&EPA United States Environmental Protection Agency Solid Waste And Emergency Response 5403W EPA510-F-94-005 August 1994 UST Program Facts Detecting Releases Why have release detection? The U. S. Environmental Protection Agency designed part of the technical regulations for underground storage tanks (USTs) to make sure releases or "leaks" from USTs are discovered quickly before contamination spreads from the UST site. Owners and operators are responsible for detecting leaks from their tanks and piping. Who needs leak detection? All USTs must now have leak detection. USTs installed after December 22,1988 must have leak detection when they are installed. USTs installed before December 22,1988 had compliance deadlines that varied with the age of the USTs. By December 22,1993, all of these "older" USTs had to be in compliance with leak detection requirements. What are the leak detection methods? Owners and operators of petroleum USTs must use at least one of the seven leak detection methods below, or other methods approved by their state agency. 1. Automatic tank gauging systems use monitors permanently installed in the tank. These monitors are linked electronically to a nearby control device to provide information on product level and temperature. During a test period of several hours when nothing is put into or taken from the tank, the gauging system automatically calculates the changes in product volume that can indicate a leaking tank. This method does not work on piping. 2. Groundwater monitoring senses the presence of liquid product floating on the groundwater. This method requires installation of monitoring wells at strategic locations in the ground near the tank and along the piping runs. To discover if leaked product has reached groundwater, these wells can be checked periodically by hand or continuously with permanently installed equipment This method is effective only at sites where groundwater is within 20 feet of the surface. 3. Vapor monitoring senses and measures product vapor in the soil around the tank and piping to determine the presence of a leak This method requires installation of carefully placed monitoring wells. Vapor monitoring can be performed periodically using manual devices or continuously using permanently installed equipment. 4. Secondary containment and interstitial monitoring involves placing a barrier between the UST and the environment. The barrier provides "secondary" containment and can be a vault, liner, or double-walled structure. Leaked product from the UST is directed toward a monitor located in the "interstitial" space between the UST and the outer barrier. Interstitial monitoring methods range from a simple dip stick to automated vapor or liquid sensors permanently installed in the system. New USTs holding hazardous substances must use this method. 5. Statistical inventory reconciliation uses sophisticated computer software to determine whether a tank system is leaking. The computer conducts a statistical analysis of inventory, delivery, and dispensing data collected over a period of time and provided by the operator to a vendor. 6. Manual tank gauging can be used only on tanks 2,000 gallons or smaller. This method does NOT work on tanks larger than 2,000 gallons or on piping. This method requires taking the tank out of service for at least 36 hours each week to take measurements of the tank's contents. Tanks 1,000 gallons or less can use this method alone. Tanks from 1,001-2,000 gallons can use this method only when it is combined with periodic tank tightness ------- testing and only for 10 years after installation or upgrade of the UST. After 10 years, these USTs must use one of the leak detection methods listed above in 1-5. The additional method below can be used temporarily at all petroleum UST sites: 7. Tank tightness testing and inventory control combines two methods. Tank tightness testing requires periodic tests conducted by vendors who temporarily install special equipment that tests the soundness of the tank. Tank tightness testing must be used in combination with inventory control. Inventory control is an ongoing accounting system, like a checkbook, kept by the UST owner or operator to detect leaks. Inventory control requires taking daily accurate measurements of the tank's contents and performing monthly calculations to prove that the system is not leaking. Tank tightness testing and inventory control can be used only for 10 years after installation or upgrade of an UST. After 10 years, these USTs must use one of the leak detection methods listed above in 1-5. What does piping need? Pressurized piping needs automatic line leak detectors (these can be automatic flow restrictors, automatic flow shutofis, or continuous alarm systems). Pressurized piping also needs one of the following: groundwater monitoring, vapor monitoring, secondary containment and interstitial monitoring, or an annual tightness test of the piping. Suction piping needs no leak detection if it meets two design requirements: 1) piping slopes so that the product drains back into the tank when suction is released, and 2) piping has only one check valve located closely beneath the pump in the dispensing unit Suction piping not meeting these design requirements must use one of the following: tightness test of the piping every 3 years, groundwater monitoring, vapor monitoring, or secondary containment and interstitial monitoring. Reporting and recordkeeping necessary? UST owners and operators need to report to the regulatory authority data about the UST, including description of the leak detection method. If operation of the leak detection method indicates a possible leak, UST owners and operators need to report the potential release to the regulatory authority. UST owners and operators must keep records on leak detection performance and upkeep. These include the previous year's monitoring results, the most recent tightness test results, performance claims by the leak detection device's manufacturer, and records of recent maintenance and repair. "Detecting Releases" is one in a series of fact sheets about underground storage tanks (USTs) and leaking USTs. The series is designed to help EPA, other federal officials, and state authorities answer the most frequently asked questions about USTs with consistent, accurate information in plain language. Keep the fact sheets handy as a resource. This fact sheet addresses federal regulations. You may need to refer to applicable state or local regulations, as well. For more information on UST publications, call the RCRA/Superfund Hotline at 800424-9346. RtcyclMi/ftocyctabl* Printed with Soy/C¬a Ink on paper that contains at least 50% post-consumer recycled fiber ------- |