A drill rig and excavator work at the bottom of a pump station shaft

Pump Station 4 Shaft

Michels Construction, Inc. was selected to design/build a secant shaft as temporary earth retention for an excavation about 71 feet below ground to allow installation of a new water pump station. The 145-foot diameter ring consisted of 110 1.5m diameter secant shafts installed to top of rock (71 feet) with an additional 10 feet into rock.

Michels Construction used a Liebherr 36 drill rig to install segmental casing to the top of rock. A second Liebherr 36 with a modified kelly bar to allow for air flow was used with a cluster drill to hammer out rock sockets. Then, the pour crew tremie poured each shaft to the top of the casing and pulled casing out of the ground with a 1.5-meter oscillator. Every other shaft has an 82-foot-long W36x232 beam installed in its center.

The new pump station improves the sewer system to prevent flooding along Interstate 290.