Purpose and Scope This recommended practice applies to underground storage tank systems (USTSs) used to store petroleum products at marketing and distribution facilities. This recommended practice does not apply to fuel oil storage systems with a capacity of less than 1100 gallons that are connected to heating systems@ underground tanks used to store liquefied petroleum gas or natural gases@ used-oil USTSs@ loading-rack flush tanks@ or vapor recovery knockout tanks. This recommended practice does not apply to above-ground storage tanks or to pipes that are partially buried. The correct management of USTSs is essential to the proper functioning of marketing and distribution facilities and is necessary to prevent releases of petroleum products@ which may cause fire and safety hazards and/or environmental damage. Proper USTS management also increases the overall efficiency of the facility by reducing the possibility of product loss and operational errors. In some circumstances@ site-specific features@ such as topographical conditions@ structures@ walls@ water tables@ soil conditions@ or proximity to buildings and adjoining property@ may dictate the use of practices other than those set forth in this publication. The authority having jurisdiction should take these special circumstances into account in deciding whether to employ particular provisions of this recommended practice in government regulations. This recommended practice describes procedures and equipment to assist in providing adequate leak and release prevention@ detection@ investigation@ and corrective action. Over the years@ API has developed approaches to safeguarding against leaks and releases from USTs and has published a number of documents that summarize these recommendations@ including API Recommended Practice 1604@1615@1621@1631@1632@ and Publication 1628. A number of other supportive publications on the management of USTSs and fire protection are available from API