Standard for Steel Underground Tanks for Flammable and Combustible Liquids

1.1 This Standard sets forth minimum design and construction requirements for non-pressure horizontal cylindrical steel tanks that are used for underground storage of flammable and combustible liquids.

In addition to this Standard’s traditional safety requirements for underground steel tanks that primarily evaluate structural integrity and mitigate environmental hazards from loss of liquid containment under expected normal conditions; optional construction and/or performance requirements, and associated ratings, intended to address more severe conditions associated with Climate Change are included in Annex F.

1.2 These minimum requirements cover single wall tanks with or without multiple compartments and double wall tanks with provision for leak detection monitoring of the interstice.

NOTE: The designs identified in this Standard are satisfactory for vacuum and/or electronic monitoring devices. (Refer to Figure 1.)

1.3 This Standard also provides design criteria for integral connections (connection rings/collars) for spill containment sumps or manway risers and components that are integral or built-in to the tank.

NOTE: These requirements do not cover products not integral to the tank, such as spill containment sumps.

1.4 These minimum requirements cover tanks which are fabricated, inspected and tested for leakage before shipment from the factory as completely assembled vessels.

1.5 The requirements in this Standard are for the construction of stationary tanks and do not cover their installation, maintenance and operation. The installation, maintenance and operation of these tanks may be covered by any of, but not limited to, the following documents:

1. In Canada:

1. National Fire Code of Canada, Part 4;
2. CSA B139, Installation code for oil burning equipment;
3. API RP 1615, Installation of Underground Petroleum Storage Systems;
4. CCME PN 1326, Environmental Code of Practice for Aboveground and Underground Storage Tank Systems Containing Petroleum and Allied Petroleum Products;
5. Regulations of the appropriate authority having jurisdiction.

2. In the United States:

1. API RP 1615, Installation of Underground Petroleum Storage Systems;
2. NFPA 30, Flammable and Combustible Liquids Code;
3. Regulations of the appropriate authority having jurisdiction.

1.6 These requirements do not cover factory-applied external corrosion protection systems.  Refer to UL 1746, External Corrosion Protection System for Steel Underground Storage Tanks, and ULC-S603.1, External Corrosion Protection Systems for Steel Underground Tanks for Flammable and Combustible Liquids.

1.7 Except for optional Climate Change Adaptation requirements in Annex F, these requirements do not cover special evaluations for resistance to, or use after, earthquakes, floods, high wind events, or other natural disasters.

NOTE: See the note at the beginning of Annex F for further information on the terms “Adaptation” and “Mitigation”, as they pertain to Climate Change.