Special measures were needed this week to recover soil samples in this restricted space!

The planned redevelopment of a commercial site near London into new housing required a 23m deep borehole to be undertaken in a 3.6m high loading bay.

The low celling height precluded the use of standard rotary drilling rigs which were required to retrieve core samples of the underlying chalk for geotechnical and geoenvironmental analysis.

After a site walkover and measuring the celling height, CGL arranged with a specialist contractor to modify one of their rigs to reduce the mast height. In addition a pit was excavated in the concrete floor to increase the available effective working height and to enable the use of the maximum capacity of the rig.

In order to set up the drilling rig the mast had to be raised carefully in stages by the experienced operators, making use of the horizontal and vertical rotational capability of the rig’s mast. Once in place the set up enabled high quality core samples of the chalk to be recovered and the project was completed within the proposed timeframe and budget.

CGL uses a range of techniques and specialist contractors to carry out site investigations in complex situations including confined spaces, remote locations and difficult ground conditions.