Deep Bore Soakaways, Devon

Deep-bore soakaway drains were recommended by Ruddlesden geotechnical following observations made during conventional soakaway testing in accordance with BRE DG 365 at a proposed residential development site in Torbay.

Previous geotechnical investigation and near-surface geophysics, undertaken as part of a solution feature investigation, had indicated that the use of conventional shallow soakaway drains could lead to the loss of near surface soils through underlying cavernous limestone, potentially leading to a heightened long term subsidence risk of the ground.

It was considered that the careful use of deep bore soakaways could mitigate this risk, by transferring surface water into competent limestone at depth, beneath the weathered zone where concentrated flows could trigger subsidence of the ground.

The installation of the deep bore soakaways was supervised by Ruddlesden geotechnical, who also carried out in-situ constant head permeability testing post-installation, to confirm the performance of the soakaway drains and the design parameters.