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LG 152-2 -6- Guidance 6 - Guidance (LG) Letter 113. LG 113 can be found on our website at: http://www.waterboards.ca.gov/ust/leak prevention/W13/index.html It is important to note that regulated piping begins where piping exits/enters the tank and continues to the point where piping extends above the surface of the ground (e.g., at a shear valve). Statute does not provide an exemption for single - walled piping transitions contained in sumps, or single -walled piping transitions in UDCs, or fill piping contained in sumps. The following options may be used to satisfy the requirements for single -walled piping transitions contained in sumps; single -walled piping transitions contained in UDCs; and fill piping contained in sumps: L The entire piping length, including piping within sumps or UDCs, must be double -walled and continuously monitored using vacuum, pressure, or interstitial liquid level measurement methods; or ii. The interstitial space between the primary (i.e., single -walled transition pipe or fill piping) and secondary containment (i.e., sump, UDC) must be continuously monitored using vacuum or pressure. (Note: Interstitial liquid level measurement would not be appropriate for this option.); or iii. The single -walled transition pipe or fill piping must be contained within a double -walled sump and/or double -walled UDC that either: (1) extends to the surface or (2) has a double -walled product tight lid that is continuously monitored using vacuum, pressure, or interstitial liquid level measurement methods. The secondary containment (of the sump or UDC, including penetration fittings) must be continuously monitored using vacuum, pressure, or interstitial liquid level measurement methods. Pursuant to Section 2637(a)(6) of Title 23, CCR, portions of the UST system which are continuously monitored using vacuum, pressure, or interstitial liquid level measurement methods are exempt from periodic secondary containment testing. Therefore, periodic secondary containment testing is not required for secondary containment of tank and piping that are continuously monitored using vacuum, pressure, or interstitial liquid level measurement methods. Please note that annual certification of the leak detection equipment is still required. B. What components of USTs installed on or after July 1, 2004 are required to be monitored in accordance with H&S Code, Section 25290.1(d)? Section 25290.1 requires that the "underground storage tank system" be designed and constructed with a continuous monitoring system. Tank and product piping monitored using constant vacuum, pressure, or interstitial liquid level measurement methods satisfy this requirement through Section 25290.1(e). However, other parts of the UST system not subject to Section 25290.1(e) must satisfy the monitoring requirement in Section 25290,1(d). These components include, but are not limited to, riser piping and access points on top of the tank, California Environmental Protection Agency rLd RencfedPaper