Overview
The Upper River Des Peres and River Des Peres Tributaries Storage Tunnel will capture and store combined sewer overflows (CSO) during heavy rain events until it can be treated at the Lemay Wastewater Treatment Plant. Improvements will directly benefit water quality in Deer, Black, Hampton, and Claytonia Creeks as well as the River Des Peres.
Residents in this part of St. Louis County are served by a combined sewer system where wastewater from homes and businesses mixes with stormwater from streets, rooftops, and other surfaces in the same pipe. When there are heavy rains, the system can overflow, causing untreated sewage and rainwater, called combined sewer overflows, to be released directly into nearby rivers and streams.
The project consists of the following key elements:
- Main tunnel: Approximately 6-miles long, 18-foot inside diameter
- Three (3) connecting tunnels: Each between approximately 3,000 and 4,500 feet in length and12-foot inside diameter. The total length for the three connecting tunnels is approximately 11,800 feet.
- Seven (7) large-diameter construction shafts ranging between 20 and 65-foot inside diameters
- Sixteen (16) intake structures with drop shafts to the tunnels
The tunnels will be constructed at depths ranging from 90 to 240 feet below ground surface in rock with cast-in-place concrete final linings. The tunnel will run between City of St Louis, near its border with Shrewsbury in the south, to University City in the north. A pump station and multiple consolidation sewers will be constructed under separate contracts to complete the program.
The project is currently in Phase 2, Final Design, with construction anticipated in 2030. During design, the team is identifying and refining alignments for the tunnel and supporting near-surface sewers with the goal of reducing as many CSOs as possible while minimizing impacts to private property.
As construction approaches, MSD Project Clear will work closely with impacted customers and local governments so they know what to expect. Despite the significant scale of the tunnel construction, most of it will take place deep underground and will not be noticeable at the surface.
The Upper River Des Peres and River Des Peres Tributaries Storage Tunnel Fast Facts
Estimated Construction Cost: $565 million
Project Design: through 2027
Construction Start (anticipated): 2030
Construction Completion (anticipated): 2039