Tunnel construction starts on Honolulu wastewater project

The three-mile (4.8km) line running mostly under Oneawa Hills is a gravity sewer tunnel that will convey wastewater flows and store wastewater to prevent overflows and spills. Tunnelling will start at the Kailua treatment plant, approximately 62ft below ground, and the tunnel will be approximately 35ft below ground at the Kaneohe Pretreatment Facility.

The contract for the Kaneohe-Kailua gravity sewer tunnel project was awarded to the joint venture group of Southland Contracting, Inc. and Mole Construction, Inc. (Southland Mole JV) and the construction management contract was awarded to local
construction management firm Bowers + Kubota. Wilson Okamoto Corporation is the project's civil engineer, with McMillen Jacobs Associates as the tunnel engineer and YK Engineers, LLC the project's geotechnical engineer.

Southland Mole JV is using a 13ft (4m) diameter Robbins TBM. According to The Robbins Company, the TBM is refurbished with some components from Southland's recently completed Jollyville Tunnel in Texas. In order to move the tunnel away from populated areas, designers introduced an isolated curve in the tunnel alignment of 500 ft radius, requiring the TBM to be specially designed. Operators will also follow a procedure of 1/2 strokes while navigating the curve.

"This is a big win for Oahu," said Caldwell, "Consider the benefits to our environment, to job stimulation and to neighborhoods on the Windward side that will have a safe, out-of sight wastewater system with incredible storage capacity."

Aikahi Elementary School's robotics team named the TBM "Pohakulani" which means "Rock Girl" in Hawaiian.