Illinois Governor JB Pritzker has signed into law a ban on carbon sequestration activities near the Mahomet Aquifer, the sole source of drinking water for nearly one million central Illinois residents. The legislation, which takes effect January 1, 2026, marks a significant victory for environmental advocates and local communities who have long fought to protect the region’s water supply from potential contamination risks.

The Mahomet Aquifer serves as the primary drinking water source for residents across 15 counties in east-central Illinois, stretching from the Illinois River to the Indiana border. In March 2015, the U.S. Environmental Protection Agency designated a portion of the aquifer as a sole source aquifer under the Safe Drinking Water Act, recognizing that contamination could pose significant public health risks and that no reasonably available alternative drinking water sources exist in the region.​

The aquifer currently provides an estimated 53 to 58 million gallons of drinking water daily to approximately 500,000 to one million people, including residents of Champaign, Urbana, Savoy, and more than 100 other communities.

The bill received bipartisan support during its passage through the Illinois General Assembly. The legislation passed in the Illinois Senate on April 10, 2025 and cleared the House on May 20, 2025.

Governor Pritzker signed the bill into law on August 1, 2025.

The legislation amends the Illinois Environmental Protection Act to prohibit any person from conducting carbon sequestration activity within a sequestration facility that overlies, underlies, or passes through a sole source aquifer. Specifically, the law bans the underground injection and long-term storage of carbon dioxide streams into geologic formations beneath the Mahomet Aquifer’s designated sole source area.​​

The law also establishes the Mahomet Aquifer Advisory Study Commission to study and review the safety of carbon capture and storage in the region. The commission will consist of state agency directors, legislative appointees, and other stakeholders, and must hold public meetings within the Mahomet Aquifer area. The Prairie Research Institute at the University of Illinois at Urbana-Champaign will conduct a comprehensive study on the potential for carbon sequestration in the area, submitting annual status reports starting in December 2027 and a final report by December 31, 2030. The commission will then issue its own final report to the governor and General Assembly by December 31, 2031, before dissolving on January 1, 2032.

The push for aquifer protection intensified following reported leaks at Archer-Daniels-Midland’s (ADM) carbon sequestration facility in Decatur, Illinois, just a few miles from the Mahomet Aquifer. In March 2024, ADM detected a leak at its Class VI carbon storage site, the only operating EPA-approved Class VI project in the country not used for enhanced oil recovery.​

The U.S. EPA determined in August 2024 that ADM had violated Safe Drinking Water Act regulations when at least 8,000 metric tons of liquified carbon dioxide and other fluids leaked into “unauthorized zones” roughly 5,000 feet below the surface. ADM later revised its estimate of the carbon dioxide leak to between 2,670 and 3,940 metric tons. In September 2024, a second leak involving brine was discovered. The EPA issued a proposed enforcement order, and ADM voluntarily paused carbon injections in late September 2024.

In July 2024, Governor Pritzker signed the Safety and Aid for the Environment in Carbon Capture and Sequestration (SAFE CCS) Act, which established statewide regulations for carbon capture and storage projects, including a two-year moratorium on carbon dioxide pipelines. However, the SAFE CCS Act did not specifically ban carbon sequestration beneath the Mahomet Aquifer, prompting local legislators and environmental groups to push for additional protections.

The legislation establishes some of the nation’s most stringent protections against carbon sequestration near vital water sources and could serve as a model for other states grappling with similar concerns.