02.08 What are the primary problems or failures of underground tanks?

The primary causes of failure for underground tanks have historically been (a) corrosion failures to the tank shell, or (b) leakage through top openings when the tank is overfilled. UST regulations enacted in 1988 addressed these common causes of failure, so that they are no longer prevalent, so the common problems have changed.

When installed in accordance with the manufacturers requirements, problems with tanks themselves are not common. The problems are more likely to occur with tank sumps, tank accessories, and piping.

1. Water intrusion into tank or interstice through improper pipe connections on top of tank.
2. Water intrusion into sump through (a) improperly installed or failed sump penetration fittings, (b) conduit that is not internally sealed, c) improper installation or failure of tank to sump seals, (d) surface water entry through top of sump where manways not raised to divert water, or backfill around sump is not open and free flowing.
3. Damage to tank or sump from surface loads where manway covers not properly isolated from tank sumps.
4. Flotation of tanks during installation because of inadequate ballast procedures.
5. Water intrusion at fill pipe spill containers and internal leakage of spill containers.
6. Piping leaks from (a) ground movements, (b) thermal changes, c) ground freeze / thaw, (d) high water table fluctuations, (e) surface loads, (f) ground settlement, (g) damage from construction

To minimize these problems:

1. Specify quality components.
2. Confirm that contractor submittals address the compatibility of tank sumps, sump penetration seals, and piping.
3. Confirm that contractor submittals address tank ballast calculations, along with procedures for ballasting tanks during construction.
4. Require installation and inspection checklists.
5. Require re-testing of fuel system components after backfill, when damage or movement is most likely to occur.
6. Require inspection and certification of system by contractor prior to end of warranty period.