30 CFR 57.4505 - Fuel lines to underground areas.
Fuel lines into underground storage or dispensing areas shall be drained at the completion of each transfer of fuel unless the following requirements are met:
(3) Located in areas free of combustible materials or in areas where any exposed combustible materials are coated with one inch of shotcrete, one-half inch of gunite, or other noncombustible material with equivalent fire protection characteristics.
Title 30 published on 2013-07-01
no entries appear in the Federal Register after this date.