Air Hammer Wells

Air Hammer or Percussion Drilling is used when the water table is deep and/or drilling must pass through rock.  The drill bit is repeatedly hit with a compressed air driven piston to crush the material at the base of the bore hole.  Cuttings are removed by the compressed air.  This type of drilling is expensive but is the only option for deep wells or wells in solid rock.  St Paul Partners has contracted with several well drilling companies in Tanzania, including Hydro Tech Tanzania Ltd and Aqua Well Drilling Ltd.  The photo below shows the Aqua rig at Kiwele as they hit water.  Notice the pulverized sand around the well that had been removed during the drilling.  The next step is to install casing (6" PVC pipe) with a slotted screen at the bottom to admit water.  The well is then "developed" by flushing with water under pressure to remove fine particles and develop channels for water to flow in the aquafer.

Deep wells often need a powered submersible pump that lifts water to the surface to fill storage tanks.  At Kiwele, water was found at 30-40 meters and the well was drilled to 80 meters.  Pressure in the aquafer pushed the water level up to a meter from the surface allowing a hand pump to be used on this well.