Terms related to ground water and water quality, as used in this report, are defined below. Aquifer is a formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to wells and springs. Confined aquifer is synonymous with artesian. A confined well is a well that derives its water from an artesian or confined water body. The water level in a confined well stands above the top of the confined water body it taps. Confining bed is a body of relatively "impermeable" material stratigraphically adjacent to one or more aquifers. Hydraulic conductivity is the rate at which water of the prevailing kinematic viscosity is transmitted through a unit area of aquifer at right angles to the direction of flow, under a unit hydraulic gradient. Milligrams per liter (mg/L) is a unit for expressing the concentration of chemical constituents in solution. Milligrams per liter represents the weight of constituent per unit volume of water. Potentiometric surface is a surface which represents the static head in an aquifer, defined by the levels to which water will rise in tightly cased wells. Storage coefficient is the volume of water an aquifer releases from or takes into storage per unit surface area of the aquifer per unit change in head. Transmissivity is the rate at which ground water of the prevailing kinematic viscosity is transmitted through a unit width of an aquifer under a unit hydraulic gradient. Water table is that surface in an unconfined groundwater body at which the pressure is atmospheric.