Case Studies

Colnebrook, Scour Protection

Client – Osborne

Value – £275,000

Duration – 4 weeks

Type – Scour protection


The River Colne crosses a railway over bridge in Wraysbury, Surrey. The flow of the river can create a scour effect to both the bridge foundations and the river banks, both on the approach to, and downstream of, the structure.

Suttle Projects were contracted as 2nd tier supplier, through Network Rail CP5 framework contractor, Osborne, to install scour protection, in the form of a diver filled grout mattress. This was anchored at either extent of the bridge’s envelope by rock armour trench construction. Due to the large flow, and low structure headroom, it was impractical to de-water the structure, either fully or in phases, at this location.

Suttle Projects’ bespoke Mermaid underwater excavator was utilised to progressively excavate to depths of up to 1.5m, in the live channel. The worksite was isolated with a silt curtain during excavation.  Once the excavation of each bay was completed, we installed a grout mattress with the assistance of a five-man HSE compliant dive team.  Again, using our innovative excavator, the river bed was restored to its pre-contract level, with a proportion of the original bed material, to facilitate the recovery of bio-diversity at the site, in the shortest time frame.