Scores of abandoned underground storage tanks, or USTs, lie hidden below the streets and yards of San Francisco. Once used for gas station petroleum supplies or home heating-oil storage, these tanks — now old and frequently leaky —pose a threat to public health and the environment. In response to the hazard of neglected USTs, state and local agencies such as the California Environmental Protection Agency and the S.F. Department of Public Health.

As a property owner in the city, what exactly do these laws require you do? First, be aware that you remain legally responsible for what might lie under your immediate property, as well as what is beneath any bordering street, sidewalk, alley or other adjacent area subject to an easement. If you have reason to believe a UST exists in any of these places, you must make a reasonable effort to locate the tank. If you do discover one, you are obligated to file a plan for closing or removing the tank within 30 days.

All closures and removals of USTs require the approval of the S.F. Department of Health, compliance with both the municipal Health Code and the California Health and Safety Code, as well as the payment of applicable fees. Even though tank sealing or removal can be extremely disruptive and quite expensive, you should not overlook the potential existence of a UST on your property. If you ignore your obligations and are later found in violation of the law, you may be liable to the City and County of San Francisco for costs incurred in cleaning up and abating the UST's effects.

Finally, if you are buying a property in San Francisco, you should obtain an inspection to determine the presence of abandoned USTs — especially if you are considering removing the inspection contingency in the purchase contract. As stated above, if a UST is found on the property, its contamination can be extremely expensive to clean up.

For further information on tank closure and removal, contact a licensed contractor or environmental consultant specializing in USTs. You may contact the Environmental Health Section of the S.F. Department of Public Health at (415) 252-3800 for a referral.