LE MARS COAL GAS SITE
LE MARS, PLYMOUTH COUNTY, IOWA
Media for consideration regarding potential human exposure include: soil, air and groundwater. The potential routes of human exposure for each media at the Le Mars Coal Gas site are:
- Soil -- Ingestion and dermal contact.
- Air -- Inhalation of vapors and dust resuspended from media containing contamination.
- Groundwater -- Ingestion and dermal contact.
To evaluate the public health significance of contamination at Le Mars Coal GasSite specific information (e.g.locationconcentrationlikelihood exposureetc.) and environmental data were reviewed. Soil (surface subsurface)sediment groundwater are contaminated with SVOCs VOCs TPH. highest concentrations detected in subsurface located approximately 6 to 17 feet bgs.
There were a limited number of surface soil samples collected on and off site. Detectable levels of VOCs, SVOCs, and inorganic compounds were found. However, if these sample results are representative, then adverse health effects are not expected to occur.
The nearest residence is located approximately 50 feet south of the site. Inhalation of vapors and resuspended dust from areas containing contamination is unlikely. VOCs detected in surface and subsurface soil samples and groundwater do not pose a health risk.
Le Mar City obtains water from a series of municipal wells located throughout the city. Municipal Wells No. 4 and No. 8 are located downgradient of the site and supply water to the north reservoir. Groundwater samples collected from Municipal Wells No. 4 and No. 8 indicate that Municipal Well No. 8 has been impacted by site-related constituents. However, detected concentrations were below levels of concern. Also, the groundwater from all municipal wells is blended and no single well within the blended system contributes more than 40% of the total system output.(2) Private residential drinking water wells do not exist downgradient from the site within city limits (at least 3000 feet). Six residential wells are within one mile of the site.
Based on the concentration of benzo(a)pyrene detected in Well No.8, short-term or long-term exposure is not expected to result in adverse effects. Long-term exposure to concentrations above the health-based comparison levels could pose a health risk. Discussions with the Le Mars water superintendent have indicated that Municipal Wells No.4 and No. 8 will be used for stand-by purposes in the future (approximately 10 years).(2) Based on the information reviewed for this health consultationit is unlikely that children were exposed to unacceptable concentrations of site constituents from Le Mars Coal Gas in past.
IDPH has not identified any current exposure scenarios for children at the Le Mars Coal Gas site. The greatest potential for exposure is from the public drinking water supply via the Le Mars Municipal Well system. Municipal Wells No. 4 and No. 8 are nearest the site. Municipal Well No. 8 had detectable levels of B(a)P during one sampling event in 1997. However, the concentration was below the health-based comparison value.
The most likely future scenario where children may be exposed to constituents of concern from the Le Mars Coal Gas site is from the public drinking water supply via the Le Mars Municipal Well system. The contaminant plume has not been fully delineated to the north and south. If the Municipal Wells No. 4 and No. 8 are impacted in the future, exposure to unacceptable levels of contamination may occur.