TO all the other environmental hazards connected with homeownership - radon, asbestos and foam insulation among them - must now be added underground oil tanks.
These aging domestic fuel tanks are now considered time bombs, potentially able, through corrosion and leaks, to pollute the local ground water supply and burden unsuspecting property owners with fines, liability and marketability headaches. Among the recommended precautionary measures are draining and removing the entire underground tank system and changing to a safer way of storing fuel.
No figures are available on the number of homes affected, although it could be as high as one in five of all homes using oil for heating. Underground fuel storage, for instance, has long been common on Long Island, according to the Long Island Oil Heat Institute, which represents retail oil dealers. The Institute estimates that about 124,000 Long Island homes have these underground tanks.
Most such tanks are 35 to 50 years old. When checked during a routine test or in connection with removal or replacement, about one in two is usually found to have some sort of leak, said Warren Cronacher, president of Taucher Cronacher, professional engineers and home inspectors of Rockville Centre, L.I. The cause is normally condensation settling as water at the bottom of the tank, which, over time, corrodes the steel. This happened recently to Frank and Margaret Costanza, who had an underground tank at their 38-year-old home in Patchogue, L.I.
Experts explain that the idea of burying the storage tank became popular with suburban builders as a way to provide a larger storage capacity without relinquishing living space inside the house or creating a fire hazard. Having a larger storage capability let the homeowner buy fuel in bulk, often at a discount during the summer when prices were lower. Burying the tank was also viewed a way of hiding an unsightly above-ground tank in the yard alongside the house.
The homeowner with an underground tank who takes no action is likely to face problems on several levels. First, growing environmentalist concerns are encouraging an increasing number of towns, counties and states to enact strict domestic pollution control regulations that could subject recalcitrant owners to heavy fines.
For example, Maine now requires all underground fuel storage tanks, regardless of size or use, to be registered and regularly tested. Since last October any tank over 15 years old in designated areas must be removed. By October 1991 all underground fuel storage tanks in Maine must go. Penalties for noncompliance can reach $10,000.
Communities in Vermont, New Hampshire, California, New York and Massachusetts, among other states, are enacting similar statutes. In Nassau and Suffolk counties on Long Island, for instance, only domestic tanks holding more than 1,100 gallons are currently covered by regulation. But this may change.
A case in point is the environmentally conscious suburban town of Simsbury, Conn. Maintaining that state regulations were too lax, that community is now debating an ordinance to require underground storage tanks of any size to be registered. Those 18 years or older may have to be removed.
''A lot of places are tightening up,'' said Alan Mooney, president of Criterium Engineers of Portland, Me., who regularly conducts seminars on hazardous materials around the county.
IRRESPECTIVE of local requirements, lawyers insist that homeowners with these tanks should get rid of them as fast as possible. If a leak is discovered requiring special cleanup or there are claims by neighbors of groundwater pollution, the costs will probably not be covered by either the normal ''all risks'' homeowner policy or any additional liability coverage.
That was the hard lesson learned by the Costanzas of Patchogue, who have spent about $3,000 so far for tank removal and clean-up of the polluted ground around their tank. The denial of their claim by Utica Mutual, their insurance company, was upheld by the New York State Insurance Department, whom their state representative had contacted a year ago on their behalf.
The Costanzas also face a bill that could reach $60,000 from the State Department of Environmental Conservation, which, after discovery of the spill, required a full year of monitoring of the spill area by means of specially dug site wells.
According to Jack Lyons, sales manager at O. R. Cote & Company of Springfield, Mass., which specializes in tank removal, homeowners can remove their tanks or have them drained and filled with sand to keep the ground from caving in. Each procedure costs about $1,300.
But some homeowners may not have a choice, said Mr. Lyons. If the tank was buried very close to the foundation, removal might risk the stability of the structure.
Once a tank is removed, the alternatives are a tank above ground, a tank that sits in the basement or any other suitable utility area, or changing to natural gas or electric heating.
Nevertheless, getting rid of an underground tank should be viewed as helping a property retain value and market appeal, said Mr. Merriam, the land use lawyer, since these homes could become as suspect as those with asbestos or a high radon level - especially as the liability for leaks, even prior to closing, will fall upon the new owner.
Mr. Merriam recommends that anyone buying a home with an underground tank at least require that it be tested for leaks as part of the contract. Testing costs about $500. Mr. Kessler, the Costanzas' lawyer, said he is urging real estate lawyers to alert buyers to that need. In fact, he said, buyers might also wish to insist the tank be removed before closing.
Just who will pay is not clear. ''It's negotiable,'' said Mr. Kessler.
However, in the current weaker marketplace the burden is likely to be on the seller.