | 11.064 | 1,464/3,124 | 20 EMEG-adult 0.04 CREG |
B2 |
| Off | 0.27 | 0.03 | 69/111 | |||
| Anions & Cations | ||||||
| Arsenic (AS) | On | 1,080.0 | 26.247 | 694/2,259 | 200 EMEG- adult 0.4 CREG |
A |
| Off | 4.63 | 3.39 | 14/65 | |||
| ICP Metals | ||||||
| Copper (CU) | On | 2,340 | 20.246 | 1,710/1,892 | None | |
| Lead (PB) | On | 3,440 | 43.158 | 712/1,981 | 500 EPA Action Level | |
| Off | 41.2 | 22.15 | 17/17 | |||
Table 10 - Contaminants of Potential Concern: Sediment - RMAED run of 9/8/93
| Analyte Groups/Analyte ** Inclusion of analytes in this scoping table does NOT mean exposure to listed analytes will necessarily cause adverse health effects.** |
On-/Off- Post |
Maximum Detect (ppm) |
Average Detect (ppm) |
Frequency | Comparison Value (ppm) & Source |
EPA Cancer Class |
| Triazines | ||||||
| Atrazine (ATZ) | On | 9,700.0 | 2,262.78 | 10/27 | 20,000 RMEG- adult |
|
| Organochlorine Pesticides (OCPs) | ||||||
| Aldrin (ALDRN) | On | 1,000.0 | 12.65 | 122/183 | 20 EMEG-adult 0.04 CREG |
B2 |
| Dieldrin (DLDRN) | On | 240.0 | 6.101 | 112/182 | 40 EMEG-adult 0.04 CREG |
B2 |
| Off | 0.37 | 0.037 | 14/58 | |||
| Anions & Cations | ||||||
| Arsenic (AS) | On | 16.5 | 8.339 | 9/127 | 200 EMEG-adult 0.4 CREG |
A |
| Beryllium (BE) | On | 3.37 | 1.327 | 56/109 | 4000 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 does NOT mean exposure to listed analytes will necessarily cause adverse health effects.** |
On-/Off- Post |
Maximum Detect (µg/m3) |
Average Detect (µg/m3) | Frequency | Comparison Value (µg/m3) & Source |
EPA Cancer Class |
| Volatile Halogenated Organics (VHOs) |
||||||
| 1,2-Dichloroethane (12DCLE) | On | 20.0 | 0.21 | 513/2383 | 0.04 CREG | B2 |
| Off | 0.355 | 0.1998 | 11/45 | |||
| Carbon tetrachloride (CCL4) | On | 20.0 | 0.9476 | 2,141/2,373 | 10 EMEG 0.07 CREG |
B2 |
| Chlorobenzene (CLC6H5) | On | 20.0 | 0.5023 | 50/2,383 | None | |
| Off | 0.0614 | 0.045 | 4/45 | |||
| Chloroform (CHCL3) | On | 29.5 | 0.5768 | 1,714/2,374 | 0.04 CREG | B2 |
| Off | 0.347 | 0.115 | 40/45 | |||
| Methylene chloride (CD2CL2/ CH2CL2) |
On | 74.4 | 2.435 | 1,526/2,059 | 30 EMEG 2 CREG |
B2 |
| Off | 0.452 | 0.3207 | 42/45 | |||
| Tetrachloroethylene (TCLEE or PCE) | On | 20.0 | 1.552 | 1,390/2,377 | 600 EMEG 2 CREG |
B2-C |
| Off | 0.49 | 0.316 | 23/45 | |||
Table 11 - Contaminants of Potential Concern: Air - RMAED run of 8/10/93
| Analyte Groups/Analyte ** Inclusion of analytes in this scoping table does NOT mean exposure to listed analytes will necessarily cause adverse health effects.** |
On-/Off- Post |
Maximum Detect (µg/m3) |
Average Detect (µg/m3) |
Frequency | Comparison Value (µg/m3) & Source |
EPA Cancer Class |
| Volatile Aromatic Organics (VAOs) | ||||||
| Benzene (C6H6) | On | 20.0 | 1.991 | 2,085/2,373 | 2 EMEG 0.1 CREG |
A |
| Off | 0.361 | 0.3066 | 45/45 | |||
| Organosulfur Compounds - Herbicide Related (OSCHs) |
||||||
| Chlorophenylmethyl sulfone (CPMSO2) | On | 1.94 | 0.3429 | 25/448 | None | |
| Chlorophenylmethyl sulfoxide (CPMSO) | On | 1.74 | 0.3621 | 12/448 | None | |
| Organochlorine Pesticides (OCPs) | ||||||
| Aldrin (ALDRN) | On | 0.2 | 0.00945 | 175/1,649 | 0.0002 CREG | B2 |
| Chlordane (CLDAN) | On | 1.7 | 0.1728 | 431/2,064 | 0.003 CREG | B2 |
| Dieldrin (DLDRN) | On | 1.73 | 0.015 | 957/1,998 | 0.0002 CREG | B2 |
Table 11 - Contaminants of Potential Concern: Air - RMAED run of 8/10/93
| Analyte Groups/Analyte ** Inclusion of analytes in this scoping list does NOT mean exposure to listed analytes will necessarily cause adverse effects.** |
On-/Off- Post |
Maximum Detect (µg/m3) |
Average Detect (µg/m3) |
Frequency | Comparison Value (µg/m3) & Source |
EPA Cancer Class |
| ICP Metals / Anions & Cations | ||||||
| Arsenic (AS) | On | 0.0139 | 0.00114 | 517/1,633 | 0.0002 CREG | A |
| Off | 0.00342 | 0.0010 | 19/24 | |||
| Mercury (HG) | On | 2.74 | 1.13 | 37/890 | 0.06 EMEG | |
| Cadmium (CD) | On | 0.028 | 0.00265 | 252/1,641 | 0.2 EMEG 0.0006 CREG |
B2 |
| Off | 0.00322 | 0.00127 | 12/24 | |||
Table 12A - Historical Range of Contaminants Detected in On- and Offpost Biota.
| Comparison Value (ppm) |
||||||
| Arsenic (AS) |
Largemouth bass | Tissue | On | 2.0-2.2 | 0.5-2.0 FDA Allowable Level |
BRI |
| Pheasant | " | On | <0.25-1.82 | IEARC | ||
| Mercury (HG) |
Largemouth bass |
" | On | 0.55 ave. | 1.0 FDA Action Level |
A |
| Carp | " | Off | 0.052-0.155 | A | ||
| Pike | " | On | 0.405 ave. | IEARC | ||
| Mallard duck |
" | On | <0.050-0.066 (21.8) |
IEARC/ (BRI) | ||
| Pheasants | " | On | 0.106-0.32 | IEARC/ BRI | ||
| Mourning dove |
" | On | 0.05-0.40 | IEARC/ BRI | ||
| Aldrin (ALDRN) |
Mallard duck |
" | On | 0.005-0.20 | 0.3 FDA Action Level |
BRI |
| Mourning dove |
" | On | 0.0227-1.3 | IEARC | ||
| Dieldrin (DLDRN) |
Channel catfish |
" | On | 0.0301-0.618 | 0.3 FDA Action Level |
IEARC |
| " | Off | 0.251 | A | |||
| Carp | " | Off | 0.235 | A | ||
| Northern pike |
" | On | 0.202--0.470 | IEARC | ||
| Bluegill | " | On | 0.0194-0.515 | IEARC | ||
| Largemouth bass |
" | On | 0.0199-0.860 | IEARC A | ||
| Mallard | " | On | 0.01-4.53 (81.6) |
IEARC (BRI) | ||
| Pheasant | Tissue | On | 0.02-5.95 | IEARC BRI | ||
| Pheasant | Liver | Off | 0.380 | A | ||
| Deer | Liver | On | 0.101-0.281 | IEARC OOURI | ||
| Mourning dove |
Tissue | On | 7.80-32.0 (56.0) |
IEARC (IEARC) | ||
| Chicken | Tissue | Off | 0.23 | A | ||
| Liver | Off | 0.23 | A | |||
| Egg | Off | 0.0179 | A | |||
| Cow | Tissue | Off | 0.053-0.078 | A | ||
| Endrin (ENDRN) |
Channel catfish |
Tissue | On | 0.101 | 0.3 FDA Action Level |
IEARC |
| Bluegill | " | On | 0.0976 | IEARC | ||
| Largemouth bass |
" | On | 0.0478-0.0518 | IEARC | ||
| Mallard | " | On | 0.02-0.104 | IEARC BRI | ||
| Mourning dove |
" | On | 0.14-1.30 | IEARC BRI | ||
| DDT | Largemouth bass |
" | On | 0.144-0.299 | 5.0 FDA Allowable Level for fish (additive with DDE) |
IEARC |
| Pheasant | " | On | 0.03 | BRI | ||
| Mourning dove |
" | On | 0.04-0.308 | IEARC BRI | ||
| DDE | Channel catfish |
" | On | 0.0661-0.376 | IEARC | |
| Northern pike |
" | On | 0.118-0.602 | IEARC | ||
| Largemouth bass |
" | On | 0.0718-0.613 | IEARC | ||
| Mallard | Tissue | On | 0.101-0.408 | IEARC | ||
| Mallard | Liver | On | 0.101-0.638 | IEARC | ||
| Pheasant | Tissue | On | 0.0701-0.430 | IEARC | ||
| Liver | On | 0.109-0.810 | IEARC | |||
| Mourning dove |
Tissue | On | 0.04-0.942 | IEARC BRI | ||
| Chicken | Tissue | Off | 0.106 | OOURI | ||
| Chlorophenylmethyl - sulfide (CPMS) |
Mourning dove |
" | On | 0.3-1.46 | None | BRI |
| Mallard | " | On | 0.04 | BRI | ||
| - sulfone (CPMSO2) |
Pheasant | " | On | 0.36-14.5 | None | BRI |
| Mourning dove |
" | On | 0.22-2.53 | BRI | ||
| - sulfoxide (CPMSO) |
Mallard | " | On | 0.25-0.26 | None | BRI |
| Dibromochloropropane (DBCP) |
Pheasant | " | On | 0.03 | None | BRI |
(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 the samples 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 also
listed in "( )".
Table 12B - Onpost contaminant accumulation: 1994 Biomonitoring Program (USFWS,
1995).
| Species | Sample Type | Dieldrin (a) (ppm) |
DDE (b) (ppm) |
HG (c) (ppm) |
| Coots | Liver | 0.038 - 0.226 | 0.017 - 0.023 | 0.155 - 0.137 |
| Brain | 0.052 | -- | -- | |
| Muscle | 0.017 - 0.065 | 0.051 | -- | |
| GI Contents | 0.018 - 0.038 | -- | -- | |
| Carcass | 0.080 | 0.025 | -- | |
| Redhead ducks | Liver | 0.090 - 0.373 | 0.017 | 0.812 - 1.58 |
| Brain | 0.027 - 0.071 | -- | -- | |
| Muscle | 0.027 - 0.068 | 0.019 | 0.375 | |
| GI Contents | 0.046 - 0.062 | -- | -- | |
| Eggs | 1.2 | 0.159 | -- | |
| Canada geese | Liver | 0.029 - 0.039 | -- | -- |
| Brain | -- | -- | -- | |
| GI Contents | __ | __ | __ | |
| Mallard ducks | Liver | 0.023 - 0.053 | 0.017 - 0.025 | 0.111 - 0.256 |
| Brain | -- | -- | -- | |
| Muscle | -- | -- | 0.082 - 0.095 | |
| GI Contents | 0.054 | -- | -- | |
| Mourning doves | Liver | 0.104 - 0.533 | -- | -- |
| Muscle | 0.021 - 0.026 | 0.018 | -- |
Nature and Extent of Contamination
This section discusses the nature and extent of contamination north of RMA in the Offpost Study Area and in the "EPA Study Area" west of RMA in Commerce City. The Offpost RI, RI Addendum reports, and the Chemical Sales Company Interim Public Health Assessment (CDPHE, 1992a) were the primary sources of information for these media. Other sources of information 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 the RMAED 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 the Offpost Study Area. The groundwater contaminant data incorporated in the Offpost RI (ESE, 1988), the RI Addendum (HLA, 1992a), and the Endangerment Assessment/Feasibility Assessment (HLA, 1992b) represent data collected from 1985 to 1991. This "historical" data serves to describe the character and extent of Offpost contamination which, depending on the sampling locations, is the character of that contamination before, during and/or after the implementation of interim remedial actions (IRAs) and the construction and operation of groundwater 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 those IRAs/BCSs were ongoing during collection of the 1985-1993 data-set for Offpost domestic drinking water wells. Thus, that data-set (see Table 5A & B) provides a historical perspective of Offpost groundwater quality in the Alluvial and Arapahoe Aquifers during that interval. The "maximum detection" value given often records the maximum contaminant-levels early in the clean-up process and the "average detection" values given reflects a generalized, cumulative, sliding-average measuring both the area-wide levels of contamination in the groundwater plumes, and in many cases, the progressive effects of the IRAs/BCSs.
To assess the current levels of Offpost groundwater contamination, Tables 5A & B also incorporates data extracted from the RMAED on the detections recorded between October 1990 and December 1993 from those Offpost Study Area domestic water wells. The detections recorded for that period were a more recent set of sampling data from the ongoing Domestic Well Sampling Program conducted by the Tri-County Health Department and recorded in the RMA database. Because of the large number of wells sampled, a rotating schedule for well sampling is used. Thus, when the database was queried in April 1994, the "most recent" sample collected from any given Off Post Study Area domestic or drinking water well was a sample collected 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 incorporated later in the Assessment in Tables 13, 14, and 17 when examining pathways of human exposure and 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 the area 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 the trends in contamination and the effects of the remedial activities undertaken so far.
Historically, diisopropyl methylphosphonate (DIMP); dicyclopentadiene (DCPD); dieldrin, and endrin, have been the most widespread and consistently detected semivolatile organic compounds (SVOCs) in groundwater of the Offpost Study Area. Of those chemicals, DIMP is the 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 with RMA, DIMP has received considerable attention from state and federal authorities. Due to it's mobility in groundwater, DIMP has served as a good indicator for the extent of RMA-related groundwater contamination. The EPA has evaluated the available toxicological studies performed 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 Quality Control Commission, recognized the scientific disagreement among competent scientific experts in this matter and thus adopted an "interim" groundwater standard. The Commission also recognizes the potential for future modification should additional relevant information become available.
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 the state of Colorado to derive it's interim groundwater standard, is not appropriate for assessing potential risks to humans exposed to DIMP in drinking water. Until a subsequent study proves otherwise, the Bucci study appears to be the best study on which to assess the potential for human 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 is inconclusive because of apparent reporting problems in the Aulerich report, the inadequacy of the pathologic examinations of the animals, uncertainty about the experimental conditions, and lack of original laboratory data (Doull, 1990). There are several methodological flaws that make the Aulerich study inappropriate for determining potential health risks to people exposed to DIMP in drinking water, but the most significant is that necropsies were not performed in the Aulerich 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 not undertaken, and thus, Aulerich is not an appropriate study upon which to base a drinking water standard. Please refer to Appendix B for more information about DIMP.
The ATSDR Division of Toxicology is currently preparing a Toxicological Profile on DIMP that will 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 of public health. The ATSDR toxicological profile is intended to succinctly characterize the toxicological and adverse health effects information for the specific chemical being described, in this case, DIMP. Each profile identifies and reviews the key literature (that has been peer-reviewed) that describes a chemical's toxicological properties. If sufficient toxicological information exists, the profile will provide the following: 1) An examination, summary, and interpretation of available toxicological information and epidemiological evaluations on a chemical to determine the levels of significant human exposure for the chemical and the associated acute, subacute, and chronic health effects; 2) A determination of whether adequate information on the health effects of each substance is available or in the process of development to 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 testing needed to identify the types or levels of exposure that may present significant risk of adverse health 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 final Toxicological Profile is prepared.
DIMP: The Effect of the Conceptual Agreement
The Conceptual Agreement of June 13, 1995 (Colorado, 1995) includes components that ensure continued operation of all Boundary Containment Systems (BCSs) including the Offpost System and the Onpost RMA pump and treat systems (Component #15); acquisition, by Shell and the Army, of an additional 4,000 acre-feet of water for the South Adams County Water and Sanitation District water supply system (Component #16); and the requirement that RMA and Shell Oil Company pay for and construct a water distribution system to provide municipal water to all existing well owners within the DIMP plume north of the Arsenal. The plume will be defined by the extent of DIMP detected above the detection limit of 0.392 ppb (for an approximation see Fig. 6). Thus, municipal water or an alternative water source will be supplied to 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 the ROD for the RMA Offpost Operable Unit (HLA, 1995). The remedy adopted will eliminate 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 from the RMA north and northwest boundaries to the South Platte River. In 71 of 89 samples collected from monitoring wells in the Offpost Study Area, DIMP was above the Certified Reporting Limit of 0.392 ppb (HLA, 1992a, Table 2.5). In general, the highest concentrations of DIMP offpost occur between the RMA northern boundary and the O'Brian Canal. The highest observed concentrations were 5800 ppb in the First Creek paleochannel and 860 ppb in the northwest paleochannel (HLA, 1992b, p. I-12, I-13).
The more recent DIMP concentrations in domestic drinking water wells through December 1993 are shown to range from 950 to 0.392 ppb (see Table 5A). The maximum detection of 950 ppb DIMP 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 supplied with bottled water. That well is now used as an irrigation well and as a monitoring well. Based upon sampling completed in April 1994, the concentration range of DIMP in both Alluvial and 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 Study Area north of both the northern and northwestern RMA boundaries. The highest concentrations of dieldrin have been found in wells located in the First Creek paleochannel, ranging from 0.6 to 0.87 ppb. Dieldrin plumes have also been interpreted in limited areas in the northern paleochannel and in two areas north of the northwestern RMA boundary. Detectable concentrations of dieldrin in the northern paleochannel and northwestern paleochannel ranged from 0.05 to 0.14 ppb (HLA, 1992b, p. I-13). Dieldrin was detected at 0.06 ppb in only one garden 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 wells immediately north of the northern RMA boundary. The maximum concentration of endrin was 0.748 ppb from monitoring well 37309, located approximately 1500 feet north of RMA. Endrin was also detected in groundwater samples collected from wells in the central portion of the northern paleochannel (HLA, 1992b, p. I-13). The 1990 - 1993 sampling of drinking water wells 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 other SVOCs detected include the pesticides atrazine, malathion, and parathion; the organosulfur compounds 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 organochlorine pesticides (OCPs). Atrazine was detected in 21 Offpost Study Area wells, with the maximum concentrations 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 distributions in offpost groundwater differ. CPMSO was generally only found in samples collected from wells installed in the northern paleochannel, whereas CPMSO2 was generally only found in samples collected from wells located in the First Creek paleochannel. CPMSO was generally found at levels higher than those reported for CPMSO2. CPMSO was detected at concentrations up to 82.2 ppb in the northern paleochannel. CPMSO2 was also detected in the First creek paleochannel at concentrations up to 21.0 ppb (HLA, 1992b, p. I-14). CPMSO and CPMSO2 were not detected in the Offpost Study Area drinking water wells samples collected during the 1990 -1993 sampling round (see Table 5A).
The distribution of the additional OCPs (aldrin, isodrin, chlordane, DDE, and DDT) is similar to the previously discussed distribution of the OCPs dieldrin and endrin. The maximum concentrations of these compounds generally occur in the First Creek paleochannel, usually in the area 500 to 1000 feet north of the NBCS. Generally, only sporadic, isolated occurrences of these compounds were observed in the Offpost Study Area north of the RMA northwestern boundary (HLA, 1992b, p.I-14).
Volatile Organic Compounds
The volatile organic compounds (VOCs) most frequently detected in the Offpost Study Area groundwater 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 been found primarily downgradient of the NWBCS and in the northern paleochannel. Chloroform was generally not found in the First Creek paleochannel. Concentrations of chloroform emanating from the northern RMA boundary are higher than concentrations in the Offpost Study Area north of the northwestern RMA boundary. The highest concentrations of chloroform measured in monitoring wells were at the north end of the northern paleochannel (200 to 400 ppb). The highest concentration of chloroform detected in the northwestern paleochannel was 19.8 ppb (HLA, 1992b, p. I-14). The range of chloroform detected in the 1990 - 1993 sampling of 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 potential concern (see Table 8). Those detections were largely limited to First Creek immediately north of 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 Burlington Canal/O'Brian Canal (HLA, 1992b, p. I-19). Distribution of the contaminants is very limited in extent and may be related to discharges from the RMA sewage treatment plant. As discussed in the 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 Offpost Study Area from the 1940s to the mid-1970s. Aldrin was used in the early 1950s to protect cotton against boll weevils and in the 1970s for soil application in grain crops and termite control. In Colorado, dieldrin was used to control insects in field vegetables, grain, and fruit crops 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 may still be used for certain restricted uses such as subsurface insertion for termite control and dipping non-food roots (HLA, 1992b, p. I-7).
ATSDR has reviewed the Offpost surface soil data incorporated in the RMAED database and has determined that chlordane (CLDAN), dieldrin (DLDRN), and arsenic (AS) occur in concentrations high enough to be considered contaminants of potential concern in the Offpost Study Area (see Table 9). However, the occurrence of those contaminants is relatively infrequent and concentrations average tens to hundreds of times lower than Onpost concentrations for those chemicals. Permissive evidence is presented in the Offpost Endangerment Assessment that suggests that eolian deposition of RMA-derived OCPs may be responsible for the slightly elevated levels of those pesticides detected immediately north of RMA (HLA, 1992b, p. I-18, Figs. 16-17). The highest levels of chlordane and dieldrin detected in the Offpost area seem to reflect a pattern more consistent with documented off site use of those pesticides (HLA, 1992a, p. 91-94). The arsenic detections may reflect natural soil variations and other non-RMA influences.
Sediment
ATSDR reviewed the Offpost sediment data recorded in RMAED (see Table 10) and did not note sediment contamination at levels of potential concern. The OCPs and DBCP were the most frequently detected, at levels below appropriate comparison values, and those detections were localized along First Creek. Scattered detections along the canal/ditch system were recorded but may 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 of Colorado and the EPA have conducted off-site monitoring and Offpost Study Area air quality conditions have been simulated from Onpost data. The data amassed on Offpost air quality is incorporated in the RMAED database. ATSDR reviewed the data generated from a data base query 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 Table 11).
The air quality data amassed Onpost and that incorporated in the EPA Toxic Chemical Release Inventory database (TRI, 1994) strongly suggest that the occurrence of most of the air contaminants 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 Arsenal indicates a possible Offpost source for all air-borne contaminants except 1,2-dichloroethane (12DCLE) and chlorobenzene (CLC6H5). Contamination sources for those chemicals in off-site locations beyond the Zip Codes queried in TRI or synthesis of those chemicals within the mix of ambient 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 Onpost wildlife species provides valuable information on potential levels of contamination in off post biota. A record of contaminant accumulation in Onpost biota for the interval from 1973 to 1984 was compiled in the Biota Remedial Investigation (ESE, 1989b). That record was supplemented with data collected for 1988 to 1990 for the Onpost Integrated Endangerment Assessment and Risk 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 or do travel to off-post locations, mallard ducks (mercury and dieldrin), pheasants (dieldrin), and mourning doves (aldrin, dieldrin, and endrin) have been found to contain levels of hazardous substances greater that FDA Action Levels. Some, but not all, of the higher levels of contaminant accumulation in those species are found in the earlier samples collected.
In 1993, the USFWS initiated the Biomonitoring Program (BMP) for the Rocky Mountain National Wildlife Refuge. Among the many objectives of that program, data is being gathered to ascertain in waterfowl using Onpost lakes and wetlands contain significant concentrations of contaminants. Because mourning doves use the Refuge but may be hunted and consumed off of the Refuge data has also been collected by USFWS to assist in the evaluation of the potential human health risk that may arise from consumption of these birds.
Table 12B gives the Onpost waterfowl and mourning dove contaminant accumulation data compiled by the USFWS for the 1994 BMP (see USFWS, 1995). Although not all data had been received when this assessment was prepared, the data indicate detectable dieldrin accumulation in 12 of 15 waterfowl samples of liver tissue analyzed and 3 of 8 mourning dove liver samples. Of those liver tissue detections only one waterfowl sample (0.373 ppm) and one mourning dove sample (0.533 ppm) exceeded the 0.3 ppm FDA Action Level. The maximum concentration of dieldrin detected in this suite of samples was 1.2 ppm dieldrin found in 4 redhead duck eggs. This same duck had the highest overall liver, brain, and muscle concentrations of dieldrin. The eggs also had the only detection of DDT (0.02 ppm) and the highest concentration of DDE (0.159 ppm). The highest liver concentration of DDE (0.035 ppm) was also found in this redhead duck. The male redhead collected with this female had the highest concentration of dieldrin in GI contents.
The two juvenile Canada geese were collected for the 1994 BMP because most geese on the RMA Refuge are resident and may indicate whether contaminant accumulation occurs on the Refuge. The dieldrin levels measured in those geese liver samples range from 0.029 to 0.039 ppb. which is in the low end of the range of the other waterfowl liver dieldrin values (0.023 to 0.373 ppm). These data indicate that waterfowl may be accumulating contaminants from the Refuge aquatic habitats (USFWS, 1995). However, the dieldrin, DDE, and HG levels detected in 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 ducks collected in 1994 would not represent a human health threat.
Examination of the historical data compiled in Table 12A shows that, in the past, analyses of mourning 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 of contaminants 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 this ecosystem the USFWS collected additional contaminant accumulation data on this species during 1994. A total of 12 birds were collected and samples of brain, liver, and muscle tissue analyzed 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 Table 12B.
Dieldrin was detected in 6 of 12 doves tested, but of those positive contaminant detections only one sample of liver tissue at 0.533 ppm dieldrin was above the FDA Action levels. Edible muscle tissue of those dove tested did not contain contaminant concentration above FDA Action Levels and the indication is, based on the 1994 data, that human consumption of mourning doves 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 terrestrial environments. Sampling for the Offpost RI was initiated in the spring of 1985 and was resumed in 1988-89 for the RI Addendum. Although contamination of resident game species on RMA was previously established, information on the possible movement of wildlife from RMA to Offpost areas was lacking. Species such as pheasants and cottontail rabbits that could transport Onpost contaminants to Offpost locations were emphasized in the investigations and were studied to delineate the size of the home ranges occupied by those species.
Absence of sufficient water in streams crossing RMA boundaries precludes movement of potentially contaminated fish, but the terrestrial species are not thus limited. Investigation of migratory waterfowl and mourning doves was not conducted Offpost because it was concluded that those species appear to present a lesser potential hazard to humans due to the large range movements associated with migration and the potential dispersal of individual birds that spend some 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 the organochlorine pesticides (OCPs) aldrin, dieldrin, endrin, DDE, and DDT (see Table 12A). The biota samples collected included wildlife species commonly considered suitable for human consumption: bluegill, carp, channel catfish, and ring-necked pheasant. Agricultural biota samples 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, about 300 ft north of RMA in section 14 (T2S, R67W) and just north of the NBCS. The OCP dieldrin was the contaminant found most often in biota of the Offpost Study Area. Cow fat, chicken tissue, fish and pheasants all had detectable concentrations of dieldrin. Aldrin, endrin, and DDT were not detected in any biological samples taken in the Offpost Study Area. Mercury was detected 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 DBCP contamination in cattle, led to testing of cow's milk produced in the Offpost area. DBCP was not detected in the milk samples analyzed (HLA, 1992a, p.106).
Inspection of the biota sampling data compiled in Table 12A reveals that, of the samples collected Offpost, only the level of dieldrin detected in pheasant liver tissue (0.380 ppm) exceeds the 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 the Offpost biota samples collected, ATSDR concludes that the only contaminant of potential concern suggested by the available data is the organochlorine pesticide (OCP) dieldrin. Dieldrin has 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, wet weight basis; EBASCO, 1993, Appendix C). It follows that, in addition to potential Onpost exposure to dieldrin, off post agricultural use of dieldrin is one of the possible sources of the dieldrin detected in pheasant tissue and liver analyzed in the Offpost Study Area. Regardless of the source, dieldrin is a potential contaminant of concern in off post pheasants, even though the 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 and mourning doves, particularly given the apparent declining trend over time, those contaminants and 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 uptake in Offpost vegetables, the Army developed a vegetable testing method to develop data to evaluate this concern. The Army asked Tri-County health Department to obtain samples of garden vegetables from Offpost sites to determine what concentrations of DIMP, if any, are in Offpost vegetables. The samples were collected from the garden of private residence north of RMA on October 12, 1995 and from two large vegetable farms on November 10, 1995. The private garden was selected by the Army because it is irrigated only with water from well 1178B which has higher concentrations of DIMP remaining than any other Offpost area well. The concentration of DIMP in that well have ranged from about 150 to 950 ppb. The commercial farms were selected because they utilize a combination of groundwater (DIMP <20 ppb) and surface water (uncontaminated by DIMP).
The concentration of DIMP in vegetables irrigated with well 1178B ranged from nondetect to 920 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 than predicted 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 of concern is 1.0) associated with consumption of vegetables. The actual concentrations measured would suggest an even lower hazard quotient. Thus, based upon the available data, there appears very little, if any, risk associated with the consumption of garden vegetables irrigated with well water 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 drinking water wells with a municipal water supply system throughout the Offpost area of DIMP detection in groundwater (>0.392 ppb) may largely eliminate the use of small irrigation wells and, thereby, further eliminate any residual risk that may be associated with the consumption of garden vegetables grown in this area.
Quality Assurance and Quality Control
We have reviewed the Quality Assurance/Quality Control (QA/QC) summary information associated with the many RI-related documents. Acceptable practices and standards have been incorporated in those studies. Some samples from RMA were sent to the Eureka Lab in California. Subsequently that laboratory has been removed from EPA's list of acceptable laboratories and data produced by that laboratory has not been used in the evaluation of contaminants at RMA. Otherwise, the data used in this Assessment appears to meet established QA/QC standards.
The existence of chemical warfare agents and unexploded ordnance (UXO) is and will, until final site cleanup is completed, continue to represent a hazard at RMA. IRAs have been designed and implemented to eliminate or reduce the potential hazard from agent and munitions remaining at RMA. Component 14 of the Conceptual Agreement (Colorado, 1995) and the Onpost ROD (Foster Wheeler, 1996) specifies that munitions and munitions wastes will be located, excavated, and, if necessary, destroyed. Disposal of the UXO and associated waste and soils will be in the Onpost hazardous waste landfill. After final site cleanup undiscovered chemical warfare agents and UXO may represent a very small ongoing hazard for future land uses and users at RMA. However, because of the nature of the final remedy selected for Onpost soils and structures (e.g. Foster Wheeler, 1996, Table 5.4-11), the remaining locations of any potential munitions wastes or UXO in surface or shallow subsoils will be known and 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 monitored throughout RMA history and agent compounds have been the focus of specific actions designed to mitigate the potential for their release to the environment. Furthermore, agents generally have short half-lives when exposed to the natural elements and, with the exception of mustard that may have been trapped in voids beneath buildings, are generally not persistent in soils. Agents occur within some buildings, containment vessels, piping, and other structures within which they were manufactured, handled, demilitarized, or stored.
Figure 2.2-1 given in the RISR (EBASCO, 1992) is a map of areas at RMA that are considered to 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 agent occurrences. 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 all references to agent occurrences noted. Individual CARs for those areas where agent presence at some time was referenced were reviewed by identifying on a map all locations and sample collection 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 for all agent detections was accomplished and compared and combined with the results of the literature review. Finally, a second review in the literature and by interview with knowledgeable individuals 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 weathering effects (e.g., in soils beneath a concrete pad), chemical warfare agents are highly unstable and very rapidly degrade to breakdown products which, though still considered contaminants, do not constitute 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 by historical documentation and individual deposition in the administrative record; an account of sample collection and handling protocols for potential agent occurrence is presented in Appendix A2 of the RISR (EBASCO, 1992).
RMA has also been used historically to manufacture, store, test, demilitarize, and dispose a variety of conventional munitions. RISR Figure 2.2-2 (EBASCO, 1992, p.2-26) is a map of areas 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 RI reports. The map was drawn conservatively as a "worst-case" scenario representing the maximum possible geographic extent of potential UXO occurrences. It is emphasized that the likelihood 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 former munitions testing and disposal areas.
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