The purpose of this project was to increase conveyance capacity of the
Coldwater Trunk Sewer. The existing sewer had inadequate capacity during
wet weather events due to the inflow and infiltration of storm water into the
sanitary collection system.
Phase II consisted of constructing a sewer line from a point about 1,000 feet
east of North Lindbergh westward to a point about 1,000 feet west of
Lindbergh within the common grounds of Parc Argonne Forest.
A combination of pipe jacking and tunnel boring machine (TBM) methods
were utilized to excavate this 10’ diameter tunnel for the Metropolitan St.
Louis Sewer District. A jacking frame was used to push the TBM head ahead
of the pipe assembly as it excavated through saturated clayey and sandy soils;
large cobbles were also encountered.
Deep shafts were excavated and supported at each end of the tunnel to
facilitate assembly and removal of the TBM and jacking frame. Temporary
ground support within the shafts was provided by steel ring beams and liner
96 inch ID RCP was jacked into the tunnel behind the TBM head. Bentonite
slurry was pumped in the annular space to reduce friction during jacking
operations. The RCP was constructed utilizing Con-Shield concrete additive.
This project required extensive coordination with local regulatory agencies
and businesses, as well as multiple subcontractors and suppliers in order to
complete the project on time. A comprehensive disadvantaged business
enterprise program was also implemented on this project which required the
use of specific percentages of minority and women owned businesses.