"Surface impoundment" means a facility or part of a facility which is a natural topographic depression, artificially created excavation or diked area formed primarily of earthen material or lined with artificially created material, which is designed to hold an accumulation of liquid wastes or wastes containing free liquids. The term includes holding storage, settling and aeration pits, ponds and lagoons. The term does not include an injection well.
Nev. Admin. Code § 444.6265
NRS 444.560