PFAS/PFOS
PFAS Right-to-Know Notice: Dupo PFOS Result and Columbia Emergency Interconnection
Why This Page Exists
The Illinois Environmental Protection Agency (Illinois EPA) directed the City of Columbia to notify our customers under Illinois “Right-to-Know” requirements because a PFOS result has been detected above the applicable standard in the Village of Dupo's Community Water System. The City of Columbia has an emergency interconnection with the Village of Dupo.
This page provides Columbia-specific context and links to the official Illinois EPA Public Health Notice.
Key Points for Columbia Water Customers
This notice is triggered by Dupo’s reported PFOS result and the existence of an authorized emergency interconnection—not by a Columbia exceedance.
Columbia's drinking water is purchased from Illinois American Water Company.
Illinois American Water Co. treats surface water drawn from the Mississippi River. Dupo operates their own water treatment facility, and treats ground water drawn from wells.
The Columbia–Dupo connection is an emergency interconnect for Dupo’s benefit
Illinois EPA encourages/typically expects community water systems to maintain redundancy (including emergency interconnections) to help ensure continuity of service if a primary source is unavailable. In this case, Columbia serves as an emergency backup source for Dupo through an interconnection designed for Columbia → Dupo flow under normal operating conditions.
Columbia has multiple interconnects with Illinois American Water Co., satisfying the requirement for redundancy.
The interconnection exists to provide an emergency backup pathway for Dupo in the event Dupo needs an alternate supply.
Under normal operating conditions, Dupo water cannot flow into Columbia through this connection
Columbia operates at a higher pressure tier than Dupo. Under normal operating conditions, Dupo water cannot backflow into Columbia through the emergency interconnect due to system pressure (the hydraulic flow direction is Columbia → Dupo).
The Interconnection is not routinely used
The emergency interconnect is not used for normal operations. In fact, it was last opened in 2016 to push water from Columbia to Dupo when Dupo's treatment facility was undergoing maintenance.
Official Notices & Documents
The following are the official Illinois EPA documents referenced in the postcard notice and this webpage:
Illinois EPA Public Health Notice
WHAT ARE PFAS and PFOS?
PFAS (Per- and Polyfluoroalkyl Substances) are a group of synthetic chemicals used in many consumer and industrial products. PFOS is one type of PFAS.
The Illinois EPA Public Health Notice includes general information about PFAS, potential health considerations, and resources for additional information. Please refer to the official notices linked above.
What the City is doing
- Complying with Illinois EPA requirements for customer notification within the required timeframe.
- Providing Columbia-specific operational context so customers understand the purpose and accurate directionality of the emergency interconnection.
- Coordinating with Illinois EPA staff to ensure public-facing information is accurate and not misleading.
- Evaluating additional operational safeguards and documentation related to the emergency interconnection, consistent with regulatory guidance, including physical separation of Dupo's water system from Columbia's system.
- Does Columbia have a PFAS/PFOS exceedance?
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No.
Illinois EPA’s notification to Columbia was triggered by Dupo’s reported PFOS result and the existence of an emergency interconnection. Columbia has issued the notice because Illinois EPA has directed the City to do so under Right-to-Know requirements.
- Does Columbia receive water from Dupo?
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No.
Columbia cannot receive Dupo water under normal operating conditions. Columbia is a higher-pressure system; the emergency interconnect is configured such that the normal hydraulic direction is Columbia → Dupo.
- Why am I receiving a postcard notice?
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Illinois EPA requires public notification by approved methods. The City is following a notification approach authorized by Illinois EPA for community notification.
- What should I do?
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Please read the official Illinois EPA Public Health Notice linked above.
If you have questions, contact the Illlinois EPA using the information below.