Kaneohe-Kailua Wastewater Conveyance Tunnel

Project Narrative

The Kaneohe-Kailua Wastewater Conveyance Tunnel is an approximately 3-mile-long, 13-ft diameter gravity sewer from Kaneohe’s Wastewater Pre-Treatment Facility to Kailua’s Regional Wastewater Treatment Plant. At the western terminus of the alignment is the 77-ft. deep, 87-ft diameter Kailua TIPS Shaft; at the east end is the 40-ft deep, 30-ft diameter Kaneohe Shaft.

Brierley Associates was retained by the tunnel and shaft contractor Southland/Mole JV to provide various construction phase engineering services. Brierley was responsible for the design of the initial tunnel support for conventionally mined and bored sections of the tunnel. The conventionally mined tunnel at the TIPS shaft was constructed through weathered and unweathered Basalt rock as a 19-ft horseshoe-shaped tunnel to facilitate construction of the transition that narrowed to 16-ft for the remainder of the 300-ft long starter tunnel. At the Kaneohe shaft, a 1,000-ft long 16-ft horse-shoe shaped tunnel was conventionally mined through jet grout treated soil, alluvium and weathered Basalt rock to complete the alignment and for TBM retrieval. Support for this segment consisted of steel ribs and wood lagging or shotcrete. The majority of the tunnel was mined with a 13-ft diameter open main beam tunnel boring machine (TBM).

During construction Brierley Associates provided fulltime on-site engineering geology and tunnel engineering services. Brierley Associates was also responsible for the design of the support of excavation (SOE) systems for the near surface structures and microtunneling receiving and launching shafts.