Dogmersfield Canal Improvements

The project comprised of the construction of two sheet piled retaining walls on either side of the canal, following a landslip into the canal channel. Works also included the design and installation of ground anchors through the sheet piles and 14m into the embankment.

The land slipped material was dredged from the canal and reused to raise towpath levels and also placed into margins in front of the sheet piled walls to promote ecology. Additional works consisted of the part replacement of a brick culvert that crossed the canal.

We proposed alternative materials for the backfill behind the sheet piles and the replacement culvert. Self-compacting single size aggregate and twin-wall drain pipe were used instead of 6N and concrete pipes respectively saving significant time on installation whilst improving whole life cost.

The main sheet pile works, ground anchors and towpath were located approximately one mile from the nearest highway access and slipway and therefore, the works had to predominantly be undertaken from floating pontoons on the canal. This included all dredging, piling and ground anchor works as well as the construction of the margins. All materials had to be transported via boat and pontoon from the site compound to the works area.

The repair of the culverts required the canal to be locally emptied to allow the culvert to be exposed, excavated and replaced safely. We installed a ‘Portadam’ system to plug the canal either side of the works area with a flume to allow water to pass through without putting undue pressure on to the dam.

Stakeholder engagement was key to the success of the project.

Multiple landowners were involved requiring agreements and permissions for access and compound area.

We mitigated unforeseen delays on the project to allow the canal to be opened to boat and pedestrian traffic whilst the works were being completed.