Residential Scheme: Walthamstow, London

Evesham Avenue is located in the London Borough of Walthamstow and at the time of investigation comprised an area of terraced garages and an abandoned play area. RSA Geotechnics were instructed to undertake a site investigation for a proposed four storey residential development.

Whilst carrying out the Phase 1 desk study it became apparent that an area of the site had formerly being a pond and could potentially be a source of ground gas as well as having made ground of unsuitable materials to greater depth than elsewhere on the site. Further on-line investigation to assess the risk posed by unexploded ordnance also revealed that the site had taken a direct hit from an anti-aircraft shell destroying a row of terraced houses that had originally faced onto Evesham Avenue from the early 1900’s.

RSA Geotechnics involvement in the project included; a reconnaissance site visit and environmental desk study report; an intrusive geotechnical and geoenvironmental site investigation including a deep borehole to 20m depth; in-situ and laboratory testing; and groundwater and ground gas monitoring.

The ground investigation was organised to target the areas that could pose challenges to construction due to deep made ground resulting from both the former pond, and the WWII anti-aircraft shell.  The investigation encountered deep made ground to a depth of approximately 2.0m in the vicinity of the former pond and along the northern boundary where the shell was recorded as falling. Over the weeks following the ground investigation, ground gas monitoring wells installed as part of the project were monitored for ground gas concentrations. It was found that concentrations of ground gas did not pose a risk to end users of the development and gas precautionary measures would not be required as part of the scheme.