CAN Geotechnical has been awarded a contract to carry out slope stabilisation and scour protection work in Edale, Derbyshire, for MWH Treatment. MWH Treatment has been contracted by Severn Trent Water to decommission and demolish the existing sewage works and install a new package plant treatment works within the existing site boundary serving the local residents of Edale Mill Cottages.
In Edale, work began in March 2021 to replace an old water treatment works, necessitating the removal of the existing sewage works assets and structures, and bank stabilisation measures. This includes the temporary removal of Listed Building asset gateposts, which fall into the curtilage of Edale House (Grade II Listed Building), in order to facilitate access to the site and protect the assets during the work. In addition, the worksite is adjacent to a SSSI area.
CAN was enlisted to provide a design and build solution to stabilise the 50m length of riverbank of the River Noe adjacent to the old water treatment works in the Peak District National Park.
Following site preparation by MWH, including demolition of the old water treatment works building, CAN began work on the riverbank in mid-March. The chosen solution, designed for CAN by RSK’s in-group Geosciences team and suitable for a 60-year design life, is to install a soil nail and facing system to the slope to prevent deep seated failure and erosion of the soils, along with a scour protection system at the base of the bank to prevent further undermining by the river. Over 200 soil nails ranging from 1.5m to 7m length will be drilled into the slope and grouted in position, safely securing the 500m2 area of steep soil slope.
Working top down, 360 tracked excavator mounted drill systems will be used to install the soil nails, and the facing system comprising high tensile Tecco steel netting and coir matting will be installed to fully stabilise the upper slope. Grout interceptors and dust suppression will be utilised, to ensure the river is protected during the soil nailing works and a silt curtain will be installed downstream of the works to contain disturbed sediment, prior to installing the scour protection. The scour system will utilise rock mattress and rock rolls, provided by fellow RSK Group company Salix River & Wetland, which CAN will install using long reach excavators working from the top of the bank, with operatives using rope access to reach the work area. Minor reprofiling of the bank will be carried out at the same time, and the rock mattresses and rolls dressed with topsoil to help embed them. Pre seeded coir matting will be used to promote devegetation regrowth, seamlessly blending in the newly stabilised section with the surrounding natural riverbank environment.
For details about this, any of CAN’s other recent projects, or any of the company’s products and services, visit the company’s website at www.can.ltd.uk or call 01474 538100.