Program Overview: Contaminants being Investigated at Camp Navajo
Contaminants being investigated at Camp Navajo are the specific chemical substances that may have been spilled or disposed in such a manner as to result in residual concentrations that may pose a threat to human health and the environment. They are evaluated through the following steps:
The first phase of investigation (sometimes called a Preliminary Assessment or Archives Search), involves reviewing historic documents, maps, drawings, and photographs, and conducting interviews and site visits with current or former employees, to understand what types of activities were conducted at different sites throughout the installation. Based on the known or suspected site activities, a list is generated of the hazardous or toxic chemicals that may have been stored, used, disposed, or spilled at each site.
The second phase of investigation (sometimes called a Site Inspection) involves collecting samples at locations most likely to have been impacted by site activities and testing them for the full list of analytes. The detected analytes are compared to background levels. If they are present above background levels, they are considered for future study, making them potential contaminants of concern. The third phase of investigation (sometimes called a Remedial Investigation) involves additional sampling to determine the nature and extent of the potential contaminants of concern.
The concentrations are screened against various standards maintained by ADEQ and EPA, such as Soil Remediation Levels, Aquifer Water Quality Standards, and Surface Water Quality Standards. These standards represent conservative thresholds below which the analytes do not pose any health concern. If the concentration of an analyte is above the screening standard, it is further evaluated in a site-specific human health risk assessment. This includes looking at how people might be exposed to the chemical and how much of the chemical they could come into contact with. Exposure pathways considered include air, water, and soil, or even game or fish consumption if pertinent.
The Camp Navajo Installation Restoration Program and Open Burn/Open Detonation Area Closure Program then performs a toxicity assessment. The assessment uses the regulatory standards set by the EPA to determine any potential harmful effects of any analytes that are found to be above background levels and to which people are or could be exposed.
An ecological risk assessment also is performed using similar steps to look at the toxicity and exposure data for plants and animals. Risk is characterized for a small number of species that are representative of larger groups of species or that are environmentally important.
Finally, the Camp Navajo Installation Restoration Program and Open Burn/Open Detonation Area Closure Program completes a Risk Characterization by weighing both toxicity of any potential contaminant of concern and the exposure pathways. These are compared with the EPA standards, to identify the final Contaminants being investigated at Camp Navajo. The Camp Navajo Installation Restoration Program and Open Burn/Open Detonation Area Closure Program uses the Risk Characterization and the Ecological Risk Assessment to determine the best way to protect human health and the environment.
