The population on the island of Oahu is a very close-knit community and one that came together for the good of their island home during the construction of the Kaneohe / Kailua Sewer Tunnel Project.  The entire community, along with the City and County of Honolulu and Southland / Mole Joint Venture (SMJV), worked together to successfully construct the state’s first TBM (tunnel boring machine) bored tunnel on the islands.

The tunnel project connected the Kaneohe Wastewater Pre-Treatment Plant to the Kailua Regional Wastewater Treatment Plant, expanding the existing sewer system to alleviate overflows and respond to an EPA federally mandated consent decree.  As local support for the project grew, the City and County of Honolulu engaged the public extensively at community outreach meetings for alignment of the tunnel. This is much of the reason why the alignment follows a curved path along the spine of a mountain in the lush Oneawa Hills.

“Ultimately, the success of the project hinged on community support and approval,” said Mayor Kirk Caldwell. 

The $195 million Kaneohe-Kailua Tunnel was the first and largest gravity sewer tunnel constructed on the island, stretching three miles from the Kaneohe Wastewater Pre-Treatment Facility to the Kailua Regional Wastewater Treatment Plant. The design of the tunnel was the deepest of its kind in Hawaii. Utilizing a custom-made Robbins 13.5-foot TBM to bore through the basaltic rock conditions of the island and pump a record 14,000 linear feet of Low-Density Cellular Concrete into the tunnel.  The final liner of the tunnel was a 10-foot Hobas pipe, with over 880 pieces of 20-foot pipe being shipped to the island over an eight-month period of time.  

When SMJV arrived on the island, they worked with local officials to continue and expand the community outreach efforts. Attending public meetings, being transparent and answering questions from residents assisted in calming the fears of the residents and establishing a collaborative working relationship. This relationship was essential in the success of the project due to the need to hire many local workers to complete a project of this size in such a remote location. “Utilizing a majority local labor force was a key initiative of Southland/Mole JV” said Tim Winn. The majority of employees were hired from the local unions, making up more than 70 percent of project employees. SMJV worked with the local unions to understand the traditions of the native workers and embraced these traditions throughout the project including a tribal leader blessing of the TBM and a cleansing ceremony within the tunnel. 

The Community Engagement Program for the Kaneohe/Kailua Sewer Tunnel Project not only aided in public acceptance and project success, but it also provided numerous benefits to the community and residents for four years, including educational opportunities for local elementary schools, STEM programs and robotics teams. Students visited the site to see the TBM, and they learned how the engineering of the machine and overall project impacted its success.  

Southland/Mole JV used the project as an opportunity to shape future professionals of the heavy civil engineering and construction industry. In partnering with local elementary schools, they hosted site tours and engaged students in naming the TBM. The local elementary robotics team won the naming contest with the name Pohakulai, meaning Rock Girl in Hawaiian. 

In addition to community outreach elements, the project now provides benefits to the island – most importantly, sewer overflows are controlled. It also serves as a method for wastewater to flow without any pump to the connected wastewater treatment plant, saving energy.  “More work may be ahead for Honolulu,” said Robert Kroning, Director of Construction Services for the City and County of Honolulu.  

“The desire is to do more projects like this around the island,” he says.  

As a result of the successful construction of this unique project, the Southland/Mole JV team was awarded two International Tunnel Awards in 2018 for the project’s community engagement initiatives and Project Innovations.   

Infrastructure “Firsts On the Island”

  • First/largest use of shaft slurry wall application
  • First use of TBM in Hawaii
  • Longest tunnel in Hawaii
  • Largest/longest use of HOBAS pipes
  • First use of reverse circulation drill with an oscillator for steel casing advancement for shaft on Oahu
  • First use of low-density cellular grout for pipe backfill in Hawaii and pumped the farthest