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1. ATSDR > Public Health Assessments & Consultations

The public health assessment identifies the contaminants of concern found on and off site and describes what environmental sampling has been conducted; how contaminants of concern are distributed in different environmental media; and what other (physical or biologic) hazards are on site.

Contaminants are selected for discussion after consideration of the following factors:

• concentrations of contaminants on and off the site, or other evidence of release;

• field data quality, laboratory data quality, and sample design;

• community health concerns;

• comparisons of on-site and off-site concentrations with comparison values for noncancer and cancer outcomes; and

• other factors including evidence of carcinogenicity, absence of an appropriate comparison value, exposure to multiple contaminants, interactive effects, fate and transport, state exposure limits lower than ATSDR's, and health outcome data.

Any of the listed factors may support the identification of a substance as a contaminant of concern. The interpretation and evaluation of the factors depend on current scientific knowledge, public health policies, and professional judgment. As science and policies evolve, there may be a need to revisit a site, to reevaluate past information, or to evaluate new information.

Health comparison values are media-specific (water, soil or air) concentrations calculated from various health guidelines designed to protect public health. These values are not legally enforceable, but are used to make decisions to include the contaminants for further public health evaluation. The fact that a contaminant is discussed in this section does not mean that site-specific exposure to the substance will result in adverse health effects. Rather, the listed contaminants will receive additional public health evaluation in subsequent sections of this public health assessment.

The following health guidelines and comparison values may be used in the narrative or data tables of this section.

CLHA	Child Longer-Term Health Advisory: Derived by EPA. It is a drinking water concentration at which adverse noncancerous health effects would not be expected in children after exposure up to seven years in duration.
CREG	Cancer Risk Evaluation Guide: Derived by ATSDR from the EPA cancer slope factor (CSF). It represents a concentration in water, soil, or air at which excess cancer risk is not likely to exceed one case of cancer in a million persons exposed over a lifetime.
CSF	Cancer Slope Factor: EPA's quantitative assessment to define the relationship between the chemical dose and carcinogenic effects.
EMEG	Environmental Media Evaluation Guide: Derived by ATSDR from ATSDR's minimal risk level (MRL). It is the concentration in water, soil, or air at which daily human exposure is unlikely to result in adverse noncancerous effects.
Lead Action Level	Since 1991, EPA's regulatory level for lead in drinking water has been 15 ppb. This action level prevents known or anticipated adverse human health effects to the extent feasible.41
LTHA	Lifetime Health Advisory: Derived by EPA. It is a drinking water concentration at which adverse noncancerous health effects would not be expected.
MAAC	Maximum Acceptable Ambient Concentration: The MAAC is a state air value used as a reference or indicator to trigger possible modifications to industrial (i.e., the IWTP) processes.
MCL	Maximum Contaminant Level: Enforceable drinking water regulation established by EPA that is protective of human health to the "extent feasible" over a lifetime. MCLs take into account technological and economic feasibility.
MCLG	Maximum Contaminant Level Goal: Non-enforceable drinking water health goal recommended by EPA and set at a level at which no known or anticipated adverse human health effects are expected.
MRL	Minimal Risk Level: An estimate of the daily human exposure to a contaminant that is likely to be without a significant risk of non-cancerous adverse health effects over a specified duration.
RfD	Oral Reference Dose: EPA's estimate of a daily exposure that is likely to be without a significant risk of non-cancerous adverse health effects over a lifetime.
RMEG	Reference Dose Media Evaluation Guide: Derived by ATSDR from the EPA oral reference dose (RfD). It is the concentration in water or soil at which daily human exposure is unlikely to result in adverse noncancerous effects.

If a contaminant concentration exceeds it's health comparison value, it is designated a contaminant of concern. In addition, a contaminant is designated a contaminant of concern if they are classified as carcinogens or potential carcinogens by 1) the National Toxicology Program in the Department of Health and Human Services, 2) the EPA, or 3) the International Agency for Research on Cancer. CREGs and EMEGs are the first choice for a health comparison value. If a CREG or EMEG is not available, the following values (in order of preference) will be chosen for the health comparison value: the RMEG, the LTHA or CLHA (whichever is lower), the MCLG, or the MCL. However, some contaminants have no health comparison values. The chemical-specific scientific literature is used in the selection of these contaminants as contaminants of concern.

Contaminants exceeding health comparison values were detected at several of the IRP sites at Tinker. However, we have determined that people are not coming into contact with contamination at all of these sites. An overview of the contamination of the groundwater, soils, surface water, and other environmental media for sites which we have determined do not have completed exposure pathways is presented in Appendix C. Contamination detected at sites that have been identified to have completed exposure pathways are presented in the following discussion.

Groundwater

The past activities within Building 3001 have resulted in contamination of the on-base groundwater with chlorinated solvents and heavy metals. The primary contaminants are trichloroethylene (TCE) and chromium. Chemical tests of the valency states of the chromium indicate that most is hexavalent chromium, the most toxic form. The groundwater beneath Tinker occurs as two shallow water bearing zones overlaying a regional aquifer. The upper, non-producing portion of the regional aquifer has been divided conceptually into two zones, the upper saturated zone (5 to 70 feet below ground surface) and the lower saturated zone (50 to 100 feet below ground surface).⁴² Below these zones at depths of 250 to 700 feet the aquifer is referred to as the producing zone. The highest contaminant concentrations are beneath Building 3001 in the upper saturated zone; maximum concentrations of 330,000 ppb of TCE and 80,000 ppb of chromium were detected in monitoring wells in 1988. Maximum concentrations were 30,000 ppb TCE and 1700 ppb chromium in the lower saturated zone and 1000 ppb TCE and 1200 ppb chromium in the regional zone in the same year.⁴³

Base Supply Wells

Five of the seven base water supply wells located near Building 3001 are no longer in use. The wells currently in use are in compliance with the Safe Drinking Water Act and are not of public health concern. However, past exposures to metals detected in the active wells and to VOCs in the inactive wells are a potential concern.

Tinker's base supply wells pump water from the producing zone.⁴³ Thirty-one base wells are shown on Figure 5. Seven of those wells have been plugged: wells 6, 10, and 28 due to construction projects that required the wells to be physically eliminated and wells 16, 17, 18, and 19 due to contamination or location near contaminant plume.

Seven base water supply wells are located (see Figure 5) in the vicinity of Building 3001 (well numbers 13-19). Wells 18 and 19 are inside Building 3001 near the area of maximum groundwater contamination. In September - November, 1983, sampling of base supply wells detected VOCs significantly above health comparison values in well 18 (280 - 1642 ppb TCE). VOCs were also detected in well 19, but at much lower concentrations (ND - 5.7 ppb TCE). These wells were taken out of service that same year. During a 1984 investigation of well 18, which included pumping and testing for VOCs, TCE concentrations ranged from 1800 to 4600 ppb.⁴³ Maximum concentrations of contaminants of concern detected in well 18 and 19 during 1983 and 1984 are presented in Table 2. These wells are screened to a depth greater than 200 feet. The groundwater contamination does not extend this deep into the aquifer, therefore, the Air Force conducted a study to determine how the contamination reached these deep wells (well 18 and 19). A study in 1986 concluded that contaminants were entering both wells through corrosion holes in the upper zones and traveling downward through the casing and the annular space between the casing and the formation.⁴⁴ This cross connection of the aquifer zones was eliminated when both wells were plugged in 1986.⁴³ TCE was detected at 2400 ppb in well 18 during this investigation.

During the time wells 18 and 19 were being investigated, well 17 was inoperable and could not be sampled. Since the well was not necessary to maintain water supply capacity and it was located downgradient of the contaminant plume, the base decided the well should be plugged. This was completed in November of 1988. During the plugging operation the well was sampled and analyzed for volatile and semi-volatile organic compounds. TCE was detected at a concentration of 4 ppb. No other contaminants were detected at significant concentrations.⁴⁵

Supply wells 13-16, which are connected directly to the distribution system, were sampled approximately quarterly from September 1986 to August 1990. The parameters analyzed for included volatile and semi-volatile organic compounds and metals. Compounds detected that exceeded comparison values are presented in Table 3. Methylene chloride and phthalates are included in the table. However, these compounds were also detected in similar concentrations (1-15 ppb) in field and laboratory quality control blanks.⁴⁶

Supply well 16 was closed March 26, 1990, and was plugged in December 1990 as a precautionary measure. This well is located where groundwater contamination is known to exist in the shallow aquifer between Building 3001 and the Industrial Wastewater Treatment Plant. For the same reason, well 15 was inactivated in March 1993.⁹

Well 13 has not been in service since April 1994 due to maintenance.⁴⁷

Well 14 is still in use and monitored in accordance with the Safe Drinking Water Act (see Appendix D for a description of the Safe Drinking Water Act). These regulations are enforced by the EPA.⁴⁸ Analysis of water from wells 13 and 14 in 1989 and 1992 showed no presence of VOCs. Metals (lead, arsenic, selenium) were detected above ATSDR health guidelines in these wells in 1986-1990 (see Table 3). Some metals detected may be naturally occurring; groundwater concentrations of arsenic and selenium greater than MCLs are common in the Garber Sandstone and Wellington Formation.⁴⁹ Monthly sampling which began in July 1994 has detected no contaminants above HCVs or MCLs in well 14.⁵⁰

Arsenic was not detected above the regulatory MCL of 50 ppb. However, arsenic is a carcinogen and, therefore, is included as a contaminant of concern. Lead was detected (68 ppb) in well 13 above the MCL of 50 ppb, the value that was regulated at the time of sampling (1986). All other samples were not above the MCL. However, in 1991 EPA developed an action level of 15 ppb for lead in drinking water sources. The concentrations detected in 1986 (33 and 40 ppb) and 1988 (68 ppb) exceeded this current action level. Therefore, although not out of compliance at the time of sampling, the past exposures are a potential concern based on new scientific information. Selenium concentrations exceeded the interim MCL of 50 ppb (a value that is not legally enforceable) in 1986, 1988, 1989, and 1990.

Off-Site Wells

Off-site private residential wells have been sampled by the Air Force and the Oklahoma State Health Department (OSHD). Contaminants detected in off-site private wells near Tinker AFB that exceed health comparison values are listed in Table 4.

Air Force Sampling

During the 1990 Phase I remedial investigation of Soldier Creek, groundwater from eight off-base residential wells was sampled and analyzed for VOCs, semi-VOCs, and metals. Figure 3 shows the off-base wells sampled by the Air Force are not concentrated in one area of concern, but are located sporadically around the base. Volatile organic compounds and metals exceeding health comparison values were detected northeast of Tinker in the water from one well (GO7).⁵³ However, VOCs were not detected in two wells (G03 and G08) located immediately north/northeast of the base (adjacent to the base). Barium was detected in well G08 above health comparison values. Contamination was not detected in the other five wells sampled.

The sampling results do not establish a direct link between contamination on base and that detected to the north and northeast, and published reports demonstrate conflicting conclusions regarding off-base migration. Available data including the inconsistent distribution of contamination suggests that multiple sources may be impacting the areas in question. Tinker is continuing to investigate the area.

State Sampling

In April 1990, Tinker officials held a public meeting to present the Groundwater Remedial Action Plan for Building 3001. During the meeting, citizens expressed concern over possible contamination of nearby private drinking water wells north and east of Tinker. In response to this concern, the Oklahoma State Health Department (OSDH) initiated a program in the same month to sample private wells in the area.⁵⁴ The samples were analyzed for the regulated and unregulated VOCs listed in Appendix E. Unregulated contaminants are those contaminants that have an established monitoring requirement by EPA but do not have an associated final Maximum Contaminant Level Goal (MCLG), MCL, or treatment technique.⁵⁵

The initial sampling by the state included 26 wells that were north and east of Tinker.⁵⁴ During the next year, over 100 additional wells in the area were sampled. In March 1992, the sampling was expanded to anyone who requested sampling that lived within 0.5 miles of 29th Street and Douglas Boulevard. Sampling was actually extended beyond the 0.5 mile radius (Figure 6). This expanded sampling area accounts for the sampling of wells outside the primary area of concern.⁵⁶ Approximately 180 private wells were sampled in the state sampling program. Areas of primary concern included the Kimsey Addition neighborhood, areas (north and east) adjacent to the base, and the Evergreen Mobile Home Park.

Figure 6 shows the locations of the private wells that were sampled by the Oklahoma State Health Department. The purpose of the map is to indicate the general locations of private wells that were sampled, not the exact street address. Private wells are shown as contaminants not detected, contaminants detected below health guidelines, and contaminants detected above health guidelines. Contaminants detected included: tetrachloroethylene, trichloroethylene, 1,1-dichloroethane, cis-1,2-dichloroethene, 1,1,1-trichloroethane, 1,2-dichloroethane, 1,1-dichloroethene, chlorobenzene, benzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 1,2-dibromomethane, xylene, toluene, 2-chlorotoluene, 1,2-dichloropropane, trichlorofluoromethane, vinyl chloride, and barium. The contaminants detected above health comparison values are listed in Table 4.

Areas North and East of Tinker

Approximately 180 private wells in the areas north and east of Tinker were sampled during the state sampling program (Figure 6). Concentrations of TCE and PCE above health comparisons values were detected in a few of these wells. The maximum concentration of PCE detected was 20.1 ppb and the maximum concentration of TCE detected was 13.8 ppb.

On December 3, 1990, the Air Force began providing bottled water to residents north/northeast of Tinker who had private wells with concentrations detected above the MCL.⁵⁷ The majority of the residences were hooked up to municipal water between September 1993 - May 1994. All private wells will be sealed contingent upon the homeowners signing Conveyance and Covenant documents.⁵⁸ These documents give permission to connect the residence to the municipal water supply and to plug the private wells. Most homeowners have signed a Conveyance and Covenant document.⁵⁹ All private wells at locations where the owner has given permission were sealed by October 1994. However, at least three wells have not been sealed because the owner has not granted permission.⁶⁰ If letters of consent are not obtained, the state plans to initiate a process to condemn the wells.⁶¹

Figure 6.

Evergreen Mobile Home Park

Benzene was detected at 21.0 ppb in one of the two supply wells at the Evergreen Mobile Home Park on October 8, 1991.⁶² This concentration exceeds the MCL of 5 ppb. The supply wells at the mobile home park also supplied water to the convenience store on Douglas Boulevard.⁶² OSDH closed the contaminated well and advised the residents to use the remaining supply well for non-drinking use only. The Oklahoma Corporation Commission provided the mobile home park and the convenience store with bottled water through the EPA LUST (leaking underground storage tank) Trust Fund on October 11, 1991.⁶³ Both were supplied with municipal water in July 1993.⁶⁴ The Oklahoma Water Resources Board concluded that the underground storage tank system located at the Tank and Tummy convenience store is the probable source of benzene in the well at the Evergreen Mobile Home Park.⁶⁵

Surface Water and Sediment

Surface water and sediment samples were taken along Soldier, Crutcho, Kuhlman, and Elm Creeks (Figures 3 and 7). Soldier Creek is divided into East Soldier Creek, West Soldier Creek and Main Soldier Creek. Contaminants from the base may enter these creeks through direct discharge (as shown in outfall data), surface water runoff, storm drainage systems, and groundwater discharge. The contaminants may migrate off base in the surface water and sediment.

Soldier Creek

No contaminants exceeding health comparison values were detected in the surface water or sediment in Main Soldier Creek. Contaminants detected in surface water and sediment of East Soldier Creek that exceeded health comparison values included VOCs, semi-VOCs, and metals. Several metals detected in surface water of West Soldier Creek exceeded health comparison values. Contaminants detected in sediment of West Soldier Creek that exceeded comparison values included semi-VOCs and metals.

Forty-eight composite and grab surface water samples were collected during Phase I and II of the Soldier Creek remedial investigation (RI).⁶⁶ Composite and discrete grab surface water samples were collected from the mid-water column during Phase I and II of the RI. The composite surface water samples were analyzed for semi-volatile organics on the target compound list (TCL) in Phase I and II of the RI, metals and cyanide on the target analyte list (TAL) in Phase I of the RI, and select metals (antimony, cadmium, chromium, and lead) and cyanide in Phase II of the RI. Special Analytical Services (SAS) were performed on samples from eight of the sampling locations including alkalinity, hardness, chemical oxygen demand (COD), total suspended solids (TSS), five day biochemical oxygen demand (BOD5), total organic carbon (TOC), and nitrates. The discrete grab samples were analyzed for volatile organics on the TCL.

One hundred and forty-one composite sediment samples and 137 grab sediment samples were collected during Phase I and II of the Soldier Creek RI.⁶⁷ Composite sediment samples were collected from 0-6 and 6-12 inches during Phase I of the RI, and 0-1, 1-2, 2-3, 3-4, and 4-5 foot intervals during Phase II of the RI. The composite sediment samples were analyzed for semi-volatile organics on the TCL and metals and cyanide on the TAL in Phase I of the RI; volatiles and metals (chromium, lead, antimony, and cadmium) and cyanide were analyzed during Phase II of the RI. One location was analyzed for semi-volatile compounds during Phase II.⁶⁷ The discrete grab sediment samples were analyzed for volatile organics on the TCL during Phase I and II of the RI.

Main Soldier Creek

No contaminants exceeding health comparison values were detected in the surface water or sediment in Main Soldier Creek.

East Soldier Creek

Surface Water

Contaminants detected in surface water of East Soldier Creek that exceeded health comparison values included VOCs, semi-VOCs, and metals. Table 5 lists these contaminants, the range detected, frequency of detection, location of the sample with the maximum concentration, and the respective health comparison value.

Sediment

Contaminants detected in sediment of East Soldier Creek that exceeded comparison values included VOCs, semi-VOCs, and metals. Table 6 lists these contaminants, the range detected, frequency of detection, location of the sample with the maximum concentration, and the respective health comparison value.

The IWTP is permitted to discharge treated effluent into East Soldier Creek under the National Pollutant Discharge Elimination System (NPDES). From September 1988 to January 1994 Tinker reported approximately 700 noncompliance discharges of the NPDES permit. Graphs of the average and maximum monthly discharge concentrations from 1988-1994 are included in Appendix I. The graphs show the relationship of the NPDES permit limit, the relevant health standard, and the monthly discharge concentration (average and maximum). Table 7 lists the maximum concentrations of individual chemicals reported from September 1988 to January 1994.⁶⁸

West Soldier Creek

Surface Water

Several metals detected in surface water of West Soldier Creek exceeded health comparison values. Table 8 lists the metals, the range detected, the frequency of detection, location of the sample with the maximum concentration, and the respective health comparison value. The maximum concentration is detected at location W03 for all contaminants but manganese listed in Table 8. The concentrations of contaminants detected at this location are several fold greater than the concentrations detected at all other sampling locations on West Soldier Creek. Therefore, it appears this location may be a primary source(s) of contaminants to West Soldier Creek.

Sediment

Contaminants detected in sediments of West Soldier Creek that exceeded comparison values included semi-VOCs and metals. Table 9 lists these contaminants, the range detected, the frequency of detection, location of the sample with the maximum concentration, and the respective health comparison value. All concentrations detected during the Phase II investigation were less than the maximum concentrations detected in Phase I.

The maximum concentrations of all contaminants but manganese were detected at locations W03 and W04. This pattern of contamination coincides with the maximum surface water concentrations detected in West Soldier Creek (see above).

Figure 7.

Crutcho, Kuhlman and Elm Creeks

Contaminants detected above health comparison values in the sediments of Crutcho, Kuhlman, and Elm Creeks include inorganics, VOCs, SVOCs, and pesticides/PCBs. None of these were detected above health comparison values in surface water samples.

Baseline sediment and surface water samples were collected July 4-8 and October 26-29, 1991, from 27 of the 29 sample locations shown in Figure 7.⁶⁹ Locations 17A and 22A were not sampled as part of the baseline data collection activities. Nineteen locations are on Crutcho Creek. Six sampling locations (1-5 and 27) are on Kuhlman Creek. The remaining four locations (22, 22A, 23 and 24) are on the tributaries of Elm Creek. The samples were analyzed for the parameters listed in Appendix F.

Confirmation data collection occurred in February and May 1992. In February, sediment and surface water were sampled at 11 creek locations to better define the nature and extent of contaminants identified in the 1991 baseline samples.⁶⁹ Surface water was re-collected from seven of the eleven sampling locations in May to monitor seasonal variations in contaminant release.⁶⁹

Surface water

No concentrations of inorganics, VOCs, SVOCs, or pesticides/PCBs were detected above health comparison values in surface water samples from Crutcho, Kuhlman, or Elm creeks.

Sediment

In July 1991, sediment samples were analyzed for 26 target inorganics and in February 1992, sediment samples were analyzed for 17 target inorganics. Six inorganics were detected at concentrations above their respective health comparison values. During the 1991 sampling phase, samples were analyzed for semi-volatile organic compounds (SVOCs). The only SVOC detected above it's health comparison value was benzo(a)pyrene. Benzo(a)pyrene was detected at 350 ug/kg, exceeding the CREG of 100 ug/kg, at sampling location SDO1 on Kuhlman Creek.

In sediment samples collected in February 1992, SVOCs were present at two sampling locations. At SD01 on Kuhlman Creek, eight PAHs were detected that do not have health comparison values. At SD05 on Kuhlman Creek, five PAHs and one phthalate, di-n-butylphthalate, that do not have health comparison values were detected. The pesticide 4,4-DDD was detected in sample SD15 from Crutcho Creek at 18 ug/kg. Also, sample SD01 from Kuhlman Creek contained Aroclor-1260 (a PCB) at a maximum of 160 ug/kg. All other SVOCs detected did not exceed their health comparison values.

The contaminants which exceeded their associated health comparison values from either sampling round are listed in Table 10. The range detected, frequency of detection, location of the maximum concentration detected, and the respective health comparison value are also listed.

Ambient Air

The Air Force conducted initial ambient air sampling at the IWTP on May 19, June 6, and June 16, 1993. Initial sampling was for hydrogen sulfide, methylene chloride, toluene, xylene, chloroform, and phenol. During the initial sampling phenol was detected in one of twelve samples (24-hour averages) above the State of Oklahoma Maximum Acceptable Ambient Concentration (MAAC). The MAAC is used as a reference or indicator to trigger possible modifications to the IWTP process. Thus, the Air Force expanded the air sampling program during the fall of 1993. In March 1994, ATSDR issued a Health Consultation based on the results of the air sampling. The consultation is included in Appendix G.

Toxic Chemical Release Inventory Database

The Toxic Chemical Release Inventory (TRI), a database that contains information on releases of toxic chemicals into the environment, was searched for toxic chemical releases in the Midwest City area. The search revealed that contaminants were released into the air by Chromalloy Division in 1987, 1988, and 1989. These contaminants were aluminum oxide, nitric acid, sodium hydroxide, and 1,1,1-trichloroethane. None of the chemicals were released to other environmental media. In 1989, Solvent Manufacturing Company reported a release of toluene to the air. No data are available prior to 1987 or after 1989.

Quality Assurance and Quality Control

In preparing this public health assessment, ATSDR relied on information provided by the Air Force and its contractors, Oklahoma State Department of Health, Oklahoma Water Resources Board, and the City-County Health Department of Oklahoma County and assumed that adequate quality assurance and quality control measures were followed with regard to chain of custody, laboratory procedures, and data reporting. The validity of the analysis and conclusions drawn in this public health assessment depend on the completeness and reliability of the referenced information. ATSDR found no indication the data reviewed was invalid.

Physical and Other Hazards

Crutcho Creek is posted with a sign reading "Playing In Creek Prohibited" near the on-base school.⁵ The creek channel is concrete lined in this area and the posting is an effort to prevent accidents such as those involving skate boards and bicycles.

PATHWAYS ANALYSIS

To determine whether people living or working near Tinker AFB have been, are, or will be exposed to site contaminants, ATSDR evaluates the environmental and human components leading to human exposure. The process by which people have been, are, or will be exposed to contaminants is called an exposure pathway. An exposure pathway consists of five elements:

• a source of contamination (point of original release of a contaminant, or a contaminated medium at or near point of exposure, if original source unknown);

• contaminated environmental medium (at point of exposure; the way contaminants may be transported and transformed are considered);

• point of exposure (location, structure, or device where people contact a contaminant);

• route of exposure (means by which a contaminant enters the body: eating, breathing, touching); and

• population at point of exposure.

If all five elements exist, and people have been, are, or will probably be exposed, ATSDR considers the exposure pathway completed. A completed exposure pathway does not necessarily indicate a public health concern. If one (or more) of the elements is missing, but information suggests that it (they) could exist, ATSDR considers the pathway potential. If one or more of the elements is missing and could never exist, ATSDR eliminates the suspected pathway from further consideration.

Completed Exposure Pathways

In this public health evaluation, five completed exposure pathways have been identified. Two completed pathways involve the groundwater: past use of contaminated base supply wells at Tinker and past and possible current and future use of contaminated private wells in the neighborhoods adjacent to Tinker. Two completed pathways pertain to the surface water and sediments of Soldier, Crutcho, Kuhlman, and Elm Creeks. The fifth pathway is a result of past emissions from the IWTP to the ambient air. A summary of the pathways are presented in Table 11.

Groundwater

Past activities within Building 3001 have resulted in contamination of the on-base groundwater with chlorinated solvents and heavy metals. The primary contaminants are trichloroethylene and chromium.⁴³

Table 11. Completed Exposure Pathways
Pathway	Time	Exposure Pathway Elements
		Source	Environmental Medium	Point of Exposure	Route of Exposure	Exposed Population
Base supply wells	Past	Multiple1	Groundwater	Water taps	Ingestion	Workers
Private wells	Past Current Future	Multiple	Groundwater	Water taps	Ingestion Skin contact Inhalation	Residents
Ambient air	Past	IWTP emissions	Ambient air	Residences and businesses adjacent to IWTP	Inhalation	Residents Workers
Sediment	Past Current Future	IWTP effluent Base outfalls Off-base outfalls	Sediment	Soldier, Crutcho, Kuhlman, and Elm Creeks	Ingestion Skin contact	Children Workers
Surface water	Past Current Future	IWTP effluent Base outfalls Off-base outfalls	Surface water	Soldier, Crutcho, Kuhlman, and Elm Creeks	Ingestion Skin contact	Children Workers
1 Several potential sources of groundwater contamination were identified both on and off base. See discussion in text.

Base Supply Wells

A past completed exposure pathway has been identified for base supply wells 18 and 19. VOCs were first detected in base wells 18 and 19 in 1983 (see Table 2). Exposures ceased when these wells were closed in 1984. Base personnel who used water from supply wells 18 and 19 were exposed to the contaminants through the exposure routes of ingestion, inhalation, and dermal absorption. ATSDR was unable to determine the concentrations people were exposed to, duration of the exposure, or population that was exposed. It is likely that the concentrations that people were exposed to were less that those detected in well 18. Water is pumped into the distribution system with holding tanks positioned along the system. Therefore, the addition of uncontaminated water from other base supply wells would dilute the concentrations of contaminants in the water delivered at the tap. The maximum concentration of TCE detected in well 18 in 1983 was 1642 ppb. Therefore, even with dilution by the uncontaminated water it is likely that people were exposed to levels above the MCL of 5 ppb. An estimate of how long base wells 18 and 19 were contaminated prior to closure in 1984 is difficult to determine. Sampling was not required by the Safe Drinking Water Act prior to January 1988. Therefore, sampling results are not available to determine when the wells became contaminated. The specific group of people that used the contaminated water cannot be determined. However, water usage within the system is somewhat localized, water pumped into the distribution system from a supply well is largely used by patrons within close proximity of the holding tank for that well.⁷⁰

Base supply wells 15, 16, and 17 were closed as precautionary measures because the wells were in the vicinity of the groundwater contamination. Concentrations of VOCs of public health concern were not detected in wells 15, 16, or 17 during the time the base was using the wells as a source for the base water supply.

Base supply wells 13 and 14 are still in use. Concentrations of lead, arsenic, chromium, and selenium slightly above current ATSDR health guidelines were detected in these wells between 1986-1990. Although the concentrations were slightly above ATSDR guidelines, only one concentration (68 ppb lead in 1988) was greater than the respective MCL, the regulatory value. Groundwater concentrations of arsenic and selenium greater than MCLs are common in the Garber Sandstone and Wellington Formation.⁴⁹

The Safe Drinking Water Act requires sampling a minimum of every three years. However, to ensure a safe drinking water system on base, wells 2, 7, 12, 14, and 27 are currently sampled monthly. This will be reduced to quarterly sampling soon.

Private wells

A past completed exposure pathway was identified for private wells north and northeast of Tinker. Contamination from Building 3001 (and its associated operable units) and the IWTP have resulted in groundwater contamination within the base boundaries. Groundwater in the upper saturated zone situated near Building 3001 is moving off base to the northeast.⁵⁴ A 1991 investigation by the U.S. Army Corps of Engineers of off-base groundwater northeast of Tinker concluded that Tinker is not the source of the contamination detected by the OSDH in the private water supply wells north and northeast of the base.⁵⁴ However, after reviewing the East Soldier Creek RI, OSDH contends that groundwater contaminants at Tinker appear to be migrating off-base to the north and northeast.⁷¹ Tinker is continuing to investigate the area, on- and off-base, as part of the Building 3001 NPL site to determine the nature and extent of contamination.

Several potential sources of groundwater contamination have been identified off base in the area north and northeast of Tinker. The Oklahoma Water Resources Board concluded that the underground storage tank system located at the Tank and Tummy convenience store is the probable source of benzene in the well at the Evergreen Mobile Home Park.⁷² Four sources of groundwater contamination have been identified by the Oklahoma Corporation Commission at the intersection of 29th Street and Douglas Boulevard. All of these releases are gasoline/petroleum products from USTs. None of the releases have been accurately quantified.⁷³ Results of the site characterization indicate groundwater flow is generally to the east.⁷⁴ Therefore, this plume is a potential source of the contamination detected in private wells east of this intersection. Several potential sources of groundwater contamination exist in the area including a paint shop, salvage yard, and a vacant lot which contains dumped materials.⁶⁶

In the past, residents in the neighborhoods north and northeast of Tinker (see Figure 6) used private wells for drinking water and non-drinking purposes such as watering yards and washing cars. Volatile organic compounds were detected in some of these wells by the OSDH in 1990 and 1991. The people using contaminated wells for drinking water were exposed to contaminants through the routes of ingestion, inhalation and dermal contact. The Air Force issued bottled water to these residents in December 1990. Thus, the ingestion route of exposure ceased for residents who used the bottled water. Residences in these neighborhoods were provided municipal water from either Midwest City or Oklahoma City between September 1993 and May 1994.

As of November 1995, 12 private wells were not plugged. The owners of these wells have been advised to plug them. It is not known if all 12 wells are contaminated at levels that pose a public health hazard or if people are using the well water for potable purposes. Construction of new wells in the area northeast of Tinker is prohibited.⁷⁵ However, since groundwater remediation is incomplete, the potential exist for contamination to migrate to the 12 unplugged wells if they are near sources of groundwater contamination. Thus, current and future exposures are a potential public health hazard.

Contamination was detected in the one of two supply wells at the Evergreen Mobile Home Park on October 8, 1991. The Tank N Tummy convenience store also used drinking water from the Evergreen Mobile Home Park supply well. OSDH closed the contaminated well and advised the residents to use the remaining supply well for non-potable (non-drinking) use only. The convenience store and residents of the mobile home park were provided bottled water on October 11, 1991, by the Oklahoma Corporations Commission.⁷⁶ Thus, mobile home park residents and convenience store workers and customers were exposed to contaminated groundwater through ingestion, inhalation, and dermal contact prior to October 11, 1991. Since contaminants were not detected at levels of concern in the remaining supply well, exposure at the trailer park should have ceased when bottled water was issued. All possible exposure to contaminated water ceased at this location when municipal water was supplied in July 1993.⁶⁴

During sampling of off-base residential wells, VOCs (PCE and 1,2-dichloroethane) exceeding health comparison values were detected in the water from the Tinker Motel well. Motel guests and residents were exposed to contaminated groundwater through ingestion, inhalation, and dermal contact. The motel was provided bottled water in 1990, thus, the ingestion route of exposure ceased for people who drank the bottled water. However, the motel utilized well water for bathing and showering until it was connected to municipal water in September 1993. This well is downgradient from the contaminant plume at the intersection of 29th Street and Douglas Boulevard.^73,74 However, the plume boundaries have not been described and characterization of the plume is ongoing.

Surface Water and Sediments

Four surface water systems (creeks) serve as drainage ways for Tinker: Crutcho, Kuhlman, Soldier, and Elm Creeks. Children who live in neighborhoods north and northeast of Tinker are known to play in East Soldier Creek. No information is available about the extent to which children may play in Crutcho, Kuhlman, and West and Main Soldier Creeks. However, children have ready access to the areas where Crutcho Creek runs through neighborhoods both on and off base. Elm Creek flows through an undeveloped area on base and an industrialized area off base. Neither area is heavily populated, therefore, it is unlikely that children play in Elm Creek. Children who play in East Soldier Creek, and possibly the other creeks, are exposed to contaminants present in surface waters and sediments through the routes of ingestion, inhalation, and dermal absorption.

On occasion, workers must work in and around East Soldier Creek near Building 3001 outfalls, the IWTP, and the Douglas Boulevard Bridge. Workers could be exposed to surface water and sediment contaminants via ingestion, inhalation, and dermal contact. Tinker has an industrial hygiene office that monitors worker exposures and ensures that each worker is adequately protected via engineering controls and/or personal protective equipment.

Air

Contaminants released to the ambient air from the IWTP are dispersed by the wind. Prevailing winds are in the direction of the Kimsey Addition neighborhood and the Child Development Center. People in these areas are exposed via inhalation and dermal contact to airborne contaminants emitted to the ambient air from the IWTP. Detailed information on this pathway can be found in Appendix G.

Potential Pathways

Two potential exposure pathways were identified in this public health evaluation: foodchain contamination (garden vegetables) and exposure to surface water during an unusually elevated NPDES permit discharge to East Soldier Creek.

Foodchain

Contamination of the foodchain is possible through bioaccumulation of contaminants from sources such as contaminated water, sediment, and/or air. Vegetables and fruits grown in the neighborhoods north-northeast of Tinker may be potentially contaminated with chemicals that are in the groundwater, in the sediments of the creeks, or in the ambient air. However, contamination of the foodchain in this area is unlikely.

Watering of vegetable gardens or fruit trees with contaminated private well water may provide a route for the crops to bioaccumulate contaminants from the water. The State of Oklahoma Health Department analyzed private well water samples collected near Tinker for VOCs, but not for inorganics (metals). However, Tinker AFB sampled eight private wells (G01 - G08) and several off-base monitoring well clusters during the RI/FS investigation of Soldier Creek. The wells sampled by Tinker are identified on Figure 3.

The levels of VOCs or inorganics detected in the groundwater (both monitoring and private wells) are not expected to result in significant bioaccumulation of the contaminants in plants. Barium is the only inorganic that was detected at a level above the health comparison value. The maximum concentration detected was 1200 ppb. This concentration is not expected to result in bioaccumulation that would be of public health concern.

Contaminated sediment deposited in private gardens and yards as a result of flooding of creeks in the area is another potential route for contamination of the food chain. However, flooding along the banks of East and West Soldier Creek is not a common occurrence.⁷⁷ Therefore, significant deposition of sediments in private gardens is not expected. In addition, contamination detected in sediments along the creeks (Soldier, Crutcho, Kuhlman, and Elm) is not great enough for significant accumulation of contaminants to occur in yards and gardens as a result of infrequent flooding of the creeks. Therefore, it is unlikely that home grown fruits and vegetables are contaminated by this route.

Contamination of plants may also occur as a result of deposition of airborne contaminants on the surface of the crop (e.g., leaves or fruit) or by uptake of the contaminant by the plant tissues. The concentrations of contaminants detected in the air during the IWTP air sampling program are not expected to result in significant contamination of home grown fruits and vegetables. However, thorough washing of home grown fruits and vegetables prior to preparation for consumption is a practical means of removing chemicals that may be deposited on the surface of the plant as a result of gardening activities or atmospheric deposition.

Surface Water

Children playing in East Soldier Creek downstream of the IWTP could be exposed to contaminants if they are playing in the stream when the plant discharge is not in compliance with the NPDES permit (see Table 7). The majority of noncompliance discharges are not of health concern. The relationship of the health standard and the concentration discharged from 1988 to 1994 are presented in chemical-specific graphs in Appendix I. Those graphs show that the majority of the discharges are less than the corresponding drinking water standard.

Although exposures of this nature would occur infrequently, in 1992 Tinker installed spill control structures immediately downstream of the IWTP discharge as a preventive measure. These structures can be closed as soon as a release is suspected. In addition, Tinker plans to connect the IWTP discharge to the Oklahoma City Regional Water District System by the end of 1995. The system will remain on-line as a pretreatment prior to discharge to the City system. This action will eliminate non-compliance discharges from the IWTP into East Soldier Creek.

Agency for Toxic Substances and Disease Registry, 1825 Century Blvd, Atlanta, GA 30345
Contact CDC: 800-232-4636 / TTY: 888-232-6348 

Department of Health and Human Services