Borehole Condition Assessment, Logging, Test Pumping, Cleaning And Development
Most boreholes in East African are badly constructed. There are numerous examples of wrong gravel pack, screens put against non-productive layers and casings against productve aquifers. Also, mild steel casings that are rusting away. High quality plastic casings and screens (that can be installed to a depth of 300 m!) are only rarely used. They are not stocked by importers and have to be specially imported. In addition, many holes are too shallow, some have even run dry especially in Nairobi where groundwater levels are falling by 0.5 to 1 m per year. Also, certain types of bacteria may thrive in certain waters clogging the screens. This practice has resulted into a steady flow of requests to inspect boreholes. After inspection, advice is given either to drill a new hole or to take action in the form of re-development which often is a chemical treatment to remove silt or bacteria followed by hydraulic treatment in the form of over pumping, surging and/or jetting.