UST or AST or Vault at a retail gas station

Current and archived opinion polls from the Petroleum Equipment Institute.
Post Reply

Which would you recommend be used to store gasoline at a new Gas Station?

Aboveground Storage Tank
Underground Storage Tank
Vaulted Storage Tank
No votes
Total votes: 13

User avatar
Head Tech
Posts: 637
Joined: Mon Feb 14, 2005 8:23 am
Location: Dallas, Texas

UST or AST or Vault at a retail gas station

Post by CherokeeUST » Thu Oct 08, 2015 7:21 am

What is your opinion on using a UST or AST or Vault at a retail gas station?

We have customers who insist on using AST's or Vaults to store their gasoline. Their primary reason is that these systems are unregulated in their region.

Here are the reasons we give them for UST's being a better choice. Any thoughts on this are welcomed.

Above Ground Tanks vs. Underground Tanks for retail fueling applications

Retail Fuels Tank Fact Sheet

SUBJECT: Above Ground Tanks vs. Underground Tanks for retail fueling applications

1. All major convenience store chains and fuel retailers implement UST systems for storing their retail fuels.

2. Eighty to ninety percent of all leaks come from the lines joining the tanks to the dispensers not the tanks themselves, according to USEPA and State authorities.
a. Installing ASTs or tanks in vaults will do nothing to alleviate this problem. ASTs increase the risk of serious contamination because the best methods of line leak detection pressurized line leak detectors and interstitial monitoring are not available for ASTs.

3. AST’s must have a written SPCC plan by a licensed professional engineer on site. UST systems regulated by 40 CFR 280 are exempt from SPCC rules.

4. AST’s have to be inspected per STI Standard SP001 ( ... fault.aspx)
a. Must be visually inspected every month by Owner
b. Must be structurally inspected every five years by certified inspector
(a) Includes thickness tests
c. Must be inspected internally every ten years by certified inspector or tightness tested every year by a contractor.

5. AST's including tanks in vaults are not required by federal law to have:
a. Tank leak detection.
b. Line leak detection. Note: Pressurized line leak detection is not available for ASTs, even though underground lines are required for retail operations.
c. Spill containment at fill points.
d. Overfill prevention devices. Note: We have seen a spill of more than 2800 gallons into a vault because of the lack of overfill protection on a tank that was not visible to the delivery person.

6. Until fairly recently, most national fire codes did not provide for ASTs at retail facilities due to increased safety risks. In fact, a growing number of states have outlawed them entirely for retail purposes. One significant risk is that fuel must be pumped into the AST under pressure, discussed further, below. Any failure of the pump or connecting hose or line can easily result in injury to customers and workers from filling operations. This risk is not present for USTs, which fill by gravity flow. Any oversight by the delivery driver can lead to significant overfills and releases of fuel.

7. ASTs are extremely susceptible to damage by lightning, wind, water, vehicle impact, and terrorist action.

8. An AST accident at a retail fuel facility carries potential for major personal injury and property damage due to the likelihood for increased amounts of spillage in a mishap.

9. There are significantly higher operating costs due to:
a. The inability to take delivery of gasoline by gravity flow. This results in the need for a pump-equipped truck or tank system.
b. extra time required to fill
c. expenses for maintenance of pumps responsibility and associated lost business during down time
d. This is reflected in a higher cost of gasoline from the supplier at $.03 to .04 per gallon, which must be passed on to the customer. CUSTOMERS have lost potential fuel supply contractors due to the use of ASTs reducing competition contracting for gasoline, also adding to potentially higher prices and less fuel availability.

10. ASTs incur higher maintenance costs e.g. corrosion protection, deterioration of connections and fittings due to increased temperature fluctuations.

11. Effective 1 July 2007, the warranty on aboveground steel tanks is 10 years, changed from the previous 30 years. UST warranties are typically 25-30 years.

12. AST’s are more prone to temperature fluctuations, due to exposure to the elements. Temperature fluctuation causes a lack of accuracy in the automatic tank gauge/inventory control system, making leak detection more difficult and less accurate.

13. An AST generates more hazardous waste in the form of water removed from containment areas. Even a slight sheen is enough to necessitate the treatment of simple rain runoff as a hazardous waste, with all associated protocols. Steel ASTs tend to accumulate more water in the fuel, which also becomes hazardous waste when removed.

14. Gasoline pumped out of ASTs for dispenser calibration becomes a serious problem.
a. There is no simple way to return it to the tanks.
b. OSHA problems result if the employee attempts to climb the AST with a calibration can.
c. Not returning the gas causes inventory problems that can show up as a suspected leak.
d. Adding a pump-driven return system is expensive and requires maintenance.

15. AST’s pose more difficulty in vapor recovery testing. California is still developing reliable test protocols for Stage II vapor recovery systems involving AST systems. Repeated test failures at some installations occur for this reason.

16. ASTs have a greater potential for vapor emission due to increased temperature changes. EPA recognized this with their recent change to vapor emissions calculations for ASTs. This is another instance of greater environmental damage over a UST installation.

17. Fire Code requirements for ASTs mandate more land area for tanks and set backs, restricting traffic flow and complicating design.

18. Due to the lack of an absolutely fool-proof anti-siphon device, ASTs cannot be used for any form of 24-hour unattended fueling. Our internal policy prohibits unattended fueling with ASTs. Inspecting and maintaining the anti-siphon valve is also an additional expense.

19. Virtually everone has agreed that ASTs generally present an appearance problem. Any aesthetic fencing, if used, must be ventilated to prevent explosive hazards and confined space entry problems. This is an additional expense to install and maintain over the life of the project.

20. SPCC regulations require secondary containment of the fuel offloading area which necessitates installing an oil/water separator. Maintenance, cleanout, and disposal are another financial responsibility.

21. Using a stick to test the tanks fuel levels or test for water in the tanks is a safety hazard. Stick testing the volume of fuel in an AST prior to or after a delivery becomes a hazard for the delivery drivers or associates tasked with verifying the amount of fuel in the tanks. This is generally the most reliable way to test the fuel in the tanks for water.

SUBJECT: Vaulted Tanks vs Underground Tanks for retail fueling applications

22. The capital cost of a vaulted tank system is almost twice that of a comparable UST system.

23. Repair, maintenance, and vault inspection costs are substantially more than those for a UST system.

24. Vault sump liquid sensor, vapor sensor, and exhaust fan required. A dangerous or explosive environment can occur if vapors are not vented properly.

25. The vault is an OSHA confined space. Entry requires a written plan, permit, and the use of specialized PPE.

26. Increased corrosion of steel tank, piping, and fittings. Effective 1 July 2007, the warranty on steel tanks is 10 years, changed from the previous 30 years.

27. No EPA certified line leak detection for this kind of AST. Inaccuracy of inventory control also occurs.

28. Increased chance of overfill.

29. Few contractors with experience installing vaulted systems. [/list]
The opinions expressed here are entirely mine and are not endorsed by my employer.


Head Tech
Posts: 100
Joined: Thu Jun 19, 2003 6:59 am
Location: Dallas, Texas

Re: UST or AST or Vault at a retail gas station

Post by whittingtonm » Thu Oct 08, 2015 10:12 am

27. No EPA certified line leak detection for this kind of AST. Inaccuracy of inventory control also occurs.
I think it should be 27 and 28. Line leak detection is one important issue, inventory control is another.

Question for anyone in general: When you have a line leak in a location where an AST or vaulted subgrade AST is used by choice, is there any increased liability for not using a system with an EPA third-party-certified line leak detection method? (I know that secondary containment might be a certified method for USTs, but how hard is it to keep water and product out of the interstice? How often do you open a transition sump and smell gasoline? Isn't this at least another significant maintenance issue?)

All of those questions could be outweighed by site conditions making an AST of some sort the better choice where allowed by law or regulation, but they are questions I would probably take a look at.

Post Reply