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Pedalling the branch line benefits

Contractors have got on their bikes to speed reopening of an unused stretch of track in Bristol, so freight can be transported to and from the city's Royal Portbury Dock by rail rather than road.

Contractors always complain about difficult access to rail projects so Alfred McAlpine couldn't believe its luck when it won the £6.4M refurbishment contract for the Portishead branch line.

The 9.5km section of line has been out of use for rail freight for the last 20 years but the route has a footpath and a cycle path running parallel for almost its entire length. McAlpine could have squeezed cars and small vans along these to transport its men to various work sites, but opted instead to provide a fleet of bikes. And for the last few months the contractor's operatives, as well as those from permanent way and signalling contractor Jarvis and consulting engineer Scott Wilson, have been pedalling up and down the line to good effect.

Work on laying new track is well under way and should be complete by September, at the same time as final repairs to bridges and tunnels along the route. Testing and checking the new line will follow and the first freight trains are expected to use the line in December.

The Portishead branch line was built in 1867, but went out of use in 1981. But the line was never officially closed and the track was left in place. Twenty years on, work is under way to refurbish a 9.5km length to take freight to and from Bristol's Royal Portbury Dock. The scheme is funded by Railtrack, the Bristol Port Company and government rail freight facility grants.

Investigations into reopening the rail link began two years ago and it was found that over 400 lorry movements a day could be saved if the rail route was reestablished.

'Over the last two decades road traffic has increased greatly and the Bristol Port Company recognised the potential benefits of moving more of its freight by rail, ' says Scott Wilson project engineer Rob Lewis.

'Technically the line was still operational but 20 years of neglect had left the track and structures in a pretty poor state.'

Alfred McAlpine and Scott Wilson surveyed the line and designed remedial repairs, reconstruction and strengthening schemes for the 25 bridges and four tunnels along the route.

Permanent way also had to be upgraded to modern standards.

Clearance has been one of the main obstacles to reopening the line. Today's trains are slightly taller than those used on the route before it was abandoned.

This meant the track level has had to be lowered by up to 250mm to pass below some of the bridges and tunnels.

'Most of the track levels could be lowered without major alterations or strengthening of the structures but the 610m long Pill Tunnel presented more of a challenge, ' says Lewis. 'The line survey showed there was sufficient clearance through most of the tunnel but a 100m section had been relined, reducing clearance.'

McAlpine dug trial pits along the length of the tunnel to expose the tunnel footings and the findings suggested that underpinning of the relined section would be necessary to lower the track levels. Scott Wilson's analysis showed that a 200m section of the tunnel would have to be underpinned to allow for a 50m ramp to create a gradual gradient down to the new track level and back up again.

However, further investigation revealed that the newer lining was actually sitting on its own footing, some distance above the original tunnel foundations which were still intact. A rapid re-design showed that the underpinning was no longer needed.

'Other remedial work to the Pill Tunnel included grouting of a void between the brick lining of the tunnel and the Mercia Mudstone through which the tunnel had been driven, ' says Lewis. 'Previously water draining down the rock face had collected behind the lining but new drainage runs were installed during the grouting works to direct any water out into the tunnel and away from the brickwork.'

Elsewhere on the line one bridge had to be completely demolished and rebuilt and brick ties were installed on three viaducts. Otherwise only minor repairs have been necessary for most of the structures.

Environmental considerations have been high on the agenda because the route passes through a nature reserve which contains a number of rare trees.

Scott Wilson's environmentalists advised McAlpine on clearing work and use of herbicides. A local ecologist was also consulted to help identify some of the rarer species. 'Some of the bridges along the route had trees growing out of them which had to be cut away, ' says Lewis. 'One of the rarer tree species which had established itself on the line of the track was transplanted elsewhere under the guidance of the ecologists.'

The railway line had not actually been built over or blocked at any point along its route because it never officially closed and remains in Railtrack ownership.

But some local home owners had extended their gardens to include parts of the railway embankments.

Railtrack had to enter into some careful negotiation to resolve this issue, not least because many locals were opposed to the reopening of the railway line.

Transport of freight from the port by lorry has not been along roads near the communities which are close to the railway line. So reopening the line offered them no direct benefit, only the prospect of increased noise levels from freight trains.

To help sugar the pill Railtrack has given up land occupied by 'sitting tenants' and established new boundaries closer to the new track.

Although at this stage the line is only intended for freight use, Railtrack has investigated reinstating passenger services on the new line. Further upgrading and possibly an additional section of double track would be needed before passenger services can become a reality, but Railtrack says that the possibility has not been ruled out.

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