Progress being made on gravity sewer tunnel between Kailua and Kaneohe

Published: Jun. 18, 2015 at 10:56 AM HST|Updated: Jun. 18, 2015 at 4:14 PM HST
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KANEOHE, OAHU (HawaiiNewsNow) - City officials say after a month and a half of drilling, the Tunnel Boring Machine or TBM, is functioning well and on its 3-mile journey to create the underground space needed for the city to install Hawaii's first and largest gravity sewer line to run between the Kaneohe Waste Water Pre-Treatment Facility and the Kailua Regional Waste Water Treatment Plant.

The city's Director of Environmental Services Lori Kahikina says the TBM, also named Pohakulani, is about 1,000 feet from its original starting point at the Kailua RWWTP on April 30th. The large machine is actually digging backwards on the tunnel and upwards towards the Kaneohe side that will begin at about a 35-foot depth.

"They seem to be on target on schedule," Kahikina said. "Their rate is about 40 to 50 feet per day."

The Kaneohe-Kailua Tunnel Sewer Project is the city's second largest construction project behind rail.

It is tunneling at the Kailua RWWTP at a depth of about 65 feet below sea level and moving underground at the Aikahi Gardens residential area now, working to tunnel towards the Kaneohe WWPTF, where the incline of the gravity sewer pipe will eventually begin.

During a 12-hour shift, the tunneling generates about 1,175 tons of rock material, said officials with Southland Contracting, who's in charge of the project. Right now that dirt is being recycled into a variety of different projects for fill, including in roadwork in residential projects in the Kaneohe and Hauula areas and in the development of a new shopping center in Kapolei, Ka Makana Alii. Various companies are interested in using the materials.

So far, officials say there's been no vibration felt by residents related to the mining. As a precaution, seismographic equipment has been monitoring the area.

"So far there hasn't been any vibration of any significant amount," said Gary Weller, a member of the Kailua Neighborhood Board. "They've been monitoring it from day one and I'm very happy."

The 10-foot wide sewer line that will placed in the tunnel will use gravity, instead of electricity, to move waste water downhill from Kaneohe to the plant in Kailua. Officials say it will help prevent sewage spills and eliminate above-ground containment systems.

The project, including station upgrades, is slated to be finished in 2018.

For more information or to follow the movement of the TBM online, click here.

Related story:

160-ton machine to begin drilling underground tunnel in Windward Oahu

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