Copyright © 1997 The Seattle Times Company Features News : Sunday, February 16, 1997

Underground oil tanks are a pollution time bomb: How to deal with them

by Susan McGrath

Have you considered the possibility that there may be a body buried in your back yard? There is one in my back yard - at least I think there is. It's the body of an underground heating oil storage tank, abandoned some time before we bought the house five years ago.

At one time, 30-50 years ago, nearly every house in the city had a storage tank for oil or kerosene, either above or below ground. Many of the tanks are still in use. Many others have been abandoned, rendered obsolete by piped-in natural gas or electric baseboard heat. Most unused above-ground tanks are scrapped at the time their function is replaced. Most underground tanks have been left to rot in the ground.

Unfortunately, I can't wow you with flashy Exxon Valdez comparisons. Since residential underground storage tanks aren't regulated by the state or the feds, no one has tried to figure out exactly how many there are out there. But experts estimate that Seattle alone has tens of thousands of metal tanks rusting in the ground, some in use, others abandoned. Many homeowners, who bought their house long after it was converted to gas, as I did, have tanks and don't even know they're there.

A surprising fact about abandoned tanks is that most of them still contain oil. This is no doubt due to the impossibility of scheduling the new furnace installation to coincide with the burning of the last gallon of oil. Just how much oil is even more surprising.

Phil Suetens, of Filco, a Seattle-based tank servicing company, estimates that the average abandoned tank contains about 100 gallons of oil. On the day I spoke to him, company trucks had pumped 900 gallons of oil from five abandoned tanks. When I expressed dismay, Suetens pointed to the bright side: That these tanks had so much oil in them means they probably hadn't developed leaks yet.

Though I think we would all prefer that our planet were less heavily sown with underground storage tanks, the aging tanks themselves don't really pose a threat to soil or water. The oil is another story. Many tanks already have leaks and are contaminating the soil under them. Where they are near surface water, or where the water table is high, the oil can contaminate water.

This means you and I may well have hundreds of gallons of nasty, polluting oil lying in rusting tanks in our gardens. Clearly, dealing with these time bombs deserves the highest priority on the family To Do list. And just in case pollution doesn't inspire us to get on the ball, the state Department of Ecology offers three other reasons to exhume those buried bodies:

1. Under the Model Toxics Control Act, a tank owner may be held liable for contamination caused by a leak.
2. Corrosion can raise the possibility of cave-ins. The homeowner could be liable for any injuries incurred.
3. Before finalizing the sale of a house, banks and buyers may want proof the tank has been dealt with.
4. The fire marshal would add a fourth reason to dig up our tanks:
   
   Many city fire codes, including Seattle's, require that underground storage tanks that have been out of service for a year or more be decommissioned.

And so, to work. First, find the darn tank. If you don't already know where it is, look in the basement for a pair of pipes that come through the wall and don't go anywhere. If you can find these, you'll at least know which side of the garden to search. The ground may be sunken slightly, over the tank, or it may even bulge slightly. The tank should have a small, capped fill pipe sticking up just at ground level. You could hire some 6-year-olds to search for this. If all else fails, rent a metal detector.

Once you find the fill cap, go ahead and poke a homemade dipstick down it to see how much liquid it contains. If you want to know how much of that liquid is oil and how much is water, buy some water-reactive paste at a hardware or heating supply store, and simply follow the directions. (Basically, you smear it all over the stick. A change of color in the paste tells you how much of what is down there.)

Decommissioning an oil tank

Now that you've found it, you have some choices. Storage tanks can be decommissioned in one of three ways:

First, and ideally, you can have the tank removed. This means hiring a company (which must be International Fire Code Institute certified, in many jurisdictions) to come out and do the following:

1. Test the tank for chemicals other than water. People have been known to dump old paint, used antifreeze, dirty motor oil and worse into their abandoned tanks. Never do this. If tests show the presence of chlorinated compounds - such as those used in brake-cleaning fluid - the oil in the tank must be treated as hazardous waste, drummed up and sent to the high-tech landfill.
2. Use a dipstick coated with a special paste to show how much water lies below the oil in the tank. Most tanks have at least some. Those with holes in an area with a high water table may contain hundreds of gallons of water.
3. Pump the oil into a container truck.
4. Triple rinse the tank, pumping the rinse water back into the truck every time.
5. Render the tank inert by using dry ice or a CO2 cartridge to drive oxygen out, reducing the risk of explosion.
6. Dig up the tank - the top of which may be 4 feet below the surface - and remove it.
7. Check the hole for signs of oil. Minor leaks need not be reported, significant leaks must be reported to your county emergency management office. The company that is removing your tank can usually do the cleanup.
8. Fill in the hole.
9. Fill in any decommissioning paperwork required by the fire marshal and file it within 30 days, keeping a copy for yourself.

At this point, you've done what's required of you.

The tank service operator now takes any water to an environmental remediation outfit for treatment. Oil is sold as bunker fuel for ships. The tank itself is cut up for scrap.

Expect to pay about $750 for the tank service company, depending on how easy it is to get to the tank. Any environmental cleanup will cost extra.

A second way to deal with your tank that is sanctioned by most fire codes is identical for steps 1-4. However, the clean tank is filled with sand, concrete slurry or polyurethane foam. Pipes are cut off and capped below grade. The filler removes any possibility of cave-ins. This option costs about $500.

One disadvantage of this option is that you won't know whether your tank has leaked and contaminated soil below. Lest you consider this an advantage, let me point out that the oil can migrate through the soil and may come back to nip you in the rear.

A third choice will be available to homeowners in Seattle as of April 9. You may complete steps 1-4, then simply cut and cap below grade and leave it at that. No removal or filler required. This service should cost between $300 and $350.

If all of these options are too pricey for you, but you know you have oil buried in your garden, you can still get rid of it.

The Environmental Coalition of South Seattle (ECOSS) works with Filco to pump your oil at no charge to you. (If you have a lot of water in your tank, they'll charge you 75 cents a gallon to pump it out.) In order to sign up for this service, call ECOSS at 767-0432. They are a small outfit and may take some time to get back to you.

If you are a do-it-yourselfer kind of guy or gal, you could pump the oil through the ECOSS program and then dig up the tank and truck it to a scrap metal place. You would have to pay to drop off the tank, but this method would be cheapest. The major disadvantage of this method won't bite you until you try to sell the house: No proof you removed the tank, and no proof the soil was not contaminated.

At any rate, the moral of this story is Find Your Tank and Deal With It, Lest It Come Back To Haunt You. Susan McGrath's column runs every two weeks in the Home/Real Estate section. Send questions and comments to: The Household Environmentalist, P.O. Box 70, Seattle, WA, 98111.