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In this section ATSDR summarizes information concerning historical and current levels of bothon- and off-site contamination and identifies contaminants of potential current and future humanhealth concern. The tables in this section list those contaminants and concentrations of thosecontaminants measured in the various environmental media. ATSDR evaluates thosecontaminants in the subsequent sections of this public health assessment and determines whetherexposure to them has public health significance. Factors considered in the identification of the contaminants to be further evaluated include:

  • Concentrations of contaminants on and off the site;
  • Field data quality, laboratory data quality, and sample design;
  • Comparison of on-site and off-site concentrations with backgroundconcentrations, if available.

In the data tables that follow under the Onpost Contamination subsection and the Off-siteContamination subsection, listing of a contaminant does not mean that adverse health effectswill result from exposure to that contaminant. The human health implications of exposure tothose contaminants is discussed in the subsequent sections of the Assessment.

    The data tables include the following abbreviations:
  • CREG = Cancer Risk Evaluation Guide for 1x10-6 excess cancer risk
    • For soil or water = 10-6 x Body Weight (BW)/Ingestion Rate (IR) x Slope Factor (SF)
    • For air = 10-6/Reference Concentration (RfC)
  • EMEG = Environmental Media Evaluation Guide; c = child, a = adult
    • For soil or water = Minimal Risk Level (MRL) x BW/IR
    • For air = MRL
  • LTHA = Lifetime Health Advisory for drinking water (70-years)
  • L-THA = Longer-Term Health Advisory for drinking water (7-years)
  • MCLG = Maximum Contaminant Level Goal for drinking water
  • MCL = Maximum Contaminant Level for drinking water
  • ND = Not Detected
  • RMEG = Reference Dose Media Evaluation Guide; c = child, a = adult
    • For soil or water = Reference Dose (RfD) x BW/IR
    • For air = RfC
  • ppb = parts per billion (µg/L, g/kg)
  • ppm = parts per million (mg/L, µg/g)

For the purposes of the Remedial Investigation and this report, "target" analytes are those thatwere identified in advance of the field investigations and were deemed to have a high likelihoodof 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 quantitiesat 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 atvarying levels of confidence. Those tentatively identified compounds (TICs) differ from thetarget analytes in the degree of certification attached to the qualitative identification. Systematicreview of the TIC identified in the first phase(s) of investigation resulted in the addition offormer nontarget analytes to the list of analytes investigated in subsequent phase(s) of samplingand analysis. Of the more that 750 different chemicals handled or generated at the Arsenal, over90 were chosen as target (indicator) analytes for the remedial investigations, Onpost andOffpost. Those target analytes are also those surveyed by the environmental monitoringconducted subsequent to the RIs under the provisions of the Comprehensive MonitoringProgram (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 EnvironmentalDatabase (RMAED) and grouped by media. The data extracted is a record of all detectionsabove the Certified Reporting Limit (CRL), grouped by environmental media.

Tables 5-12 summarize the Onpost and Offpost contaminants of potential concern. Tables5A&B and 7 describe contaminants in the Offpost Study area and off-site areas west of RMAand will be discussed in the Offpost Contaminants subsection of this Assessment. The chemicalacronyms given in the tables and used in the text are the chemical acronyms defined and used inthe Army's RMAED and IRDMIS (similar to RMAED; the Army's nationwide InstallationRestoration Data Management Information System) databases. In some cases these acronymsdiffer from those used in other sources, but the RMAED/IRDMIS symbols were retained tofacilitate 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 extracteddirectly 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 thatspecies 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 contaminantsthat were frequently detected at or above levels of potential health concern are selected forfurther evaluation. The discussion that follows Tables 5-12 summarizes the areas most affectedby the selected contaminants.

In selecting the contaminants to be further evaluated in public health assessment, it is the policyof ATSDR to consider the concentration of those contaminants relative to various regulatory orhealth-based comparison values (CVs) and to the background levels that may have beendetermined for those chemicals. These CVs are used for the initial screening or selectionprocess 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 additionalscreening procedures to delimit the contaminants to be further evaluated in this Assessment. Inaddition to the comparison between the maximum detected value of the Target Analyte with thevalue of appropriate, regulatory- or health-based screening or comparison values, the followingfactors were also considered by ATSDR in the selection of the contaminants of concern:

  • Is the analyte detected frequently?
  • Is the average detected value also above the CV?
  • Have other analytes been detected from the analyte group of the chemical being evaluated, for which significant health effects are known?
  • Has the chemical being evaluated been found above CVs in other media at RMA? If so, which media?
  • Is the chemical being evaluated a public concern or a concern to public officials?
  • Are health studies being conducted in the RMA area for the chemical beingevaluated?

These additional criteria were applied in a qualitative sense to all those target analytes detectedin concentrations larger than the corresponding CVs. No specific cut-off values were developedfor use with these criteria, but rather, the overall or aggregate comparison of the analyte to thesescreening criteria was jointly reviewed by the health assessors studying the site and the lists ofpotential contaminants was formulated (see Table 5-12). When review of the contaminants of apotential pathway of human exposure indicated that and additional contaminant was important toconsider, it was added to tables.

Inclusion of an analyte in the lists given in Tables 5-12 does not imply that humanexposure to that contaminant will necessarily cause adverse health effects.

The remedial investigation reports prepared for the Onpost and Offpost Study Areas (seeEBASCO, 1992; ESE, 1988; and HLA, 1992a) document numerous source areas ofcontamination and the identify greatest relative concentration of environmental contamination inthe central portion of RMA surrounding the North and South Plants and the associatedwastewater storage and disposal facilities.

Also documented is the occurrence of isolated concentrations of specific contaminants that, insome cases, may be of high enough concentration to be of potential health concern. Onpost thenumber of those isolated "hot spots" of contamination is relatively low and as such, given thestatutory and regulatory limitations imposed on present and future RMA land use, they representrelatively little potential risk to human health. Likewise, in the Offpost areas, isolatedoccurrences of several contaminants are found. Those occurrences often show no pattern ofdistribution and probably do not specifically relate to RMA activities.

The contaminants of Onpost groundwater were not examined in detail for this Assessmentbecause use of Onpost groundwater is prohibited and because contaminated groundwater plumesare treated by the BCSs, IRA-A, or by the SACWSD Klein Treatment Plant before potentialoffpost use. Within the EPA Study Area of Commerce City the use of groundwater fromprivate, shallow alluvial aquifer wells for human consumption has been actively discouraged byEPA, CDPHE, and local health and water departments. Treated city water is supplied to thoseresidents in the Commerce City area and bottled water is currently supplied to residences of theOffpost Study Area with a trace or more of DIMP in their well water. The bottled water will bereplaced by a municipal water supply system or an alternative water supply throughout theDIMP "footprint area" (DIMP >0.392 ppb).

Toxic Chemical Release Inventory

In order to identify off-site sources that could possibly contribute to the contamination detectedat 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 ZipCode areas are 80022, 80207, 80216, 80229, 80239, 80240, and 80640. The TRI data base wasqueried for chemical releases reported within those Zip Codes for the years 1988, a year ofpotential 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 49chemical compounds to the air, land surface, and water that ranged in size from very small tolarge releases from local area manufacturing, processing, or other businesses. The chemicalcompounds released are predominately volatile and semivolatile organic compounds and, to alesser extent metals and metal compounds. The release inventory summary totals for 1988 and1991 are (in pounds):

  • Total air releases
  • 1,672,620 lbs901,705 lbs
  • Total water releases
  • 24,945 lbs38,758 lbs
  • Total land releases
  • 4,564 lbs160 lbs
  • Total environmental releases
  • 1,702,129 lbs940,623 lbs

    These off-site environmental releases will be discussed further in the following sections onOffpost air contamination and in the section on potential exposure pathways.

    Onpost Contamination

    Nature and Extent of Contamination

    Results of the Onpost remedial investigation have been published previously in 124Contamination Assessment Reports (CARs), 2 Data Presentation Reports, and 90 Phase II DataAddendum 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 contaminantsites); 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, withprimary emphasis on the soils/sewers environmental media. The findings of these numerousinvestigations have been summarize in the Remedial Investigation Summary Report (RISR;EBASCO, 1992). The contents of this summary report have been relied upon extensively in thecompilation of this overview of Onpost contamination.

    Chemicals routinely manufactured, handled, and stored at RMA over its 40-year history havebeen 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 withineach media to select "target" analytes (organic compounds and metals), and with sampleanalysis, the process for identification of "nontarget" analytes. The reader is referred to thatdiscussion for a more complete explanation of the identification of contaminants at RMA.

    Generally, the highest detected concentrations of contaminants were measured in samplescollected 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 centralportion of RMA. The most concentrated portions of contaminated plumes in the alluvial aquiferalso occur beneath contaminant sources in soils in the central, and to a lesser degree, in thewestern parts of RMA. Contaminant concentrations generally decrease as the groundwaterplumes migrate toward the western, northwestern, and northern RMA boundaries.

    Contaminant detections in air are generally lower in the Arsenal interior and are elevated nearthe 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 mobilespecies. A pattern of bioaccumulation at the upper end of the food-chain is apparent for dieldrinand, to a lesser extent, arsenic (cf. ESE, 1989b; HLA, 1992a, 1992b; EBASCO, 1992).

    Elevated contaminant concentrations detected in air, surface water, soil gas, and groundwatersamples collected at or near the southern and western RMA boundaries indicate that off-postsources have contributed to the contamination of those media (RMA, 1994).


    Consumption of Onpost groundwater is prohibited and the groundwater flow paths areintercepted by BCSs. Therefore, only generalized observations of Onpost groundwatercontamination are warranted here. Groundwater quality within RMA has been significantlyimpacted by contamination from numerous sources across the site (EBASCO, 1992). A largevariety of contaminants have been introduced into the groundwater from these sources and fromoffpost sources south and west of RMA. Principal contaminants of concern are volatile andsemi-volatile organic compounds, arsenic, fluoride, chloride, Army agent breakdowncompounds (e.g. DIMP), metals, organochlorine pesticides, and organosulfur herbicides.

    As a result of the multitude of sources, a complex array of groundwater contaminant plumesexists under RMA. Because of the intermingling of the plumes from the various sources and thevariety of contaminants emanating from the multiple sources, it is generally not possible toattribute specific plume components to specific source areas. Source areas within RMA wherecontamination is believed to have been introduced into the groundwater have been listedpreviously in Table 1.

    Because use of Onpost groundwater is prohibited and because the plumes of contaminatedgroundwater are intercepted and treated by the RMA Boundary Containment Systems beforebeing reinjected as treated water and entering offpost areas, ATSDR did not identifycontaminants of potential concern in the Onpost groundwater medium.

    ATSDR reviewed the groundwater contamination data amassed during the 1985-93 and 1990-94intervals by both the Offpost RI and the CMP, as well as the data gathered for the "EPA StudyArea" (OU2) of the Chemical Sales Company NPL site (CERCLIS No. COD007431620) andidentified the contaminants of potential concern in offpost groundwater (see Tables 5A & B and7). The reader is referred to the offpost groundwater contamination and offpost groundwaterpathways sections of this assessment for a discussion of the areal distribution and temporalpatterns of those contaminants.

    Surface Water

    Surface waters of RMA currently show little impact from previous contaminant releases, duelargely 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 surfacewaters at points of groundwater discharge or where surface runoff from contaminated soilscollects. Points where organic and inorganic contaminants have been introduced to surfacewater 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 wereplugged in 1992 and the treatment plant closed in 1994, were characterized by moderatelyelevated levels of inorganic analytes (EBASCO, 1992, p. A3-73-74).

    Historically, surface water transport was a major contaminant transport pathway, contributing tothe 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 mosthighly contaminated surface water samples were collected from the Basin A sampling station inSection 36 and the South Plants sedimentation pond in Section 1. Runoff from major stormevents or snow melt may transport contaminants present in surficial soils, although the efficiencyof this mechanism is limited for most areas. The transport of contaminants in surface waters ontoRMA from sources to the south has been documented, as has the past transport of contaminantsfrom RMA to off-post areas north of RMA.

    ATSDR reviewed the surface water contaminant data (1985-1993) incorporated in the RMAEDand selected the Onpost contaminants of potential concern given in Table 8.


    The major soil contaminants at RMA include pesticides, herbicides, lead, arsenic, copper, andagent degradation products. Mobile volatiles in soil consist of volatile halogenated organics,volatile hydrocarbons and volatile aromatic organics. Less mobile components includeorganochloride pesticides and arsenic.

    ATSDR reviewed the surface soil data (1985-93) incorporated in the RMAED and selected theOnpost contaminants of potential concern given in Table 9.


    As discussed in the Surface Water section above, surface waters of RMA are not currentlyaffected significantly, due to the reduction or elimination of water from most ditches anddisposal basins (EBASCO, 1992, p. A3-73). As a result, current RMA impact on sediments isexpected to be minimal. The detected concentrations of contaminants in sediments are, thereforedue 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 wereOCPs. A small number of samples showed the presence of metals, primarily cadmium, mercuryand arsenic (HLA, 1992a; Stollar, 1990).

    ATSDR reviewed the 1985-1993 sediment contamination data incorporated in the RMAED andselected the Onpost contaminants of potential concern given in Table 10. Of those contaminantslisted, only dieldrin has been detected in the Offpost at levels of potential concern.


    One of the major conclusions of the Onpost remedial investigations is that no ambient airproblems were detected (EBASCO, 1993, p. 8). The sampling conducted for the RI togetherwith those samples collected annually for the CMP characterize the on- and off-post influencesof RMA air quality. ATSDR has reviewed the air monitoring data compiled during the periodfrom 1985 through mid-1993. That data was obtained from a August 10, 1993 query of theRMAED. 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 haveimpacted RMA air quality, the reader is directed to the Offpost Operable Unit RemedialInvestigation (ESE, 1988, p. 2 - 24-28). Past episodes in RMA air quality and current conditionsare summarized in the annual Air Quality Data Assessment Reports (eg. Stollar, 1991). Thefollowing paragraphs generally summarize RMA air quality and also discuss the generalrelationship 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) theinflux of particulate from metropolitan Denver, and 2) remedial activity sources which help toproduce wind-blown dust, particularly during very dry periods. The TSP data amassed reflectsthe impact of the soil disturbing (excavating) phase of the Basin F IRA in 1988-89, with apronounced decrease in TSP levels around Basin F after conclusion of that phase of remedialactivities. During the height of those construction activities, the TSP levels monitored in 1988-89 decreased significantly with distance from the basin. During 1990, other constructionactivities such as in the vicinity of the Lower Derby Lake spillway, produced notable TSPeffects which were also very highly localized and decreased rapidly with distance from thesource. The record also documents episodes during which impacts from metropolitan Denvercompletely overwhelmed impacts from potential on-site RMA sources. At the eastern andnorthern boundaries of RMA, the TSP levels were well below those of metropolitan Denver andwere more representative of rural conditions.

    Respirable Particulate (PM-10)

    Respirable particulate are generated at RMA by dry windy conditions, but to a lesser extent thanfor 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 impactsalso decrease rapidly with distance from the source.


    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 IRAactivities, increases in air-borne mercury, chromium, copper, and zinc were measured. Thoseconcentrations decreased rapidly with increasing distance from Basin F. Following closure ofthe 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 volatileorganic compounds (VOCs) including bicycloheptadiene, dimethyl disulfide, benzene, toluene,and ethylbenzene. Some of the monitored emissions may have been from the heavy equipmentused 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 withdistance from the source, and levels detected at RMA boundaries were similar to or less thanthose within the urban- environment of metropolitan Denver. Monitoring conducted subsequentto 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 wereapparently released during the 1988-89 Basin F remediation efforts. The highest levels ofSVOCs 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 highestlevels of SVOCs, but at the RMA boundaries, the levels of SVOCs detected were reduced tonear-background levels. Subsequent air monitoring near Basin F has detected significantlyreduced SVOC concentrations, and all SVOC concentrations measured elsewhere at RMA wereclose to background values.

    Organochlorine Pesticides

    The organochlorine pesticides (OCPs) aldrin and dieldrin have been detected at low-levels nearthe detection limit at RMA boundaries. The highest levels detected were samples collectedduring the 1988-89 Basin F remediation effort and nearest to the Basin itself. Following thecompletion of that phase of remediation, OCP levels declined to near-background levels in thevicinity 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 othermonitoring sites in Denver. Episodes of high criteria pollutant concentrations correlate to daysof high contamination in the Denver metropolitan area or to episodes relating to other nearbypotential 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 aboveground storage tanks (about 4 million gallons) and in an engineered surface impoundment (about6.5 million gallons). The destruction of those toxic liquids was a subsequent phase of the BasinF IRA (see Table 2).

    Before the SQI was allowed to begin routine operations, a Trial Burn test burn programconsisting 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 characteristicsand the composition and concentrations of stack emissions. Based upon the performance andstack emissions data derived from the Trail Burn, the EPA approved interim operations underconservative conditions, well within human health risk limits delineated by the 1991 InterimResponse Action, Basin F Liquid Incineration Project, Draft - Human Health Risk Assessment(Weston, 1991). Subsequently EPA and the state of Colorado approved the final operatingconditions, which were well within the human health risk limits in the Final Human Health RiskAssessment for SQI (Weston, 1994).

    The Trial Burn data compiled indicated that the SQI operations were in compliance with federaland state guidelines for destruction and removal efficiency (DRE), particulate, hydrogenchloride (HCl), and carbon monoxide (CO) emissions while processing 18 gallons per minute of100% 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 organochloridepesticides (OCPs) and PCB compounds, and 25 organophosphorus pesticides (OPHPs). Asummary 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 forSuperfund (EPA, 1989b), the benchmark levels of human risk associated with the operation ofSQI described in the Final Decision Document for the IRA (Woodward-Clyde, 1990b), and thepredicted 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 be5.7E-09 to 6.3E-09 for potential off-site inhalation of arsenic in the ambient air and 2.9E-08 forpotential food chain ingestion of bis(ethylhexyl)phthalate, a compound of questioned validity inthe measured stack emissions (Weston, 1994, p. ES-5). Onpost arsenic inhalation risk wasassessed to be 1.4E-10. All values calculated were less than the benchmark 1E-06 cancer riskestablished for SQI. Likewise the noncancer risks calculated resulted in Hazard Index valueswell 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) wasincreased April 16, 1993, during the start-up phase of SQI. Every third-day sampling wasinitiated at four of RMA's air quality monitoring stations. Those stations, aligned roughly alongthe principal north-south wind direction, detected TSP, PM-10, HG, AS, metals, OCPs, andprimary gases at levels generally at or below pre-SQI baseline conditions. The concentrationsfor VOCs were also at or below pre-SQI baseline levels except for methylene chloride that wasepisodically elevated RMA-wide before and during part of the accelerated SQI samplinginterval. 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 disclosedetectable difference in ambient air quality that could be attributed to the operation of SQI underthe EPA-approved interim operating conditions (Larry Diede, EPA, March 1, 1994, personalcommunication).

    Atmospheric modeling conducted by Weston (1991) and reviewed and accepted by EPA, RegionVIII delineated very low levels of off post effects associated with SQI. The stack gas emissionsmonitored during the trial burn tests (Weston, 1993) and the CMP ambient air monitoringconducted describe Onpost and off post contaminant levels below that predicted in the DraftHuman Health Risk Assessment (Weston, 1991). The Final Human Health Risk Assessment forSQI (Weston, 1994) records the final evaluation of all test data and is the basis of the approvalfor 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 ofapproximately 11 million gallons of waste liquids. The SQI, storage tanks, and pond wereclosed in accordance with a CDPHE closure plan. The SQI was demolished an some of theprocess equipment was salvaged. All field and administrative closure activities were completedby May 30, 1996.


    During the remedial investigations (EBASCO, 1992; ESE, 1988; and HLA, 1992a) evaluationswere made of both animal and native plant tissue to determine potential contaminants ofconcern. The Biota CMP (Stoller, 1992) provides further site-specific information concerningcontaminant concentrations in RMA biota and comparisons to control sites, as well asinformation on accumulation or magnification of those contaminants in the foodchain. At thattime, no evaluation was made of agricultural plants but samples of cattle and chicken tissue, onechicken egg, and milk were analyzed. The principal contaminants found in tissue analyses arethe 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 FY1991, the USFWS, under Task 4 of the 1991 cooperative agreement with the Army, assumedresponsibility for the Biota portion of RMA's CMP. Collection and analysis of biologicalspecimens are continuing in order to more fully assess the health and dynamics of RMA wildlifeand to better understand what ecologic or human health risks may be poised by virtue of Onpostcontamination.

    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 inOnpost samples, especially dieldrin. The frequency of contaminant detections in Onpostsamples is also greater. For example, dieldrin was detected in about 60% of the Onpost samplesand in less than 6% of the Offpost samples. Additionally, comparison of analytical results overtime shows a trend of decreasing concentration of dieldrin in tissue samples of five taxonomicgroups sampled (i.e., adult mourning doves, grasshoppers, cheatgrass, sunflower, and juvenileblue-winged teal). A similar trend was also noted for endrin in adult mourning doves and DDEin sunflowers (EBASCO, 1994, p. 2-6).

    ATSDR reviewed the contaminant data amassed in the Biota RI, Offpost RI and Addendum, theCMP reports, and the Integrated Endangerment Assessment and compiled Table 12A which liststhose species commonly considered suitable for human consumption and the contaminantsdetected in those species. The paragraphs that follow are brief summaries of the character ofthose select "edible" wildlife species and the nature of the contaminant burden they carry. For amore detailed discussion of this topic, the reader is referred to the Integrated EndangermentAssessment/Risk Characterization (EBASCO, 1994, p. C.5-15 - C.5-44). Because fishing inRMA lakes is strictly regulated as a "catch and release" program, thereby eliminating humanconsumption (EPA, 1989), a discussion of Onpost aquatic species is not included here. Thespecies discussed in the following paragraphs cannot be hunted on the Arsenal, but can travel tooff-site locations where, in some areas, they may be hunted. Limitations to off-site hunting existnorth of RMA in Adams County where the discharge of firearms is prohibited west of Gun ClubRoad since 1980 and to the southeast of RMA on those lands annexed by Denver County(TCHD, 1994).


    Mule deer are more common and widespread at RMA than white-tailed deer because most of theOnpost habitat is more suitable for mule deer. White-tailed deer are essentially limited to thewooded and riparian areas of First Creek and the southern sections of RMA. Surveys show anabundant deer population at RMA. During the last four years (1989-93), the mule deerpopulation has doubled, while the white-tailed deer population has fluctuated around a relativelylower density, probably due to greater white-tail fawn susceptibility to coyote preditation. Herdpopulation and productivity studies indicate that the RMA deer populations are older than mosthunted herds (hunting of wildlife on RMA is prohibited). In fact, the cause of death of mostadult deer at RMA is old age. The good health of deer at RMA is indicated by the presence offat reserves at times of year when such reserves are not generally expected and by generallygood physical condition. Health problems have been observed in a few individuals includingretention of velvet in four deer, testicular atrophy in five deer, presence of an acid-fast bacteriumin one deer, and some abnormal hoof growth and pelage characteristics potentially diseaserelated.

    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 tissuesample (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 andcoots are susceptible to chemical contamination. At RMA those environmental media haveserved as contaminant sinks and, as a result, water bird populations have been affected. Severalepisodes of direct mortality of water birds as a result of exposure to chemical releases have beendocumented at various Onpost locations since the 1950s. An estimated minimum mortality of20,000 water birds occurred during the decade of the 1950's. In 1984 and 1986, fewer waterbird nests and broods were observed at RMA than would be indicated by habitat availability, andthere were no successful Mallard broods in 1986, while off-post reference areas exhibitednormal success. However, in 1988 through 1990, pre-flight-juvenile water birds were collectedand analyzed for contaminant burden and thus, some level of reproduction was occurring duringthose years. The relatively poor water bird reproduction success observed at RMA lakes may bethe results of contaminant effects, nest interference by fishermen, high levels of predation, orfluctuating lake levels due to remediation activities. Sampling conducted for the Biota RIdetected a low-level range of mercury (HG) in duck tissue and liver samples including a fewdetections as high as 8.9 and 21.8 ppm HG (ESE, 1989). The organochlorine pesticides were themost frequently detected contaminants. Of those, dieldrin was the most commonly detected andwas found in the range of 0.01-4.53 ppm (EBASCO, 1994, Appendix C-5), with an isolateddetection 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 thatrelative to an off-post reference area in Weld County, Colorado, pheasants are more abundant atRMA and conversely, the studies indicate mourning doves are less abundant at RMA. The dataalso suggests that pheasant and dove reproduction at RMA may be less successful at RMA thanin the off-post reference area. The apparent relative lack of reproductive success may be due toRMA contaminants, poorer habitat quality, or greater predatory pressure. As shown in Table12A, 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 ofcontaminants 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. Exposureto listed analytes does NOT implyadverse health effects will occur.
    Range of
    Comparison Value (ppb)
    & Source. EPA Cancer Class
    in ( )s.
    Volatile Halogenated Organics (VHOs)
    1,2-Dichloroethane (12DCLE)25.013.97/3884.58 - 1.572.592/1285 MCL; 0.4 CREG (B2)
    Chlorobenzene (CLC6H5)9.854.948/424NDND---100 MCL; 200 RMEG-child
    Chloroform (CHCL3)100.015.3779/52325.0 - 0.736.3619/128100 MCL (12); 6 CREG (B2)
    Tetrachloroethylene (TCLEE or PCE)81.88.9237/52014.7 - 0.9549.7210/1285.0 MCL; 0.7 CREG (B2)
    Volatile Hydrocarbons (VHCs)
    Dibromochloropropane (DBCP)0.440.3011/636NDND---0.2 MCL
    Volatile Aromatic Organics (VAOs)
    Benzene (C6H6)12.08.325/467NDND---5.0 MCL; 1.0 CREG (A)
    Organosulfur Compounds - HerbicideRelated (OSCHs)
    Chlorophenylmethyl sulfide (CPMS)2.301.563/474NDND---20 L-THA-child (13)
    Chlorophenylmethyl sulfone (CPMSO2)10.15.124/474NDND---20 L-THA-child
    Chlorophenylmethyl sulfoxide (CPMSO)17.08.588/474NDND---20 L-THA-child
    Organophosphorus Compounds -
    GB-Agent Related (OPHGBs)

    Diisopropylmethyl phosphonate (DIMP)1,620.072.61207/612950.0 - 0.39236.6191/158600 LTHA
    Dimethylmethyl phosphonate (DMMP)26.603.1311/5001.36 - 0.2160.534/159100 LTHA
    Atrazine (ATZ)5.815.234/2825.81 - 4.635.292/1053 LTHA
    Organochlorine Pesticides (OCPs)
    Aldrin (ALDRN)0.130.00316/505NDND---0.3 LTHA;0.002 CREG(B2)
    Chlordane (CLDAN)0.310.282/343NDND---2 MCL; 0.03 CREG (B2)
    Dieldrin (DLDRN)0.870.465/503NDND---2 EMEGa; 0.002 CREG(B2)
    Endrin (ENDRN)0.780.354/5090.270.271/1182.0 LTHA & MCL
    ICP Metals / Anions & Cations
    Arsenic (AS)14.46.7820/32514.0 - 2.518.146/11350 MCL; 0.02 CREG (B2)
    Lead (PB)119.067.2817/311119.0 - 65.287.5510/10615 EPA Action Level
    Mercury (HG)3.661.1023/3120.1070.1071/1052.0 MCL; 0.3 RMEG-child
    Nitrate (NIT)20,00017,173303/32526,000 - 25.48,057.589/8910,000 MCL
    Selenium (SE)24.7019.973/3no tests------50 MCL; 20 EMEG-child

    Table 5B - Denver/Arapahoe Aquifer Drinking Water Contaminants of Potential Concern - Offpost Study Area: Contaminant levelsDetected During the Period between 10/90 -12/93 (14)

    Table 5B.

    Human Health Effects at Various Hydrogen Sulfide Concentrations in Air
    Analyte Group/Analyte
    ** Inclusion of analytes in this table does NOT mean exposure tothe listed analytes will necessarily cause adverse health effects.**
    Range of 1990-1993
    Detections (ppb)
    Average of
    1990-1993 Detections
    Comparison Value (ppb)
    & Source. EPA Cancer
    Class in ( )s.
    Organophosphorus Compounds -
    GB-Agent Related (OPHGBs)
    Diisopropylmethyl phosphonate (DIMP)24.3 - 0.368.0234/132600 LTHA
    ICP Metals/Anions & Cations
    Arsenic (AS)14.4 - 2.736.737/11050 MCL; 0.02 CREG
    Lead (PB)18.6 - 5.0211.812/10015 EPA Action Level
    Nitrate (NIT)1,500,000 - 10.222,962.76/7910,000 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 tabledoes NOT mean exposure to the listed analyteswill necessarily cause adverse health effects.**
    FrequencyComparison Value (ppb)
    & Source
    Volatile Halogenated Organics

    1,1-Dichloroethylene (11DCE)58.08.745/183 (25%)7 MCL; 0.06 CREG C
    Chloroform (CHCL3)29.01.951/184 (27%)100 MCL (15); 6.0 CREGB2
    Tetrachloroethylene (TCLEE or PCE)4.52.049/185 (26%)5 MCL; 0.7 CREGB2/C
    Trichloroethylene (TRCLE or TCE)140.08.8123/185
    5.0 MCL; 3 CREGB2/C
    Volatile Aromatic Organics

    Benzene (C6H6)46.08.019/176 (11%)5 MCL; 1 CREGA
    Dibromochloropropane (DBCP)61.01.565/252 (26%)0.2 MCL

    ** Inclusion of analytes in this screening tabledoes NOT mean exposure to the listed analyteswill necessarily cause adverse health effects.**

    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).
    FrequencyComparison Value
    (ppb) & Source
    Volatile Halogenated Organics

    1,1-Dichloroethane (11DCLE)16.062 %NoneC
    1,2-Dichloroethene (12DCE)28.075 %7 MCL; 0.06 CREG C
    Tetrachloroethylene (TCLEE or PCE)120.073 %5 MCL; 0.7 CREGB2/C
    Trichloroethylene (TRCLE or TCE)190.089 %5.0 MCL; 3 CREGB2-C

    Table 8.

    Contaminants of Potential Concern: Surface Water - RMAED run of 8/10/93
    Analyte Groups/Analyte
    ** Inclusion of analytes in this screening tabledoes NOT mean exposure will necessarily causeadverse health effects.**
    Value (ppb) &
    EPA Cancer
    Volatile Halogenated Organics

    Chlorobenzene (CLC6H5)On7,500.01,028.6623/418100 MCL &

    Chloroform (CHCL3)On14,000.0568.6158/427100 MCL (16)
    6 CREG
    Tetrachloroethylene (TCLEE)On340.062.133/4235 MCL
    3 CREG
    Trichloroethylene (TRCLE)On270.046.7225/4233 MCL
    Volatile Hydrocarbons(VHCs)
    Dibromochloropropane (DBCP)On200.044.727/4580.2 MCL
    Dicyclopentadiene (DCPD)On101.035.8428/468None
    Volatile Aromatic Organics(VAOs)
    Benzene (C6H6)On2,800.0182.1623/4251 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 doesNOT mean exposure to listed analytes will necessarilycause adverse health effects.**
    Value (ppb) &
    EPA Cancer
    Organosulfur Compounds -
    Herbicide Related (OSCHs)

    Chlorophenylmethyl sulfide (CPMS)On120.046.9414/37620 L-THA (17)
    Chlorophenylmethyl sulfone (CPMSO2)On1,600.0298.3337/37620 L-THA
    Chlorophenylmethyl sulfoxide (CPMSO)On750.093.7525/37620 L-THA
    Organophosphorus Compounds -
    GB-Agent Related (OPHGBs)

    Diisopropylmethyl phosphonate (DIMP)On237.035.2118/413600 LTHA
    Atrazine (ATZ)On370.061.725/2763 LTHA &


    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 NOTmean exposure to the listed analytes will necessarilycause adverse health effects.**
    Value (ppb) &
    EPA Cancer
    Organochlorine Pesticides (OCPs)
    Aldrin (ALDRN)On122.05.8149/4360.002 CREG
    1 EMEG-adult
    Dieldrin (DLDRN)On60.86.3455/4400.002 CREG
    2 EMEG-adult
    Endrin (ENDRN)On25.03.0532/4402 MCL &

    Arsenic (AS)On20,00002,130.697/34650 MCL; 0.02
    Mercury (HG)On11.00.5558/3432 MCL
    ICP Metals
    Lead (PB)On585.091.2120/35615 EPA ActionLevel

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