Down Street Mews, Central London

Drilling of 12 x 174m ground loops for the geothermal heating of a domestic property. When the works were priced originally the boreholes were to be undertaken from existing ground level in a courtyard. To meet the 6 week drilling programme we allowed for the works to be undertaken with a sonic rig for speed and efficiency. There was a significant change in the scope of works when due to the construction programme it became necessary for the boreholes to be drilled in a basement 5m below ground level with an areas of 20m x 10m less the space required for an access ramp and a tower crane. All drilling equipment, water pumps recirculation tanks could only be placed in the basement. In addition horizontal steel beams were

installed to support the walls of surrounding building of the basement which restricted the headroom.
This meant the sonic rig was not suitable as it was too big both in footprint and height and we used a conventional rotary rig with a shortened mast. We were able to drill to 174m and install ground loops, including casing off to the top of the Chalk bedrock at 90m, in 3 to 4 days. Despite the basement flooding requiring the piling mat on which we were working having to be replaced we managed to complete the works in 12 weeks.