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MSD Combined Sewer Overflow Remediation

Owner: Metropolitan St. Louis Sewer District
Client: Jacobs
Location: St. Louis, Missouri
Services: Geophysics, Geotechnical, DrillingSoils and Materials Laboratory Testing

Overview:
Metropolitan Sewer District (MSD) has begun its $4.7 billion, 23‐year, wastewater/stormwater system overhaul to remediate the combined sewer system originally built before the Civil War and the first system to be built west of the Mississippi River. Obviously the needs and laws have changed in the last 150 years and the system needs to be improved to be compliant with USEPA and MDNR standards. These improvements will include technology updates, new sewer separators, and construction of new conveyance and storage tunnels.

Details:
The Lemay Redundant Force Main (RFM) is the initial phase of the overall combined sewer overflow (CSO) remediation. The Lemay RFM project is a second force main from the Lemay Pump Station #1 to the Lemay Waste Water Treatment Plant (WWTP) and will provide additional conveyance capacity. The RFM alignment roughly parallels the existing force main and is located slightly deeper in profile. The RFM is planned as a nominal 10‐foot diameter tunnel, 3,262 feet long through bedrock. Geotechnology is providing geotechnical, field and laboratory testing, and geophysical surveys for the RFM, and prepared a geotechnical data report that provided critical information for the geotechnical aspects of design and construction of the RFM.

The Jefferson Barracks (JB) Tunnel will be approximately 3.5 miles long, approximately 10-foot excavated diameter tunnel in rock.  The tunnel will be used to convey and store sanitary sewage and storm water pending its treatment at the Lemay WWTP near the confluence of the River Des Peres and Mississippi River in St. Louis, Missouri.  The JB Tunnel alignment generally parallels the Mississippi River from Koch Road just south of I-255 and terminates at the Lemay WWTP.  The JB Tunnel alignment generally traverses through the grounds of St. Louis Veterans Administration Medical Center, Jefferson Barracks National Cemetery, a county park, a high school, and a number of private properties.  The current alignment crosses I-255 near the south end of the alignment.  Based on preliminary data the invert of the JB Tunnel is planned to slope 18 feet from the south to the north.  A pump station will be constructed at the downstream (north) end to lift the combined sewage into the Lemay WWTP.

The River Des Peres (RDP) Tunnel, some 8.7 miles long, approximately 30-foot excavated diameter tunnel in rock, and running essentially below the existing River Des Peres channel at a depth of 220 feet is the largest element of the project.  The RDP Tunnel will be used to store and convey sanitary sewage and storm water pending its treatment at the Lemay WWTP near the confluence of the River Des Peres and Mississippi River in St. Louis, Missouri. The considered alignment crosses under railroad tracks at two locations, a rail switching yard, Interstate Highways I-44 and I-55, and the River Des Peres channel at several locations. Based on preliminary data the invert of the RDP Tunnel is planned to slope about 45 feet from the north to the south end.  A pump station will be constructed at the downstream (south) end to lift the combined sewage into the Lemay WWTP.