In February 2020, EMS Geotech were commissioned by a private homeowner to undertake a Geotechnical Ground Investigation in the Forest of Dean.

The client required information on ground conditions for the design and construction of a retaining wall to hold back an unstable slope behind an old cottage. The cottage was built in the late nineteenth century in front of a quarry, which has long since become disused and was backfilled up to the rear wall of the cottage.

A gravity retaining wall using gabion baskets was proposed to prevent the unstable slope slipping towards the property. Construction works began in 2020 to extend the property rear by cutting and removing the slope behind the cottage. The retaining wall was partially built but works had to be halted during the pandemic, leaving an exposed and unstable partially excavated cutting behind the cottage.
EMS Geotech carried out a ground investigation at the site to determine the nature of the ground, the depth of groundwater and in-situ soil strength tests for clay soils.

Trial pits were excavated to up to 3.2m depth for soil logging by an EMS Geo-environmental Engineer in accordance with BS5930:2015 and BS EN ISO 14688. Three standpipes were installed to monitor groundwater over a period of a several months. In addition, soil samples were collected to determine moisture content and bulk density of the soil.

Our Geotechnical Assessment of the site concluded that excavation of the slope should have appropriate support or be adequately shored, and that a retaining structure using gabion baskets would be suitable.