Directional drilling involves drilling a pilot hole with a precision-guided drilling rig, then pulling the new pipe back through the hole. Not all ground conditions are suitable, and not all pipe materials can be used. Only two small pits are required, one at each end of the section of pipe that is being replaced.
In Gosport it was necessary to provide a 300mm diameter main to serve a new development which meant crossing Forton Lake. The new main was installed beside the footbridge using the directional drilling technique thus avoiding large scale disruption to the creek and minimising the ecological impact.
A pilot hole was drilled first. As the drilling rods were then withdrawn the hole was enlarged with the ‘reamer’ (rusty looking barrel in centre of picture) and the pipe pulled through behind.