GEA was commissioned to undertake a desk study and ground investigation at a semi-detached house on The Boltons, for a proposed 3.0 m deep basement beneath the front garden and an 8.5 m deep basement below the rear garden, which was to be locally deepened to accommodate a swimming pool. It was also proposed to reinstate the front and rear gardens above the basements.

Access was severely limited by the layout of the existing house and the investigation was designed within the confines of the restricted access. A single cable percussive borehole was advanced to a depth of 24.5 m using a dismantlable drilling rig in the rear garden, with the drilling equipment manhandled down the passage to the side of the house.

The findings of the borehole indicated that formation levels of the 8.5 m and 10.0 m deep basement excavation would be below the groundwater table in the River Terrace Deposits and that some form of groundwater control would be required in order to construct the basement. A secant bored piled wall was installed, and this wall is now completed.