EPA does not require facilities to keep calculations of secondary containment in an Spill Prevention, Control, and Countermeasure (SPCC) plan; however, the plan must include enough detail to describe the efficacy of the measures used to comply with the requirements in 40 CFR 112.7(c). EPA recommends that the facility owner or operator maintain calculations that serve as the basis for the capacity of the secondary containment system such that if questions arise during an inspection, the calculations will be readily available for review. Calculations may be provided in the plan as part of the documentation to support the adequacy of containment measures employed at the facility. Industry guidance (e.g., API Bulletin D16, Third Edition, December 2002) recommends that facility owners or operators include any secondary containment capacity calculations or design standards with the plan.