Pump Station 4 Reconstruction

• LocationForest Park, Illinois
• TimelineJanuary - June 2020
• Construction
  MethodsSecant piles
  Drilled shafts
  Tremie pouring
  Earth retention system

Scope

Michels, one of the largest deep foundations contractors in North America, was contracted to design and install secant shafts as temporary earth retention to allow for the excavation of approximately 71 feet below grade to install a new pump station. There are a total of 110, 1.5m diameter secant shafts in a 145-foot-diameter ring. Each shaft is installed to top of rock (71 feet) with an additional 10 feet into rock.

Upon completion of the secant shafts, a single shaft will be installed in the center of the ring to dewater the site. Once IHC Construction Companies LLC has excavated to final grade, Michels will come back and install 54 rock anchors to stabilize the building. Each rock anchor will be approximately 28 feet deep.

Michels used a Liebherr 36 drill rig to install Leffer segmental casing to the top of rock. A second Liebherr 36 with a modified kelly bar to allow for the flow of air was used with a cluster drill to hammer out the rock sockets.

Following the rock drilling, the pour crew tremie-poured each shaft to the top of the casing and then pulled casing out of the ground with a 1.5 meter Leffer oscillator. Every other shaft has an 82-foot-long W36x232 beam installed in its center.

By installing a watertight secant pile shaft, the pump station can be constructed which will help prevent flooding along the interstate.