• Annular Space: The space between the casing or screen in a well and the wall of the borehole.

• Aquifer:  A body of rock or sediment that is sufficiently permeable to conduct ground water and to yield
                economically significant quantities of water to wells and springs.

• Artificial Filter Pack:  Artificially graded material surrounding the well screen in a water well.

• Bailing:  The repeated lowering, filling, raising, and emptying of a bailer to remove fluid from a well.  A bailer is
                a cylindrical tube fitted with a valve at the bottom.

• Bentonite:  A clay material used in the water well industry as a drilling mud and as a well sealing material to
                slow or stop water movement.

• Borehole:  A circular hole made by boring or drilling to access a particular geologic unit.

• Casing:  A pipe lowered into a bore hole during or after drilling and grouted into place.

• Formation:  A body of rock identified by certain geologic characteristics; term applied by drillers to a rock or
                sediment that can be described by certain drilling characteristics.

• Geologic:  Pertaining to or related to geology, which is the study of the planet Earth.

• Ground Water:  All subsurface water.

• Grouting:  The process of placing a cement or clay slurry to fill or seal fractures or spaces.

• Jetting:  The process of loosening and flushing cuttings or loosely consolidated materials from a borehole or
                well, by using a directed forceful stream (jet) of air or water.

• Neat Cement:  A mixture of Portland cement and water, in a certain proportion, used for grouting wells.

• Permeability:  The capacity of a rock or sediment to transmit fluid.

• Porosity:  The ratio of the volume of void spaces in a rock or sediment to the total volume of the rock or
                sediment.

• Water Well:  An artificial pit, hole, or tunnel, drilled, dug, driven, or jetted into the ground to a depth that
                penetrates a water-yielding formation to allow water to flow or to be pumped to the surface.

• Water Well Codes:  A set of regulations or standards to be followed and enforced for the construction of water
                wells.

• Well Development:  The act of repairing damage to the formation caused by drilling procedures and
                increasing the porosity and permeability of the materials surrounding the intake portion of the well. 

• Well Screen:  A section of well casing which has been perforated or slotted to allow inflow of water and to keep
                unwanted materials from entering the well.

• Well Yield:  The amount of water that can be withdrawn from a well per unit of time.

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