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Lemay Wastewater Treatment Plant

Lemay Wastewater Treatment Plant: Championing Sustainable Wastewater Management


In an era where sustainable urban infrastructure is increasingly critical, the Lemay Wastewater Treatment Plant in St. Louis, Missouri stands as a model of engineering excellence, environmental stewardship, and community engagement. The plant, administered by the Metropolitan St. Louis Sewer District (MSD), exemplifies how a modern wastewater treatment facility can responsibly manage urban wastewater while engaging the community and spearheading key infrastructure projects.

Population Served and Volume of Wastewater

The Lemay Wastewater Treatment Plant is a cornerstone in the wastewater management of the Greater St. Louis area. It currently serves a population of approximately 350,000 residents in St. Louis city and portions of St. Louis County. On an average day, the plant handles around 90 million gallons of wastewater, efficiently treating and returning it to the environment in compliance with stringent regulatory standards. During wet weather events, the plant has the capacity to manage a higher volume, ensuring resilience and reliability in the face of variable inflows.

Treatment Capacity and Technological Advancement

The Lemay Wastewater Treatment Plant is equipped with cutting-edge technology to treat both sanitary sewage and stormwater runoff. As one of the largest wastewater facilities in the state of Missouri, it boasts a treatment capacity of up to 200 million gallons per day (MGD) during peak wet weather conditions. The treatment process involves an integrated approach that includes preliminary screening, primary sedimentation, biological treatment through activated sludge processes, secondary clarification, disinfection, and sludge digestion.

Recent Local News and Developments

Recent developments at the Lemay Wastewater Treatment Plant have drawn considerable attention both locally and within the broader environmental engineering community. A notable project completed recently is the Secondary Treatment Expansion Project. This $120 million initiative enhances the plant’s capacity to treat increased inflows during heavy rainstorms, a critical upgrade considering the changing weather patterns and increasing frequency of extreme weather events.

Another significant accomplishment was the transition to more energy-efficient equipment, which was completed in late 2022. The integration of high-efficiency pumps, variable frequency drives, and modern aeration technology has not only reduced the plant’s operational costs but also significantly decreased its carbon footprint. Moreover, the implementation of an advanced supervisory control and data acquisition (SCADA) system has improved the facility’s ability to monitor and control the treatment processes more effectively.

Key Projects and Initiatives

1. Lemay Lewis and Clark Outfall Tunnel Project

One of the most ambitious projects in recent history is the Lemay Lewis and Clark Outfall Tunnel Project. This $292 million endeavor is designed to mitigate the combined sewer overflow (CSO) issues that have historically plagued the region. The project involves constructing a 6-mile long, 28-foot diameter tunnel that will store and transport excess stormwater and wastewater to the treatment plant during heavy rainfall events. Upon completion, slated for 2024, this project is expected to significantly reduce overflow events, thereby protecting local waterways and improving water quality.

2. Energy Generation from Biogas

The Lemay Wastewater Treatment Plant has also made strides in harnessing renewable energy. The plant utilizes anerobic digesters to process sludge, resulting in the production of biogas—a renewable energy source. In 2021, a project was initiated to capture and convert this biogas into electricity and heat, thereby enhancing the facility’s energy independence. The generated electricity helps power the plant, reducing reliance on grid electricity and lowering operational costs.

3. Green Infrastructure and Stormwater Management

Another critical focus for the Lemay Wastewater Treatment Plant is green infrastructure. By promoting permeable pavements, rain gardens, and green roofs throughout the city, MSD is working towards reducing the burden on the wastewater treatment system. These initiatives not only manage stormwater at the source but also enhance the urban environment, improve air quality, and create green spaces for the community.

Community Engagement

Community engagement is a cornerstone of the Lemay Wastewater Treatment Plant’s operations. Recognizing the importance of public involvement and education, the plant has developed comprehensive outreach programs illustrating the role of wastewater treatment in public health and environmental protection.

1. Educational Tours and Programs

The plant regularly offers educational tours, allowing school groups, community organizations, and residents to understand the complex processes involved in wastewater treatment. These tours are designed to be interactive and educational, providing participants with firsthand insights into the importance of wastewater management and the science behind it.

2. Public Meetings and Transparency

MSD holds regular public meetings to discuss upcoming projects, ongoing initiatives, and any potential disruptions that might affect the community. These meetings are a platform for residents to voice their concerns, offer suggestions, and stay informed about the developments affecting their neighborhoods. The district’s commitment to transparency has built a strong relationship with the community, fostering trust and cooperation.

3. Environmental Stewardship Programs

The Lemay Wastewater Treatment Plant actively engages with local environmental groups and participates in community clean-up events, tree planting initiatives, and educational campaigns on water conservation. By partnering with local schools and environmental organizations, the facility promotes environmental stewardship and sustainability practices within the community.

4. Digital Engagement and Communication

In today’s digital age, effective communication also extends to online platforms. MSD has leveraged social media, websites, and digital newsletters to keep the community informed about the latest news, projects, and educational resources related to wastewater management. This approach ensures that information is readily accessible and that the community remains engaged and informed.


The Lemay Wastewater Treatment Plant is more than just a facility for wastewater treatment; it is a vital entity that upholds environmental standards, drives technological advancements, and fosters community engagement. It serves as a reminder of the critical importance of sustainable infrastructure in maintaining public health, protecting the environment, and supporting urban development.

Through ongoing projects like the Lemay Lewis and Clark Outfall Tunnel and initiatives in renewable energy and green infrastructure, the plant is taking significant steps towards a sustainable future. Concurrently, its commitment to community engagement ensures that the residents it serves remain informed, involved, and supportive of these efforts.

As cities around the world grapple with the challenges of urbanization and climate change, the Lemay Wastewater Treatment Plant provides a blueprint for managing these challenges through innovative engineering, sustainable practices, and a robust community partnership. It stands as a testament to what can be achieved when technology, environmental commitment, and community cooperation converge.