November 2026 Luncheon

Join #asceSTL and the Missouri Society of Professional Engineers for our November Section Luncheon featuring Chris Pfeuffer, Everett Litton, and Erin Jearls for Tunnels to Treatment: Completing a 40-Year Plan for the Lower Meramec Sewershed.

Description:

The Lower Meramec River System Improvements program represents the realization of a regional wastewater vision first established in 1979 through collaboration between the East-West Gateway Council of Governments, Missouri Department of Natural Resources, and the Metropolitan St. Louis Sewer District (MSD). This long-range effort established a framework to improve water quality through the consolidation of treatment facilities and development of a regional conveyance system to a centralized wastewater treatment facility (WWTF).

Completion of the Lower Meramec Tunnel in 2026 represents a major milestone in implementing that vision. The 6.8-mile long tunnel extends the existing Baumgartner Tunnel to the interim Fenton WWTF, providing conveyance capacity to support regional growth and regulatory compliance. Constructed in rock at depths ranging from 78 to 286 feet below ground using a main-beam tunnel boring machine, the project required careful and challenging management of groundwater inflows within a flood prone area in South St. Louis County.

Equally important is the concurrent expansion and upgrade of the Lower Meramec WWTF, which enables the system to realize the full benefit of the new tunnel. The Lower Meramec WWTF improvements were developed as part of long-term planning efforts and regulatory commitments to expand treatment capacity and improve effluent quality.  Key upgrades included increasing the average day flow from 15 to 16 million gallons per day and increasing peak hour capacity from 60 to 100 million gallons per day.  The project also replaces aging trickling filter processes with a modern aeration system, along with repairs and replacement of critical plant equipment to improve reliability and performance.

This presentation focuses on the integrated delivery and commissioning of both the conveyance and treatment upgrades, highlighting coordination between tunnel design, construction, and plant upgrades to manage flows, maintain operations, and sequence construction. Lessons learned include the importance of aligning underground conveyance capacity with downstream treatment readiness, regional flooding, as well as sequencing from Phase I to Phase II to maintain uninterrupted service.

As Phase II approaches full completion in 2026, the Lower Meramec program demonstrates the value of sustained interagency collaboration, coordinated design phasing, and investment by the Metropolitan St. Louis Sewer District for both conveyance and treatment system upgrades. Together, these improvements increase system capacity, enhance treatment performance, and support long-term protection of water quality for the St. Louis region.

Speakers:

Chris Pfeuffer, P.E.

Metropolitan St. Louis Sewer District

Operations Division Manager

Chris Pfeuffer, P.E. graduated from the University of Missouri-Rolla, currently Missouri S&T with a B.S. in Mechanical Engineering and an M.B.A. from Fontbonne University.  He has 33 years of engineering/operations experience at MSD Project Clear including all aspects of the operations including treatment plants, pump stations, collection systems and support services (customer care, materials management, fleet, and asset management).  His current role oversees the South County Treatment Plants (Grand Glaize, Lower Meramec, and for a bit longer the Fenton).

Everett Litton, P.E.

WSP USA

Vice President and Senior Technical Principal

Everett Litton, P.E. graduated from Missouri University of Science and Technology, with bachelor’s and master’s degrees in civil engineering. He has more than 19 years of engineering experience focused on tunneling and underground infrastructure projects throughout North America. Everett Litton is a Vice President and Senior Technical Principal at WSP in St. Louis and is an active Executive Committee member with the Underground Construction Association (UCA) of SME.

Erin Jearls, P.E.

HDR

Project Engineer

Erin Jearls, P.E. graduated from the University of Missouri-Rolla, currently Missouri S&T, with a B.S. in Civil Engineering. She has 23 years of engineering experience, 20 of which she has spent employed with HDR Engineering in St. Louis. Her work has focused on wastewater engineering through collection systems, wastewater treatment facilities, and pump station design. Erin is an active member of the Missouri Society of Professional Engineers and enjoys promoting STEM outreach.