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Terry Tamminen <br />Secretaryfor <br />Environmental <br />Protection <br />July 14, 2004 <br />State Water Resources Control Board <br />Division of Water Quality <br />10011 Street • Sacramento, California 95814 • (916) 341-5752 <br />Mailing Address: P.O. Box 2231 • Sacramento, California • 95812 <br />FAX (916) 341-5808 • Internet Address: http://www.swrcb.ca.gov <br />LG 165 <br />STORAGE TANKS IN CONTAINMENT STRUCTURES <br />LOCATED BENEATH THE SURFACE OF THE GROUND <br />(Available electronically at http://www.swrcb.ca.gov/ust) <br />To: Local Agencies and Other Interested Persons <br />Arnold Schwarmnegger <br />Governor <br />The purpose of this letter is to answer some common questions that have arisen to date regarding <br />whether storage tanks in containment structures (e.g., vaults or basements) located beneath the <br />surface of the ground are underground storage tanks (USTs), and if so, whether such USTs are <br />exempt from the requirements set forth in Chapter 6.7 of the Health and Safety (H&S) Code and <br />Chapter 16 of Title 23, of the California Code of Regulations (CCR), and whether such storage <br />tanks are aboveground storage tanks (ASTs). <br />1. What are some examples of USTs that are located in containment structures <br />beneath the surface of the ground or not enclosed in earthen materials? <br />Examples of USTs that are located in containment structures beneath the surface of the <br />ground or not enclosed in earthen materials include those: in below -grade service bays <br />(e.g., motor vehicle oil change facilities); in basements that provide fuel for back-up <br />generators or vehicle fueling; and enclosed in structures that provide secondary <br />containment. <br />2. What is the definition of an UST? <br />"UST" is defined as any one or combination of tanks, including piping] connected <br />thereto, that is used for the storage of hazardous substances and that is "substantially or <br />totally beneath the surface of the ground" (explained below). Please note that certain <br />exemptions apply. [H&S Code, §25281(y)(1).] "UST system" means an UST, connected <br />piping, ancillary equipment, and containment system. [H&S Code, §25281(z).] <br />3. What is the meaning of the phrase "substantially beneath the surface of the <br />ground?" <br />An UST is considered "substantially beneath the surface of the ground" if at least 10% of <br />its system volume, including the volume of any connected piping', is located beneath the <br />surface of the ground or is enclosed below earthen materials. [Title 23, CCR, §2611.] <br />For USTs installed on or after July 1, 2003, the definition of pipe has been extended to include vent lines, vapor <br />recovery lines, and fill pipes that are beneath the surface of the ground. [H&S Code, §25290.20).] <br />California Environmental Protection Agency <br />0 Recycled Paper <br />