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LG 144 A Page 1 of 2 LG 144 MONITORING AND UPGRADE REQUIREMENTS FOR HYBRID TANK SYSTEMS (DOUBLE-WALL TANKS WITH SINGLE-WALL PIPING) CONTAINING MOTOR VEHICLE FUEL January 22, 1996 To: Local Agencies and Other Interested Parties Some motor vehicle fuel Underground Storage Tank(UST) systems installed between January 1, 1984 and July 1, 1987 have double-wall tanks and single-wall piping. These systems are generally referred to as "hybrid systems." This letter is to clarify the monitoring and upgrade requirements for hybrid systems. Section 25291(a)(7)(E) of the Health and Safety Code (H&SC) "grandfathered" hybrid systems and exempted the single-wall piping from secondary containment requirements if certain monitoring methods are used to monitor both the tank and piping. In the past, we interpreted Sections 25291(a)(7)(C) & (D) and 25292(b)(4) H&SC as follows: The tank must have inventory reconciliation, annual tightness testing, and monitoring of the interstitial space (daily manual monitoring or continuous monitoring). The piping system must have an automatic line leak detector (to perform an hourly 3 gph test)plus either an annual line tightness test(0.1 gph test) or a monthly 0.2 gph line test. Many local implementing agency inspectors and tank owners believe that these requirements are excessive. Many owners of these hybrid systems are monitoring their tanks with a continuous interstitial monitoring device that is connected to an audible and visual alarm. They check their monitoring systems annually to verify proper operation in compliance with state regulations. Owners believe,therefore, that performing inventory reconciliation and annual tightness tests on these tanks is unnecessarily redundant. These requirements do not provide an incentive for tank owners to use the more reliable continuous interstitial monitoring method instead of manual monitoring. We believe the following to be a reasonable and acceptable alternative interpretation to the one we have expressed in the past: If the interstitial space of the tank is continuously monitored. . . Monitoring the interstitial space of the double-wall tank in a hybrid system with a continuous monitoring device satisfies the inventory reconciliation and tank tightness testing requirements of Sections 25291(a)(7)(D) and 25292(b)(4) H&SC, if the continuous monitoring device is: • connected to an audible and visual alarm, and • checked annually for proper operation(in accordance with manufacturer's instructions) If the interstitial space of the tank is not continuously monitored . . . Inventory reconciliation(either manual or statistical) and an annual tank tightness test must be performed in addition to monitoring the interstitial space. DECEMBER 22, 1998 UPGRADE REQUIREMENTS Piping Hybrid motor vehicle fuel systems are grandfathered by law; therefore, there is no requirement to replace the single-wall piping of these systems with double-wall piping to meet the upgrade deadline. However, any such piping that is in direct contact with soil must be upgraded with corrosion http://www.swrcb.ca.gov/—cwphome/ust/1g-144.htm 12/17/98