Borehole drilling takes many facets depending on the results of the hydrogeological survey. The machinery and techniques to advance a borehole vary considerably according to manufacturer, geological conditions, and the intended purpose. Typically, a drilling may take two to five days depending on the type of formations encountered and the depth below ground level. Drilling involves casing of the borehole and adding the gravel pack. This is followed by borehole development which is basically cleaning of the borehole.