"Backfilling" means the process of surrounding and covering tanks, piping, and associated components after they have been installed with the type of material, such as sand or crushed stone, required by the specifications of the manufacturer of the installed equipment or, if none, the specifications shown on the approved plans.
N.H. Admin. Code § Env-Or 402.05
(See Revision Note at chapter heading for Env-Or 400) #10393, eff 9-1-13