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Ameron Dualoy° Pipe Monitoring System 21 ft line. Since this is the likely location of trapped air, extrapolation to longer lines will exaggerate the effects of the "normal' amount of air trapped when the interstice is carefully filled by gravity or pump. A field-installed line with five fittings would likely be significantly longer than the test line because of the extra fittings in the test assembly. Although it is not possible to reliably quantify the volume of air trapped in the gravity filling process, the test results indicate that the amount of air trapped during the filling was less than 300 ml. Effects of a catastrophic failure of the primary pipe The effects of a catastrophic failure of the inner pipe at two locations were measured by introducing brine into the interstice at a pressure of 40 psig. Brine was introduced at a distance of 20 ft from the reservoir and 4 ft from the reservoir. The level change was observed and the change for a one-minute exposure to the catastrophic leak was determined for both locations. Flow through the interstice The rate of flow through the interstice was determined using the data from the catastrophic leak tests. The volume of liquid per minute through the interstice was measured until the reservoir reached its maximum level. Time to alarm The time to produce a level change of 5 inches with a leak of 0.1 gal/h out of the interstice was determined by pumping brine into the interstice at a rate of 0.1 gal/h. The results of level vs. time were used to determine the time required to produce an alarm. These results can be used to estimate the alarm time for any sensor spacing with a 0.1 gal/h leak assuming that the initial level is at the midpoint of the sensors. Reservoir level sensor alarm set points A list of dual point interstitial sensors that have been evaluated by an independent third-party has been provided in Appendix C. All of these sensors were evaluated using methods that were acceptable to the NWGLDE and were subsequently listed in the "Ninth Edition, List of Leak Detection Evaluations for Underground Storage Tank (UST) Systems," November 21, 2001. This list is not all-inclusive as new monitoring systems are regularly developed. The procedures used to conduct the performance evaluation of level sensors are based on the methodology described for water sensor testing in the EPA ATGS protocol.2 . These water sensor procedures have been incorporated into an alternative protocol by Ken Wilcox Associates3 specifically for testing liquid level sensors. 2"Standard Test Procedures for Evaluating Leak Detection Methods: Automatic Tank Gauging Systems", EPA/530/UST-90/006, March 1990 3"Alternative Test Procedures for Evaluating Leak Detection Methods: Evaluation of Liquid Level Sensors", November 1997, Ken Wilcox Associates, Inc. Page 6 of 12