FES employed a combination of core drilling, drill and case techniques, and window sampling using small rigs. The company constructed a timber platform above the trench, from where they were able to drill 169 boreholes in two phases to depths between 3 and 6m. Samples and cores up to 6m in length were obtained from each of the holes using a Fraste Terra-In mini-rig and a Symmetrix drill and case system.

The FES Terra-In track mounted rig has good manoeuvrability in tight spaces and over uneven ground. With an overall width of only 740mm, an operating height of 2,500mm and a weight of 850kg, it can be used within confined premises or externally on unconsolidated ground, inclines, under walkways, bridges and other structures or, as in this case, from a platform.

Fully hydraulic, the rig's head has a dual function; for conventional rotary work or to deploy a hydraulic hammer for window sampling and probing.

A small cathead fitted to the top of the mast, together with a hydraulic stabiliser in the base of the mast, enables the rig to be used with a standard SPT trip hammer to provide a lifting capacity of 2.5 tonnes to extract sample tubes, casing and drillstring respectively.

MJ Information No: 20055