For most of the time that the underground tank upgrade/closure requirements have been around, the DEP only allowed tanks to be abandoned in place where structural issues made removal unfeasible, and they even required the certification of a professional engineer. However, late in 1997 the Department opened the gates to allow abandonment as a pure closure option, as long as their prescribed procedure was followed. This made many owners pursue abandonment, under the assumption that is would be the less expensive option. Sometimes it is, but there are some pitfalls.

To properly abandon a tank, it must be fully cleaned and filled with an inert material acceptable to the state and local agencies. Most often the material is sand, concrete slurry or foam. The DEP accepts all of these, but the local construction officials vary, particularly with foam. Some accept it, some reject it, and others will review it case-by-case. Further, the material use to fill the tank must fill all voids, rendering the tank incapable of containing liquids and structurally sound. To do this with sand, you must essentially tear open the entire tank surface. Usually, if you can do that, removing the tank is just as feasible. Thus, you are left with concrete or foam, and these materials cost about five times as much as the same volume of sand. For example, the sand to fill one 20,000 gallon tank could cost over $7,500.00 versus about $1,500.00 for sand.

There are other concerns with tank abandonment. If the tank is regulated (subject to the closure/upgrade) requirements, samples must still be taken below the tank’s centerline. This involves punching holes through the bottom of the tank under confined space conditions, and often into the groundwater table, which has obvious implications. Further, if you fill the tank before receiving sample results, that mistake is very difficult to undo. But, the other choice is to leave it empty with holes in the bottom or attempt to "patch" those holes temporarily. This dual mobilization effort also increases cost.

There are of course, many advantages. Even if the tank is feasibly removable, the cost of tearing up and disposing of asphalt or concrete and its subsequent replacement can be expensive. Plus, the disturbance to the site can interfere with site operations, not to mention the public image of excavation and removal. Also, various utilities are often installed over the tanks, whose damage can be avoided if excavation is not performed.

If the tank is removable, that is usually the best option, and it is many times less expensive. A final consideration is this. When you go to sell your property and are asked if you have tanks, which answer would you rather give? "Yes, but they have been abandoned, etc., etc." Or, would you rather respond with a resounding "No."