PUBLIC HEALTH ASSESSMENT
NORTH RAILROAD AVENUE PLUME
ESPAÑOLA, RIO ARRIBA COUNTY, NEW MEXICO
CONCLUSIONS, RECOMMENDATIONS, AND PUBLIC HEALTH ACTIONS
The Public Health Action Plan describes the actions designed to mitigate or prevent adverse human health effects that might result from exposure to hazardous substances associated with site contamination. Based on the findings of this PHA, no specific public health actions are warranted at the site. However, ATSDR will continue to collaborate with the appropriate federal, state, and local agencies to pursue the implementation of the recommendations outlined in this document. In addition, ATSDR will continue to review any new environmental and health outcome data associated with the NRAP site and include results in future updates of this document, if deemed necessary.
Robert Knowles
Environmental Health Scientist
Division of Health Assessment and Consultation
Annmarie DePasquale
Environmental Health Scientist
Division of Health Assessment and Consultation
Maria Teran-Maciver
Community Involvement Specialist
Division of Health Assessment and Consultation
Patrick Young
Regional Representative
Office of Regional Operations
Joe Maloney
Health Education Specialist
Division of Health Education and Promotion
Steve Inserra
Epidemiologist
Division of Health Studies
Dean Seneca
Tribal Coordinator
Division of Health Assessment and Consultation
Morris Maslia
Research Environmental Engineer
Division of Health Assessment and Consultation
. Española, New Mexico. June 2001.. September 2002.APPENDIX A: INFORMATION ON THE SEPARATE PETROLEUM-RELATED GROUNDWATER PLUME
Introduction
The initial release of the Public Health Assessment (PHA) for the North Railroad Avenue Plume Site (NRAP) site, issued in September 1999, included a brief evaluation of the limited data available for a separate petroleum plume, located within the City of Española (1). This appendix summarizes the information presented in the initial PHA and provides contact information for more information on this site as the investigative process at the source(s) of the petroleum plume proceeds. This updated PHA does not evaluate any additional data available for the site, because the investigation of the petroleum plume is part of a separate, on-going environmental investigation conducted by the State of New Mexico Environment Department (NMED). Based on the data available at the time of the initial release, individuals were not likely to be exposed to contaminants from the tetrachloroethylene (PCE) plume and the petroleum-related plume at the same time. Therefore, further evaluation of the petroleum plume was not evaluated as part of this update, which focuses on the potential exposures associated with the PCE contamination from the NRAP site.
Background Information
In addition to impact from the Norge Town facility, shallow groundwater in the vicinity of the City of Española has become contaminated with petroleum hydrocarbons from two leaking underground storage tanks. The tanks are associated with the Exxon El Centro and the Circle K Store, located in the vicinity of the plaza area of Española and southwest of the Norge Town facility. The principal contaminants reported are benzene, toluene, ethylbenzene, and xylenes, which are frequently referred to as BTEX contaminants. The BTEX groundwater plume is overlain largely by a public plaza and commercial development. The shallow BTEX plume underlies a few businesses and service facilities and possibly some homes on Hill Street (2).
Two air sparging treatment systems were installed by NMED to remediate the petroleum contamination levels in groundwater. Air and volatile organic compounds (VOCs) from the petroleum products entrained from the contaminated groundwater were withdrawn from below ground and discharged into the surrounding air without treatment. Remedial operations began in 1995 and were terminated after about a year without completing remediation. To evaluate the potential for exposure to airborne contaminants by nearby residents, air emissions from the treatment system were sampled during its operation. In addition, emission sample results were used to model the concentrations that could be expected at the nearest resident.
BTEX contaminants have been detected in numerous monitoring wells, which have been installed to collect environmental contamination data. It should be noted that individuals in the community are not supplied groundwater from monitoring wells. In 1995, high levels of PCE were detected in groundwater samples collected from monitoring wells installed as part of the investigation of the BTEX contaminant plume. It is thought that groundwater associated with the deeper PCE plume from the Norge Town facility migrated to the plaza area and was detected in the monitoring wells installed to investigate the petroleum plume. Additionally, it is possible for BTEX contamination to impact the groundwater at nearby private wells. However, all the available data from the private non-drinking and drinking water wells indicate that these wells have not been impacted by BTEX contamination at this time. Surface water and sediment in the Rio Grande and the adjacent ditches have not been impacted by contaminants associated with the BTEX groundwater plume.
Site Investigations
Air samples from emission stacks, collected during the treatment system operation, were analyzed for the presence of benzene, ethyl benzene, toluene, and xylenes. The emission sample analyses did not include PCE or TCE, which may have also been present in the plume being treated. The results of the sampling indicate the presence of benzene, toluene, ethylbenzene, and xylenes at levels ranging from 31 to 110 milligrams per cubic meter (mg/m3). Sampling showed nonmethane hydrocarbon emissions totaled 9,300 mg/m3. The concentrations released at the elevated stacks are higher than would occur in the normal breathing zone after mixing with ambient air. Therefore, air data was modeled to estimate more likely exposure concentrations to nearby individuals. Air modeling indicated lower concentrations at the nearest homes and the school and the junior high school (3),(4). Appendix A, Table 1 provides summaries of the air sparging stack sample results and the modeled data.
Appendix A, Table 1 Air Emissions Data: Source and Modeled (µg/m3)
| Chemical | Source1 | Nearest Resident (Modeled)2 | Jr. High School (Modeled)2 | CV | CV Source | ||
| Annual Avg. |
Maximum 1-hr. |
Annual Avg. |
Maximum 1-hr. |
||||
| Benzene | 38,000 | 0.10 | 2.0 | 0.0070 | 2.0 | 0.10 4.0 50 |
CREG Int. EMEG/MRL Acute MEG/MRL |
| Toluene | 62,000 | 0.15 | 6.0 | 0.10 | 5.0 | 80 400 1,000 |
Chronic EMEG RfC Acute EMEG/MRL |
| Ethylbenzene | 31,000 | 0.10 | 2.0 | 0.070 | 2.0 | 1,000 | Chronic RMEG/RfC |
| Xylenes | 110,000 | 0.30 | 10 | 0.20 | 10 | 100 700 1,000 |
Chronic EMEG/MRL Int. EMEG/MRL Acute EMEG/MRL |
| TNH | 9,300,000 | 22 | 900 | 200 | 1,000 | NA | NA |
Notes:
1. Maximum detected concentration from samples collected at
two emission stacks (contaminant source).
2. Concentrations have been modeled based on the maximum detected concentrations
at the source.
Shaded concentrations indicate that comparison value(s) have been exceeded.
µg/m3 = micrograms per cubic meter
CV = Comparison Value
TNH = Total Nonmethane Hydrocarbons
NA = not available
CREG = Cancer Risk Evaluation
Int. = intermediate
EMEG = Environmental Media Evaluation Guide
RMEG = Reference Dose Media Evaluation Guide
MRL = Minimal Risk Level
RfC = Reference Concentration
Public Health Implications
Workers and others in the vicinity of the treatment unit used in 1995 were likely exposed via inhalation to petroleum-related chemicals in the past. While toluene, ethylbenzene, and xylenes were also detected in air samples (below their respective health-based value), the main constituent of concern in the BTEX plume regarding exposure is benzene. The estimated 1-hour maximum concentrations and annual average of benzene in ambient air are below ATSDR's screening value for non-carcinogenic health effects (for example, Environmental Media Evaluation Guide). However, benzene concentrations exceed the health-based levels for cancerous effects (for example, Cancer Risk Evaluation Guide).
Benzene has been shown in human and animals studies to cause various types of cancers, in particular leukemia. Key human studies indicate that cancer resulted among individuals exposed to benzene via inhalation for at least 10 years at concentrations that are many thousands of times greater than the concentrations associated with the air sparging units (5). Benzene emitted from the sparging units was quickly diluted by the large volume of ambient air. Because the remediation system was operational for only 1 year, exposure to benzene in ambient air was limited and health effects resulting from exposure are unlikely.
Conclusions of the Initial PHA
Recommendations of the Initial PHA
Contact for Additional Information
For additional information, including details on the status of the investigation of the petroleum-related groundwater plume in the plaza area of the City of Española, please contact the following person:
Chris Meehan
New Mexico Environment Department
Superfund/Grant
1190 St. Francis Dr., Rm N-2300
Santa Fe, NM 87505
505-476-3777
e-mail: chris_meehan@nmenv.state.nm.us
Figure 1. Vicinity Map, PCE Groundwater Plume
Figure 2. Site Map and Demographic Information
APPENDIX C: EXPLANATION OF EVALUATION PROCESS (6)
Step 1 - The Screening Process
In order to evaluate the available data, ATSDR used comparison values (CVs) to determine which chemicals to examine more closely. CVs are the contaminant concentrations found in a specific media (for example: air, soil, or water) and are used to select contaminants for further evaluation. CVs incorporate assumptions of daily exposure to the chemical and a standard amount of air, water, and soil that someone may inhale or ingest each day. CVs are generated to be conservative and non-site specific. These values are used only to screen out chemicals that do not need further evaluation. CVs are not intended to be used as environmental clean-up levels or to indicate that health effects occur at concentrations that exceed these values.
CVs can be based on either carcinogenic (cancer-causing) or non-carcinogenic effects. Cancer-based comparison values are calculated from the U.S. Environmental Protection Agency's (EPA) oral cancer slope factor (CSF) or inhalation risk unit. CVs based on cancerous effects account for a lifetime exposure (70 years) with an unacceptable theoretical excess lifetime cancer risk of 1 new case per 1 million exposed people. Non-cancer values are calculated from ATSDR's Minimal Risk Levels (MRLs), EPA's Reference Doses (RfDs), or EPA's Reference Concentrations (RfCs). When a cancer and non-cancer CV exists for the same chemical, the lower of these values is used in the comparison for conservatism. The chemical and media-specific CVs utilized during the preparation of this PHA are listed below:
An Environmental Media Evaluation Guide (EMEG) is an estimated comparison concentration for which exposure is unlikely to cause adverse health effects, as determined by ATSDR from its toxicological profiles for a specific chemical.
A Reference Dose Media Evaluation Guide (RMEG) is a comparison concentration that is based on EPA's estimate of the daily exposure to a contaminant that is unlikely to cause adverse health effects.
A Cancer Risk Evaluation Guide (CREG) is a comparison concentration that is based on an excess cancer rate of one in a million persons and is calculated using EPA's cancer slope factor (CSF).
A Maximum Contaminant Level (MCL) is a contaminant concentration that EPA deems protective of public health, and may consider the availability and economics of water treatment technology.
A Life Time Health Advisory (LTHA) is developed by EPA and is considered a lifetime exposure level for contaminants specifically in drinking water (assuming 20% of an individual's exposure comes from drinking water) at which adverse, non-carcinogenic health effects would not be expected to occur.
A Risk-Based Concentration (RBC) is developed by EPA Region III and used primarily in the initial screening process of a baseline risk assessment. EPA toxicity factors have been combined with standard default assumptions in order to generate these values.
Preliminary Remediation Goal (PRG) is a screening tool, generated by EPA Region IX, which is used at the early stages of human exposure evaluation and clean-up considerations at contaminated sites. PRGs are risk-based concentrations derived from standardized equations, combining exposure assumptions and EPA toxicity data. These values are generic and do not take into account available site-specific information.
Step 2 - Evaluation of Public Health Implications
The next step in the evaluation process is to take those contaminants that are above their respective CVs and further identify which chemicals and exposure situations are likely to be a health hazard. Separate child and adult exposure doses (or the amount of a contaminant that gets into a person's body) are calculated for site-specific exposure scenarios, using assumptions regarding an individual's likelihood of accessing the site and contacting contamination. A brief explanation of the calculation of estimated exposure doses for the site is presented below. Calculated doses are reported in units of milligrams per kilograms per day (mg/kg/day).
Exposure Dose Estimation
When chemical concentrations at the site exceed the established CVs, it is necessary for a more thorough evaluation of the chemical to be conducted. In order to evaluate the potential for human exposure to contaminants present at the site and potential health effects from site-specific activities, ATSDR estimates human exposure to the site contaminant from different environmental media by calculating exposure doses. A brief discussion of the calculations and assumptions is presented below.
Ingestion of Contaminants Present in Drinking Water
Exposure doses for ingestion of contaminants present in drinking water were calculated using the maximum detected concentration of PCE or TCE from the sample data, in milligrams per liter (mg/L), multiplied by the drinking water ingestion rates of 2 liters per day (L/day) for adults and 1 L/day for children. The multiplication product was divided by the average body weights for adults and children are 70 kg (154 pounds) and 16 kg (35 pounds), respectively.
Additionally, an exposure frequency of 365 days per year and exposure duration of 14 years (based on the available data and groundwater modeling efforts) to 20 years (worst-case scenario) was incorporated into the dose calculations.
Inhalation of Contaminants Present in Drinking Water
For the evaluation of contaminants released (or volatilized) from water to the surrounding air during showering or bathing, it was assumed that the dose from inhalation was equal to the dose from ingestion of an additional 1 liter/day of drinking water(7). This is considered a protective approach, because actual exposures via inhalation are more likely to be overestimated, rather than underestimated, when this approach is utilized.
As with the ingestion dose calculation, an exposure frequency of 365 days per year and exposure duration of 14 years (based on the available data and groundwater modeling efforts) to 20 years (worst-case scenario) incorporated into the dose calculations.
Direct Skin (or Dermal) Contact with Contaminants Present in Drinking Water
It was assumed that dermal exposure with drinking water occurred primarily during showering and bathing. Dermal absorption depends on numerous factors, including the area of exposed skin, anatomical location of the exposed skin, length of contact, concentration of the chemical in contact with the skin, chemical-specific permeability factors, and other factors. Because chemicals differ greatly in their potential to be absorbed through the skin, each chemical needs to be evaluated separately. The assumed receptor weights, exposure frequency, and exposure duration are the same as described in the ingestion of drinking water calculation discussion.
Exposure doses for dermal contact with contaminants during showering and bathing, the maximum detected concentration measured in groundwater samples, in mg/L, was multiplied by the skin surface area exposure (18,150 and 7,195 cubic centimeters for adults and children, respectively), the chemical-specific permeability constant, and an exposure time of 15 minutes per day.
Direct Skin (or Dermal) Contact with Contaminants Present in Non-Drinking Water
As discussed in the dermal evaluation of drinking water above, dermal absorption depends on a variety of factors, including the specific exposure situation and the properties of each individual chemical. Dermal exposure to contaminants present in non-drinking water was assumed to occur in event this water source was used to fill swimming pools. The maximum detected concentration detected in private non-drinking water samples, measured in mg/L, was multiplied by the same surface areas used to calculate the dermal dose for drinking water exposure, the chemical-specific permeability constant(8), and an exposure time of 2 hours per day to calculate the dermal dose.
Non-Cancer Health Effects
The doses calculated for exposure to each individual chemical are then compared to an established health guideline, such as a MRL or RfD, in order to assess whether adverse health impacts from exposure are expected. These health guidelines, developed by ATSDR and EPA, are chemical-specific values that are based on the available scientific literature and are considered protective of human health. Non-carcinogenic effects, unlike carcinogenic effects, are believed to have a threshold, that is, a dose below which adverse health effects will not occur. As a result, the current practice for deriving health guidelines is to identify, usually from animal toxicology experiments, a No Observed Adverse Effect Level (or NOAEL), which indicates that no effects are observed at a particular exposure level. This is the experimental exposure level in animals (and sometimes humans) at which no adverse toxic effect is observed. The NOAEL is then modified with an uncertainty (or safety) factor, which reflects the degree of uncertainty that exists when experimental animal data are extrapolated to the general human population. The magnitude of the uncertainty factor considers various factors such as sensitive subpopulations (for example; children, pregnant women, and the elderly), extrapolation from animals to humans, and the completeness of available data. Thus, exposure doses at or below the established health guideline are not expected to result in adverse health effects because these values are much lower (and more human health protective) than doses, which do not cause adverse health effects in laboratory animal studies. For non-cancer health effects, the following health guidelines are described below in more detail. It is important to consider that the methodology used to develop these health guidelines does not provide any information on the presence, absence, or level of cancer risk. Therefore, a separate cancer evaluation is necessary for potentially cancer-causing chemicals detected in samples at this site. A more detailed discussion of the evaluation of cancer risks is presented in the following section.
Minimal Risk Levels (MRLs) - developed by ATSDR
ATSDR has developed MRLs for contaminants commonly found at hazardous waste sites. The MRL is an estimate of daily exposure to a contaminant below which non-cancer, adverse health effects are unlikely to occur. MRLs are developed for different routes of exposure, such as inhalation and ingestion, and for lengths of exposure, such as acute (less than 14 days), intermediate (15-364 days), and chronic (365 days or greater). At this time, ATSDR has not developed MRLs for dermal exposure. A complete list of the available MRLs can be found at http://www.atsdr.cdc.gov/mrls.html.
References Doses (RfDs) - developed by EPA
An estimate of the daily, lifetime exposure of human populations to a possible hazard that is not likely to cause non-cancerous health effects. RfDs consider exposures to sensitive sub-populations, such as the elderly, children, and the developing fetus. EPA RfDs have been developed using information from the available scientific literature and have been calculated for oral and inhalation exposures. A complete list of the available RfDs can be found at http://www.epa.gov/iris
If the estimated exposure dose for a chemical is less than the health guideline value, the exposure is unlikely to result in non-cancer health effects. Non-cancer health effects from dermal exposure was evaluated slightly differently that ingestion and inhalation exposure. Since health guidelines are not available for dermal exposure, the calculated dermal dose was compared with the adjusted oral health guideline value (RfD or MRL). The oral health guideline value was adjusted using the gastrointestinal absorption factor to account for an "absorbed dose" (for dermal exposure) rather than an "administered dose" (for ingestion exposure). To make this modification, the oral health guideline value is multiplied by the gastrointestinal absorption factor.
If the calculated exposure dose is greater than the health guideline, the exposure dose is compared to known toxicological values for the particular chemical and is discussed in more detail in the text of the PHA. The known toxicological values are doses derived from human and animal studies that are summarized in the ATSDR Toxicological Profiles. A direct comparison of site-specific exposure doses to study-derived exposures and doses found to cause adverse health effects is the basis for deciding whether health effects are likely to occur.
Cancer Risks
Exposure to a cancer-causing compound, even at low concentrations, is assumed to be associated
with some increased risk for evaluation purposes. The estimated excess risk of developing cancer
from exposure to contaminants associated with the site was calculated by multiplying the site-specific adult exposure doses, with a slight modification, by EPA's chemical-specific Cancer Slope
Factors (CSFs or cancer potency estimates), which are available at http://www.epa.gov/iris .
Calculated dermal doses were compared with the adjusted oral CSFs which were adjusted using the
gastrointestinal absorption factor to account for an "absorbed dose" (for dermal exposure) rather than
an "administered dose" (for ingestion exposure). To make this modification, the oral CSF was
divided by the gastrointestinal absorption factor.
An increased excess lifetime cancer risk is not a specific estimate of expected cancers. Rather, it is an estimate of the increase in the probability that a person may develop cancer sometime during his or her lifetime following exposure to a particular contaminant. Therefore, the cancer risk calculation incorporates the equations and parameters (including the exposure duration and frequency) used to calculate the dose estimates, but the estimated value is divided by 25,550 days (or the averaging time), which is equal to a lifetime of exposure (70 years) for 365 days/year.
There are varying suggestions among the scientific community regarding an acceptable excess lifetime cancer risk, due to the uncertainties regarding the mechanism of cancer. The recommendations of many scientists and EPA have been in the risk range of 1 in 1 million to 1 in 10,000 (as referred to as 1 x 10-6 to 1 x 10-4) excess cancer cases. An increased lifetime cancer risk of one in one million or less is generally considered an insignificant increase in cancer risk. An important consideration when determining cancer risk estimates is that the risk calculations incorporate several very conservative assumptions that are expected to overestimate actual exposure scenarios. For example, the method used to calculate EPA's CSFs assumes that high-dose animal data can be used to estimate the risk for low dose exposures in humans. As previously stated, the method also assumes that there is no safe level for exposure. Lastly, the method computes the 95% upper bound for the risk, rather than the average risk, suggesting that the cancer risk is actually lower, perhaps by several orders of magnitude.
Because of the uncertainties involved with estimating carcinogenic risk, ATSDR employs a weight-of-evidence approach in evaluating all relevant data. Therefore, the carcinogenic risk is also described in words (qualitatively) rather than giving a numerical risk estimate only. The numerical risk estimate must be considered in the context of the variables and assumptions involved in their derivation and in the broader context of biomedical opinion, host factors, and actual exposure conditions. The actual parameters of environmental exposures have been given careful and thorough consideration in evaluating the assumptions and variables relating to both toxicity and exposure. A complete review of the toxicological data regarding the doses associated with the production of cancer and the site-specific doses for the site is an important element in determining the likelihood of exposed individuals being at a greater risk for cancer. A table with the numeric and qualitative cancer risk estimates for each of the completed exposure pathways is presented below.
Cancer Risk Estimates
| Pathway | Route(s) of Exposure | Chemical | Numeric Cancer Risk Estimate | Qualitative Cancer Risk Estimate |
| Drinking Water - Public Water Supply1 | Ingestion Inhalation Direct Contact |
PCE-monitoring well | 3.7x10-4 to 5.3x10-4 | Moderate |
| TCE-monitoring well | 5.3x10-6 to 7.5x10-4 | Low | ||
| Non-Drinking Water - Private Well Supply |
Direct Contact | PCE | 2.6 x 10-5 | Low-Moderate |
| TCE | 4.2 x 10-6 | Low | ||
| Chloroform | 7.5 x 10-7 | Insignificant | ||
| 1,2-DCA | 2.3 x 10-8 | Insignificant |
1. Drinking water supply estimates are based on data collected from monitoring wells in the vicinity of the contaminated public supply wells (Bond and Jemez wells). The ranges presented for the numeric cancer risk estimates for the public water supply reflect the results of calculations based on a 14-year exposure duration (based on groundwater modeling efforts) and a 20-year exposure duration (worst-case scenario; assumes exposure from the time operations began at the Norge Town facility).
Appendix C, Table 1. Exposure Pathways for NRAP Site
| PATHWAY NAME | ENVIRONMENTAL MEDIA & TRANSPORT MECHANISMS | POINT OF EXPOSURE | ROUTE OF EXPOSURE | EXPOSURE POPULATION | TIME | NOTES | COMPLETE/ POTENTIAL EXPOSURE PATHWAY? |
| Groundwater; Public Water Supply | Movement of contaminants discharged from the lint trap from soil to groundwater | Municipal Drinking Water | Ingestion, inhalation (showering), direct contact | City water supply users | Past | -PCE and TCE detected -Public water supply data available: 1989 to 1991 -Monitoring well data available: 1992 to 1999 |
YES |
| Groundwater, Private Wells (Non-Drinking Water Purposes) |
Movement of contaminants discharged from the lint trap from soil to groundwater | Private Wells | Direct Contact | Residents with private wells | Past, Present, Future | -PCE, TCE, DCE, chloroform detected -Data available for seven private wells within Española |
YES |
| Indoor Air | Volatilization of contaminants from soil and groundwater to indoor air | Air within buildings overlying the groundwater plume | Inhalation | Workers, residents, etc. | Past, Present, Future | -1,1-Dichloroethene, 1,2,4-trimethylbenzene detected -Data available Las Cumbres Learning Services, Inc. (office, classroom), Jr. High School library, and private residence on Chavez Street |
YES |
| Outdoor Air | Volatilization of contaminants from soil and groundwater to outdoor air | Outdoor air in areas overlying the groundwater plume | Inhalation | Workers, residents, etc. | Past, Present, Future | -PCE, 1,2,4-trimethylbezene detected -Data available from Las Cumbres play area and the lint trap (source) |
YES |
| On-Site Soil | Movement of contaminants discharged from the lint trap to soil | Surface soil in the vicinity of the Norge Town facility (lint trap) | Incidental ingestion, inhalation, direct contact | Workers, trespasser, store patron (limited) | Past, Present, Future | -PCE, naturally-occurring metals -Data available for area surrounding source (1996-1999) -Exposure is considered very limited and not of public health concern |
NO |
| Off-Site Soil | Movement of contaminants discharged from the lint trap to soil | Surface soil in areas in close proximity to the Norge Town facility | Incidental ingestion, inhalation, direct contact | Residents | Past, Present, Future | -No contaminants of concern detected in soil sampled collected from the Las Cumbres facility in 1999 | NO |
| Groundwater, Private Wells (Drinking Water Purposes) | Movement of contaminants discharged from the lint trap from soil to groundwater | Private Wells | Ingestion, inhalation (showering), direct contact | Residents | Past, Present, Future | -No contaminants detected in the only potable private
well located within the plume boundary (within the City of Española),
which is not in use. -No contaminants have been detected in private wells located on the Santa Pueblo |
NO |
| Surface Water | Movement of contaminants from groundwater to surface water | Rio Grande and associated drainage ditches | Direct contact | Residents | Past, Present, Future | -No contaminants have been detected in surface water samples collected in 1996 and 1999 | NO |
| Sediment | Movement of contaminants from groundwater to surface water to sediment | Rio Grande and associated drainage ditches | Direct contact | Residents | Past, Present, Future | -No contaminants have been detected in sediment samples collected in 1996 and 1999 | NO |
| Fish Uptake | Discharge of contaminants from groundwater to surface water (Rio Grande) | Fish Consumption | Ingestion | Residents | Past, Present, Future | -No fish tissue samples have been collected. -Surface water has not been impacted by the site, based on data collected in 1996 and 1999. -PCE is not likely to bioaccumulate in fish. |
NO |
| Animal Uptake | Discharge of contaminants from groundwater to surface water that is given to livestock | Livestock Consumption | Ingestion | Residents | Past, Present, Future | -Surface water has not been impacted by the site, based
on data collected in 1996 and 1999 -PCE is not likely to bioaccumulate in livestock
|
NO |
. Searched October 2001.Next Section Table
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