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Customer: Solomon Islands Water Authority Contract: Construct Location: Honiara, Solomon Islands   |
Fast Facts:
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The new Kukum Highway Sewer Pipeline Project was awarded to McConnell Dowell in late 2022 by the Solomon Island’s Water Authority. The project is the first stage in a long-term plan to improve sanitation in nearby residential, institutional, industrial, and recreational facilities, the Urban Water Supply and Sanitation Sector Project (UWSSSP).
People also refer to the project as ‘Telekom to Fisheries’ as the new pipeline alignment will run from the Ministry of Fisheries building through the Ranadi Roundabout to the Telekom building when complete.
One kilometre of gravity-fed pipeline and half a kilometre of pressure main, manholes and lateral connections are being installed Kukum Highway. The highway is a main arterial road to Honiara, so extensive traffic management is in place along the alignment. This ensures the safety of the team working on the road reserve and in one lane while enabling the other lane to remain open reducing disruption to drivers.
The trenching methodology includes a combination of trench shields and sheet piles. At the Western end of the project, the 710mm diameter gravity pipeline has been installed up to 7.0m deep; in this section, a sheet piled trench has been used to provide safe shoring. The shallower sections of pipe, where the excavation is less than 4.5m, are being excavated using a trench shield shoring system.
Challenges
The project has provided challenges for the team, most were issues dealt with regularly, but one risk was a unique concern. The crew successfully managed hard ground conditions, deep excavations, and a high-water table, which added complexity to the job. The more significant complication was the high risk of uncovering Unidentified Explosive Objects (UXO) leftover from World War Two during excavation.
The team uncovered many UXOs during excavation in the first stages of work and adapted their methodology to identify UXOs earlier during excavation. The change in methodology requires full-time attendance from a qualified UXO Surveyor at every trench location; the Surveyor will scan each layer of excavation in 1m depths. The Solomon Islands Explosive Ordinance Department then removes any UXOs identified. This has affected the pace of excavation but is the safest way for work to continue.
Stages 6, 5, and 2 were completed at the end of 2024, and the team is on target to complete Stages 1, 3 and 4 in early 2025.
The next stage of the UWSSS Project includes building a new wastewater screening plant and pump station, an outfall, and installing connections from private properties to this trunk sewer.
