A slotted or screened tube or pipe, positioned vertically in an underground tank excavation, that permits an operator to check conditions in the excavation and, in particular, to determine whether there may be a leak in the tank system.

One or more observation wells can be placed adjacent to the tanks and/or piping. The lower end of the tube descends to a point below the bottom of the tank. The upper end of the tube is at grade level. Through use of vapor or liquid detection instruments lowered into the observation well, the operator can determine if gasoline or other product is present in the excavation.