An integral part of the Devon Coast to Coast National Cyle Route is the crossing of the River Walkham, near Tavistock. The cycle route follows the old railway but the original railway viaduct was demolished in the 1960’s, so the only option for cyclists was to negotiate the steep sides of the Walkham Valley. A new bridge was proposed and Frederick Sherrell Limited undertook an initial desk study and walkover inspection on behalf of the Local Authority. This indicated that there were mine workings in the vicinity of the bridge site and potential difficult ground conditions associated with demolition debris (from the original railway viaduct) on the valley sides and alluvium in the valley floor. The desk study was used to plan the ground investigation which included trial pits, probe drilling, geophysics and an underground inspection of an old mine tunnel.
Variable thicknesses of alluvium and made ground meant that multi-piled foundation bases were the most appropriate foundation option. A sacrificial pile was tested to verify that the load carrying capacity was as expected. During construction an engineering geologist from Frederick Sherrell Limited attended the site to monitor the piling works and to check the exposed ground conditions. The bridge opened in 2012