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State Water Resources Control Board <br /> Ltnda S.Adams Division of Water Quality Arnold Schwaraenegger <br /> Secretaryfor 10011 Street,Sacramento,California 95814♦ (916)341-5866 Governor <br /> Environmental Protection Marling 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.-Qov/ust) <br /> To: Local Agencies and Other Interested Persons <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 /> The ELD test method must be: <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/operator's of UST systems installed prior to July 1, 20031 and located within <br /> 1,000 feet'of 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 Prdtection Agency <br /> ��Recycled Paper <br />