Following prolonged heavy rainfall during a succession of large storms, increased water levels and flow of Tarn Brook in Brookhouse, Lancashire caused significant erosion to a riverbank. A row of residential gardens back onto the beck and the sloping riverbank beneath one house failed, collapsing into the beck, and undermining the resident’s garden. If the unstable slope was allowed to continue retreating a large area of the garden would have been lost and the house itself would potentially have been at risk.

CAN were called upon to help solve the problem and came up with a design and build solution to stabilise the slope in situ, preventing any further slippage and further erosion by the river. The design required 20no. R32 hollow bar soil nails and a composite erosion matting and steel mesh facing to over the upper slip area to stabilise it. Before any works at the toe could commence, the beck had to be redirected with a dam created and an over pumping system installed to dry the work area and allow access to build the solution.

Due to the limited access nature of the worksite, specialist slope mounted A-frame drill rigs were utilized, with operatives using rope access techniques to work on the steep slope. New slope drainage was then installed and 28m³ of gabion baskets were constructed to buttress the toe of the slope and protect against further river erosion, secured to the sandstone bedrock with vertical shear dowels.

CAN created a concrete foundation at the toe to act as a platform for the gabion baskets to sit on, which were then constructed and filled in situ with locally sourced Limestone. On completion of the stabilisation works the origional slope profile was reinstated using engineered fill, and a soil filled geocell system was installed over the face, encouraging natural revegetation.

Duration:   6 weeks

Client:         Private Homeowner

Location:    Brookhouse, Lancaster