Dearborn CSO Control Project, Contract #8

Description: Construction of a CSO treatment shaft including solids screening and disinfection technology, modification of existing diversion chambers, construction of junction structures, CSO collector sewers, and a disinfection facility (chemical storage and control building) for overflow control.

Construction of the 104’ diameter by 155’ deep treatment shaft consisted of the following:

  • Performed combination of cementitious and chemical (acrylamide) soil grouting above the bedrock interface, depths ranging from 90’ to 120’. Total chemical grout injected was over 150,000 gallons.
  • Performed combination of cementitious and chemical (acrylamide) rock grouting in limestone bedrock, depths ranging from 120’ to 220’. Total chemical grout injected was over 30,000 gallons.
  • Design-built a 144’ diameter tight sheeted starter shaft with reinforced concrete ring beams to a depth of 50’ that was used as the launching pad and protection shaft from Rouge River flooding for the 104’ inside diameter shaft constructed as a self-sinking circular caisson with 7.5’ reinforced, cast in place concrete walls.
  • Sinking Caisson construction extended to a depth of 105’ seated and pinned into bedrock.
  • Design-built a bentonite injection system in aid of the sinking caisson.• Design-built an eductor dewatering system to reduce groundwater pressures at a critical strata.
  • Excavation of 115’ diameter by 45’ of depth of 13,000 cyd of limestone bedrock.• Installed rock anchor bolts and shotcrete to stabilize the vertical face of the excavated bedrock.
  • The bottom of the treatment shaft is equipped with chopper pumps to discharge the solids settled during operation back to the sewer system.
  • The shaft includes reinforced concrete interior baffle and partition walls to channel inflow of sewage.
  • Appurtenant structures include an influent and effluent channel, modifications to existing diversion chambers, and construction of new structures.

Associated Infrastructure consisted of the following:

  • Cast-in-place 14’x16’ box culvert to divert inflow from appurtenance structures into the shaft.
  • Disinfection facility (Control Building) to house the chemical storage tanks and associated controls.
  • Design-built 20’ by 60’ double sheeted PZ-27 shaft within the Rouge River, required to install 84” CSO concrete influent piping.