Aquifer. A formation, group of formations, or part of a formation that is water bearing. Also called groundwater reservoir. Background well.-A well located at a sufficient distance from a gypsum stack, slime pond, or other cultural influence, so that water from a well would represent natural groundwater quality. Barometric condenser. A contact condenser that uses a long, vertical pipe into which condensate and cooling liquid flow to accomplish their removal by the pressure created at the lower end of the pipe. Beneficiation. Recovery of phosphate particles from the phosphate ore (matrix) by treatment. Treatment includes sieving or flotation. Cooling pond.-A pond of large surface area that receives effluent process water from a gypsum stack. The warm process water is cooled before returning to the plant. Cooling ponds are generally diked with earth to 10 to 20 feet above land surface. Diammonium phosphate pond.-Similar to a cooling pond but one which receives effluent process water from the production of diammonium phosphate (DAP). DAP is a major component of some fertilizers. Gypsum stack.-Large piles of gypsum (CaS0 4 .2H20) produced as an effluent byproduct of the production of phosphoric acid. Gypsum stacks are frequently greater than 100 feet in height and cover several tens of acres. Matrix. Phosphate-bearing ore or strata consisting of phosphate particles, clay, and sand. Phosphatic clayey waste-disposal pond.-A pond constructed above land surface to provide storage of fine to collodial phosphatic material received from a beneficiation plant. Synonymous with "slime pond." Phosphogypsum.-An effluent byproduct of chemical processing and phosphoric acid production. It is a slurry composed of process water and gypsum. It is disposed of in Florida in a slurry discharge into settling ponds by the wet-stacking method using the upstream method of construction, which results in a gypsum stack. Piezometer.-The basic device for the measurement of hydraulic head is a tube or pipe in which the elevation of a water level can be determined. In the laboratory, the tube is called a manometer; in the field, the pipe is called a piezometer. ix Slime pond.-Synonymous with "phosphatic clayey waste-disposal pond." It is a local term used in the phosphate mining area. A large-volume settling pond used to store clayey wastes (slimes) from a phosphate mine and beneficiation plant. Slurry.-A pumpable suspension of fine solid material, such as clay and gypsum, in liquid. Also, a mixture of water and phosphate ore (matrix) produced by high-pressure water to facilitate transportation. Scrubber.-A device for the removal, or washing out, of entrained liquid droplets or dust, or for the removal of an undesired gas component from process gas streams.