24 C O N T E X T 1 1 0 : J U LY 2 0 0 9 incidents, discussions with the insurers relating to the likely costs and timetabling of repairs took time. It was around 12 months after the incident that the go-ahead for repairs was finally given.While this allowed time for ordering new stone and preparing a suitable specification for the works, it left British Waterways with the problem that the works would have to be undertaken during the winter months, when weather conditions are not ideal for the use of lime mortars. There was the possibility of delaying the works until the following spring, but British Waterways was under increasing pressure from the county and parish councils to undertake the works as soon as possible. A further difficulty was that the road could be closed for only a week to facilitate the works. It was therefore necessary for BritishWaterways and its contractors to establish a specification which would restore the historic form and appearance of the bridge while ensuring that the works could be completed during the road closure period. The specification identified a lime-based mortar mix to be used during the works, and prescribed a method of aftercare to encourage a comparatively quick initial set for the mortar, sufficient to ensure that the road could be reopened at the end of the week. It was concluded that in order to achieve performance within the short time-frame, and taking into account the challenging conditions that the parapet was subject to, an eminently hydraulic lime should be used, combined with sand and aggregate to achieve a relatively coarse mix. This mix closely matched the colour and texture of the original mortar. Weather protection to allow the mortar to cure consisted of an insulated cover of hessian, fleece and plastic sheets to ensure protection of the completed works. Once on site, the weather conditions deteriorated, with the north west of England suffering some of the coldest temperatures for many years. Following discussions with the stone masons, a process of working was agreed whereby a window of approximately two hours a day was identified as viable for rebuilding the parapets with lime mortar. Around midday, the heat from the sun raised the air temperature sufficiently to work to the mortar specification. The masons were required to assess the weather each morning to ensure that they managed the maximum amount of fixing work each day. Close liaison was maintained by all parties throughout the works at Borwick Bridge, both to ensure efficient delivery, but also more importantly to monitor the setting and performance of the mortar.This careful approach paid off, and ensured a satisfactory initial set of the mortar within the tight timetable imposed by the need to reopen the road to traffic. Similar conditions were experienced at Claughton Lane Bridge, another bridge damaged by vehicle impact. Here again a serious impact dislodged a substantial section of the parapet, leaving the highway exposed to the canal below. Again there was great pressure to reopen the road as soon as possible.The road is straight for a considerable distance on the approach to the bridge, which leads to vehicles crossing at relatively high speeds. As the bridge narrows slightly towards its peak, it was a concern that introducing water-filled barriers or other traditional safety devices would narrow the bridge carriageway further, increasing the likelihood of further damage. Lateral thinking was required. The solution was a system of simple metal poles which clamped to the remaining parapet, providing a safe barrier while avoiding any further damage to the historic fabric.This innovative solution remained in place for a number of months, maintaining road safety while insurance matters were resolved. The works were timetabled for the week following the Borwick Bridge project, falling foul of the same spell of cold weather. But lessons learned from the works performed the previous week allowed the project to progress more smoothly, and Claughton Bridge was repaired ahead of schedule. The experience of repairing canal bridges sensitively and efficiently is increasing the skills base and appreciation of the importance of waterways heritage, and underlining the importance of consulting, forming partnerships and garnering local support. British Waterways continues to engage with other agencies and landowners to find ways and means of reducing damage to vulnerable historic buildings and would be interested to hear from other organisations that face similar difficulties. Andrew Tegg is heritage advisor, north west, for BritishWaterways. Claughton Lane Bridge before (left) and after repair work
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