PUBLIC HEALTH ASSESSMENT
ROCKY MOUNTAIN ARSENAL
ADAMS COUNTY, COLORADO
Off-Site Sources of Contaminants
Off-site sources of contaminants are included here in recognition of their relative importance in contributing to Onpost contamination of surface water and groundwater. Surface water and groundwater contamination that enters RMA along the southern boundary is notable. Routes of surface water transport from offpost sources to the south include the Peoria and Havana Interceptors. Contaminants in surface water entering RMA from the south include volatile organic compounds, organophosphorus and organosulfur compounds, semivolatile halogenated organics, pesticides, arsenic, and zinc. Concentrations are within the range of surface water contamination observed elsewhere at RMA. The occurrence of many of these compounds is consistent with manufacturing and industrial activity south of RMA (EBASCO, 1992, p. 2-22).
Groundwater entering RMA from the south and southeast contains detectable nitrate, VOCs, and VOC-associated breakdown products. Numerous sites contribute to the groundwater contamination of the area such as the Chemical Sales Company site, a major source of trichloroethane (TRCLE or TCE) contamination (discussed below) or a site at 49th and Havana, less than one and one-half miles upgradient of the Western Study Area, a documented source of tetrachloroethene (TCLEE or PCE) and TCE contamination to groundwater (EBASCO, 1992, 2-22; CDM, 1993, p 5-24).
Plumes originating off-post merge with RMA plumes as they follow alluvial paleochannels that flow under the Western Study Area. The VOC and nitrate plume that flows below the Western Study Area and eventually flows off-post at the western boundary appears to consist largely of contamination originating off-post (EBASCO, 1992, p. 2-22; CDM, 1993, p. 6-1 - 6-15).
EPA Studies and the EPA Study Area (Chemical Sales Company)
In 1981, a random national survey of drinking water systems was conducted by EPA. The sampling and analyses completed during this survey detected several organic chemicals in the South Adams County Water and Sanitation District (SACWSD) wells. Additional sampling in 1982 and 1985 confirmed these results. As a result of these findings, EPA began an RI/FS of an area located west of RMA and south of the RMA Offpost Study Area and OU (HLA, 1992b, p. I-9).
RMA was suspected as one of the potential sources of contaminants in the EPA Study Area because of the history of waste disposal practices on that site. In response, the Army constructed the Klein Water Treatment Plant for SACWSD. Further investigation by EPA's Field Investigation Team indicated that source areas other than RMA were contributing to much of the groundwater contamination detected within the study area. Groundwater monitoring wells installed on the Chemical Sales Company site, an NPL site (CERCLIS No. COD0077431620) and a major source of contamination, and elsewhere in and adjacent to the northern portion of the former Stapleton International Airport have since confirmed that there are several sources of groundwater contamination west and south of RMA (HLA, 1992b, p. I-9; CDM, 1993).
Several sources of trichloroethene have been documented south of Offpost Study Area in or near Commerce City. Also, investigations by EPA and the Army along the western sections of RMA have detected the presence of a trichloroethene plume entering Township 3 South, Range 67 West (T3S, R67W), Section 9 along the southern boundary of RMA. Although trichloroethene has been detected in selected dewatering wells and the influent sump of the Irondale system, no trichloroethene has been detected in the effluent sump of the system. Because of the potential for multiple trichloroethene sources upgradient of the Offpost Study Area, trichloroethene detected in the area between 80th and 88th Avenues remains under the jurisdiction of EPA, apart from the remediation process underway at RMA (HLA, 1992b, p. I-10; Shell, 1995).
RMA Offpost Study Area and Operable Unit
A RMA Offpost Study Area was initially established to assess potential effects of RMA-related contamination beyond the RMA boundary. On the basis of north and northwesterly flow directions of groundwater and surface water, the boundary of the Offpost Study Area was defined to include the area bound by 80th Avenue, the South Platte River, Second Creek, and the north and northwest boundaries of RMA. The Offpost Study Area also includes the surface waters of Barr Lake, the O'Brian Canal, and Burlington Ditch from 80th Avenue to Barr Lake (see Figure 2).
The Offpost Operable Unit is defined by the RMA Federal Facility Agreement (USEPA, 1989, p.15) as that portion of the Offpost Study Area where hazardous substances, pollutants, or contaminants from RMA that require remediation (HLA, 1992b, p. I-1). The Offpost OU originally encompassed the entire Offpost Study Area north of RMA, but as data has been gathered and the extent of contamination defined, the Offpost OU has been reduced in size and is now defined as a portion of the Offpost Study Area north of RMA and is designated as the contaminated groundwater within the unconfined flow system (alluvial aquifer; see Fig. 5) that require remediation (HLA, 1995).
As a result of the detection of chemicals in the Offpost Study Area, the Army initiated a regional sampling of hydrogeologic surveillance program requiring the quarterly collection and analysis of samples from more than 100 onpost and offpost wells and surface-water stations. This program was carried out under the direction of the RMA Contamination Control Program, established in 1974 to ensure compliance with federal and state environmental laws. The objectives of this program were to evaluate the nature and extent of contamination and to develop response actions to control chemical migration. Potential and actual chemical sources were assessed, and chemical migration pathways were evaluated. As a result of this evaluation the three previously discussed groundwater intercept and treatment systems (ICS, NWBCS, and NBCS) were constructed to minimize offpost discharge of RMA chemicals via groundwater. All three systems are currently in operation to intercept and treat contaminated groundwater and to recharge treated water (HLA, 1992b, p. I-8).
From 1975 to the present, numerous groundwater monitoring programs have been conducted at RMA. The Army designed and implemented the 360 Degree Monitoring Program to monitor regional groundwater and surface water. The Army designed and implemented the boundary system monitoring program to support the operation of the boundary control systems (HLA, 1992b, p. I-8).
The RMA Offpost Contamination Assessment Report (CAR) (ESE, 1987a) incorporated data from several studies to depict the distribution and concentrations of offpost contamination north and northwest of RMA. The scope of this investigation was intended to address critical data gaps required to evaluate a comprehensive set of multimedia exposure pathways. In the mid-1980s, the potential for contamination of private wells was investigated. These were referred to as Consumptive Use (CU) Studies, Phases I, II, and III. The CU Phase I and Il studies (ESE, 1985; ESE, 1986) addressed the RMA offpost area bounded to the south by East 80th Avenue, to the northwest by the South Platte River, and to the east by Second Creek (HLA, 1992b, p. I-8, I-9).
In the CU Phase III study (ESE, 1987b), the Army conducted an inventory of privately owned drinking water wells in an area bound by East 80th Avenue on the south, East 96th Avenue on the north, the South Platte River on the west, and RMA on the east. The objectives of the study were as follows: locate all shallow domestic wells (less than 100 feet) in the study area, sample a representative number of the located wells, and assess the groundwater quality of the shallow alluvial aquifer (HLA, 1992b, p. I-9).
Data collection consisted of compiling new hydrogeologic and chemical data relevant to the Offpost Study Area. Data were obtained by drilling new wells and borings, collecting groundwater and surface water samples for analysis, measuring groundwater levels and surface water flows, conducting aquifer tests, and obtaining sediment samples for analysis (HLA, 1992b, p. I-11).
The Offpost Operable Unit RI (ESE, 1988) assessed the possible off-site effects of RMA-related contamination throughout a 27 sq mi area. The highest levels of the groundwater contamination were found to lie in the area between the north boundary of RMA and the Burlington Ditch. Here, two major groundwater plume groups have been delineated as shown in Figure 5. Those plume groups are termed the North Plume Group (north and northwest of the RMA north boundary) and the Northwest Plume Group (west and north of the RMA northwest boundary). Those plumes of contaminated groundwater will be discussed in greater detail in subsequent sections of this Assessment.
Surface water and sediment samples were collected in the Offpost Study Area to define chemicals in the media. Samples were collected from streams, creeks, impoundments, and lakes that were suspected pathways for migration of onpost contamination to the Offpost Study Area. The data were used to evaluate contamination in surface water and sediment as well as to evaluate surface water and groundwater interaction (HLA, 1992b, p. I-11).
Biota and air-quality condition were evaluated using onpost and offpost information collected during past and current studies. Input from the Offpost CAR was used to assess transport of chemicals and impacts on biota in the Offpost Study Area from onpost conditions. Data from the Onpost Air RI Report (ESE, 1988) were used to assess the potential for migration of airborne chemicals to the Offpost Study Area (HLA, 1992b, p. I-11).
The Offpost Operable Unit RI Addendum (HLA, 1992a) was prepared to document further Assessment of the extent of contamination in various media (groundwater, soil, surface water, sediment, and biota) within specific geographic areas.
The Offpost remedial investigations (ESE, 1988; HLA, 1992a) conducted at RMA found contaminants present in groundwater, surface water, soil, and sediment in the Offpost Study Area north and northwest of RMA. Additionally, the data presented in the Offpost RI and Addendum indicate that the areas south and east of RMA, including the Montbello community area, have not been contaminated by RMA-related chemicals. The Offpost risk assessment (HLA, 1992b) concluded that, consistent with EPA definitions, the levels of contamination in surface water, soil, and sediment do not pose an unacceptable threat to human health or to the environment. Therefore, groundwater contamination is the focus of the Offpost OU (USEPA, 1993; HLA, 1995).
On June 13, 1995, after public comments had been received on this public health assessment, the U.S. Army, Shell Oil Company, the state of Colorado, the U.S. Environmental Protection Agency, and the U.S. Fish and Wildlife Service signed an "Agreement for a Conceptual Remedy for the Cleanup of the Rocky Mountain Arsenal" ("the Conceptual Agreement"; Colorado, 1995). The Conceptual Agreement incorporates 28 specific components of the conceptual remedy that were incorporated in the sitewide alternatives for water, structures, and soil as presented in the final Detailed Analysis of Alternatives report and carried forward as integral components in the Proposed Plan released in October 1995 (RMA, 1995). Some of the conceptual remedy components are integral components of both the on-post and off-post remedial programs that were considered in the selection of the preferred alternatives.
The ROD for the Offpost Operable Unit incorporates the Offpost components of the Agreement (Colorado, 1995) and was signed December 19, 1995 (HLA, 1995). Similarly, the Onpost ROD, signed June 11, 1996, also incorporates the relevant components of the Conceptual Agreement (Foster Wheeler, 1996). The selected remedy recorded in those RODs is extensive and thorough. Soil cleanup activities may take as long as 18 years to complete, but other components of the final cleanup, such as actions undertaken as IRAs or ongoing BCSs, are in-place and operative now.
The 28 specific components outlined in the Conceptual Agreement which form the conceptual basis for the final cleanup decisions incorporated in the RODs include provisions for Onpost cleanup of surface and subsurface soils in specific locations, for UXO clearance, and for demolition and disposal of all contaminated structures. The decisions recorded in the RODs provide for the ongoing operation of all existing groundwater pump and treatment systems including the Irondale, Northwest Boundary, and North Boundary containment systems as well as the system installed north of the RMA boundary in the Offpost area. Further, the RODs provide that the U.S. Army and Shell Oil Company will, working with the South Adams County Water and Sanitation District (SACWSD), provide 4,000 acre feet of water, a system of water distribution lines, and individual residence hook-ups for all existing well owners within the Offpost area delineated by the plume of DIMP-contaminated groundwater. The extent of that plume, the DIMP "Footprint Area", will be determined as that area where the last quarterly groundwater monitoring results detects DIMP at levels greater than 0.392 ppb (the current detection limit for DIMP). The RODs also specify that, if DIMP is subsequently detected at levels greater than 8 ppb in additional existing or newly drilled wells, the Army and Shell will pay for hook-up to the water distribution system or provide a deep well or other permanent solution.
The combined effect of the numerous components of the final remedial actions to be undertaken in the Onpost and Offpost areas will be to eliminate or greatly minimize potential human exposure to RMA contaminants and thereby result in a final cleanup that is protective of human health. In this context, this public health assessment is descriptive of the potential human health hazards associated with the Onpost and Offpost areas of RMA prior to the completion of the final remediation tasks.
ATSDR staff, Dr. W. Mark Weber, Ms. Linda West, and Dr. Glenn Tucker, the regional representative, made a site visit to RMA March 22-26, 1993. Other agencies also in attendance were the U.S. Environmental Protection Agency, Colorado Department of Public Health & Environment, Rocky Mountain Arsenal personnel and contractors, and the U.S. Fish and Wildlife Service. Representatives from Shell were also present. On the first day, on-post and off-post areas of RMA were surveyed and the following observations were noted:
Offsite, a windshield survey was conducted to view the off-site neighborhoods and rural areas. The western and southern offpost areas are more densely populated than the remaining segments of the perimeter. Residential and commercial development occurs on the western boundary of RMA in the Commerce City and Montbello areas. Some small home gardens were observed in this area. In the northwestern and northern offpost areas development is less dense and more lands are devoted to agricultural uses or left vacant. Remedial investigations have termed this northwest and north area the Offpost Study Area. Many of the lands being used for agricultural purposes in the Offpost Area utilize either sprinkler or ditch irrigation systems. Truck-farming products from those lands include sweet corn, cucumbers, tomatoes, beans (Connally Mears, EPA, 03/23/93, personal communication, site visit) and cabbage (Jeff Edson, CDPHE, 03/24/93, personal communication, site visit). Private wells are used for both irrigation and for domestic purposes. In those areas where DIMP has been detected at any level in domestic wells, CDPHE has supplied bottled water. A large turf farm and a small auto salvage business were also observed in this area.
East of RMA there are a few scattered houses and mobile homes and fields devoted to dry-land agriculture and grazing livestock. The new Denver International Airport was being constructed on those lands at a distance of 3-9 mi east of the RMA boundary. Airport and access road construction was occurring during the time of the site visit.
The Montbello neighborhood is located adjacent to the southeastern RMA boundary and is largely a residential neighborhood with numerous homes, some small gardens, schools, day care facilities, businesses, restaurants, and other related commercial facilities. The southwestern boundary area contains primarily light and heavy industry. The northernmost runway extension of Denver's now closed Stapleton International Airport lies in this area and the main terminal facilities are 3-4 mi south of the RMA boundary.
Several local agencies provided information about RMA. Those agencies include: Colorado Department of Public Health & Environment, Colorado State University, Tri-County Health Department, South Adams County Water and Sanitation District, and Adams County Planning and Development. Citizens and elected officials also provided information. Pertinent information has been incorporated from those representatives into appropriate sections of this public health assessment.
Demographics, Land Use, and Natural Resource Use
Demographics
RMA is located in Adams County, Colorado, approximately 9 miles northeast of downtown Denver. Some areas to the south and west of the site are densely populated neighborhoods, while the areas to the north and east are much more sparsely populated. Stapleton Airport (now closed) is immediately to the south of RMA; a prison which had over 1,200 inmates in 1990 is north of Stapleton and south of interstate highway I-70. Population and housing data from the 1990 Census for the Montbello community south of the site and for other areas of potential concern west and north of the site are included in Table 3.
Montbello is a densely populated (5,082 persons per square mile), middle-class community in Denver County located south of the site and east of the former Stapleton International Airport. Montbello had a 1990 population of 17,582. Nearly 60 percent of the population were black, which was almost five times higher than the county percentage. Only 12.6 percent were of Hispanic origin, which was about half the county average. There was a slightly higher percentage of children under age 10 and a substantially lower percent of persons age 65 and older, along with a high average number of persons per household; these trends suggest the presence of a large number of younger families in their childbearing years. Over 70 percent of all households were owner occupied in 1990, indicating a non-transient population (i.e., renters tend to move much more frequently than homeowners).
The area west of RMA, Commerce City, in Adams County is not as densely populated as Montbello but still had over 1,700 persons per square mile. In contrast to Montbello, over 85 percent of the 1990 population of that area were white and over one-third of the population claimed Hispanic origin. The percentages under age 10 and age 65 and over were similar to the Adams County averages. Over 60 percent of households were owner occupied, which suggests a relatively non-transient population.
In contrast, the Offpost Study Area just north of RMA is more rural in character and is more sparsely populated (see Table 3). Only 1,405 persons lived in that 27 square mile area in 1990. Other aspects of the demographic character of the area are similar to the character of Adams County of which it is a part. Over 70 percent of all households were owner occupied in 1990.
To the east of RMA, the newly opened Denver International Airport represents a major
change
in landuse. Those previously open grasslands are undergoing many landuse changes as will the
future demographic character of that area.
Table 3 - Rocky Mountain Arsenal Population and
Housing Data Table (5)
| Criteria | Montbello area (6) (SE of RMA) |
Commerce City area (7) (W of RMA) |
Offpost Study Area (8) (N of RMA) |
Adams Co. |
Denver Co. |
| Total persons | 17,582 | 20,536 | 1,405 | 265,038 | 467,610 |
| Total area (sq. mi.) | 3.46 | 12.04 | 23.03 | 1,192 | 153 |
| Persons per sq.mi. | 5,082 | 1,706 | 61 | 222 | 3,051 |
| Percent Male | 49.2 | 50.0 | 52.8 | 49.6 | 48.7 |
| Percent Female | 50.8 | 50.0 | 48.2 | 50.4 | 51.3 |
| Percent White | 29.5 | 85.4 | 90.2 | 86.7 | 72.1 |
| Percent Black | 59.7 | 2.6 | 0.4 | 3.3 | 12.8 |
| Percent American Indian, Eskimo, or Aleut | 0.9 | 1.2 | 0.6 | 0.9 | 1.2 |
| Percent Asian or Pacific Islander | 3.4 | 1.1 | 1.6 | 2.6 | 2.4 |
| Percent Other races | 6.5 | 9.7 | 7.2 | 6.5 | 11.5 |
| Percent Hispanic origin | 12.6 | 34.0 | 10.8 | 18.6 | 23.0 |
| Percent Under Age 10 | 16.7 | 17.9 | 15.8 | 17.3 | 13.8 |
| Percent Age 65 and older | 2.8 | 9.8 | 8.1 | 7.6 | 13.9 |
Table 3 (continued) - Rocky Mountain Arsenal Population and Housing
Data Table (9)
| Criteria | Montbello area |
Commerce City area |
Offpost Study Area |
Adams Co. |
Denver Co. |
| Households (10) | 5,579 | 7,184 | 485 | 96,353 | 210,952 |
| Persons per household | 3.15 | 2.83 | 2.9 | 2.72 | 2.17 |
| % Households owner-occupied | 70.8 | 62.0 | 73.8 | 65.5 | 49.2 |
| % Households renter-occupied | 29.2 | 38.0 | 26.2 | 34.5 | 50.8 |
| % Households mobile homes | 0.5 | 10.9 | 13.4 | 10.9 | 0.3 |
| % Persons in group quarters | 0.0 | 1.1 | 0.0 | 1.0 | 2.3 |
| Median value, owner-occupied households ($) | ~65,000 | ~55,000 | ~106,500 | 71,500 | 79,000 |
| Median rent paid, renter-occupied households ($) | ~400 | ~350 | ~325 | 373 | 339 |
Land Use and Land Use Controls
Present Land Uses - Onpost
With respect to its former high level of activity, the RMA property can be viewed as a closed industrial site. RMA employed as many as 3,000 people when it was a fully operational production facility for chemicals, explosives, agricultural chemicals, and pesticides. Currently there is relatively little activity on the base. The primary activities that do occur involve administration, remediation, and maintenance of the facility.
The current land uses at the RMA site has been classified as industrial-commercial, and recreational. The industrial classification was related to the commercial nature of the existing buildings: an army administration building, fire department, groundwater treatment facilities, rail classification yard, and a post office (EBASCO, 1990).
The recreational land-use classification of RMA has been related to USFWS uses of RMA including guided tours and the regulated "catch and release" fishing from several RMA lakes (EBASCO, 1990). The recreational classification includes individuals classified as biological/maintenance workers, regulated/casual visitors, and recreational visitors (EBASCO, 1994, p. 3-5).
The greatest proportion of acreage at the site is presently classified as a natural habitat for wildlife, which includes a bald eagle management area on the southeastern section (EBASCO, 1990).
Restrictions Limiting Onpost Land Use
As a result of the Superfund Amendments and Reauthorization Act (SARA) of 1986 and other factors, an agreement was made among the EPA, U.S. Army, U.S. Department of the Interior, ATSDR, and Shell Oil Company. This agreement, called the Federal Facility Agreement (FFA; EPA, 1989, p. 97-101), set forth the following restrictions on RMA:
Additional discussion on restrictions limiting both present and projected future on-site land uses is given in the following discussion of Projected Future Land Uses - Onpost.
Projected Future Land Uses - Onpost
Future, site-specific, land-use at RMA decisions have largely been made. Beginning with the FFA (EPA, 1989) it was agreed and required that significant portions of RMA will be available for public benefit including, but not limited to, wildlife habitats and parks. The FFA also provided that limited areas of RMA may also be used for commercial and industrial uses.
The passage of the Rocky Mountain Arsenal Wildlife Refuge Act of 1992 (106 STAT 1961; "RMA Refuge Act") codified and further restricted and defined many of the projected uses delineated in the FFA. Foremost, the statute sets aside the majority of the acreage of RMA for management as a unit of the National Wildlife Refuge System (cf 16 U.S.C. 668dd et seq.) by the U.S. Fish and Wildlife Service (USFWS). As set forth in Section 4 of the Act (106 STAT. 1964-65), the refuge is established for the following purposes:
The refuge act also includes prohibitions against future annexation by local government entities and against the construction of public roads through the refuge. Specific provisions are made for disposal of Arsenal lands for commercial, highway, and other public use purposes. Lands to be disposed are:
The disposal of real property described in the act is subject to the perpetual restrictions that are attached to any deed to such property and that prohibit:
The transfer of real property from the Secretary of Army to the Secretary of Interior (USFWS) may only occur after the Administrator of the EPA certifies that environmental cleanup response actions required at the Arsenal have been completed, except operation and maintenance associated with those actions. It is further specified that the Secretary of Army shall retain jurisdiction, authority, and control over the following real property at the Arsenal:
Onpost Land Use Prohibitions, IRAs, and BCSs - The Additive Effect
As described, land use restrictions and/or limitations on the uses of environmental media were specified in the FFA (USEPA, 1989) and made statutory requirements in the RMA Refuge Act of 1992 (106 STAT 1961). Those restrictions include prohibiting groundwater consumption, minimizing exposures to surface water and sediments, hunting and fishing for consumptive purposes, and other consumptive pathways such as ingestion of vegetable, meat and dairy products (EBASCO, 1994, p. 3-1 - 3-7). Those Onpost land use controls result in elimination or further reduction of completed or potential pathways of exposure of humans to RMA contaminants.
The land use controls are, in effect, added levels of mitigation or environmental protection which are added to the effects resulting from the active and ongoing Interim Response Actions (IRAs) and the boundary groundwater containment systems (BCSs). As summarized in Table 4, the net result of this detailed mosaic of mitigation is the a significant reduction or elimination of number of possible pathways of human exposure to RMA contaminants.
The remaining potential pathways of Onpost human exposure to those contaminants include exposure to contaminated surface soils/sediments and potentially contaminated air. Those present and future Onpost pathways are the focus of subsequent sections of this Assessment.
Present Land Uses - Offpost
Land usage around RMA is characterized by a varied pattern of heavy and light industrial, residential, and agricultural designations (ESE, 1988; HLA, 1992a). Agriculture predominates to the north and east, residential use to the west and south, and commercial uses primarily to the west. Heavily industrialized areas are intermixed with residential zones to the west and south. Commerce City, to the west, is associated with heavy industry such as petroleum refineries and construction equipment yards. Gravel and sewage treatment facilities to the northwest are located near the South Platte River.
The industry which occupied the most acreage adjacent to RMA is the, now closed, Stapleton International Airport. This airport was, in 1990, the fifth largest in the United States and experienced rapid growth in recent years. The new Denver International Airport (DIA) on lands to the east of RMA opened in 1995. Originally, DIA was proposed to expand onto RMA land. Those plans were rejected because of both the loud airport noise affecting nearby residential areas and because of the time required to clean up RMA (EBASCO, 1990).
Several residential areas border the RMA property, primarily to the northwest, west, and south (e.g., Commerce City, Irondale, Montbello). Adult and childhood activities associated with residences (e.g., outdoor play, school activities, home gardening) have been documented previously (Woodward-Clyde, 1990; HLA, 1992b).
Since 1950, off-site agricultural land has been used primarily for grain crops, as temporarily idle fields, and, to a lesser extent, pasture lands. This area includes approximately 2,500 to 2,700 acres of irrigated farm land. Water for most of this land is supplied primarily by a combination of several irrigation ditches traversing the Offpost Study Area just a short distance northwest of the RMA boundary (ESE, 1989a).
The primary field crops for this area are winter wheat, hay, barley, corn for grain and silage, sugar beets, and oats. Other crops grown include sorghum, dry beans, and spring wheat. Of the field crops listed, winter and spring wheat, barley, sugar beets, and dry beans are all produced for human consumption (ESE, 1989a).
Pastureland and livestock are not as important to local agricultural as are the grain fields. Pastureland is confined to limited areas, most of which is contiguous to the O'Brian Canal and the Fulton Ditch (ESE, 1989a).
Information obtained from the Adams County Agricultural Extension Service indicates several feedlots and beef/dairy cattle operations have operated within about 20 miles of RMA, to the northwest, north, and east (Weston, 1994, p. 3-7).
The current land use within the RMA Offpost Study Area is predominantly agricultural and rural residential with localized commercial/industrial land uses and open spaces. Areas within the Offpost Study Area are largely used for rangeland and dryland farming, with some rural residential areas and scattered areas of intensive agricultural use. Certain areas within the Offpost Study Area are currently zoned and developed for commercial/industrial activities. Commerce City, which is located west of RMA has recently annexed lands within the Offpost Study Area. Another geographic feature in the Offpost Study Area is Barr Lake State Park (HLA, 1992b, p. I-7).
Farming in the Offpost Study Area ranges from large grain operations covering square miles to small subsistence farms to vegetable gardens. A number of these farms also maintain livestock. Subsistence and hobby farmers often consume a portion of their diet from locally produced vegetables and livestock produced in the Offpost Study Area.
Intentional application of pesticides for pest control purposes likely accounts for the presence of some concentrations of pesticides in Offpost Study Area soil. Many of the pesticides detected in Offpost Study Area soil are or have been commercially available and may have been applied for agricultural or residential uses. Those pesticides include organochlorine pesticides (OCPs) and chlorinated hydrocarbon insecticides. The OCPs aldrin, endrin, dieldrin, and isodrin detected in Offpost Study Area soil have been used as insecticides in areas similar to the Offpost Study Area from the l940s to the mid-1970s. Aldrin was used in the early l950s to protect cotton against boll weevils and in the l970s for soil application in grain crops and termite control. In Colorado, dieldrin was used to control insects in field vegetable, grain, and fruit crops (Mullins, 1971) and against termites and locusts. Endrin was also used to control a wide range of pests. These insecticides were banned for general uses in 1975 by the EPA. Aldrin and dieldrin may still be used for certain restricted uses such as subsurface insertion for termite control and dipping of non-food roots.
Projected Future Land Use - Offpost
Evaluation of projected future land use at the Offpost Study Area indicates that areas of commercial/industrial and recreational land use will increase (Adams County Planning Commission, 1987). Rural residential (including agricultural) land use is expected to decrease in the Offpost Study Area (HLA, 1992b).
As an outgrowth of the Offpost remedial investigations, the Offpost Study Area was subdivided into zones that differed in the degree or character of contamination. Six zones, differing primarily on the pattern of groundwater contamination were delineated. Because existing land use, population density, and water use varies throughout the Offpost Study Area, the existing and projected future land use was then determined for each of the six groundwater contamination zones (HLA, 1993, p. 25-26, Fig. 6.1). Rural residential land use in Zones 1, 2, and 6 on the Offpost Study Area are expected to remain in rural residential use with use of available groundwater for domestic and irrigation uses. Zones 3 and 4, largely purchased and vacated by Shell Oil Company are expected to remain unoccupied until after remediation of these Offpost lands is complete. Then those zones will likely become residential or commercial/industrial. It is further forecast that the commercial/industrial land uses of Zone 5 will continue with the resulting limited potential for human exposure to the area groundwater.
Summary: The Cumulative Effect of Land Use Controls, IRAs, and BCSs
The cumulative effect of the IRAs and BCSs implemented from 1979-present and the Onpost land and resource use restrictions adopted or imposed is a substantial reductions or the elimination of many potential pathways of human exposure to contaminants. Other measures have been taken that temporarily or permanently greatly minimized the potential for human exposure to contaminants and reduced the number of possible pathways for exposure. These measures include: the state of Colorado providing bottled water, on an interim basis, to many private well users in the Offpost Study Area and the Shell Oil Company purchase of real estate located in the areas of greatest groundwater contamination, thereby eliminating well water use (and potential foodchain contamination) in those areas. Taken together those remediation and mitigation measures have served to greatly reduce the number of potential pathways of human exposure and the concentration of contaminants in those pathways.
Even though only a small percentage of the contamination emanating from RMA sources affected the Commerce City area west of RMA, the effect of the RMA remediation program has also substantially reduced or eliminated pathways of human exposure to non-RMA contaminants in the Commerce City EPA Study Area as well.
The cumulative effects of completed and ongoing remediation and mitigation measures are
summarized in Table 4. The remaining potential Onpost pathway of exposure to contaminated
surface soil and air-borne contaminants and the potential Offpost pathways of human exposure
to contaminated groundwater, contaminated air, and foodchain components (wild game animals)
are indicated in this table. Those pathways will be further evaluated in the following sections of
this Assessment.
Table 4 - Summary of Remaining Pathways -
Environmental Media and Mitigative Measures
| MEDIA | |||
| Groundwater | Offpost - Exposure to contaminants eliminated
or reduced by BCSs, IRAs, and land use controls.
Inorganic and organic chemical contaminants occur beyond BCSs. Some Offpost wells contain
contaminants at levels above regulatory or health based values.
Onpost - Use of groundwater prohibited; no pathway remaining. | ||
| Surface Water | Offpost - Onpost IRAs minimize Offpost
effects. No present pathway of exposure identified.
Onpost - Incidental exposure to lake water while fishing is possible, but it is not expected to result in adverse health effects. | ||
| Soil | Offpost - Low levels of contamination occur
locally, but no pathway of exposure has been
identified. Shell Oil Co. land purchases and revegetation provisions (Component 22: Colorado,
1995) minimize potential for human exposure to contaminants.
Onpost - Land use and access controls eliminate or reduce exposure to high levels of contaminants. Incidental exposure of public & workers to low levels of contaminants may occur. | ||
| Sediment | Offpost - Low levels of contamination occur
locally. No pathway of exposure has been identified.
Onpost - Incidental exposure is possible, but not expected to result in adverse health effects. | ||
| Biota | Offpost - Potential exposure limited by Onpost
IRAs and land use controls, and ecologic factors.
Onpost - Catch and release fishing regulations effectively preclude ingestion of contaminants. | ||
| Air | Offpost - IRAs have eliminated past pathways of
exposure and minimize potential exposures.
Observed low levels of contamination are not site-specific to RMA.
Onpost - IRAs and land use controls eliminate or minimize exposure. | ||
| Structures |
Onpost - IRAs and regulatory controls eliminate or minimize pathways of exposure to contaminants. |
Natural Resource Use
On-Site Water Use
There are several lakes located on the southern sections of the arsenal: Upper Derby, Lower Derby, Mary, and Ladora Lakes. Ladora Lake is the only natural lake. The other lakes were created using water from the Highline Lateral. The Highline Lateral is an aqueduct that is connected to the main Highline Canal, which brings water from the Rocky Mountains into the Denver area.
Surface water drainage at RMA has been complicated by the industrial land uses and associated drainage diversions. However, Onpost water is primarily drained by the First Creek and Sand Creek Lateral. Water from the First Creek and Sand Creek Lateral is then intercepted by the O'Brian Canal and the Burlington Ditch. Both the O'Brian Canal and the Burlington Ditch are irrigation ditches, which transport water for off-site agricultural purposes. Both the O'Brian Canal and the Burlington Ditch flow to Barr Lake but only the Burlington Ditch continues northeastward across the agricultural lands flanking the South Platte River (ESE, 1988).
Drinking water uses of Onpost groundwater and surface water are prohibited by the Federal Facility Agreement (EPA, 1989). Regulated, nonconsumptive, "catch and release" fishing is permitted in some Onpost RMA lakes (EPA, 1989; 106 STAT. 1966).
Off-site Water Use
Off-site water use (i.e., potable water sources, recreational fisheries) was identified within a 12.5 mile radius of RMA (cf. ESE, 1988). The Colorado Department of Natural Resources (DNR) Water Conservation Board, the DNR's State Engineering Board (Water Quality), water treatment plants in Adams County and Denver County, and the Denver Department of Health (Water Quality) were contacted to identify potable surface water sources (Weston, 1994, p. 3-8). Those water bodies designated as potable water supplies were Standley Lake and Marston Lake Reservoir. Standley Lake is located about 10 miles west of RMA and Marston Lake Reservoir is located approximately 1.25 miles southwest of the site.
The surface drainage in the upland area surrounding RMA is generally toward the northwest; drainage from RMA flows to the South Platte River, which flows in a north-northeasterly direction (ESE, 1988). Therefore, it is unlikely that surface water drainage from RMA would have any effect on potential drinking water sources such as Marston Lake Reservoir or Standley Lake.
Potential fishing areas within the 6-mile radius of RMA were identified during the preparation of the Onpost and Offpost Study Area human health exposure assessments (EBASCO, 1990; ESE, 1989). In addition, the DNR Fish and Game Department (Division of Wildlife) and local parks were contacted for fishing information (Weston, 1994, p. 3-8).
Except for the limited "catch and release" fishing on-site at RMA, no lakes, ponds, or reservoirs were identified as designated fishing areas within a 3-mile radius of the RMA. However, lying in the area between a 3- to 6-mile radius of RMA are several lakes and ponds designated as recreational fishing areas.
The only lake located northeast of the Arsenal is Barr Lake, a nonpotable water body, which is located approximately 3.7 miles from the boundaries of RMA. Barr Lake is classified as a wildlife refuge on its southern portion, and its northern half is used for recreational purposes, such as sport fishing. The surface waters of Barr Lake are included in the RMA Offpost Study Area.
Four smaller water bodies located in Adams County, all approximately 5 miles west of RMA, were identified as designated recreational fishing areas: Clear Creek Pond, Engineers Lake, Rotella Park Pond, Grandview Ponds 1 to 4, and three Adams County Fairgrounds ponds.
Numerous gravel pit have been developed along the valley of the Platte River. Those pits result in large pond that now support fish populations. TCHD (1994) reports that residents are consuming fish caught form these ponds that may have not been previously inventoried as potential fishing areas.
Biological Habitat
RMA lies within the High Plains District of the North Temperate Grassland biome (EBASCO, 1992, p. A1-14). The region is dominated by a mosaic of grassland communities with a diverse component of wildflowers. Tall grass species are common in moist sites and short grasses prevail in dry areas. Historical patterns of land use have altered the original patterns of vegetation. Much of the off-post area north and east is used either as cropland or pasture. Most of the areas to the south, west, and northwest are heavily urbanized. Onpost and off-post human activity has disturbed soils and vegetation over large areas resulting in vegetation dominated either by a variety of crops, grasses, or weed species and early successional species typical for the region.
Regional wildlife is dominated by species of prairie, steppe, and savannah communities. The wildlife inhabiting RMA are those found in similar habitats off post. RMA supports large populations of some species such as prairie dog, deer, hawks, and eagles. In contrast to surrounding areas where those species are hunted or disturbed by human activities, the fenced enclosure of RMA provides a sanctuary for wildlife. Its large acreages of diverse, open habitats interspersed with lakes, small intermittent streams, small wooded areas, and tall grass/weed cover-areas, along with an absence of hunting pressure and low levels of human disturbance, have contributed to an abundance of many wildlife species in numbers greater than occur off post.
Vegetation
Vegetation at RMA is dominated by five broad community types: weedy forbs, cheatgrass/weedy forbs, cheatgrass/perennial grassland, native perennial grassland, and crested wheatgrass. Trees, shrubs, and minor communities of sagebrush, rubber rabbitbrush, yucca grassland, cottonwood/willow stands, bottomland meadows, cattail marshes, and ornamental trees and shrubs are interspersed within the five broad community types. Further information is given in the Biota RI Report (see EBASCO, 1992, p. A1-15).
Wildlife and Wildlife Resource Management
The wildlife resources of the RMA area are diverse. The character and management of these wildlife resources influences possible human consumptive uses. The following paragraphs give a brief overview there resources and uses.
The fish species of RMA are those species most common to the region. First Creek supports plains killifish, fathead minnows, and some green sunfish. North Bog supports carp and fathead minnows. Largemouth bass, bluegill, bullhead, channel catfish, and northern pike are found in Lower Derby Lake, Lake Mary, and Lake Ladora. Sport fishing in those lakes is restricted to catch and release.
Sport fishing is permitted in nearby off-post waters such as the South Platte River and Barr Lake to the northeast of RMA.
Waterfowl are numerous at RMA and the lake and wetland areas of Barr Lake. Canada geese, and ducks are known nesters in those areas. Wading birds observed at RMA are the great blue heron and the black-crowned night heron. Pelicans have also been observed at RMA. Hunting of waterfowl is not permitted on RMA.
Upland bird species of RMA include ring-necked pheasant and mourning doves. While these birds cannot be hunted on post, they may be taken on the adjacent off-post lands.
in addition to significant raptor use of RMA during the summer, a large population of raptors use RMA during the winter. This high density is attributable to the abundance of prey and perching habitat, coupled with the lack of human disturbance. Long-eared and short-eared owls are fairly common at RMA and are year-long residents. Great horned owls and barn owls are also common year-long residents here. The number of barn owls on RMA is difficult to determine though, because they typically inhabit buildings such as the South Plants which makes counting their number difficult. Rough-legged hawks, ferruginous hawks, red-tailed hawks, golden eagles, and bald eagles are common winter residents. Of those species, the bald eagle is listed as of July 4, 1994 as threatened under the provision of the Endangered Species Act of 1973 (16 USC 1531-1536, 1538-1540) and the ferruginous hawk is candidate for listing.
The Bald Eagle Management Area, a 6,700-acre area in the eastern and southern portions of RMA, is managed and maintained by the U.S. Fish and Wildlife Service. Locally, the bald eagle's diet consists primarily of prairie dogs and rabbits. During the winters of 1987 and 1988, eagles were rarely observed fishing on RMA lakes (EBASCO, 1992, p. A1-18).
Of the mammal populations at RMA, the most conspicuous and extensive population is that of black-tailed prairie dogs. Also common are both mule deer and white-tailed deer. Surveys conducted at RMA in 1986-1987 found about 350 mule deer and 125 white-tailed deer or a total of about 18 deer/sq mi (EBASCO, 1992, p. A1-18). The USFWS estimated that in 1993 the deer population had increased to about 500 mule deer and 150 white-tailed deer, or more than 24 deer/sq mi (USFWS, 1993b, p. 12). Such population densities are high for the region, and both species are more abundant at RMA than off post (EBASCO, 1992, p. A1-18).
Conservation and management of RMA wildlife resources is accomplished through a cooperative agreement between the U.S. Fish and Wildlife Service (USFWS) and the Army. The USFWS has three areas of responsibility under this agreement: contaminants, conservation and mitigation, and public relations. Under the first responsibility, the USFWS reviews contaminant-related documents pertaining to RMA and identifies ways to minimize fish and wildlife exposure to contaminants and makes recommendations to the Army on ways to implement those protective measures. The Service conducts extensive investigations to determine the effects of contaminants on wildlife health at the Rocky Mountain Arsenal national Wildlife Area. The Service also has initiated a long-term biomonitoring program in 1993 specifically to address the affect of contaminants on fish and wildlife and to monitor and evaluate the effects of remediation on pathways of wildlife exposure to those contaminants. Currently, USFWS and several universities are studying at least 20 species of fish and wildlife. Second, the USFWS utilizes its technical skills to conserve and protect wildlife and to mitigate habitat loss during site cleanup. Third, the USFWS helps to publicize the wildlife resources of RMA and undertakes programs that enable local community members to learn more about the resources to be found at RMA (EBASCO, 1992, p. A1-19). In the five year period ending November 1994 over 153,000 people have been involved in the Onpost activities and tours and over 177,000 people have participated in outreach activities such as presentations and special programs (RMA, 1991, p. 32; Long, 1994, Personal Communication).
The availability of health information sources or "health outcome data" was investigated to assess community health concerns and possible health conditions related to chemicals associated with RMA. Health outcome data are records of birth, death, and illness (e.g., investigations of rates of disease in a community, health studies by universities or other researchers, new cases of cancer, deaths from cancer, and medical discharge records).
County level data, such as cancer registries, can be used to determine the general health of an area's population. By reviewing such data, increases in specific diseases within the county can be identified. Knowledge of diseases that are prevalent in an area is important because some may be caused by exposure to environmental contaminants. By identifying clusters of disease that may be linked to chemical exposures, sometimes areas can be targeted for further investigation.
Care should be taken in evaluating such health data, however, especially if there is a significant difference in the size of the population at risk of exposure to site contaminants and the size of the smallest population unit for which health outcome data are available. For example, likely adverse health effects caused by site contaminants would not be apparent if the number of at-risk people in the community is 100, but the smallest group for which data is available for is based on a group of 100,000. With careful evaluation, the data can provide general occurrences of diseases in an area.
At RMA, there have been numerous site-specific activities conducted by several different agencies. A variety of investigations, activities, and population-specific exposure studies have been conducted to investigate whether adverse health effects have occurred and whether those adverse health effects might possibly be related to past exposure to RMA hazardous substances through drinking water and inhaling wind-dispersed substances that have or may have migrated from RMA.
The following is a list of activities/investigations that have occurred or are on-going at, or adjacent to, RMA (see the Health Outcome Data Evaluation section of this assessment for additional information on these studies):
Health Consultation on Rocky Mountain Arsenal. Agency for Toxic Substances & Disease Registry. 1988. (ATSDR, 1988a)
Preliminary Health Assessment for Rocky Mountain Arsenal. Agency for Toxic
Substances & Disease registry. December 1988.
(ATSDR, 1988b)
Final Health Consultation on Rocky Mountain Arsenal Basin F. Agency for Toxic Substances & Disease Registry. July 20, 1989. (ATSDR, 1989)
Medical Evaluations of Irondale Trailer Park Residents - Unpublished Data. Memo from Dr. Ellen Mangione, Colorado Department of Public Health & Environment, Dated March 31, 1989. (CDPHE, 1989)
Survey of Health Complaints - Unpublished Data. Tri-County Health Department. December - January 1989. (TCHD, 1989)
Risk Calculations - Unpublished Data. Colorado Department of Public Health & Environment. 1989. (ATSDR, 1993a)
Cancer Incidence in the Northeastern Denver Metro Area: Report of the Ad Hoc Panel. Colorado Department of Public Health & Environment, Disease Control and Environmental epidemiology Division. August 1993. (CDPHE, 1993a)
Cancer Incidence in the Montbello Area, Denver, Colorado. Colorado Department of Public Health & Environment (CDPHE). Letter from Michael P. Wilson, CDPHE. August 9, 1993. (CDPHE, 1993b)
Final Report - Rocky Mountain Arsenal Pilot Study, Part I: Analysis of Exposure to Arsenic and Mercury. Agency for Toxic Substances & Disease Registry, Division of Health Studies and Colorado Department of Public Health & Environment, Division of Disease Control and Environmental Epidemiology. September 1993. (ATSDR, 1993a)
Draft for Public Comment - Rocky Mountain Arsenal Pilot Study, Part II: Analysis of Exposure to Diisopropylmethylphosphonate, Aldrin, Dieldrin, Endrin, Isodrin and Chlorophenylmethylsulfone. Agency for Toxic Substances & Disease Registry, Division of Health Studies; Colorado Department of Public Health & Environment, Division of Disease Control and Environmental Epidemiology; and Colorado State University, Department of Environmental Health. September 1995. (ATSDR, 1995)
Draft for Public Comment - Reproductive, Neurobehavioral and Other Disorders in Communities Surrounding the Rocky Mountain Arsenal. Colorado State University, Department of Environmental Health. September 1995. (CSU, 1995)
Mortality Among Workers at a Pesticide Manufacturing Plant. Amoateng-Adjepong, et al. Jour. of Occupational and Environmental Medicine, v. 37, n. 4, p. 471 - 478. April 1995.
Identifying and addressing community health concerns about hazardous waste sites is an important part of the public health assessment process. This part of the document identifies community concerns about possible site-related health effects. ATSDR is not empowered, however, to investigate or make recommendations on other community concerns dealing with property values or legal liability issues.
Community health concerns about RMA were gathered during two separate Public Availability Sessions. During January 29 - February 1, 1993, ATSDR met with citizens in the Montbello neighborhood; thirty-two citizens attended. About half of those persons came seeking information on the SQI IRA and the possible environmental or health effects of that action. Throughout the drafting of this Assessment, ATSDR has inquired about and identified health concerns from discussions with our ATSDR Regional Representatives, Tri-County Health Department, Colorado Department of Public Health & Environment, EPA, and other local officials.
During November 1-4, 1993, ATSDR held eight Public Availability Sessions in Commerce City, Cherry Creek, Montbello, and Henderson. Although those sessions were publicized through our regional representatives, newspapers, radio, television, and approximately 1800 flyers, only seventeen citizens attended those sessions. After those sessions, ATSDR contacted local physicians and health professionals to follow up on specific health conditions and concerns. At the sessions, there were specific health concerns mentioned as well as concerns about the current status of SQI, DIMP in groundwater, present air quality, and future effects from remediation of on-site soils. ATSDR will continue to address additional community health concerns as they are identified through our ATSDR Regional Representatives in Denver, Colorado.
The Army asked Tri-County Health Department to establish a public telephone "hotline" to provide the public an easy way to express their health concerns associated with the startup and operation of the RMA Submerged Quench Incinerator (SQI; Dan Collins, TCHD, Dec. 13, 1993, Personal Communication). The "hotline" was established on December 15, 1993. ATSDR has reviewed the Tri-County Health Department SQI Hotline records for additional health concerns related to RMA.
The community health concerns listed below have been brought to ATSDR's attention. These community health concerns are evaluated in the Public Health Implications section of this Assessment.
Remediation Concerns:
Specific Health Concerns:
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