Notice to Proceed for Hawaiian sewer tunnel 27 Jan 2014
Peter Kenyon, TunnelTalk
- The Southland/Mole JV is awarded construction of the 15ft diameter Kaneohe-Kailua Wastewater Conveyance Tunnel by the City and Council of Honolulu, Hawaii. Construction is scheduled to begin October, following preliminary works and demolitions, with completion scheduled for June 2018 in order to comply with a Federal Consent Order.
- Notice to Proceed for the approximately 16,337ft (4,979m) TBM bored tunnel was issued on January 6, with the Southland/Mole JV confirmed as low bidder with a contract price that came in just below the Engineer's Estimate of US$175 million (Table 1). Bid spread between the seven companies and JVs that submitted proposals was $78.9 million, with a price variation between low and high bids of 51.6%.
Tunnel and existing force main alignments
- The total bid includes a basic bid for the main tunnel, plus three additional alternatives that are all included in the project scope. Alternative 1 is the Kailua diversion pipelines and structures (on the downstream end of the tunnel within the City and County's Kailua Wastewater Treatment Plant). Alternative 2 is the Kaneohe Diversion pipelines and structures (on the upstream end of the tunnel within the City and County's Kaneohe Wastewater Pre-Treatment Facility).
- Alternative 3 is the Kawa Stream Crossing, which comprises pipelines and structures on the upstream end of the tunnel that crosses Kawa Stream into the City and County's Kaneohe Wastewater Pre-Treatment Facility.
- Construction management is awarded to Bowers & Kubota Consulting, while engineering design was completed by Wilson Okamoto Corporation and Jacobs Associates. The tunnel, which TunnelTalk understands will be excavated using a refurbished machine, is designed as a hard rock drive, with 95% of the alignment excavated through basaltic rock. Rockbolts, wire mesh and steel arch support will be installed as necessary, and upon completion a fiberglass pipe with an i.d. of 10ft will be backfilled into the tunnel. The Southland/Mole JV can expect difficult tunneling conditions at both ends of the alignment. According to the project scope section of the Bidder's Statement of Qualification: "Most of the sewer diversion pipelines and shafts at [the Kailua and Kaneohe ends of the alignment] will be installed in highly variable and difficult ground conditions deep below the groundwater table."
Project presentation at NAT 2012
- The upstream end of the new sewer pipe at Kaneohe Waste Water Pre-Treatment Facility (Kaneohe) will divert flows from the existing effluent pump station and associated 42in diameter force main to the tunnel through new diversion structures, pipelines, a junction structure and drop shaft. The drop shaft will be approximately 30ft diameter and will also be used to facilitate tunnel construction prior to build-out and connection to the existing conveyance system. At the downstream end of the new sewer pipe at Kailua Regional Waste Water Treatment Plant (Kailua), flows will enter a new pump station constructed within a large 87ft diameter shaft for treatment. The pump station shaft will also serve as the primary mining and launch shaft for the TBM. Flows from the existing Kailua plant will also be diverted to the pump station by a new near-surface pipeline and 33in i.d. drop shaft, which will connect to the 10ft diameter sewer pipe via a drop shaft and adit pipe. In addition, an 8ft i.d. diameter access shaft will be constructed at the existing Board of Water Supply (BWS) Kapaa Water Tank site.
|Table 1. Kaneohe-Kailua Wastewater Conveyance Tunnel bids|
|Contractor/JV||Basic bid||Alt.1||Alt.2||Alt.3||Total bid|
|SJ Louis Construction||180,219,400||20,944,400||14,402,000||6,158,600||221,724,400|
|JV Hawaiian Dredging/Samsung||187,008,600||19,780,000||17,300,500||8,018,600||232,107,700|
|Michels/Jay Dee JV||204,326,000||26,426,030||19,620,000||7,118,600||257,490,630|
|BCCI Hawaii JV||211,319,000||24,225,000||19,880,450||7,003,200||262,427,650|
Revised Alternative-7 tunnel alignment
- Work will now begin demolishing facilities at Kailua to clear the way for drill+blast construction of the 87ft diameter shaft that will house the new pump station and also serve as the TBM launch site.
- The project is intended to alleviate stress on the aging 42in sewer force main that currently runs under Kaneohe Bay Drive. The initial plan had been to replace this with a new force main under Kaneohe Bay (Fig 1), with the tunnel solution rejected as too costly. But a review of the design-life cost of a tunnel compared to the force main replacement proposal prompted a rethink, and at Environmental Impact stage it was also determined that a tunnel was a more sustainable solution. At this stage it was also decided to alter the alignment of the centre section of the tunnel so as to run further away from populated areas - the so-called Alternative 7 (Fig 2).
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