Are above ground tanks acceptable...in place of diking.

OSHA interpretation letter responding to whether double-wall above-ground tanks may replace diking for secondary containment under 29 CFR 1910.106(b)(2)(vii). It cites NFPA 30 Committee conditions, including a 12,000-gallon capacity limit, above-liquid-level piping connections, overfill alarms at 90% and automatic stop at 95%, and 3 ft tank spacing.