Project Briefing

Lining avoids draining canal

British Waterways

Locaton: Monmouthshire & Brecon Canal

Technique: EcoCIPP lining

Main Contractor: OnSite Central

Sub-Contractor: Perco Engineering Services

The original canal engineers incorporated stone or brick-built culverts at points where the canal intersected natural streams. Some are now overgrown, leaking or have even collapsed. Making major repairs to these structures normally involves damming off and draining a section of the canal so that the bed can be excavated and the culvert opened up from above.

Culvert repairs on the Monmouthshire and Brecon canal are the responsibility of OnSite, as part of its cleaning contract for British Waterways. Onsite uses its own ‘Portadam’ equipment to limit the amount of canal drainage required but it is often very costly to get excavation plant to site, because of access difficulties in rural areas.

Perco convinced OnSite that the EcoCIPP system, with its strong GRP liner, could be used to line the culverts, without excavation, to provide both a leak-free watercourse and structural reinforcement to the stonework.
The diameters of the six stone culverts ranged from 600mm to 900mm. ‘Each one was an individual case,’ commented Brian Perkins, Civil Engineering Manager with OnSite: ‘Some were siphon culverts and some were blocked up and overgrown by trees. Others had become flattened in section, so that in a 900mm culvert, Perco used a 700mm circular liner and we put in a structural grout to each side. The flexibility of the EcoCIPP system gave us a number of options and the fact that it uses a UV-cured liner meant we did not need to get a boiler truck to each site.

‘Our usual procedure would be to dam off and drain a 25m to 30m section of the canal, dig out three or four metres, complete the work and then replace the puddling clay.’

With some head walls to dismantle and rebuild, along with camera inspection, jetting and vacuum clean-out required, the speed of the lining process was also a major asset to Onsite. The canal was only closed during October and November for the refurbishment work. The project was successfully completed in the allotted time, as part of a £9-10 million scheme by British Waterways to repair and upgrade 25km of the canal and to prevent flooding in the area around Abergavenny.