Ala Wai Sewer Improvement Project Update: Microtunneling Pit Work Continues-Jan. 8, 2007 Update

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Contractors are close to finishing a key portion of what will become the receiving microtunneling pit on the makai side of the Ala Wai Canal, at the corner of Kuhio Avenue and Kaiolu Street, near the Beachwalk Pump Station.

Contractors are installing a concrete compression ring around the 24 drill piles to make sure that receiving pit doesn’t collapse inward. They will then dig a pit, roughly 37 by 34 feet and 30 feet deep.


The receiving pit has to be dug before the microtunneling operation on the mauka side of the canal, near the Ala Wai Community Gardens, can begin.

Contractors have dumped a foot of rock on the floor of that mauka pit, now 44 feet deep, to help with drainage issues. They also installed sump pipes to insure the work can be conducted on dry ground. And a second beam has been installed to make sure the pit doesn’t crush inward.

All this prep work is part of the Beachwalk Wastewater Emergency Bypass project, and a prelude to the microtunneling operation, in which a ten foot long machine will bore its way under the canal, and then under Kaiolu Street in Waikiki, pulling with it a series of new sewer pipes.

As part of the microtunneling operation, contractors have set up a large machine to separate the materials that will be tunneled out from under the canal and Kaiolu Street. This machine, called a shaker, takes in a combination of water and bentonite, a type of clay, and the rock and other materials being excavated. The bentonite is mixed in water and injected into the microtunnel hole to make a sort of soup. That allows workers to get all the materials out, and the water and bentonite is then recycled back into the microtunneling operation. The rock and other debris is separated in the shaker and then hauled away.

The microtunneling process means Kaiolu Street won’t have to be trenched. It was on Kaiolu Street that an aging pipe burst last March, leading to a massive wastewater spill. That triggered this emergency project, now in phase two.

The first phase involved construction of an emergency bypass. That is up and running, utilizing a series of pipes and pumps set up temporarily along both sides of the canal.

Check this site – – for weekly updates. Also a reminder that the project hotline continues to be manned Monday thru Friday from 8am to 5pm. That number is 808-203-5777.