Code of Federal Regulations Title 40. Protection of Environment § 40.149.2 Definitions

(a) Aquifer means a geological formation, group of formations, or part of a formation that is capable of yielding a significant amount of water to a well or spring.

(b) Recharge means a process, natural or artificial, by which water is added to the saturated zone of an aquifer.

(c) Recharge Area means an area in which water reaches the zone of saturation (ground water) by surface infiltration;  in addition, a major recharge area is an area where a major part of the recharge to an aquifer occurs.

(d) Sole or Principal Source Aquifer (SSA) means an aquifer which is designated as an SSA under section 1424(e) of the SDWA.