1. Find out what’s in the tank.

Most underground residential tanks are easy to find. If you have trouble locating your tank, try following the fuel lines from the house, locating the tank vent pipes, or use a hand probe or metal detector.

To find out if there’s still oil in the tank:

Remove the filler cap.
Insert a long stick into the tank until it touches bottom.
Remove stick – If there is oil in the tank you will be able to see it on the stick.

Sometimes a tank will contain oil and water, or primarily water (the water will settle to the bottom, the oil will float on top). You can check for water by putting a small amount of water- reactive paste on the end of the stick and inserting the stick into the tank. If there is water in the tank, the paste will turn color. The paste can be purchased from American Distributing Co.

2. Have all unused heating oil removed from your tank.

The Department of Ecology strongly recommends that you have all unused heating oil removed from your tank. Removing the unused oil is the easiest, least costly, and single-most important action you can take to prevent contamination of soil and groundwater. After the heating oil has been pumped out of your tank, you should think about having your tank removed or “closed in place.”

NOTE: If you have an unused heating oil tank, do not re-fill it unless it has been checked by American Distributing Co., and never put household waste like paint, antifreeze, or used motor oil into an unused residential heating oil tank.

Have your tank removed

The Department of Ecology recommends that you have the tank removed because:

a) If the tank has leaked, it will be easier to find and clean up any contaminated soil.
b) Often, home buyers and lending institutions require assurance that the property is not contaminated before agreeing to complete property transactions. The best way to provide that assurance is to remove the tank and sample the soil in the pit.

Tank removal allows visual inspection of the area under the tank and more accurate soil sampling. Remember to keep reports of tank removal and soil samples for your records. Below are some of the activities a certified Tank Decommissioning contractor should perform when removing your tank.

Pump all remaining oil from your tank.
Clean out any sludge in the bottom of the tank.
Excavate down to top of tank.
Remove or cap all lines.
Remove potentially explosive vapors from the tank.
Remove the tank from the ground.
Remove the tank from the ground and backfill the hole.
Properly dispose of the tank.

Have your tank “closed in place”

This is a popular option for residential tanks – especially if removal isn’t possible. But before choosing this alternative, consider the future of your property.  Potential buyers or lenders may require you to remove the tank, and a filled tank is harder to remove (unless it has been filled with foam).  Below are some activities a certified Tank Decommissioning contractor should perform before filling your abandoned oil tank in place.

1. Pump all remaining oil from your tank.
2. Clean out any sludge in the bottom of the tank.
3. Remove or cap all lines.
4. Fill the tank with inert solid material, such as a weak cement slurry and sand.
5. Plug or cap all openings in the tank.