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/__% PEI/RM 200-17 _ <br />4. TANK SECONDARY <br />CONTAINMENT INTEGRITY <br />TESTING <br />4.1 General. Double -walled tanks have interstitial <br />spaces that can be tested for integrity. <br />There are two methods for testing the integrity of tank <br />secondary containment systems: dry and wet. Dry test <br />methods use a partial vacuum to determine the integrity <br />of the containment. To perform a wet test on an existing <br />liquid -filled tank interstitial space, the liquid level in <br />the interstitial space is raised and is monitored for a <br />specified period of time to determine if the containment <br />has integrity. <br />A tank secondary containment integrity test does not <br />necessarily determine whether the primary tank is tight <br />because portions of the primary tank, such as tank fit- <br />tings and manway openings, may not be included in the <br />containment integrity test. <br />4.2 Tank Secondary Containment Integrity Testing <br />— Dry Test Method <br />4.2.1 Purpose. This method is used to test the <br />integrity of the dry secondary containment of a <br />UST. <br />4.2.2 Description of Test. A partial vacuum is <br />drawn on the interstitial space and it is monitored <br />for a specified period of time. If the vacuum level is <br />maintained, the containment system has passed the <br />test. The vacuum test time depends on the volume <br />of the annular space and site conditions. <br />4.2.3 Test Conditions. The primary tank may <br />contain any level of product. No bulk deliveries <br />shall occur during the test. <br />FIGURE 4-1. A cutaway view of a double -walled tank. <br />FIGURE 4-2. Schematic of the dry test method apparatus. <br />0 pei.org <br />