| 37 New Plymouth District Council : Inglewood WWTP REGIONAL DEVELOPMENT T T Sue Russell The concrete mattress uses two layers of special fabric that are stitched together and placed into a specially prepared area around the edge of the pond. Futureproofing the wastewater process Creating, connecting, and caring for the Taranaki community Site development · Earthworks · Three waters Hard landscaping · Concrete works · Surfacing 103 Corbett Road, New Plymouth 06 755 9697 fultonhogan.com Recent upgrades at New Plymouth District Council’s Inglewood wastewater treatment plant will protect the integrity of the facility into the future. NPDC Senior Project Manager James Mitchell is part of a team dedicated to continually assessing and, where necessary, modernising water and wastewater infrastructure for the Council. “We’re about improving performance, rectifying any issues affecting the system and renewing old plant. The team oversees design, construction and commissioning of projects of any size and scale,” he says. At Inglewood, a town 18km south-east of New Plymouth, work to upgrade a large wastewater holding pond has recently finished. Around the pond, new technology was used to renew and strengthen the pond’s stop banks, using a system seldom seen in New Zealand but one that James says proved to be exactly the right system. “The option we ended up using is a little bit different from more standard bordering of ponds. It is called a concrete mattress.” The concrete mattress uses two layers of special fabric that are stitched together and placed into a specially prepared area around the edge of the pond. Like an air mattress, except using concrete instead of air, the mattress is filled and as it grows in size and weight it conforms to the shape of the prepared embankment. The mattress is folded into a trench at the top, which helps to hold it all in place. “On top of that, we used low-carbon concrete to fill the mattress, which has reduced the environment impact of the project,” says James. To help position the concrete mattress right, the wastewater pond was emptied to make digging and construction easier. James says the concrete mattress is very popular in the UK and throughout Europe and he can see how, in the future, it may well be used again, given the speed of its construction. BTW Company helped with the design, including an initial options assessment that led to the selection of the concrete mattress technology. James says the project was thoroughly successful and it provided companies with the opportunity to understand and implement relatively unknown technologies. “The main contractor, Fulton Hogan, were really impressed with the technology. We appointed the company following a tender process and from go to woah the construction took about two months to complete. Fulton Hogan certainly did a great job working with our team. They helped us refine the design a little and the project came in on time and to budget.” At NPDC, there is a small team that focuses on improving and renewing water and wastewater facilities, and typically have more than 20 different projects on the go at any time. NPDC’s wastewater catchment area extends out from New Plymouth and includes Ōākura, Bell Block, Waitara, and Inglewood. The Council’s water reticulation also provides service to these towns as well as Ōkato to the south and Urenui, Onaero, Tikorangi and Lepperton to the north. James has been with the Council 18 months now, having a mechanical engineering background. He says one of the aspects of working in the water and wastewater infrastructure space is the wide range of projects that cross his desk and the innate challenges that come with them. “We have a lot of ageing infrastructure to attend to and we’re fortunate to have excellent contractors and subcontractors we engage with. It’s very satisfying to see plant upgraded and new technologies used that we know will bring lasting benefits to the region,” says James. “Fulton Hogan certainly did a great job working with our team. They helped us refine the design a little and the project came in on time and to budget.”
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