Water & Wastewater Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/1029929
www.wwtonline.co.uk | WWT | OCTOBER 2018 | 17 • UTILITY AVOIDANCE WHEEL Developed by the Civil Engineering Contractors Association (CECA) in association with Kier, BAM Nuttall, Skanska, Morrison Utility Services, UK Power Networks Services, Barhale, Crossrail and UKCG, the Mechanical Excavation Utility Avoidance Wheel can be used to assess how to proceed when working around gas, electric and third-party pipelines. "It's a nice, simple device that gives an idiot-proof guide to where something might be located, what the safe dig distances are, what the appropriate practice is to use," K M Plant's Murray Ambler-Shattock says. "When these are used properly, they're very effective." • SAFE WORKING PRACTICE • DATA AND MAPPING A ccording to PAS128 – a specification for underground utility detection, verification and location – quality practice depends on 'active service detection', where the location of services is an activity that is kept entirely separate from that of excavation. That means plans should be sought and checked through all appropriate channels before arriving at the site, with a CAT (cable avoidance tool) and genny (signal generator) then used to detect the buried utilities and verify the information. "PAS128 includes some really good, positive advice about the desktop records request process, using site clues to marry those records with what is on site as well as the use of locating equipment and trial holes to identify assets," Broome says. "It's a really good benchmark which is replicated around the world." The reality is that much of what happens in practice can fall short of that benchmark. The CAT and genny should be used by utility survey experts and not L SBUD revealed in its Digging Up Britain report that it had received 2,268,868 searches in 2017, representing an increase of 27 per cent on the previous year. Still, given that the total number of work projects is estimated at 4 million annually, that would suggest almost half take place without a thorough asset search. "It's not just us that sees this," Broome says. "I've just come back from Australia where they've got almost all the asset owners covered by the Dial Before You Dig service and they're still seeing a 25 per cent growth every year in enquiries. There's always lots of people that might not have searched before they start digging." Ambler-Shattock suggests there is a 50/50 split between those who take strike avoidance sufficiently seriously and those who do not. site operatives, but 57 per cent of those responding to a 2012 Civil Engineering Contractors Association (CECA) survey said that had not been the case in their experience. In addition, 86 per cent said service location was not carried out as a separate exercise, and the same percentage said the genny was not used as much as it should be. One contractor commented: "When you have gangs going through CAT and genny training, it might be done by a firm pulled in to educate the sub-contractors. You're sitting in a room with people who should be paying attention and they're on their phones, gambling on football matches or whatever, instead of listening to what they're being told. They then go out to site half-knowing how to do the job and, frankly, that's not good enough. "I'm a bit old fashioned. I'll scan a couple of feet, then dig, then scan, then dig, then scan, then dig. You get guys who wander about a bit but don't think they've picked anything up so just crack on." However, detection may not be "Diligent people are only as good as the records they can pull," he adds. "If we find gas mains aren't where they're supposed to be, or fibre optics are on the wrong side of the road, we will send it back and notify the utility, but we'll pull the maps six months later and find nothing has been done. "In an ideal world, you'd have a situation where as soon as you're scanning and locating, that's uploaded to some cloud-based centralised system that updates a kind of pseudo-BIM network, so every time something is located in physical reality, that precise location is uploaded to a central library. "There needs to be a significant change in the approach to these things. If that requires legislation or an operational standard that is accepted within the industry as 'the rules', so be it." possible even when the technology is used as intended: the CAT and genny cannot pick up plastic pipes – oŸen used for low-pressure gas and water – unless there is a trace wire. Although surveys can be carried out for water pipes using soundwaves, gas remains problematic. Where possible, K M Plant makes use of air lances and vacuum excavation to minimise the strike risk on undocumented, or incorrectly documented, underground assets when working in congested areas. Some jobs may allow for alternative solutions to further minimise the risk – Ambler-Shattock suggests horizontal directional drilling, which removes the need to open cut trenches and can sometimes avoid the danger zone entirely – but ultimately good practice comes down to a genuine commitment to adopting the best methodology. "It's more important to work safely than fast," he says. "It's not about finishing so you can go home at 3pm, it's about finishing so you can go home." 1,212,139 2013 2015 2014 2016 2017 +20% +11% +10% +27% 1,449,744 1,617,801 1,780,399 2,268,868 TOTAL NUMBER OF UTILITY SEARCHES PER YEAR Source: LSBUD