50 | Selwyn District Council: Darfield Watermain Upgrade T T Bernadette Cooney Better services for growing townships With Darfield being one of New Zealand’s largest communities without a reticulated wastewater network, this project addresses urgent infrastructure needs. “The new system will collect wastewater from both communities and convey it to the Pines treatment plant.” REGIONAL DEVELOPMENT The Selwyn District Council’s Darfield-Kirwee Wastewater Pipeline Project is making good progress, with 35% of the $2.4M pipeline construction completed by the end of 2024. The pipeline project represents a transformative step for the two fast-growing communities of Darfield and Kirwee, enabling a reticulated wastewater network for new developments for the first time. With Darfield being one of New Zealand’s largest communities without a reticulated wastewater network, this project addresses urgent infrastructure needs while setting the stage for future development. Currently, most residents and businesses rely on septic tanks and on-site treatment plants, a wastewater management system that relies heavily on discharges to ground, a method increasingly unsuitable for Darfield and Kirwee’s expanding populations. With projections suggesting these townships will grow from 4373 residents to over 13,000, the need for a centralised wastewater solution had become critical and council began consultation on wastewater servicing as part of the 2021 Long Term Plan process. Following community consultation, the council secured $10.66 million in government funding through the post-Covid -9 Water Stimulus Package. Selwyn District Council’s head of capital works, Kamal Narang, says the first stage was the completion of the trunk pipeline to the Pines Wastewater Treatment Plant near Rolleston. To date, 27 kilometres of the main pipeline have been constructed, linking Darfield and Kirwee to the Pines, with construction of local networks in Darfield and Kirwee now underway. Residents can expect temporary road closures along Telegraph Road and surrounding streets to accommodate this phase, with work continuing into 2025. “The new system will collect wastewater from both communities and convey it to the Pines treatment plant,” says Kamal, “providing the infrastructure that the town needs to enable growth.” As part of the Long-Term Plan, council has budgeted to extend wastewater reticulation to existing properties between 2027 and 2038, preceded by council’s community engagement to address funding and connection costs. The pipeline features impressive engineering capabilities, including a pressure rating of 1000 kPa and depths of up to eight metres for installations like the Darfield pump station. Additional key factors include 54 manholes installed, two pump stations completed, 114 metres of pipeline installed in a single day at peak productivity and 20,000 cubic metres of material reused on-site, reducing environmental impact. The scope of works includes the installation of 1500 metres of sewer trunk pipes linking existing reticulation laid by new developments upstream of the Horndon and Kimberley Street intersection and downstream of the Owen Drive and Telegraph Road intersection. The new sewer trunks range from 175mm to 300mm pipes at an average depth of 2.7 metres. The project has also incorporated a water main upgrade to replace aging asbestos-cement pipes along the same route. “We are targeting the growth areas of Darfield and its central business district first,” says Kamal. “Reticulation of the existing township has been budgeted in the LTP between 2027 and 2038. Prior to the roll-out of the network, council will engage with the community on how servicing costs can be met.” The Darfield-Kirwee Wastewater Reticulation Project is successfully progressing in stages, and is expected to be fully operational by 2034. 03 354 8204 | luke@ssdl.co.nz www.subsurfacecivildrilling.co.nz SUBSURFACE CIVIL & DRILLING LTD • Trenchless Installations • PE & Butt Welding • Civil Works • Underground Infrastructure • Hydro Excavation (Hire) • Ground Penetrating Radar (GPR) • Drainage / Water Reticulation
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