Kaneʻohe-Kailua Wastewater Treatment and Conveyance Project

The City & County of Honolulu embarked on the development of alternatives to treat and convey wastewater between the Kaneʻohe Wastewater Pre-Treatment Facility to the Kailua Regional Wastewater Treatment Plant.

The City selected WOC to manage the implementation of a three-prong process approach that consisted of the preparation of a Preliminary Engineering Report (PER) evaluating various alternatives, Environmental Impact Statement (EIS), and an extensive community outreach process. This process led to the selection of a three-mile long gravity sewer tunnel to store and convey wastewater from the Kaneʻohe Wastewater Pre-Treatment Facility to the Kailua Regional Wastewater Treatment Plant.

The new 10-foot gravity sewer tunnel alternative conveys wastewater, replacing the existing conveyance system. In addition, the sewer tunnel also provides storage for wet-weather events that could potentially overwhelm the existing sewer system. The tunnel goes under Oneawa Hills to connect the two wastewater facilities. The tunnel was excavated primarily with a tunnel boring machine (TBM). There is one intermediate shaft located approximately mid-way for emergency access.

WOC managed a team of more than a dozen specialty consultants for the design & construction of the project. Civil engineering scope included preparation of construction plans related to site improvements at both wastewater facilities.

Planning services included the preparation and processing of an EIS, a Conservation District Use Application – Board Permit; Stream Channel Alteration Permit (SCAP), Section 10, and CZM Coastal Zone Management Federal Consistency Certification for the Kawa Stream Crossing; and Special Management Area (SMA) Permit.

WOC also prepared a Traffic Impact Assessment Report and Construction Management Plan.

Services Provided: Planning, Civil Engineering, Transportation & Traffic Engineering