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Wildlife crossing major roads are always at risk of being killed. The A422 brick arch bridge over the Farthinghoe stream in South Northampton was in need of urgent repair and strengthening to accommodate fire engine & traffic loading up to 40 tonnes.
Following discussions with the EA, a requirement to provide both a structural solution and to accommodate safe movement of mammals including otters through any new structure was required.
The bridge was constructed of a skew brick arch section, which had previously been repaired, but this was now failing, along with signs of radial cracking occurring. The bridge had been extended in 1971 with a corrugated steel arch which was also now showing signs of corrosion. The structure is shallow, 15m long with a flat invert and straight walls, which arches across to a height of 1816mm with a span of 3000mm.
Due to operational restraints on this structure, a bespoke prefabricated GRP segmental liner was chosen as the most cost effective, nondisruptive solution with a 100 year design life. Working with our partners Channeline International (manufacturer of the GRP units) a profile with a 48mm thick liner incorporating a 500mm mammal ledge/shelf was designed and accepted by all parties involved.
These units normal take 8 weeks to be manufactured and shipped by sea to the UK once the dimensions and profile of the units have been verified. However, because of local pressures from the residents and local Authority, it was decided to air freight the units from Dubai to the UK hence reduction the delivery time by 50%.
Following digging out of the riverbed and installing a new gravel bed, our installation team successfully installed and grouted the GRP units, all within a 2 week period.
Another very successfully completed job undertaken to structurally repair a bridge and help to look after our wildlife friends.

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