NewsIn Brief

Repairing Alcantarillados: Shedding UV light on the problem

Repairing sewers by no-dig methods is quicker and less disruptive than excavation. But when the pressure is really on, as it was on a £1.7million project for Severn Trent Water (STW) to repair 2500-metres of sewers, Lanes has UV light technology which allows the company to renovate pipes in double quick time.

The Victorian sewerage system in the historic spa town of Buxton was struggling to cope. Three kilometres of pipes were in danger of collapse; the number and frequency of blockages was increasing — and so was the risk of flooding incidents.

A rehabilitation scheme using no-dig techniques was planned to remedy the situation, but it had to be scheduled around other works, including new water pipeline installation for Nestlé’s £35 million bottling plant, new electricity mains and main road resurfacing. Added to that Derbyshire County Council was keen to minimise the impact on the community and tourist economy so timescales would be tight, and sites often had to be reinstated the same day.

That is why main contractor NMCNomenca brought in Lanes and its ultra fast UV equipment.

Explains Lee Bow, Lanes Project Manager: “Using UV light we can cure a liner at, typically, one metre a minute* compared to an average 8- to 12-hours to cure a liner with hot water. That meant we could reduce the installation ‘window’ for each liner greatly.

“There are other savings too. For instance, the fibre-glass matting liners are pre-impregnated with polyester resin so there is no wet-out process, nor a need to keep liners refrigerated; there are no scaffold towers to be erected and dismantled, no water boilers and no fleet of vehicles — a single unit carries all the equipment for each install, with the liner simply stored in a wooden crate and positioned by the access point. And of course there is no contaminated wastewater to be disposed of afterwards. All of this considerably lessens the carbon footprint.”

The UV process is straightforward. A camera unit is dispatched through the pipe with a nylon pull-cord attached. This brings back the steel winch line, which in turn allows the liner to be drawn through the pipe, before end elements are fitted.

In the control unit, the operator enters data including liner length, thickness and diameter. The UV light train, propelled by computerised winch, and hot air compressor are introduced and, whilst the compressor inflates the liner, the UV lights cure the resin, whilst relaying a visual back to a camera operator.

In Buxton, Lanes installed a total of 43 individual liners rehabilitating 2,500 meters of sewer in work phased to an agreed schedule and within exacting deadlines. Diameters ranged from 150mm to 490mm and liner lengths from one-meter patch repairs up to 192-metres.

Chris Jones of NMCNomenca commented: “With Severn Trent Water, as part of the AMP5 framework, and in partnership with Derbyshire County Council, the sewer rehabilitation of Buxton was a success that benefited local residents, businesses and tourists alike. Working closely with Poceros de Madrid, and by driving efficiency through innovation, we were able to achieve the demanding construction programme.”