Water & Wastewater Treatment Magazine
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28 | NOVEMBER 2019 | WWT | www.wwtonline.co.uk could not find any comparable device and complete package delivery system, with a patent in place." The robot was trialled on numerous sites in 2018 before being deployed in March 2019 on a sewer regeneration pro- ject in Malmesbury, Wiltshire, where it helped avoid an all- day dig and achieved an 85 per cent cost saving. The utility firm was mobi- lised to renovate a 52-metre long stretch of sewer, which was 150mm in diameter, with numerous defects. The sewer was routed along Abbey Row, which is a one-way street due to its nar- row width. The road is a main artery and the necessary road closure meant a five kilometre detour. According to Wessex Water, the highways author- ity Wiltshire County Council was reluctant to allow a road closure due to disruption it might cause. It was even more so when informed that the sewer length had four locations where there was up to 21 per cent defor- mation, and as this degree of deformation could severely reduce the long-term capa- bilities of the polyester lining proposed. In addition, the manhole downstream was off-highway. In the weeks before lining, Wessex Water surveyed the sewer and measured it contin- uously with its in-house laser to ensure the robotics with a maximum diameter of 116-mil- limetres over the wheels could The Knowledge Innovation Zone be deployed under the defects. The Re-Rounder robot was used to avoid the four excava- tion points, and works were restricted to a 48-hour window over the weekend. Works commenced with a sewer cleaning and the stents were installed within three hours. Wessex Water estimates that if it had excavated down into the sewers, it would have needed four gangs, all working long hours on the Saturday, down to the two metre depth and reinstatement. It also says the cost sav- ings of using the robot were considerable. Generally, the excavations between two and three metres deep would have cost between £5,000 and £7,000 each, whereas the robot interventions were a fraction of that. Regarding the design of the liner in Malmesbury, it was designed against American ASTM F1216 for a 'fully deterio- rated' structural lining for the deepest section of the sewer at three metres. Instead, the company's long-term framework con- tractor Onsite Central Ltd, installed a three per cent undersized lining, and post lining. By all accounts, it was not readily evident to the eye where the stents had been placed without knowing the meterage. Over the weekend, many passing residents stopped and enquired as to the device being used. Wessex Water had personnel on site specifi- cally to answer questions and promote the benefits of all the trenchless technology being used on the day. "Customers and residents like to express their apprecia- tion that utilities such as ours are constantly searching to mitigate the impact of our necessary repair interventions upon their day-to-day activi- ties," Britton says. "We're firmly of the mind that with these new tools, most of the 'keyhole surgery', to continue the cardiovascular theme, are now available to clients such as us, to avoid excavation. "We do not claim any credit for the expansion concepts which we have copied from heart surgery for the stent but believe it is ideal in over- coming unnecessary loss of cross-sectional area, on small diameter sewers, which can least afford the loss of hydrau- lic capacity. "The next size of robotics will be a joint 225/300mm, which is currently under design. With greater diameters come greater depth of cover and, had a 300mm diameter machine been available to us some five years ago, a collapsing sewer in running sand in Poole, which cost some £250,000, chasing the defect over 15 metres, could have been saved for just a few thousand pounds. "The Re-Rounder brings us a more holistic ability to repair collapsing sewers and it's great that other people in the industry see the benefits of this technology. Going forward, my team and I are excited to be able to further reduce the company's need to excavate repairs." "The Re-Rounder brings us a more holistic ability to repair collapsing sewers and it's great that other people in the industry see the benefits of this technology." SEWER NETWORKS