No dig technology in Drain Relining and Sewer Rehabilitation: pushing back the boundaries
The Beatles famously sang about potholes in Blackburn’s roads back in the 1960s* but today’s state-of-our-roads debate is still a contentious one. More so because neither joe nor josephine public are inclined to distinguish between street works necessary for the installation and repair of utility pipes and cables, and road repairs required to keep the wearing course in good order. For them, it is all the same. And the public perception is that road works in general are badly co-ordinated and a nuisance to road users.
According to The Asphalt Industry Alliance’s 2009 ALARM (Annual Local Authority Road Maintenance) survey, local authorities battling to maintain their highways are also coping with nearly two million deep trenches for utility and service provision works. The average number of utility openings per authority stands at 13,212 in England, 11,432 in London and 4,613 in Wales.
Deep trenches for pipes or cables cut through several layers of the road surface and the survey warns that the resulting scars make it more difficult to maintain the roads. It is a thorny issue. A staggering £8.5 billion is apparently needed to bring the roads of England and Wales up to scratch, yet local authorities say that they still only receive around half of the road maintenance budget they need.
Clearly then, anything which reduces the need for full excavation and digging — and therefore minimises disruption to the public and expense to the public purse — is to be embraced. And the wastewater utility sector is in a fortunate position to be able to use advanced technology to its advantage, both financially and in the efficiency stakes.
Back in the early 90s, the alternative to simply digging up the road came from the USA. ‘No dig’ technology for drain repair involved inserting a flexible pipe into an existing damaged sewer, and curing it in place — effectively creating a pipe within a pipe. It was revolutionary, and early adopters of the system were few and far between. However, the test of time and the practical achievements have seen trenchless sewer rehabilitation to go, part of the way at least, to answering some of the local authorities’ prayers, not to mention the utilities companies’ too.
National drainage experts Lanes (specialists in drain jetting and repairs) has offered pipe relining since the concept came to Europe and has repeatedly taken the technology to new levels. Andy Brierley, MD of the group’s sewer renovation division, explained: “New materials, ever more refined techniques, and liaising with the international industry at large has allowed us to break through old boundaries – and in some case, blow them out of the water, so to speak!
“The reline team regularly trials new materials and techniques and works closely with industry bodies and global manufacturers to develop ever newer and better methods, products and practices.
“Advances in associated equipment, such as remote camera units and robotic cutting tools, have also facilitated advances in the reline process itself. More and more accurate and sophisticated pre-work surveys of sewers means more control, with fewer unforeseen operational hitches during installation resulting in faster completion, and therefore, of course, less overall disruption to the public.”
At Conwy Bridge in North Wales, Lanes achieved a first and, at the same time, opened up a whole raft of new possibilities by relining a pressurised main sewer. It was an industry landmark and Lanes subsequently won a UKSTT award for innovation.
The 300mm diameter pipeline main was suspended underneath the bridge, 200 feet above the estuary. Quite apart from health and safety issues of operatives working at height on platforms and potentially massive disruption to bridge users and traffic flow through the town, the traditional replacement of the sewer was estimated at many thousands of pounds.
Relining would cost a fraction of the price and reduce the project time enormously. But could it be done? A rising main creates a vacuum when in use, so would require a special liner to withstand the internal pressure. In addition, the central section of the 300mm diameter sewer changed to a square profile (350mm x 150mm box section) before reverting to round again. The single liner would need the flexibility to adhere to the internal profile of the pipe in each case.
“Even five years ago, attempting this would have been unthinkable, but constant improvements in materials, equipment and control are driving us to greater achievements on an almost daily basis,” commented Andrew.
“For Conwy Bridge, we sourced a high-grade, structural, fibre glass, composite weave liner from Hong Kong and commissioned the epoxy resin, with which the liner was to be impregnated, especially for the project from Helsinki. This combination would give the pipeline mechanical strength enabling it to retain its integral structure under vacuum conditions.
“It also allowed it to accommodate the changing shape of the pipe and, going forward, to manage movement in the pipe and bridge caused by traffic flow.
“Using compressed air to invert the liner through the pipe, and steam to cure and set it instead of water in both cases made the process even quicker so that, in the end, the actual relining of 174-metres of pressurised main sewer took just 12 hours, and the clients — in this case both United Utilities and Dwr Cymru, and main contractor Daniel — were delighted.”
It is not only technology that is driving the industry onwards and upwards. The introduction of New Roads and Street Works Act (NRSWA) 17 years ago began legislation and procedures which have continued to evolve and develop to reflect customer expectations and political demands. The 2004 Traffic Management Act, similarly, increases the pressure on all parties to improve co-ordination in an attempt to reduce overall congestion caused by the effects of street work.
A high profile sewer renovation scheme in MP Jack Straw’s Blackburn constituency earlier this year, demanded that disruption be minimised and that businesses, shopping centre pedestrians, the local law courts and road users be inconvenienced as little as possible for the duration.
Lanes worked with contractor Balfour Beatty Utility Solutions and United Utilities to consult every potentially affected business and shop before, during and after the project to reline the Victorian, brick-built, egg-shaped sewer. The local highways department monitored the site closely because they were interested in the contractors’ approach to protecting the public at town centre work sites, with safety fencing, pedestrian walkways, risk assessments, etc.
In fact the renovation involved only a partial road closure, was completed two days ahead of the 10-day schedule, and the bottom line was probably a fraction of the cost it would have been to repair or replace the sewer by excavation. And there was not a single complaint from joe (or josephine) public, the road users or the local business community.
So whilst this project was innovative because renovating egg-shaped sewers is a relatively recent achievement, the overall success was not just about the science of the reline process itself.
It was also about a concerted programme of communications and meticulous traffic management. All the stakeholders knew what was happening and what to expect on a daily basis as teams carried out face-to-face customer service visits and provided detailed signage on lamp posts.
Local businesses and the public were happy that everything feasible was being done to minimise disruption and reduce the inconvenience. And the rehabilitation of the sewer on Northgate has not contributed a single pothole to Blackburn’s current tally.
* The Beatles’ “A Day in the Life” written by John Lennon refers to ‘4000 holes in Blackburn, Lancashire’. ‘4000 Holes’ is also the name of Blackburn Rovers FC’s fanzine.
About the Author
Lanes for Drains is the largest independent drainage specialist in the UK
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