Water & Wastewater Treatment Magazine
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www.wwtonline.co.uk | WWT | XXXX 20XX | 27 "Trenchless technology is not oen covered in civil engineering courses and so when designers look at projects, under time and budget constraints, they will oen sign off on a technique they're familiar with rath- er than spend time evaluating alternatives unless it's required because of a particular challenge," Izzard says. "Even then, it's all too oen thought of as a one-off." The UKSTT has a university outreach programme to give undergraduates and lecturers access to trenchless technology modules, specifically focused on methods, application, design parameters and opera- tion. It can also arrange for free technical sessions on the latest developments for companies wishing to expand their under- standing of the potential savings. However, Murray Ambler-Shattock, strategic operations manager at award- winning trenchless specialists K M Plant Hire & Groundworks Ltd, says not everyone in the industry is committed to exploring new solutions. "You deal with a lot of dyed-in-the-wool mindsets," Ambler-Shattock says. "Some of the personnel who've come up through the works side of the industry have done the same thing the same way for 30-plus years and aren't changing for anyone. "We've spoken to company seniors who weren't aware of the available technologies as, although some personnel were aware of the benefits, the suggestion to use them wasn't passed upwards, or the value and benefits weren't adequately conveyed, so the opportunity to deliver cost and time sav- ings was missed. "The world is changing fast, and they're beginning to catch up, but a lot of the industry is still probably 15 years behind where it should be, and I think they might even acknowledge that." Barriers Although the lack of knowledge, experi- ence and motivation represent some of the biggest hurdles to widespread adoption, there are circumstances in which trenchless solutions are not viable. In much of London, for example, the underground utilities are hugely congested and, like anywhere else, the records of what lies beneath the surface are not always accurate or complete. As a result, certain trenchless techniques can pose too high a risk of service strikes to be worthwhile. "The risk of damaging surrounding utilities in our congested underground infrastructure is becoming an increas- ingly sensitive issue," Kobus Services Ltd managing director Simon Drain says. "Because of this, contractors are oen reverting to traditional, non- trenchless techniques for safety." Open-cut techniques carry their own risk of strikes, of course, and some no-dig techniques almost eliminate the possibil- ity. That is the case with trenchless repair, which might involve a cured-in-place-pipe technique using water-safe patching materi- als to reline it, or spraying the inside of the pipe with epoxy or cement mortar. Repair techniques are better established for use in sewers and drainage, though, and pipe replacement might also prove more cost-effective in the long run. "There are always going to be situations where a repair is cost-effective, minimally disruptive and a practical solution," Drain www.wwtonline.co.uk | WWT | JUNE 2018 | 27 says. "However, on older infrastructure, such as black poly, copper and lead service pipes, it seems short-sighted and impracti- cal to repair the pipe, whether trenchlessly or otherwise. "Usually, a leaking pipe is a sign that the pipe is reaching end of life, so why make a quick, cheap repair that in all likelihood will leak again in the not too distant future and require further repairs or replacement?" There are a number of trenchless replacement options that only require small excavations for access and pose minimal risk of utility strikes. • TRENCHLESS TECHNIQUES There is a vast range of trenchless technologies currently available, including the following: Slip lining Inserting one or more pipes inside the existing pipeline. While low-cost, the technique results in a reduction of bore. Pipe pulling Used to remove lead, galvanised iron, copper and plastic service pipes, the technique uses a steel pulling cable to remove the old pipe and pull its replacement into the original pathway. Pipe bursting A 'bursting head' is passed through the existing pipe, forcing it into the surrounding ground to create space for a replacement. The technique can be used to install higher bore pipes but is only suitable for use if the surrounding ground is sufficiently so and there has to be awareness of any nearby utilities. Impact moling Soil displacement hammers create a void into which small diameter pipes can be pulled. The technique can be used to install new pipelines but can only cover short distances. Horizontal directional drilling (HDD) Also known as horizontal boring, the technique involves drilling at an angle using a back reamer to create the void for a new pipeline. The technique can be used to go long distances – and under potential problem areas including motorways, watercourses and airports – through the use of intersectional drilling, which involves drilling from either side and meeting in the middle. HDD allows for the installation of large bore pipelines and is generally extremely cost effective, but there may be challenges with avoiding buried utilities and drilling through rock. Cured-in-place-pipe (CIPP) A resin-saturated lining tube is forced against the inside of the pipeline until it cures to repair problematic sections. Although more commonly used in sewers and drainage, there are materials suitable for use with potable water. CIPP offers a low-cost means of repair, although replacement may be preferable in the case of pipelines that are approaching end of life. United Utilities is among the companies making use of directional drilling