Health Consultation Potential for TCE Exposure in Indoor and Ambient Air at the Source Area: Baytown Township Groundwater Contamination Site Baytown Township, Washington County, Minnesota EPA Facility ID: MND982425209 Prepared by the Minnesota Department of Health JULY 17, 2009 Prepared under a Cooperative Agreement with the U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Agency for Toxic Substances and Disease Registry Division of Health Assessment and Consultation Atlanta, Georgia 30333 Health Consultation: A Note of Explanation A health consultation is a verbal or written response from ATSDR or ATSDR’s Cooperative Agreement Partners to a specific request for information about health risks related to a specific site, a chemical release, or the presence of hazardous material. In order to prevent or mitigate exposures, a consultation may lead to specific actions, such as restricting use of or replacing water supplies; intensifying environmental sampling; restricting site access; or removing the contaminated material. In addition, consultations may recommend additional public health actions, such as conducting health surveillance activities to evaluate exposure or trends in adverse health outcomes; conducting biological indicators of exposure studies to assess exposure; and providing health education for health care providers and community members. This concludes the health consultation process for this site, unless additional information is obtained by ATSDR or ATSDR’s Cooperative Agreement Partner which, in the Agency’s opinion, indicates a need to revise or append the conclusions previously issued. You May Contact ATSDR Toll Free at 1-800-CDC-INFO or Visit our Home Page at: http://www.atsdr.cdc.gov HEALTH CONSULTATION Potential for TCE Exposure in Indoor and Ambient Air at the Source Area: Baytown Township Groundwater Contamination Site Baytown Township, Washington County, Minnesota EPA Facility ID: MND982425209 Prepared By: The Minnesota Department of Health Under a Cooperative Agreement with: Public Health Service Agency for Toxic Substances and Disease Registry U.S. Department of Health and Human Services Atlanta, Georgia FOREWORD This document summarizes public health concerns at a groundwater contamination site in Minnesota. It is based on a formal site evaluation prepared by the Minnesota Department of Health (MDH). A number of steps are necessary to do such an evaluation: Evaluating exposure: MDH scientists begin by reviewing available information about environmental conditions at the site. The first task is to find out how much contamination is present, where it is found on the site, and how people might be exposed to it. Usually, MDH does not collect its own environmental sampling data. We rely on information provided by the Minnesota Pollution Control Agency (MPCA), U.S. Environmental Protection Agency (EPA), and other government agencies, businesses, and the general public. Evaluating health effects: If there is evidence that people are being exposed—or could be exposed—to hazardous substances, MDH scientists will take steps to determine whether that exposure could be harmful to human health. The report focuses on public health—the health impact on the community as a whole—and is based on existing scientific information. Developing recommendations: In the evaluation report, MDH outlines its conclusions regarding any potential health threat posed by a site, and offers recommendations for reducing or eliminating human exposure to contaminants. The role of MDH in dealing with individual sites is primarily advisory. For that reason, the evaluation report will typically recommend actions to be taken by other agencies—including EPA and MPCA. However, if there is an immediate health threat, MDH will issue a public health advisory warning people of the danger, and will work to resolve the problem. Soliciting community input: The evaluation process is interactive. MDH starts by soliciting and evaluating information from various government agencies, the organizations responsible for cleaning up the site, and the community surrounding the site. Any conclusions about the site are shared with the groups and organizations that provided the information. Once an evaluation report has been prepared, MDH seeks feedback from the public. If you have questions or comments about this report, we encourage you to contact us. Please write to: Community Relations Coordinator Site Assessment and Consultation Unit Minnesota Department of Health 625 Robert Street N. / Box 64975 St. Paul, MN 55164-0975 OR call us at: (651) 201-4897 or 1-800-657-3908 (toll free call—press "4" on your touch tone phone) On the web: http://www.health.state.mn.us/divs/eh/hazardous/index.html 2 I. Summary of Background and History Executive Summary In 2004, the source of the trichloroethylene (TCE) at the Baytown Township Groundwater Contamination Site was discovered at what is now a small market and gas station in Lake Elmo, Minnesota. Remedial actions are under way to remove the TCE from the groundwater at the source through air stripping. Based on indoor and ambient air data collected to date, it appears that any exposures to TCE at the source area are minor for employees or visitors at the market, and do not represent a public health concern. Purpose This purpose of this Health Consultation is to evaluate the potential for exposure to TCE in indoor and ambient air at the source of the TCE contamination in Lake Elmo. The Minnesota Department of Health (MDH) was requested to evaluate TCE data for the site by the Minnesota Pollution Control Agency (MPCA) and the owners of the market and determine if TCE exposure was of concern from a public health standpoint. Background The Baytown Township Groundwater Contamination Site was first discovered in 1987, and investigation and response actions by state and local entities have been ongoing since that time. The Site is primarily the result of the disposal or spillage of an unknown quantity of trichloroethylene (a.k.a. trichloroethene, or TCE) at what was once a metal fabricating shop located in the city of Lake Elmo; other minor sources may also exist. The Site consists of an area of groundwater contamination that is in excess of six square miles, and affects four major groundwater aquifers. The MDH has enacted a Special Well Construction Area (SWCA) at the Site to regulate the construction of new wells. The boundaries of the SWCA, which essentially define the Site, are shown in Figure 1. Also shown in Figure 1 are the location of the source of the TCE contamination mentioned above and the Lake Elmo Airport, a major surface feature of the Site that was once considered the most likely source of the TCE. Several hundred private water supply wells in Baytown and West Lakeland Townships, and private and public wells in the City of Bayport have been impacted by the TCE contamination. The highest current concentration of TCE in a private well (approximately 100 micrograms per liter; g/L) has been found at the Lake Elmo Airport. Exposure to TCE above Minnesota health- based criteria in private wells (i.e., the MDH Health Risk Limit (HRL) of 5 g/L) is currently being prevented by requiring property owners to have new private water supply wells constructed to deeper, clean aquifers where possible, or by the use of large, whole-house granular activated carbon (GAC) filtration units for existing private wells and new private wells where a clean aquifer is not available or feasible and concentrations of TCE exceed the HRL. GAC filters for private wells are typically provided by the MPCA. However, for wells on properties platted after April 9, 2002, GAC filters are not provided by the MPCA. To protect public health in these cases, Baytown and West Lakeland Townships, with the assistance of MDH, enacted ordinances to ensure that newer homes not provided GAC filters by the MPCA will have appropriate GAC filter systems installed and maintained by the homeowners. To date, approximately 200 GAC systems are in place on private wells in Baytown and West Lakeland 3 Townships and the City of Bayport due to levels of TCE at or above the HRL, and are being tracked and managed by the MPCA or the two townships. Additional private well owners with levels of TCE below the HRL have installed GAC filter systems on their own. One municipal well serving the City of Bayport water supply had TCE levels in excess of the federal Maximum Contaminant Level (MCL) of 5 g/L. A treatment system (air stripper) was installed by the MPCA to remove TCE to below detectable levels. Two other municipal wells in Bayport have also shown low levels of TCE, typically around 1 g/L. General information on the geology and hydrogeology of the area, previous investigations, and past response activities at the Site was most recently summarized in a Public Health Assessment (MDH 2004). The generation of nitrite from nitrate within GAC filter systems in operation on certain wells at the Site was reviewed in a Health Consultation dated November 9, 2007 (MDH 2007a). This Health Consultation will focus on the potential for exposure to TCE in air at the source of the TCE contamination in Lake Elmo, both inside the building at the Site as well as in ambient air as a result of a groundwater treatment system installed at the Site. Groundwater conditions at and downstream of the source will be reviewed in a future document. Identification of the TCE Source For many years, the Lake Elmo Airport was considered the most likely source of the TCE at the Site because of its history of aircraft operation, maintenance and repair, and the Metropolitan Airports Commission (MAC) was considered the responsible party under state and federal Superfund law. In 2002, after many years of investigation at the Lake Elmo Airport failed to identify a significant source of TCE, the MAC asked their consultant, Conestoga-Rovers & Associates (CRA) to review historical records for the City of Lake Elmo, located “upstream” in terms of groundwater flow.