Ground & Water’s approach – Additional investigation in the form of machine excavated trial pits, windowless sampler boreholes and deeper cable percussion boreholes, were undertaken to confirm the previous site data, analyse the impact of demolition and undertake a further groundwater risk assessment. In addition, a coal tar hazard assessment was required on the areas of tarmac hardstanding, still remaining onsite.
Outcome – Following completion of these works, Ground & Water was able to analyse both old and new data to determine a foundation scheme, which included both traditional strip footings where dense sandy Head Deposits were noted and piled foundations, where soft clays meant foundation loads were too high or where deep Made Ground was encountered. These findings advantaged the client, as expensive piles had been previous recommended across the entire site.
The geo-environmental side of the report analysed the effect of demolition on the site and allowed for the use of the demolition capping as a break layer to limit any further remedial works required. This was tied in with a further groundwater risk assessment, which indicated no unacceptable risk to controlled waters. A PAK marker survey combined with lab testing indicated that no coal tar based tarmac was present onsite.