Cahokia Heights 2024 Clean Water Act Case Summary

On December 10, 2024, the Environmental Protection Agency (EPA), Department of Justice (DOJ), and the state of Illinois announced a settlement agreement with the city of Cahokia Heights, IL. The settlement resolves violations of the federal Clean Water Act (CWA) and the Illinois Environmental Protection Act resulting from the city’s failure to properly operate its sanitary sewer system. The settlement requires that Cahokia Heights pay a $30,000 civil penalty and implement an estimated $30 million in extensive compliance measures.  

• Overview of Cahokia Heights, IL Sewer Collection System
• Summary of the Violations
• Summary of Environmental and Health Impacts
• Summary of Environmental Benefits
• Overview of Consent Decree
• Comment Period
• Contact Information

Overview of Cahokia Heights, IL Sewer Collection System

Cahokia Heights owns and operates the city’s separate sanitary sewer collection system that extends over approximately 16 square miles and serves approximately 21,000 residents. It consists of approximately 90 miles of gravity sewers, four miles of force mains, over 2,000 manholes, and 69 lift stations. Cahokia Heights does not have a national pollutant discharge elimination system (“NPDES”) permit from the EPA or an authorized state under the Clean Water Act.

Summary of the Violations

The complaint against Cahokia Heights alleges that on at least 300 occasions since November 2019, Cahokia Heights discharged sanitary sewage from a clean out in its sewer system and from other locations into local waterways without an NPDES permit issued pursuant to CWA section 402 in violation of section 301 of the Clean Water Act.  

In addition, Cahokia Heights’ failure to properly operate and maintain its sewer system resulted in discharges of sanitary sewage to waters of the state in violation of the Illinois Environmental Protection Act and its implementing regulations.

Summary of Environmental and Health Impacts

Summary of Environmental Benefits

The rehabilitation of Cahokia Heights’ sanitary sewer system is expected to substantially reduce the number of sanitary sewer overflows in the community, thereby reducing the potential for adverse human health and environmental impacts.

Overview of Consent Decree

The proposed consent decree requires Cahokia Heights to reduce the number of sanitary sewer overflows from its sewer system by 

• Evaluating the condition and hydrologic capacity of its sanitary sewer, and
• Implementing various measures that will require frequent cleaning and repair to maintain the sewers in good working order and to potentially increase the capacity of the sewer system.

The following is an overview of the work the city must perform:

Phase 1:

• Cahokia Heights will conduct more than 80 near-term capital improvement projects, such as constructing an interceptor to re-route wastewater flow, system-wide repairs, and various investigations and assessments.
• The city is required to begin the systematic cleaning of the entire sewer system and implement a Wet Weather SSO Investigation Plan for a majority of the sanitary sewer system to determine the sources and causes of the city’s ongoing wet weather sanitary sewer overflows. 
• By September 2029, Cahokia Heights is required to prepare a Sewer Condition Assessment Report describing in detail the deficiencies discovered during the condition assessment.  
• By December 2029, the city must complete a Phase 1 Sewer Condition Rehabilitation Plan, which will require the city to repair or replace sewer lines and defective manholes. The rehabilitation plan must be implemented pursuant to a schedule to be approved by EPA. 

Phase 2:

• The city is required to determine whether it continues to experience capacity related sanitary sewer overflows. If capacity related sanitary sewer overflows remain a problem, then the city is required to prepare a Sewer Capacity Alternatives Analysis Plan.  The city will then be required to implement a Sewer Capacity Remediation Plan to improve sewer capacity.
• Cahokia Heights is required to investigate areas of the sanitary sewer system not evaluated in Phase 1 to determine the condition for the remainder of the sewer system and prepare a second Sewer Condition Assessment Report, as well as a second Sewer Condition Rehabilitation Plan describing the corrective measures to repair the additional sewer system defects by December 2035. The rehabilitation plan must be implemented pursuant to a schedule to be approved by EPA.

The city is required to keep the community informed about the work, have plans in place for emergencies, and update its operations by creating digital maps and monitoring in real-time known overflow points.

Comment Period

The proposed consent decree was lodged in the U.S. District Court for the Southern District of Illinois on December 10, 2024. The consent decree is subject to a 60-day comment period. Information on how to provide comments and a copy of the proposed consent decree are available on the Justice Department’s Propose Consent Decree webpage.  

Contact Information

For additional information on this settlement, please contact: 

James Vinch, Attorney Advisor
Water Enforcement Division 
Office of Enforcement and Compliance Assurance
1200 Pennsylvania Avenue, NW
Washington, D.C. 20460
vinch.james@epa.gov