Organic. (1) Characteristics of, pertaining to, or derived from living organisms. (2)
Pertaining to a class of chemical compounds containing carbon.
Orifice. (1) An opening with closed perimeter, usually sharp edged, and of regular form
in a plate, wall, or partition through which water may flow; generally used for the
purpose of measurement of control of water. (2) The open end of a small tube, such as
a pitot tube, piezometer, etc.
Oxidation. Loss of electrons; as when a metal goes from the metallic state to the
corroded state (opposite of Reduction). Thus, when a metal reacts with oxygen, sulfur,
etc., to form a compound as oxide, sulfide, etc., it is oxidized.
Packer. In well drilling, a device lowered in the lining tubes which swells automatically
or can be expanded by manipulation from the surface at the correct time to produce a
watertight joint against the sides of the borehole or the casing, thus entirely excluding
water form higher horizons.
Pathogenic. Disease producing.
Peak Demand. The maximum monetary load placed on a water plant or pumping
station. This is usually the maximum average load over a period of time such as peak
hourly demand, peak day demand, or instantaneous peak demand.
Perched Groundwater. Groundwater that is separated from the main body of
Percolation. (1) The movement of flow of water through the interstices or pores of a
soil or other medium. (2) The flow or trickling of a liquid downward through a contact or
filtering medium. The liquid may or may not fill the pores of the medium.
Permeability. The property of a material which permits appreciable movement of water
through it when saturated and actuated by hydrostatic pressure of the magnitude
normally encountered in natural subsurface water. Perviousness is sometimes used in
the same sense as permeability. The rate of permeability is measured by the quantity
of water passing through a unit cross section in a unit time when the gradient of the
energy head is unity.
Person. An individual, corporation, company, association, partnership, state,
municipality, or Federal Agency.
Perviousness. The property of a material that permits appreciable movement of water
through it when it is saturated and the movement is actuated by hydrostatic pressure of
the magnitude normally encountered in natural subsurface water. More properly called