Archived News Release: January 6, 2023 - City of Ann Arbor drinking water remains safe to drink. City drinking water comes from the Huron River and groundwater wells that are monitored regularly before and after treatment to ensure your water remains safe from 1,4-dioxane and other contaminants.
Background on the 1,4-dioxane plume: From 1966 to 1986 Gelman Sciences improperly disposed of industrial solvent, causing a plume of 1,4-dioxane contamination in groundwater that is currently four miles long by one mile wide beneath the City of Ann Arbor and Scio Township. Gelman sciences is responsible for containing the plume, as ordered by the 1992 Consent Judgement and the three subsequent amendments approved by Washtenaw County Circuit Court. Gelman continues to pump groundwater to the surface and treat it using advanced oxidation, and Gelman is also responsible for connecting properties to municipal water if they have wells exceeding health-based limits for 1,4-dioxane.
Oversight of the monitoring and remediation has been provided by Michigan Department of Environment, Great Lakes, and Energy (EGLE) during the past 30 years. In April 2021, EGLE Director Liesl Clark sent a letter to the Environmental Protection Agency (EPA) Region 5 requesting the EPA reinitiate assessment of the Gelman site for the National Priorities List process. EPA's site inspection is underway. The process of determining whether the site should be on EPA's NPL is expected to take three years, and EPA's process for developing a cleanup plan for a new site can take more than a decade. In the meantime, EGLE will continue to oversee the site according to the Washtenaw County Circuit Court's Consent Judgment and the three approved amendments.
City's monitoring strategy: The City of Ann Arbor has been monitoring its water sources and the plume for more than 30 years to ensure the long-term safety of the city's drinking water. In 2022, city staff installed additional sentinel wells between the leading edge of the plume and Barton Pond to provide advanced warning if the plume migrates toward our source water. The city also uses residential test well sampling data to identify the outer limits of the plume and to help understand its migration pathways. The sentinel well and residential well monitoring will ensure the city has sufficient time to respond and protect the city's water before contamination ever has a chance to reach our drinking water source.
What does the city do if a well in Ann Arbor Township tests higher than normal? City staff communicate regularly with the Washtenaw County Health Department who have responsibility for public health impacts associated with exposure to the plume in residential wells. Washtenaw County Health Department has conducted additional sampling at the impacted well in Ann Arbor Township and at nearby wells to confirm the positive test results. If 1,4-dioxane levels are confirmed to be above health-based limits at this location, the State of Michigan will initiate plans to connect them to City of Ann Arbor water.
Where can you find City of Ann Arbor's 1,4-dioxane testing data? The city continues to test intake and drinking water regularly to ensure it remains safe to consume. Test result data is provided on our website: www.a2gov.org/DrinkingWater. Check out the quick link at the top of our home page to 1,4 Dioxane Testing data,which is update monthly.
As always, please continue to contact us if you have questions about your drinking water at [email protected] or in the case of an emergency you can reach us by phone at 734.794.6426.
Becky Lahr, PhD, City of Ann Arbor Drinking Water Quality Manager
