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.i TRU-CHEK® Monitoring System double wall protection at itl1b . Xerxes DWT -II double wall tanks with the TRU-CHEK® system option are factory -filled with a brine solution in the interstice between the two tank walls. The brine also partially fills a reservoir affixed to the top of the tank. This creates a hydrosta- tic pressure that enables owners/users to monitor both the primary tank and the secondary tank walls. The TRU-CHEK® system provides a simple and precise method to perform a tank -tightness test. It was developed in conjunc- tion with Dr. Robert Plunkett, Sc.D., consulting engineer (pro- fessor emeritus(, University of Minnesota. TRU-CHEK® has received third -parry verification from Underwriters Laboratories. TRU-CHEK® testing meets the EPA criteria for tank -tightness testing, which states that a test must be able to detect a leak rate of 0.1 gallon per hour from any portion of the tank that routinely contains product. The test has a 95% probability of detection (PD( and a 5% probability of false alarm (PFA(. In other words, out of 100 chances, the test detects leaks 95% of the time. The test must also account for the effects of thermal expan- sion or contraction of the product, vapor pockets, tank defor- mation, evaporation, condensation and the location of the water table. TRU-CHEK® is capable of detecting a loss rate as small as the NFPA 329 criteria of 0.05 gallons per hour. In addition, on extended tests, TRU-CHEK® testing offers 99% PD and I% PFA. The TRU-CHEK® test offers significant benefits to the owner/operator: 1.A wide range of tank sizes can be tested, including Xerxes DWr-II tanks up to 20,000 gallons. 2. Product can be dispensed during the 95%/5% test. 3. No waiting time is required to start the test as long as a fill of new product does not vary more than 20°F from the existing product temperature. How continuous monitoring works If both the inner and outer walls are tight, the reservoir level will be stable. If there is a fracture in the inner wall (Diagram A(, the brine level in the reser- voir will go down. The brine level will also go down if there is a leak in the outer wall (Diagram B(. With a high-water table and "wet -hole" conditions (Diagram C(, a leak in the outer wall will cause the brine level to go up if the height of the water table above the leak is 30% greater than the brine level above the leak. See Xerxes TRU-CHEK® brochure for more details. lim probe points. - The system shall provide intrinsic safety at the probe locations: 4.1 Reservoir Probe The probe shall be constructed of a material which is suitable for prolonged, complete immersion in the monitoring liquid. Diagram A Reservoir Level Down Diagram B Reservoir Level Down 1 'J Diagram C ----�- -�—� Reservoir — Level Up - �- .� Water Level Above Tank �— Fracture Outer Wall 7.0 The monitoring systems shall be installed in accordance with the manufacturer's installation instructions, and all applicable federal, state, and local laws and regulations. 1a