Foundation risk assessment for the Chalk Group aquifer – compliance with current UK guidance

London in the UK lies within the London Basin Syncline (London Basin) a folded geological structure comprising Chalk Group bedrock, a principal aquifer used for potable supply, overlain by secondary aquifers and aquitards of Tertiary strata. Bedrock is often overlain by superficial strata of poor water quality. Pollution risks arise where aquifers become connected e.g. via deep foundations. The UK regulatory regime relating to groundwater protection was updated in 2017, but ancillary best practice guidance was not. As a result, assessments made by developers and their consultants may not meet regulatory requirements, and this discord can result in time consuming and costly protracted liaison, re-design and incorporation of mitigation measures. A case is described where lack of appreciation of the difference between site-specific and published data pertaining to aquifer type and existing connectivity led to over-precautionary controls, time-lag for development and increased costs. An approach to bring UK best practice in line with 2017 guidance is required, and a suggested approach is to provide a points-based scoring system utilising the new 2017 aquifer vulnerability data, but to update this on a site-specific basis and include additional site-specific and proposed construction method details. If agreed in principle by stakeholders in advance, this would reduce costs and delays.