42 | Complex project delivers The pipe takes the treated water from the pump-station at the Te Maunga ponds to the sand dunes by way of a new 1.7km 1200mm pipeline. HEB Construction BOP T T Hugh de Lacy REGIONAL DEVELOPMENT Delivering the landward section of the Te Maunga wastewater outlet project to the Tauranga District Council for $3.4m less than the tendered price of $14.4m was just one of the factors in the Bay of Plenty branch of HEB Construction’s winning Category Four (projects over $5m) in the 2023 Civil Contractors Bay of Plenty Awards. It was a highly complex project involving both the Te Maunga and Chapel Street Wastewater Treatment pipelines, with the landward section of the 600mm diameter outfall pipe into the ocean being critical to Tauranga’s infrastructure. This section of the pipe takes the treated water from the pump-station at the Te Maunga ponds to the sand dunes by way of a new 1.7km 1200mm pipeline. The new pipe greatly increases the Te Maunga outfall system’s hydraulic capacity, eliminating the risk of continuing with the existing concrete under-sized pipeline that was rapidly reaching the end of its useful life. The new pipeline had to be built under and alongside the existing one without interrupting its flow, and then the retained section of existing pipe, beyond the connection point, had to be re-lined using a cured-in-place-pipe (CIPP) system that greatly extends its operational life. The new PE pipe, formed by continuous welding, was laid through a narrow open corridor just 20m wide, and installed within an existing 1800mm diameter pipe duct under the Tauranga Eastern Link (TEL) and KiwiRail’s East Coast line, using a trenchless technique. Connections were then made to the Te Maunga pump-station, the ultra-violet disinfection plant and to the existing Maranui Street outfall. “Working with our specialist sub-contractor NZ Lining, and with the TCC’s operations team, we were able to offer an alternative to the council, eliminating a temporary complex bypass pipeline,” HEB Construction’s Bay of Plenty Civil Area Manager, Chris Whitham, says. “The alternative was completed well within the three-day shut-down window, and offered a significant price reduction.” “The project was carried out in a highly sensitive environment, with nearby houses and businesses – including two retirement villages, KiwiRail and Waka Kotahi – potentially exposed to noise and vibration risks. “The works were also sited right next to sensitive wetlands and around live treated waste-water flows, so we had to put in a lot of planning for our Environmental Management Plan, including preconstruction site trials to check the impact of our equipment on our neighbours. “We then set up a 2.4 metre noise wall that reduced the noise to an acceptable level.” The trenching from the pump-station to the UV plant passed between two protected wetland area. “This meant our site crews had to think outside the box to enable the installation of our slide rail trench shoring system, and the methodology to get the new pipeline into the trench,” Chris says. Impact Engineering would like to congratulate Heb Construction on their award. Impact Engineering has been supporting/partnering with a number of locally approved civil contractors over the past decade. Our workshop here in Tauranga has an extensive array of fabrication equipment and an awesome team to assist with client and consultants requirements. 07 578 8751 info@pipefitters.co.nz 140 Birch Avenue, Tauranga
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