Storage Tanks
General

Aboveground tanks are preferred when the following conditions are important factors:

1. The facility owner / operator has had a prior environmental problem with a UST.
2. The property is leased and the owner prohibits underground tanks.
3. The facility may require future relocation, expansion, or removal of the tanks.
4. The facility has a high underground water table, or high rock elevation, or other consideration such as required shoring that significantly increases the cost of an underground installation.

Underground tanks are preferred when the following conditions are important factors:

1. The use of aboveground tanks is restricted or prohibited by local fire code or zoning.
2. The space limitations of the site would not allow for the footprint and setbacks required for ASTs.
3. The facility owner / operator believes that the underground tanks are more secure against vandalism.
4. The visual / aesthetic / architectural aspects of the building require an underground tank.
5. Gravity overflow protection from generator day tanks is a critical concern.
6. Gravity filling of the tanks is a critical concern, based on local fuel supply availability.
7. Cold weather considerations are critical and heating of tanks and piping is undesirable.

Positives:

1. Inherent visual security that there are no leaks.
2. Lesser requirements for period testing for regulatory compliance.
3. Lower cost of installation – usually.
4. Easier access for modification or maintenance.
5. Easier to remove or relocate.
6. Can be installed by the general mechanical contractor, specialty tank contractor not required.

Negatives:

1. Space requirements.
2. Visual / aesthetic impairment.
3. Higher security requirement and potential for vandalism.
4. Safety issues for tank top access.
5. Requires delivery truck to be pump equipped.
6. Potential for overfills, spills, siphoning of fuel.
7. Requirement for pump return flow from day tanks.
8. Cold weather and hot weather issues.
9. Day / night thermal changes may increase condensation.
10. Perception of fire hazard.
11. Local use prohibitions or size limitations.
12. Inspection and maintenance of open dike areas if used.

Positives:

1. Widely accepted without size limitations.
2. Saves space at ground level and allows for site access by driving above tanks.
3. No visual / aesthetic impairment.
4. More secure against vandalism.
5. Well defined regulatory requirements.
6. Stable thermal environment.
7. Allows for fuel delivery by gravity.
8. Allows for gravity overflow return from day tanks.
9. Secure from fire hazards.

Negatives

1. Higher requirements for periodic testing for regulatory compliance.
2. Perception of greater environmental risk based on past experience.
3. Requirement for environmental liability insurance to meet regulations.
4. Higher cost of installation – usually.
5. Difficulty to expand, modify, relocate, or remove.
6. Requires specially licensed installation contractors.

Aboveground tanks will typically be less expensive, but not dramatically once all requirements are met for foundations, security, overfill prevention and other requirements.

Special requirements that will increase the costs of an aboveground tank:

1. fire-rated tank construction.
2. heating of tanks and piping.
3. double containment of aboveground piping with steel pipe secondary.
4. special fire suppression.
5. special access stairs and platforms for tank top access.
6. security fences or architectural enclosure walls.
7. seismic requirements for aboveground piping supports.

Special requirements that will increase the cost of an underground tank:

1. Excavation requirements that include shoring, dewatering, rock excavation, or underground utility protection.
2. Piping lengths and slopes that require additional burial depth for the tank.
3. Full ballast capacity design for the hold-down concrete slab.

Underground and aboveground tanks, shop fabricated and UL listed, are widely available up to 40,000 gallon capacity, and to 50,000 gallon capacity in some areas. Aboveground tanks that are field fabricated, API design tanks are available in higher capacities.

RELATED:

• Storage Tanks – Underground
• Storage Tanks Aboveground
• Storage Tanks in Building