INTRODUCTION
This 1.77-hectare site was occupied by a business park of single-storey steel framed warehouses, plus car repair garages built on an area previously occupied by a petrol station.

The site was earmarked for mixed residential and commercial properties with underground parking. The Harrison Group was commissioned to drill a variety of cable percussion boreholes to a depth of 40m and undertake window sampling and hand excavated trial pits.

SCOPE OF WORK
Harrison Group's first task was to commission an Unexploded Ordnance (UXO) desk study as this part of London was razed during WW II. The study concluded that there was a high risk of ordnance.

With this issue uppermost, all locations were scanned with a magnetometer before setting up drilling rigs. Boreholes were progressed using standard 150mm diameter casing. At two-metre intervals the casing was partially withdrawn, a magnetometer probe was lowered to the base of the borehole and surveying for UXOs was carried out.

Window sampling was carried out across the area occupied by the petrol station to confirm whether contamination was present. Hand excavated trial pits were used to assess the foundation design of existing structures. Reinstatement was carried out on completion.

Following the investigation, Harrison Group produced an interpretative report focusing on foundation designs and ground engineering parameters.

CONCLUSION
With both expected contaminants and potentially lifethreatening hazards this site required painstakingly methodical treatment. However the variety of borehole excavation methods Harrison Group employed – and the additional security afforded by magnetometer surveys - enabled the client to make an informed decision on redevelopment potential and associated costs.