Hazardous Sites and Substances in Minnesota
Update: Perfluorochemicals and the City of Oakdale Public Water Supply
As you are aware, local and state agencies are continuing to monitor levels of perfluorochemicals (PFCs) in wells serving the Oakdale public water supply. The purpose of this page is to let you know about what has happened since the problem was discovered, and the steps that have been taken to address the issue.
Water Filtration Plant
On October 30, 2006, the city began operating a new filtration plant designed to remove PFCs from water coming from city wells #5 and #9. Well #9 is the city’s newest and largest capacity well. The design and construction of the plant was financed by the 3M Company. The plant will operated by city staff with the ongoing costs paid by 3M.
The plant uses large granular activated carbon (GAC) filters to remove PFCs from the water. Testing by the Minnesota Department of Health show that the filters remove most PFCs from the water. The special material in the filters is made from raw materials (such as coconut shells) that are high in carbon. Heat is used to increase (activate) the surface area of the carbon, allowing it to trap organic chemicals as the water passes over it. Eventually the ability of the carbon to trap chemicals is used up and the carbon must be replaced. Periodic testing of the wells and filters tells the operators when it is necessary to change the carbon.
The city’s water filtration system eliminates most PFCs from the Oakdale Municipal water supply. In the summer when demand for water is the highest, the city may need to use other wells that are not treated but will minimize the levels of PFCs in the water supply by careful management of the system. This management strategy depends on water demand during the peak summer months, the amount of rainfall, and on citizens taking steps to conserve water when possible. We strongly encourage citizens to cooperate with the permanent odd/even watering ban (with exemptions for new grass and certain businesses), to repair plumbing leaks promptly and to use other water conservation measures as much as possible. The city is also committed to replacing other city wells that have been impacted by PFCs with at least one new well (being financed by 3M) that will be free of PFCs.
Beginning in late 2004, the Minnesota Department of Health (MDH), working with the City of Oakdale and 3M, began testing drinking water from the wells that serve the Oakdale public water supply for PFCs. Initially the testing was for PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate), but the later, as new lab methods became available, the list of chemicals was expanded to include five more PFCs:
- Perfluorobutane sulfonate (PFBS),
- Perfluorobutanoic acid (PFBA),
- Perfluoropentanoic acid (PFPeA),
- Perfluorohexane sulfonate (PFHxS), and
- Perfluorohexanoic acid (PFHxA).
Some of these chemicals have been detected in groundwater samples from monitoring wells at the Abresch disposal site in Oakdale and the Washington County Landfill in Lake Elmo.
MDH has tested seven city wells on a monthly (now quarterly) basis and reported results to the city. PFCs have been detected in measurable amounts in four wells and levels lower than the detection limit in two wells. Testing of the five chemicals more recently included has found PFBA, PFPeA, PFHxS, and PFHxA at low levels, and no detections of PFBS. Three of the additional chemicals (PFPeA, PFHxS, and PFHxA) were only found in wells that had previous detections of PFOA and PFOS. However, PFBA was detected at very low levels in wells that previously had no detections of PFCs. The city also has an eighth city available that has had no detections of PFCs. Levels of PFCs in the city water system are below current MDH health guidelines.
We will continue to give you updates as new information and developments arise.
For more information, please contact us.
Washington County (general groundwater issues)
Public Health & Environment, 651-430-6655
City of Oakdale (utility operator)
Brian Bachmeier, Public Works Director, 651-730-2730
Chris Sonterre, Water Superintendent, 651-730-2740
Minnesota Pollution Control Agency: Perfluorochemicals
Environmental Protection Agency: Perfluorooctanoic Acid (PFOA) and Fluorinated Telomers