Excavation and fill is ranked by the difficulty in working with the soil and the site. Depreciate piping with tanks over a 20-yr. life. Costs are averages for completely-installed tanks, including fittings, access manway, excavation and backfill. The schedule is designed to allow flexibility in terms of type and capacity of the tank. The user can choose a total cost, cost per gallon, or the overall average cost per gallon.
Most tanks are steel.
However, newer installations owned by major oil companies typically install fiberglass tanks.