Anatomy of a Drilled Bedrock Well

Using a drill rig, well drillers begin by drilling a hole about 9" in diameter through the overburden sediment overlying bedrock. When bedrock is encountered, drilling continues until competent bedrock is reached, generally between 10 and 20 feet. Steel casing is then installed in this hole and sealed to the bedrock. This casing seals the well from potential contaminants from surface infiltration. Drilling continues through the bottom of the casing until water-bearing fractures are encountered. Ground water fills the well to a level based on local geologic conditions. A submersible pump is then lowered into the well to bring water to the surface. The well casing protrudes out of the ground surface and is covered with a sanitary cap to prevent contamination. The water in the well above the pump is in storage and is available to be pumped out when needed. A bedrock well with low yield can still provide enough water for household use if the well boring itself holds enough water in storage to meet periods of peak demand.

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Last updated on October 6, 2005