Jet Grouting Strengthens Emergency Sewer Project

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Contractors on the Beachwalk Wastewater Emergency Bypass team are turning to a technology with proven track record in sewer work.

Residents and visitors along both sides of the Ala Wai Canal will be watching over the next couple of months as contractors “jet grout” roads and pits, a prelude to putting a wastewater pipe underground.


“Jet grouting is a means of stabilizing bad soils,” said Craig Nishimura, deputy director of the City Department of Design and Construction. “A grout mix is injected into the ground to create a relatively solidified soil layer.”

The jet grouting machine drills down, often very deep, and leaves behind a concrete column of underground pillars. Contractors use a silo capable of storing 52 tons of cement. One of those silos now sits in a city park being used as a temporary construction yard, near Ala Wai Elementary and Iolani schools.

Residents along the mauka side of the Ala Wai Canal will see jet grouting machinery over the next two months as contractors work to solidify and make water proof a huge pit that will be used to launch the micro tunneling machines.

This pit was recently the focus of intense and noisy pile driving, in which 55-foot sheet piles were driven into the ground.

Jet grouting generates a fraction of the noise caused by pile driving. Most of the jet grouting noise is “ambient” construction sounds caused by generators and vacuum trucks used in the process.

Jet grouting on Kaiolu Street in Waikiki will start sometime next month. Last month, contractors jet grouted the Diamond Head entrance to Ala Moana Beach Park to seal out groundwater during installation of a 48-inch sewer pipe.

When jet grouting roads, as opposed to deep pits, contractors don