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HEALTH CONSULTATION

GENERAL MOTORS CORPORATION SITE
SIOUX CITY, WOODBURY COUNTY, IOWA


DISCUSSION

Media for consideration regarding potential human exposure at this site include: soil, air and groundwater. The relevant routes of human exposure for each media are:

  • Soil -- Ingestion and dermal contact.
  • Air -- Inhalation of vapors and dust resuspended from areas containing contamination.
  • Groundwater -- Ingestion and dermal contact.

Based on the information and data reviewed, soil (surface and subsurface) and groundwater are contaminated with VOCs and TPH.

The nearest resident is located on a steep bluff approximately 300 feet north 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.

Sioux City obtains water from a municipal well field located southeast, east and northeast of the site. Well No.4 and Well No. 3 are located approximately 500 feet and 1000 feet, respectively, from the southeastern corner of the site. Analysis of samples from municipal wells revealed that 1,2-DCA was present in Well No. 3 which is screened from approximately 130-312 feet. Private residential wells do not exist near the site.

Based on the concentration of chlorinated VOCs detected in Well No.3, short-term exposure is not expected to result in adverse effects. Some of the chlorinated VOCs are classified by EPA as probable human carcinogens. Long-term exposure to levels above the chemical specific clean-up levels could pose a health risk. However, long-term exposure is unlikely due to the location of the contamination, the absence of site-related compounds in the municipal wells, decreased pumping rates in Wells No. 3 and No. 4, and the evidence of biodegradation. However, if the municipal wells are pumped at greater rates, then detectable levels of chlorinated VOCs may result.

Children's Health Section:

It is unlikely that children were exposed to constituents from the GMC site in the past. Discussions with Sioux City Water Plant personnel indicate that chlorinated VOCs have not been detected in the past.

IDPH has not identified any current exposure scenarios for children at the GMC site. The greatest potential for exposure is from the public drinking water supply via the Sioux City Municipal Well system. Municipal Wells No. 3 and No. 4 are nearest the site. Municipal Well No. 3 had detectable levels of 1,2-DCA during one sampling event in 1994. However, since 1994, Sioux City Municipal Wells No. 3 and No. 4 have been operating at a reduced pumping rate.

The most likely future scenario where children may be exposed to constituents of concern from the GMC site is from the public drinking water supply via the Sioux City Municipal Well system. If the Municipal Wells No. 3 and No. 4 are pumped at higher rates (normal rates) due to seasonal demand or other reasons then site contaminants may be detected in those wells.

 

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