Bramhope tunnel is one of the wonders of the railway age, one of the longest and certainly one of the wettest tunnels ever built in England. Constructed between 1845 and 1849, water pouring through faults in the sandstone was a major hazard and one of the reasons that 24 'navigators' out of the original total workforce of 2,300 lost their lives in its building and that the tunnel cost over £2 million, more than four times the original estimate.

The water was still a problem 150 years later as ponding round the track bed forced a 48km/hr speed limit through this 3.6km section of the main rail link between Leeds and the Thirsk area. That, combined with the fact that 50 years of maintenance had raised the track level by some 200mm, reducing train clearance to a bare minimum, necessitated this year's major rebuild in the tunnel costing around £10 million. The Main Consultants, Corus Rail Consulting called on Polypipe Civils Ltd. to design and manufacture a drainage system to replace the stone-built Victorian box culvert drain. Simon Barraclough, Network Rail's Project Manager for the work said "It [the Victorian culvert] was damaged and blocked with ballast. We looked at replacing the drain but it was not cost-effective. Also the replacement system has better flow characteristics".

Polypipe Civils' Technical Department at Loughborough spent almost 12 months designing, drawing and agreeing a system that included maintenance access every 30 metres along the length although the piping is relatively low maintenance.

The main element is the Ridgidrain Advanced Drainage System [ADS] in 500mm inside diameter, a twin-wall perforated pipe that combines great strength and superior flow with extremely light weight [around 6% of the equivalent in concrete]. The outer wall has high ring stiffness plus excellent chemical, impact and abrasion resistance while the blue inner wall makes CCTV surveying simple and has very low friction characteristics. Since the pipe is supplied in 6 metre lengths, installation is comparatively speedy. In all 573 units of 500mm perforated, 55 units of 600mm half-perforated , 380 units of 300mm perforated and 31 units of 150mm perforated were required for the project plus the necessary accessories such as couplings, junctions etc. For the convenience of contractors (Main contactor: First Engineering, Subcontractor Wrekin Construction) all catchpit units were fabricated in the Loughborough factory and delivered ready for installation. The drainage system, once installed, was surrounded by granular bed and surround for stability and easy access.

The complete contract - relaying both up and down tracks plus installing the drainage - had to be completed within one month to keep the railway disruption to a minimum. Working within the tunnel's confined space was, as Mr Barraclough put it, "A logistical nightmare" since multiple heavy machinery units had to be in place and in the correct order at all times. "You have to get everything right." he said "If you get out of step it has follow-on consequences all the way down the line."

In fact effective preparation and groundwork meant that the contract ran comparatively smoothly and trains can now negotiate the Bramhope tunnel at up to 100km/hr once again. The Victorian builders would have been proud of their successors.

22nd October 2003