Due to a recent change to the Seattle Fire Code, underground oil tanks may no longer be decommissioned without being filled with an inert solid material, such as slurry, concrete, or foam.
In the past, tanks could be decommissioned by simply having them be emptied, rinsed, and capped. Now, in addition, they must be filled.
The City further cautions:
Applicants should carefully review the merits of their options before choosing a method of decommissioning. Tanks suspected of leaking should be removed from the ground rather than abandoned in place. The Seattle Fire Department cannot predict and does not attempt to predict, what future regulations may require of tanks abandoned in place under the current guidelines. A tank abandoned in place now may later require removal at additional cost and potential hazard.