Underground Storage Tanks

The interior of a structurally sound tank may be lined with a thick layer of noncorrodible material. The lining material and application method must be both comply with applicable industry codes. The lining used must also meet the same federal requirements as for repaired tanks (40 CFR 280.33). Note: Flexible inner liners (bladders) that fit inside a tank do NOT meet the tank interior lining requirements. Tanks using only an interior lining for corrosion protection must pass an internal reinspection in 10 years and every 5 years after that to make sure that the lining (and tank itself) is sound. You must keep records of these inspection results.

The steps involved in internal lining are:

1. sludge and residue are removed from the tank
2. the interior of the UST is cleaned to a white metal surface
3. the UST is checked for structural soundness
4. any necessary repairs are made
5. the interior is lined with a noncorrodible material
6. the UST is inspected periodically.

1. First, the UST is cleaned by removing sludge and residue. This slide shows a worker wearing appropriate confined-space protective gear while cleaning the UST. Sludge and residue need to be put in appropriate containers and disposed of properly. Tank lining firms may include this service as part of their activities. Also notice the rustiness (orange-red color) of the tank interior. Before the tank can be relined, the inner surface must be properly prepared.

2. Proper preparation of the interior surface of the UST requires that it be "sand" blasted with a pressurized spray of abrasive material (industry code specifies acceptable kinds of abrasives) until a "white metal" surface appears. This surface should be rough rather than smooth, because the lining will "anchor" better to a more textured surface.

3. The next step is application of the lining material. Professionals apply a thick (at least 1/8th inch) layer of noncorrodible material that bonds to the inside of the UST and forms a rigid, liquid-tight lining.

4. After the tank has been lined, a "spark" test is done to check for "holidays" (small gaps) in the interior lining. The T-bar wand that the worker is using has sufficient voltage to throw a 3-inch arc or spark if it can find a path through the "holiday" in the noncorrodible lining to the metal surface of the UST's interior. Holidays are marked and corrected. Note that this worker is NOT wearing appropriate safety gear.

5. The cured lining then needs to be tested for uniform thickness and hardness. This slide shows how the thickness is measured.

6. This slide shows how the hardness of the noncorrodible lining is measured.

Finally, the UST lining must pass periodic reinspections. The first takes place 10 years after the lining is installed and every 5 years thereafter. Reinspections require the tank to be emptied and purged, before the interior lining can be inspected according to industry code.

Top of page