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0 <br />Linda S. Adams <br />Secretaryfor <br />Environmental Protection <br />11 <br />Division of Water Quality <br />10011 Street, Sacramento, California 95814♦ (916) 341-5866 <br />Mailing Address: P.O. Box 2231, Sacramento, California 95812 <br />FAx (916) 341-5808 ♦ Internet Address:. http://www.waterboards.ca.gov <br />June 12, 2007 <br />LG 161-4 <br />ENHANCED LEAK DETECTION <br />(Available electronically at http://www.waterboards.ca.gov/ust) <br />To: Local Agencies and Other Interested Persons <br />Arnold Schwarzenegger <br />Governor <br />The purpose of this letter is to provide a general overview of the enhanced leak <br />detection (ELD) requirements and to answer the most common questions regarding <br />ELD that have arisen to date. This letter is intended as a working document and may be <br />periodically updated as new information becomes available and as new questions arise. <br />What is ELD? <br />ELD is a test method that ascertains the integrity of an underground storage tank (UST) <br />system by the introduction and external detection of a substance that is not a <br />component of the fuel formulation stored in that UST system. [Cal. Code Regs., Title 23, <br />§ 2644.1, subd. (a)(1)] <br />• Third -party certified; and <br />• Capable of detecting both vapor and liquid phase releases at a leak rate of at least <br />0.005 gallons per hour (gph), with a probability of detection of at least 95% and a <br />probability of false alarm no greater than 5%®. [Id. § 2644.1, subd. (a)(2)] <br />Who is regUired to perform ELD? <br />Owners/operators of UST systems installed prior to July 1, 20031 and located within <br />1,000 feetof a public drinking water well must perform ELD. [Health & Saf. Code, §§ <br />25292.4; 25292.5; Cal. Code Regs., Title 23, §§ 2640, subd. (e); 2644.1, subd. (a)(3)] <br />The SWRCB UST Program is responsible for notifying owners/operators of facilities that <br />are subject to the ELD requirement. <br />What is a public drinking water well? A "public drinking water well' is a <br />wellhead that: <br />■ Provides drinking water to a public water system;2 <br />■ Is regulated by the State Department of Health Services (DHS); <br />and <br />1 USTs installed on or after July 1, 2003 are those systems that are installed and monitored in accordance with <br />Health and Safety Code, section 25290.1. <br />2 A "public water system" is a system that provides water for human consumption through pipes -or other constructed <br />conveyances that has 15 or more service connections or regularly serves at least 25 individuals daily at least 60 days <br />out of the year. [Health & Saf. Code, § 116275] <br />California Environmental Protection Agency <br />0 Recycled Paper <br />