PUBLIC HEALTH ASSESSMENT
ROCKY MOUNTAIN ARSENAL
ADAMS COUNTY, COLORADO
In this section ATSDR summarizes information concerning historical and current levels of both on- and off-site contamination and identifies contaminants of potential current and future human health concern. The tables in this section list those contaminants and concentrations of those contaminants measured in the various environmental media. ATSDR evaluates those contaminants in the subsequent sections of this public health assessment and determines whether exposure to them has public health significance. Factors considered in the identification of the contaminants to be further evaluated include:
In the data tables that follow under the Onpost Contamination subsection and the Off-site Contamination subsection, listing of a contaminant does not mean that adverse health effects will result from exposure to that contaminant. The human health implications of exposure to those contaminants is discussed in the subsequent sections of the Assessment.
For the purposes of the Remedial Investigation and this report, "target" analytes are those that were identified in advance of the field investigations and were deemed to have a high likelihood of being present at RMA based upon knowledge of the activities that occurred there. The "nontarget" analytes are those compounds that were not expected to be present in large quantities at RMA and that were not specifically analyzed for by a USAEC certified method. However, some of the analytical methods used permitted tentative identification of nontarget analytes at varying levels of confidence. Those tentatively identified compounds (TICs) differ from the target analytes in the degree of certification attached to the qualitative identification. Systematic review of the TIC identified in the first phase(s) of investigation resulted in the addition of former nontarget analytes to the list of analytes investigated in subsequent phase(s) of sampling and analysis. Of the more that 750 different chemicals handled or generated at the Arsenal, over 90 were chosen as target (indicator) analytes for the remedial investigations, Onpost and Offpost. Those target analytes are also those surveyed by the environmental monitoring conducted subsequent to the RIs under the provisions of the Comprehensive Monitoring Program (CMP).
To determine which RMA-related contaminants are potentially of public health concern, ATSDR reviewed the analytic data complied during the interval from 1985 through mid-1993. These data were selected because they have been subject to the most rigorous quality control and quality assurance procedures. The data review was extracted from the RMA Environmental Database (RMAED) and grouped by media. The data extracted is a record of all detections above the Certified Reporting Limit (CRL), grouped by environmental media.
Tables 5-12 summarize the Onpost and Offpost contaminants of potential concern. Tables 5A&B and 7 describe contaminants in the Offpost Study area and off-site areas west of RMA and will be discussed in the Offpost Contaminants subsection of this Assessment. The chemical acronyms given in the tables and used in the text are the chemical acronyms defined and used in the Army's RMAED and IRDMIS (similar to RMAED; the Army's nationwide Installation Restoration Data Management Information System) databases. In some cases these acronyms differ from those used in other sources, but the RMAED/IRDMIS symbols were retained to facilitate possible future comparisons of the data recorded here with future RMAED queries. The frequency of detection given in those tables is the number of detections recorded for all the samples obtained and analyzed for that media, during the specified time interval.
Data for contaminants detected in Onpost and Offpost biota (see Table 12A) was extracted directly from the Offpost RI (ESE, 1988), the RI Addendum (HLA, 1992a), the Onpost Biota RI (ESE, 1989), and the Integrated Endangerment Assessment (EBASCO, 1993) to ensure that species and contaminant data was properly paired.
Many of the contaminants found in or near RMA have been detected at specific sites, or site-types. Others are ubiquitous throughout the affected area, on- and off-post. The contaminants that were frequently detected at or above levels of potential health concern are selected for further evaluation. The discussion that follows Tables 5-12 summarizes the areas most affected by the selected contaminants.
In selecting the contaminants to be further evaluated in public health assessment, it is the policy of ATSDR to consider the concentration of those contaminants relative to various regulatory or health-based comparison values (CVs) and to the background levels that may have been determined for those chemicals. These CVs are used for the initial screening or selection process undertaken to identify those contaminants that may need to be evaluated for their public health implications.
Because more than 90 Target Analytes were suspected at RMA, ATSDR used additional screening procedures to delimit the contaminants to be further evaluated in this Assessment. In addition to the comparison between the maximum detected value of the Target Analyte with the value of appropriate, regulatory- or health-based screening or comparison values, the following factors were also considered by ATSDR in the selection of the contaminants of concern:
These additional criteria were applied in a qualitative sense to all those target analytes detected in concentrations larger than the corresponding CVs. No specific cut-off values were developed for use with these criteria, but rather, the overall or aggregate comparison of the analyte to these screening criteria was jointly reviewed by the health assessors studying the site and the lists of potential contaminants was formulated (see Table 5-12). When review of the contaminants of a potential pathway of human exposure indicated that and additional contaminant was important to consider, it was added to tables.
Inclusion of an analyte in the lists given in Tables 5-12 does not imply that human exposure to that contaminant will necessarily cause adverse health effects.
The remedial investigation reports prepared for the Onpost and Offpost Study Areas (see EBASCO, 1992; ESE, 1988; and HLA, 1992a) document numerous source areas of contamination and the identify greatest relative concentration of environmental contamination in the central portion of RMA surrounding the North and South Plants and the associated wastewater storage and disposal facilities.
Also documented is the occurrence of isolated concentrations of specific contaminants that, in some cases, may be of high enough concentration to be of potential health concern. Onpost the number of those isolated "hot spots" of contamination is relatively low and as such, given the statutory and regulatory limitations imposed on present and future RMA land use, they represent relatively little potential risk to human health. Likewise, in the Offpost areas, isolated occurrences of several contaminants are found. Those occurrences often show no pattern of distribution and probably do not specifically relate to RMA activities.
The contaminants of Onpost groundwater were not examined in detail for this Assessment because use of Onpost groundwater is prohibited and because contaminated groundwater plumes are treated by the BCSs, IRA-A, or by the SACWSD Klein Treatment Plant before potential offpost use. Within the EPA Study Area of Commerce City the use of groundwater from private, shallow alluvial aquifer wells for human consumption has been actively discouraged by EPA, CDPHE, and local health and water departments. Treated city water is supplied to those residents in the Commerce City area and bottled water is currently supplied to residences of the Offpost Study Area with a trace or more of DIMP in their well water. The bottled water will be replaced by a municipal water supply system or an alternative water supply throughout the DIMP "footprint area" (DIMP >0.392 ppb).
Toxic Chemical Release Inventory
In order to identify off-site sources that could possibly contribute to the contamination detected at or near RMA, a search of the Toxic Chemical Release Inventory (TRI, 1994) was conducted. Reporting locations within Zip Codes areas surrounding the Arsenal were searched. Those Zip Code areas are 80022, 80207, 80216, 80229, 80239, 80240, and 80640. The TRI data base was queried for chemical releases reported within those Zip Codes for the years 1988, a year of potential health concern, and 1991, the most recent year incorporated in that database.
In general, the data extracted for the years 1988 and 1991 discloses releases of about 49
chemical compounds to the air, land surface, and water that ranged in size from very small to
large releases from local area manufacturing, processing, or other businesses. The chemical
compounds released are predominately volatile and semivolatile organic compounds and, to a
lesser extent metals and metal compounds. The release inventory summary totals for 1988 and
1991 are (in pounds):
| 1988 | 1991 | |
| 1,672,620 lbs | 901,705 lbs | |
| 24,945 lbs | 38,758 lbs | |
| 4,564 lbs | 160 lbs | |
| 1,702,129 lbs | 940,623 lbs |
These off-site environmental releases will be discussed further in the following sections on Offpost air contamination and in the section on potential exposure pathways.
Nature and Extent of Contamination
Results of the Onpost remedial investigation have been published previously in 124 Contamination Assessment Reports (CARs), 2 Data Presentation Reports, and 90 Phase II Data Addendum Reports prepared for each potential hazardous waste site and for each nonsource area (the balance of each square-mile section on post not considered likely to contain contaminant sites); 4 media reports, prepared for the water, structures, air, and biota environmental media; and 7 Study Area Reports (SARs), prepared for each geographical study area at RMA, with primary emphasis on the soils/sewers environmental media. The findings of these numerous investigations have been summarize in the Remedial Investigation Summary Report (RISR; EBASCO, 1992). The contents of this summary report have been relied upon extensively in the compilation of this overview of Onpost contamination.
Chemicals routinely manufactured, handled, and stored at RMA over its 40-year history have been detected on post in the soil/sewers, water, air, structures, and biota environmental media. The RISR (EBASCO, 1992, p. A2 - 1-91) documents a systematic, reiterative process within each media to select "target" analytes (organic compounds and metals), and with sample analysis, the process for identification of "nontarget" analytes. The reader is referred to that discussion for a more complete explanation of the identification of contaminants at RMA.
Generally, the highest detected concentrations of contaminants were measured in samples collected from soils, surface water, and groundwater in the central sections of RMA (EBASCO, 1992, p. A3-1). Most of the structures classified as contaminated are located in the central portion of RMA. The most concentrated portions of contaminated plumes in the alluvial aquifer also occur beneath contaminant sources in soils in the central, and to a lesser degree, in the western parts of RMA. Contaminant concentrations generally decrease as the groundwater plumes migrate toward the western, northwestern, and northern RMA boundaries.
Contaminant detections in air are generally lower in the Arsenal interior and are elevated near the RMA boundaries, especially at monitoring stations nearest population centers (cf. Stollar, 1991; Weston, 1994).
The distribution of target analytes in biota is sporadic and subject to variable habitats for mobile species. A pattern of bioaccumulation at the upper end of the food-chain is apparent for dieldrin and, to a lesser extent, arsenic (cf. ESE, 1989b; HLA, 1992a, 1992b; EBASCO, 1992).
Elevated contaminant concentrations detected in air, surface water, soil gas, and groundwater samples collected at or near the southern and western RMA boundaries indicate that off-post sources have contributed to the contamination of those media (RMA, 1994).
Groundwater
Consumption of Onpost groundwater is prohibited and the groundwater flow paths are intercepted by BCSs. Therefore, only generalized observations of Onpost groundwater contamination are warranted here. Groundwater quality within RMA has been significantly impacted by contamination from numerous sources across the site (EBASCO, 1992). A large variety of contaminants have been introduced into the groundwater from these sources and from offpost sources south and west of RMA. Principal contaminants of concern are volatile and semi-volatile organic compounds, arsenic, fluoride, chloride, Army agent breakdown compounds (e.g. DIMP), metals, organochlorine pesticides, and organosulfur herbicides.
As a result of the multitude of sources, a complex array of groundwater contaminant plumes exists under RMA. Because of the intermingling of the plumes from the various sources and the variety of contaminants emanating from the multiple sources, it is generally not possible to attribute specific plume components to specific source areas. Source areas within RMA where contamination is believed to have been introduced into the groundwater have been listed previously in Table 1.
Because use of Onpost groundwater is prohibited and because the plumes of contaminated groundwater are intercepted and treated by the RMA Boundary Containment Systems before being reinjected as treated water and entering offpost areas, ATSDR did not identify contaminants of potential concern in the Onpost groundwater medium.
ATSDR reviewed the groundwater contamination data amassed during the 1985-93 and 1990-94 intervals by both the Offpost RI and the CMP, as well as the data gathered for the "EPA Study Area" (OU2) of the Chemical Sales Company NPL site (CERCLIS No. COD007431620) and identified the contaminants of potential concern in offpost groundwater (see Tables 5A & B and 7). The reader is referred to the offpost groundwater contamination and offpost groundwater pathways sections of this assessment for a discussion of the areal distribution and temporal patterns of those contaminants.
Surface Water
Surface waters of RMA currently show little impact from previous contaminant releases, due largely to the reduction or elimination of water from most ditches and disposal basins (EBASCO, 1992, p. A3-73). RMA-related contaminants are introduced to the onpost surface waters at points of groundwater discharge or where surface runoff from contaminated soils collects. Points where organic and inorganic contaminants have been introduced to surface water in detectable concentrations include Basin A and the South Plants sedimentation pond. Water flowing into First Creek from the sewage treatment plant, until the sanitary sewers were plugged in 1992 and the treatment plant closed in 1994, were characterized by moderately elevated levels of inorganic analytes (EBASCO, 1992, p. A3-73-74).
Historically, surface water transport was a major contaminant transport pathway, contributing to the rapid and efficient spread of contaminants in basins, ditches, lakes, ponds, and land at RMA. Use of the disposal ditches and process water system has now been discontinued. The two most highly contaminated surface water samples were collected from the Basin A sampling station in Section 36 and the South Plants sedimentation pond in Section 1. Runoff from major storm events or snow melt may transport contaminants present in surficial soils, although the efficiency of this mechanism is limited for most areas. The transport of contaminants in surface waters onto RMA from sources to the south has been documented, as has the past transport of contaminants from RMA to off-post areas north of RMA.
ATSDR reviewed the surface water contaminant data (1985-1993) incorporated in the RMAED and selected the Onpost contaminants of potential concern given in Table 8.
Soils
The major soil contaminants at RMA include pesticides, herbicides, lead, arsenic, copper, and agent degradation products. Mobile volatiles in soil consist of volatile halogenated organics, volatile hydrocarbons and volatile aromatic organics. Less mobile components include organochloride pesticides and arsenic.
ATSDR reviewed the surface soil data (1985-93) incorporated in the RMAED and selected the Onpost contaminants of potential concern given in Table 9.
Sediment
As discussed in the Surface Water section above, surface waters of RMA are not currently affected significantly, due to the reduction or elimination of water from most ditches and disposal basins (EBASCO, 1992, p. A3-73). As a result, current RMA impact on sediments is expected to be minimal. The detected concentrations of contaminants in sediments are, therefore due primarily to past practices.
Sediments were sampled from Onpost lakes and ponds, the Offpost Barr Lake, diversion ditches, and natural drainages on- and offpost. A wide variety of contaminants, including VOCs, SVOCs, organochlorine pesticides (OCPs) and metals were detected in Onpost sediments. During Offpost sampling activities in 1986 and 1988, the primary target analytes detected were OCPs. A small number of samples showed the presence of metals, primarily cadmium, mercury and arsenic (HLA, 1992a; Stollar, 1990).
ATSDR reviewed the 1985-1993 sediment contamination data incorporated in the RMAED and selected the Onpost contaminants of potential concern given in Table 10. Of those contaminants listed, only dieldrin has been detected in the Offpost at levels of potential concern.
Air
One of the major conclusions of the Onpost remedial investigations is that no ambient air problems were detected (EBASCO, 1993, p. 8). The sampling conducted for the RI together with those samples collected annually for the CMP characterize the on- and off-post influences of RMA air quality. ATSDR has reviewed the air monitoring data compiled during the period from 1985 through mid-1993. That data was obtained from a August 10, 1993 query of the RMAED. The air contaminants of potential concern identified are given in Table 11.
For an excellent overview of on- and off-post air quality and historical events that may have impacted RMA air quality, the reader is directed to the Offpost Operable Unit Remedial Investigation (ESE, 1988, p. 2 - 24-28). Past episodes in RMA air quality and current conditions are summarized in the annual Air Quality Data Assessment Reports (eg. Stollar, 1991). The following paragraphs generally summarize RMA air quality and also discuss the general relationship between the high levels of RMA air contamination, the Basin F remediation effort, and off-post sources.
Total Suspended Particulate
Total suspended particulate (TSP) at RMA can be attributed to two principle sources: 1) the influx of particulate from metropolitan Denver, and 2) remedial activity sources which help to produce wind-blown dust, particularly during very dry periods. The TSP data amassed reflects the impact of the soil disturbing (excavating) phase of the Basin F IRA in 1988-89, with a pronounced decrease in TSP levels around Basin F after conclusion of that phase of remedial activities. During the height of those construction activities, the TSP levels monitored in 1988-89 decreased significantly with distance from the basin. During 1990, other construction activities such as in the vicinity of the Lower Derby Lake spillway, produced notable TSP effects which were also very highly localized and decreased rapidly with distance from the source. The record also documents episodes during which impacts from metropolitan Denver completely overwhelmed impacts from potential on-site RMA sources. At the eastern and northern boundaries of RMA, the TSP levels were well below those of metropolitan Denver and were more representative of rural conditions.
Respirable Particulate (PM-10)
Respirable particulate are generated at RMA by dry windy conditions, but to a lesser extent than for TSP. No violations of the annual or PM-10 standards have been noted at RMA. Remediation activities have resulted in minor, localize increases in PM-10 levels. Those impacts also decrease rapidly with distance from the source.
Metals
Ambient concentrations of metals across RMA are generally proportional to levels of TSP. Maximum concentrations have been detected on high wind-speed days. During Basin F IRA activities, increases in air-borne mercury, chromium, copper, and zinc were measured. Those concentrations decreased rapidly with increasing distance from Basin F. Following closure of the basin in 1989, the monitored levels of metals decreased to baseline conditions.
Volatile Organic Compounds
During the Basin F remediation, on-site activities appeared to be the source of several volatile organic compounds (VOCs) including bicycloheptadiene, dimethyl disulfide, benzene, toluene, and ethylbenzene. Some of the monitored emissions may have been from the heavy equipment used during the remediation. Chloroform was identified near Basin F and the South Plants. VOCs released during the 1988-89 Basin F remediation activities decreased rapidly with distance from the source, and levels detected at RMA boundaries were similar to or less than those within the urban- environment of metropolitan Denver. Monitoring conducted subsequent to that Basin F remediation activities showed a significant decline in the level of most VOCs. The VOCs detected during the 1989-90 CMP (Stollar, 1991) were attributed to near-by off-Arsenal sources.
Semi-Volatile Organic Compounds
Several semi-volatile organic compounds (SVOCs) including aldrin, dieldrin, and endrin were apparently released during the 1988-89 Basin F remediation efforts. The highest levels of SVOCs detected were in the immediate vicinity of Basin F during those remediation efforts. Data collected downwind from and at the northeast perimeter of Basin F showed the highest levels of SVOCs, but at the RMA boundaries, the levels of SVOCs detected were reduced to near-background levels. Subsequent air monitoring near Basin F has detected significantly reduced SVOC concentrations, and all SVOC concentrations measured elsewhere at RMA were close to background values.
Organochlorine Pesticides
The organochlorine pesticides (OCPs) aldrin and dieldrin have been detected at low-levels near the detection limit at RMA boundaries. The highest levels detected were samples collected during the 1988-89 Basin F remediation effort and nearest to the Basin itself. Following the completion of that phase of remediation, OCP levels declined to near-background levels in the vicinity of Basin F as well.
Criteria Pollutants
The ambient concentrations of the criteria pollutants, including sulfur dioxide, nitrogen dioxide, carbon monoxide, and ozone measured at RMA have generally been cleaner than at other monitoring sites in Denver. Episodes of high criteria pollutant concentrations correlate to days of high contamination in the Denver metropolitan area or to episodes relating to other nearby potential sources.
The Submerged Quench Incinerator
The Submerged Quench Incinerator (SQI), constructed specifically to incinerate Basin F liquids, was selected as the preferred alternative to destroy Basin F liquids that were stored in above ground storage tanks (about 4 million gallons) and in an engineered surface impoundment (about 6.5 million gallons). The destruction of those toxic liquids was a subsequent phase of the Basin F IRA (see Table 2).
Before the SQI was allowed to begin routine operations, a Trial Burn test burn program consisting of three runs performed under identical test conditions was conducted on June 10-12, 1993. The objectives of the Trial Burn were to monitor incinerator performance characteristics and the composition and concentrations of stack emissions. Based upon the performance and stack emissions data derived from the Trail Burn, the EPA approved interim operations under conservative conditions, well within human health risk limits delineated by the 1991 Interim Response Action, Basin F Liquid Incineration Project, Draft - Human Health Risk Assessment (Weston, 1991). Subsequently EPA and the state of Colorado approved the final operating conditions, which were well within the human health risk limits in the Final Human Health Risk Assessment for SQI (Weston, 1994).
The Trial Burn data compiled indicated that the SQI operations were in compliance with federal and state guidelines for destruction and removal efficiency (DRE), particulate, hydrogen chloride (HCl), and carbon monoxide (CO) emissions while processing 18 gallons per minute of 100% Basin F liquid at an average incinerator temperature of 1,835 F (Weston, 1993).
Stack emissions were sampled for 69 semi-volatile organic compounds, 28 organochloride pesticides (OCPs) and PCB compounds, and 25 organophosphorus pesticides (OPHPs). A summary of those sampling results is given in the Final Trial Burn Report (Weston, 1993).
The Trial Burn results were evaluated consistent with the EPA Risk Assessment Guidance for Superfund (EPA, 1989b), the benchmark levels of human risk associated with the operation of SQI described in the Final Decision Document for the IRA (Woodward-Clyde, 1990b), and the predicted emissions and associated risks as analyzed in the Draft Human Health Risk Assessment (Weston, 1994). The calculated cancer risk for various subpopulations was determined to be 5.7E-09 to 6.3E-09 for potential off-site inhalation of arsenic in the ambient air and 2.9E-08 for potential food chain ingestion of bis(ethylhexyl)phthalate, a compound of questioned validity in the measured stack emissions (Weston, 1994, p. ES-5). Onpost arsenic inhalation risk was assessed to be 1.4E-10. All values calculated were less than the benchmark 1E-06 cancer risk established for SQI. Likewise the noncancer risks calculated resulted in Hazard Index values well below the benchmark risk of 1E+00 established for this facility (Weston, 1994, p. ES-6).
Based upon the findings of the Final Human Health Risk Assessment for SQI (Weston, 1994), the incinerator began operating under routine operating conditions in April, 1994.
Ambient Air Monitoring and the SQI
The ambient air sampling frequency of the Comprehensive Monitoring Program (CMP) was increased April 16, 1993, during the start-up phase of SQI. Every third-day sampling was initiated at four of RMA's air quality monitoring stations. Those stations, aligned roughly along the principal north-south wind direction, detected TSP, PM-10, HG, AS, metals, OCPs, and primary gases at levels generally at or below pre-SQI baseline conditions. The concentrations for VOCs were also at or below pre-SQI baseline levels except for methylene chloride that was episodically elevated RMA-wide before and during part of the accelerated SQI sampling interval. Off-site sources of that VOC are suggested (Jim Armstrong, EBASCO, March 7, 1994, personal communication). Thus, the data compiled during this interval did not disclose detectable difference in ambient air quality that could be attributed to the operation of SQI under the EPA-approved interim operating conditions (Larry Diede, EPA, March 1, 1994, personal communication).
Atmospheric modeling conducted by Weston (1991) and reviewed and accepted by EPA, Region VIII delineated very low levels of off post effects associated with SQI. The stack gas emissions monitored during the trial burn tests (Weston, 1993) and the CMP ambient air monitoring conducted describe Onpost and off post contaminant levels below that predicted in the Draft Human Health Risk Assessment (Weston, 1991). The Final Human Health Risk Assessment for SQI (Weston, 1994) records the final evaluation of all test data and is the basis of the approval for routine operation granted by EPA and the state of Colorado.
The SQI was shut down in July 1995 following the successful completion of the treatment of approximately 11 million gallons of waste liquids. The SQI, storage tanks, and pond were closed in accordance with a CDPHE closure plan. The SQI was demolished an some of the process equipment was salvaged. All field and administrative closure activities were completed by May 30, 1996.
Biota
During the remedial investigations (EBASCO, 1992; ESE, 1988; and HLA, 1992a) evaluations were made of both animal and native plant tissue to determine potential contaminants of concern. The Biota CMP (Stoller, 1992) provides further site-specific information concerning contaminant concentrations in RMA biota and comparisons to control sites, as well as information on accumulation or magnification of those contaminants in the foodchain. At that time, no evaluation was made of agricultural plants but samples of cattle and chicken tissue, one chicken egg, and milk were analyzed. The principal contaminants found in tissue analyses are the organochlorine pesticides (OCPs), arsenic, and mercury (see Table 12A).
By 1993, the Biota CMP resulted in the collection of more than 1,200 biological samples. In FY 1991, the USFWS, under Task 4 of the 1991 cooperative agreement with the Army, assumed responsibility for the Biota portion of RMA's CMP. Collection and analysis of biological specimens are continuing in order to more fully assess the health and dynamics of RMA wildlife and to better understand what ecologic or human health risks may be poised by virtue of Onpost contamination.
The data collected discloses that biota of the central portion of RMA are the most contaminated. In comparison to Offpost samples, contaminant concentrations in tissue samples are higher in Onpost samples, especially dieldrin. The frequency of contaminant detections in Onpost samples is also greater. For example, dieldrin was detected in about 60% of the Onpost samples and in less than 6% of the Offpost samples. Additionally, comparison of analytical results over time shows a trend of decreasing concentration of dieldrin in tissue samples of five taxonomic groups sampled (i.e., adult mourning doves, grasshoppers, cheatgrass, sunflower, and juvenile blue-winged teal). A similar trend was also noted for endrin in adult mourning doves and DDE in sunflowers (EBASCO, 1994, p. 2-6).
ATSDR reviewed the contaminant data amassed in the Biota RI, Offpost RI and Addendum, the CMP reports, and the Integrated Endangerment Assessment and compiled Table 12A which lists those species commonly considered suitable for human consumption and the contaminants detected in those species. The paragraphs that follow are brief summaries of the character of those select "edible" wildlife species and the nature of the contaminant burden they carry. For a more detailed discussion of this topic, the reader is referred to the Integrated Endangerment Assessment/Risk Characterization (EBASCO, 1994, p. C.5-15 - C.5-44). Because fishing in RMA lakes is strictly regulated as a "catch and release" program, thereby eliminating human consumption (EPA, 1989), a discussion of Onpost aquatic species is not included here. The species discussed in the following paragraphs cannot be hunted on the Arsenal, but can travel to off-site locations where, in some areas, they may be hunted. Limitations to off-site hunting exist north of RMA in Adams County where the discharge of firearms is prohibited west of Gun Club Road since 1980 and to the southeast of RMA on those lands annexed by Denver County (TCHD, 1994).
Deer
Mule deer are more common and widespread at RMA than white-tailed deer because most of the Onpost habitat is more suitable for mule deer. White-tailed deer are essentially limited to the wooded and riparian areas of First Creek and the southern sections of RMA. Surveys show an abundant deer population at RMA. During the last four years (1989-93), the mule deer population has doubled, while the white-tailed deer population has fluctuated around a relatively lower density, probably due to greater white-tail fawn susceptibility to coyote preditation. Herd population and productivity studies indicate that the RMA deer populations are older than most hunted herds (hunting of wildlife on RMA is prohibited). In fact, the cause of death of most adult deer at RMA is old age. The good health of deer at RMA is indicated by the presence of fat reserves at times of year when such reserves are not generally expected and by generally good physical condition. Health problems have been observed in a few individuals including retention of velvet in four deer, testicular atrophy in five deer, presence of an acid-fast bacterium in one deer, and some abnormal hoof growth and pelage characteristics potentially disease related.
Tissue analyses indicate that both deer species are relatively free of contaminant accumulation. The highest level of dieldrin detected in deer was 0.281 ppm in one mule deer liver tissue sample (EBASCO, 1994, Appendix C-5). No other contaminants have been reported.
Mallards and other Water Birds
By virtue of their close association with surface water bodies and sediments, waterfowl and coots are susceptible to chemical contamination. At RMA those environmental media have served as contaminant sinks and, as a result, water bird populations have been affected. Several episodes of direct mortality of water birds as a result of exposure to chemical releases have been documented at various Onpost locations since the 1950s. An estimated minimum mortality of 20,000 water birds occurred during the decade of the 1950's. In 1984 and 1986, fewer water bird nests and broods were observed at RMA than would be indicated by habitat availability, and there were no successful Mallard broods in 1986, while off-post reference areas exhibited normal success. However, in 1988 through 1990, pre-flight-juvenile water birds were collected and analyzed for contaminant burden and thus, some level of reproduction was occurring during those years. The relatively poor water bird reproduction success observed at RMA lakes may be the results of contaminant effects, nest interference by fishermen, high levels of predation, or fluctuating lake levels due to remediation activities. Sampling conducted for the Biota RI detected a low-level range of mercury (HG) in duck tissue and liver samples including a few detections as high as 8.9 and 21.8 ppm HG (ESE, 1989). The organochlorine pesticides were the most frequently detected contaminants. Of those, dieldrin was the most commonly detected and was found in the range of 0.01-4.53 ppm (EBASCO, 1994, Appendix C-5), with an isolated detection of 81.6 ppm dieldrin in one mallard sample (ESE, 1989b).
Upland Game Birds
Upland game birds such as ring-necked pheasants and mourning doves are present at RMA.
Studies conducted to assess the impact of contaminants on those upland game birds found that
relative to an off-post reference area in Weld County, Colorado, pheasants are more abundant at
RMA and conversely, the studies indicate mourning doves are less abundant at RMA. The data
also suggests that pheasant and dove reproduction at RMA may be less successful at RMA than
in the off-post reference area. The apparent relative lack of reproductive success may be due to
RMA contaminants, poorer habitat quality, or greater predatory pressure. As shown in Table
12A, arsenic, mercury, organochlorine pesticides, organosulfur compounds - herbicide related,
and dibromochloropropane (DBCP) have been detected in Onpost pheasants or mourning doves.
With few exceptions, the most frequent historical detections of and the highest levels of
contaminants have been found in the mourning dove samples.
Table 5A - Alluvial/Unknown Aquifer Drinking Water Contaminants of Potential Concern - Offpost Study Area: Comparison of
Historical Detections (1985-93) with Levels Detected During the Period Between 10/90-12/93 (11)
| Analyte Group/Analyte List is for screening purposes. Exposure to listed analytes does NOT imply adverse health effects will occur. |
Maximum Historical Detection (ppb) |
Average Historical Detections (ppb) |
Historical Frequency (1985-93) |
Range of 1990-1993 Detections (ppb) |
Average 1990-1993 Detections (ppb) |
1990-1993 Detection Frequency |
Comparison Value (ppb) & Source. EPA Cancer Class in ( )s. |
| Volatile Halogenated Organics (VHOs) | |||||||
| 1,2-Dichloroethane (12DCLE) | 25.0 | 13.9 | 7/388 | 4.58 - 1.57 | 2.59 | 2/128 | 5 MCL; 0.4 CREG (B2) |
| Chlorobenzene (CLC6H5) | 9.85 | 4.94 | 8/424 | ND | ND | --- | 100 MCL; 200 RMEG-child |
| Chloroform (CHCL3) | 100.0 | 15.37 | 79/523 | 25.0 - 0.73 | 6.36 | 19/128 | 100 MCL (12); 6 CREG (B2) |
| Tetrachloroethylene (TCLEE or PCE) | 81.8 | 8.92 | 37/520 | 14.7 - 0.954 | 9.72 | 10/128 | 5.0 MCL; 0.7 CREG (B2) |
| Volatile Hydrocarbons (VHCs) | |||||||
| Dibromochloropropane (DBCP) | 0.44 | 0.30 | 11/636 | ND | ND | --- | 0.2 MCL |
| Volatile Aromatic Organics (VAOs) | |||||||
| Benzene (C6H6) | 12.0 | 8.32 | 5/467 | ND | ND | --- | 5.0 MCL; 1.0 CREG (A) |
| Organosulfur Compounds - Herbicide Related (OSCHs) | |||||||
| Chlorophenylmethyl sulfide (CPMS) | 2.30 | 1.56 | 3/474 | ND | ND | --- | 20 L-THA-child (13) |
| Chlorophenylmethyl sulfone (CPMSO2) | 10.1 | 5.12 | 4/474 | ND | ND | --- | 20 L-THA-child |
| Chlorophenylmethyl sulfoxide (CPMSO) | 17.0 | 8.58 | 8/474 | ND | ND | --- | 20 L-THA-child |
| Organophosphorus Compounds - GB-Agent Related (OPHGBs) |
|||||||
| Diisopropylmethyl phosphonate (DIMP) | 1,620.0 | 72.61 | 207/612 | 950.0 - 0.392 | 36.61 | 91/158 | 600 LTHA |
| Dimethylmethyl phosphonate (DMMP) | 26.60 | 3.13 | 11/500 | 1.36 - 0.216 | 0.53 | 4/159 | 100 LTHA |
| Triazines | |||||||
| Atrazine (ATZ) | 5.81 | 5.23 | 4/282 | 5.81 - 4.63 | 5.29 | 2/105 | 3 LTHA |
| Organochlorine Pesticides (OCPs) | |||||||
| Aldrin (ALDRN) | 0.13 | 0.003 | 16/505 | ND | ND | --- | 0.3 LTHA;0.002 CREG(B2) |
| Chlordane (CLDAN) | 0.31 | 0.28 | 2/343 | ND | ND | --- | 2 MCL; 0.03 CREG (B2) |
| Dieldrin (DLDRN) | 0.87 | 0.46 | 5/503 | ND | ND | --- | 2 EMEGa; 0.002 CREG(B2) |
| Endrin (ENDRN) | 0.78 | 0.35 | 4/509 | 0.27 | 0.27 | 1/118 | 2.0 LTHA & MCL |
| ICP Metals / Anions & Cations | |||||||
| Arsenic (AS) | 14.4 | 6.78 | 20/325 | 14.0 - 2.51 | 8.14 | 6/113 | 50 MCL; 0.02 CREG (B2) |
| Lead (PB) | 119.0 | 67.28 | 17/311 | 119.0 - 65.2 | 87.55 | 10/106 | 15 EPA Action Level |
| Mercury (HG) | 3.66 | 1.10 | 23/312 | 0.107 | 0.107 | 1/105 | 2.0 MCL; 0.3 RMEG-child |
| Nitrate (NIT) | 20,000 | 17,173 | 303/325 | 26,000 - 25.4 | 8,057.5 | 89/89 | 10,000 MCL |
| Selenium (SE) | 24.70 | 19.97 | 3/3 | no tests | --- | --- | 50 MCL; 20 EMEG-child |
Table 5B - Denver/Arapahoe Aquifer Drinking Water Contaminants of Potential Concern - Offpost Study Area: Contaminant levels
Detected During the Period between 10/90 -12/93 (14)
| Analyte Group/Analyte ** Inclusion of analytes in this table does NOT mean exposure to the listed analytes will necessarily cause adverse health effects. ** |
Range of 1990-1993 Detections (ppb) |
Average of 1990-1993 Detections (ppb) |
1990-1993 Detection Frequency |
Comparison Value (ppb) & Source. EPA Cancer Class in ( )s. |
| Organophosphorus Compounds - GB-Agent Related (OPHGBs) | ||||
| Diisopropylmethyl phosphonate (DIMP) | 24.3 - 0.36 | 8.02 | 34/132 | 600 LTHA |
| ICP Metals/Anions & Cations | ||||
| Arsenic (AS) | 14.4 - 2.73 | 6.73 | 7/110 | 50 MCL; 0.02 CREG (B2) |
| Lead (PB) | 18.6 - 5.02 | 11.81 | 2/100 | 15 EPA Action Level |
| Nitrate (NIT) | 1,500,000 - 10.2 | 22,962.7 | 6/79 | 10,000 MCL |
Table 6 - Contaminants of Potential Concern: Onpost Alluvial Aquifer Groundwater Contributing to Irondale/Western
Plume (RMA monitoring results from 4/84-2/89; source EBASCO, 1992, p. A3 - 114-11).
| Analyte Groups/Analyte ** Inclusion of analytes in this screening table does NOT mean exposure to the listed analytes will necessarily cause adverse health effects.** |
Maximum Detect (ppb) |
Average Detect (ppb) |
Frequency | Comparison Value (ppb) & Source |
EPA Cancer Class |
| Volatile Halogenated Organics (VHOs) |
|||||
| 1,1-Dichloroethylene (11DCE) | 58.0 | 8.7 | 45/183 (25%) | 7 MCL; 0.06 CREG | C |
| Chloroform (CHCL3) | 29.0 | 1.9 | 51/184 (27%) | 100 MCL (15); 6.0 CREG | B2 |
| Tetrachloroethylene (TCLEE or PCE) | 4.5 | 2.0 | 49/185 (26%) | 5 MCL; 0.7 CREG | B2/C |
| Trichloroethylene (TRCLE or TCE) | 140.0 | 8.8 | 123/185 (66%) |
5.0 MCL; 3 CREG | B2/C |
| Volatile Aromatic Organics (VAOs) |
|||||
| Benzene (C6H6) | 46.0 | 8.0 | 19/176 (11%) | 5 MCL; 1 CREG | A |
| Dibromochloropropane (DBCP) | 61.0 | 1.5 | 65/252 (26%) | 0.2 MCL | |
Table 7 - Contaminants of Potential Concern: Off-Post Alluvial Aquifer Groundwater - Irondale/Western Plume
(EPA sampling in Chem. Sales Co. OU2 - 1987, 1988, 1989; source CDPHE, 1992a, p. 20).
| Analyte Groups/Analyte ** Inclusion of analytes in this screening table does NOT mean exposure to the listed analytes will necessarily cause adverse health effects.** |
Maximum Detect (ppb) |
Frequency | Comparison Value (ppb) & Source |
EPA Cancer Class |
| Volatile Halogenated Organics (VHOs) |
||||
| 1,1-Dichloroethane (11DCLE) | 16.0 | 62 % | None | C |
| 1,2-Dichloroethene (12DCE) | 28.0 | 75 % | 7 MCL; 0.06 CREG | C |
| Tetrachloroethylene (TCLEE or PCE) | 120.0 | 73 % | 5 MCL; 0.7 CREG | B2/C |
| Trichloroethylene (TRCLE or TCE) | 190.0 | 89 % | 5.0 MCL; 3 CREG | B2-C |
Table 8 - Contaminants of Potential Concern: Surface Water - RMAED run of 8/10/93
| Analyte Groups/Analyte ** Inclusion of analytes in this screening table does NOT mean exposure will necessarily cause adverse health effects.** |
On-/Off- Post |
Maximum Detect (ppb) |
Average Detect (ppb) |
Frequency | Comparison Value (ppb) & Source |
EPA Cancer Class |
| Volatile Halogenated Organics (VHOs) |
||||||
| Chlorobenzene (CLC6H5) | On | 7,500.0 | 1,028.66 | 23/418 | 100 MCL & LTHA |
|
| Chloroform (CHCL3) | On | 14,000.0 | 568.61 | 58/427 | 100 MCL (16) 6 CREG |
B2 |
| Tetrachloroethylene (TCLEE) | On | 340.0 | 62.1 | 33/423 | 5 MCL 3 CREG |
B2-C |
| Off | 7.34 | 3.65 | 4/143 | |||
| Trichloroethylene (TRCLE) | On | 270.0 | 46.72 | 25/423 | 3 MCL | |
| Volatile Hydrocarbons(VHCs) | ||||||
| Dibromochloropropane (DBCP) | On | 200.0 | 44.7 | 27/458 | 0.2 MCL | |
| Dicyclopentadiene (DCPD) | On | 101.0 | 35.84 | 28/468 | None | |
| Off | 48.4 | 20.34 | 12/147 | |||
| Volatile Aromatic Organics(VAOs) | ||||||
| Benzene (C6H6) | On | 2,800.0 | 182.16 | 23/425 | 1 MCL | |
Table 8 (continued) - Contaminants of Potential Concern: Surface Water - RMAED run of 8/10/93
| Analyte Groups/Analyte ** Inclusion of analytes in this screening table does NOT mean exposure to listed analytes will necessarily cause adverse health effects.** |
On-/Off- Post |
Maximum Detect (ppb) |
Average Detect (ppb) |
Frequency | Comparison Value (ppb) & Source |
EPA Cancer Class |
| Organosulfur Compounds - Herbicide Related (OSCHs) |
||||||
| Chlorophenylmethyl sulfide (CPMS) | On | 120.0 | 46.94 | 14/376 | 20 L-THA (17) | |
| Chlorophenylmethyl sulfone (CPMSO2) | On | 1,600.0 | 298.33 | 37/376 | 20 L-THA | |
| Off | 170.0 | 64.867 | 3/145 | |||
| Chlorophenylmethyl sulfoxide (CPMSO) | On | 750.0 | 93.75 | 25/376 | 20 L-THA | |
| Off | 1,200.0 | 617.95 | 2/145 | |||
| Organophosphorus Compounds - GB-Agent Related (OPHGBs) |
||||||
| Diisopropylmethyl phosphonate (DIMP) | On | 237.0 | 35.21 | 18/413 | 600 LTHA | |
| Off | 550.0 | 68.36 | 14/154 | |||
| Triazines | ||||||
| Atrazine (ATZ) | On | 370.0 | 61.7 | 25/276 | 3 LTHA & MCL |
|
| Off | 12.2 | 8.17 | 8/60 | |||
Table 8 (continued) - Contaminants of Potential Concern: Surface Water - RMAED run of 8/10/93
| Analyte Groups/Analyte ** inclusion of analytes in this scoping table does NOT mean exposure to the listed analytes will necessarily cause adverse health effects.** |
On-/Off- Post |
Maximum Detect (ppb) |
Average Detect (ppb) |
Frequency | Comparison Value (ppb) & Source |
EPA Cancer Class |
| Organochlorine Pesticides (OCPs) | ||||||
| Aldrin (ALDRN) | On | 122.0 | 5.81 | 49/436 | 0.002 CREG 1 EMEG-adult |
B2 |
| Off | 0.117 | 0.113 | 3/137 | |||
| Dieldrin (DLDRN) | On | 60.8 | 6.34 | 55/440 | 0.002 CREG 2 EMEG-adult |
B2 |
| Off | 6.7 | 1.019 | 7/140 | |||
| Endrin (ENDRN) | On | 25.0 | 3.05 | 32/440 | 2 MCL & LTHA |
|
| Anions/Cations | ||||||
| Arsenic (AS) | On | 20,0000 | 2,130.6 | 97/346 | 50 MCL; 0.02 CREG |
A |
| Off | 280.0 | 15.42 | 30/108 | |||
| Mercury (HG) | On | 11.0 | 0.55 | 58/343 | 2 MCL | |
| ICP Metals | ||||||
| Lead (PB) | On | 585.0 | 91.21 | 20/356 | 15 EPA Action Level | |
| Off | 65.4 | 41.73 | 3/112 | |||
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