IDPH compared the concentration of each chemical detected during sampling with appropriate comparison values used to select contaminants for further evaluation for carcinogenic and noncarcinogenic health endpoints. Chemicals at levels that exceeded comparison values or those for which no comparison value exists were selected for further evaluation. A discussion of each of the comparison values is found in Attachment 4.
On-site groundwater samples collected in 1994 did not contain site-related contaminants. Arsenic was detected in a well at 68.7 parts per billion (ppb). Although the concentration is slightly elevated, arsenic is a naturally-occurring element with widespread distribution throughout Illinois groundwater. The presence of arsenic in the well is most likely not related to the site. No other contaminants were identified at levels above comparison values; however, some well water contained manganese, iron, chloride, and sulfate at levels above secondary (aesthetic) standards.
Results of the 1995 on-site surface soil and sediment sampling identified the presence of low levels of polycyclic aromatic hydrocarbons (PAHs). The PAH benzo(a)pyrene was slightly elevated in one sediment sample at 0.13 parts per million (ppm) . PAHs are commonly-found contaminants associated with crude oil, coal, and gasoline. They are produced whenever substances are burned and are present in products made from fossil fuels. Benzo(a)pyrene is one of the most potent and well-studied PAHs. Inorganic contaminants, including arsenic and heavy metals, were not detected at levels that might cause adverse health effects if persons are exposed to them.