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8: COMPLETING INSTALLATION 8.1. TAKING DIAMETER MEASURE #4. 8.1.1. When the tank has been backfilled to subgrade (but before placement of concrete or asphalt), take the last required tank diameter measurement. Record it as Measurement #4 on the Tank Installation Checklist and determine whethertank deflection is within the allowable limits shown in the Installation Manual. 8.1.2. In a tank with a wet interstitial space, the level of the monitoring fluid may have changed during backfill. Therefore, the level of the monitoring fluid must be checked and/or adjusted for proper level after backfill and top slab placement is completed. 8.2. MONITORING TANKS 8.2.1. It is the responsibility of the tank owner and/or operator to determine the appropriate monitoring system and method if one is to be used. 8.3. MONITORING SINGLE-WALL TANKS 8.3.1. Single-wall tank installations may require release detection monitoring, which can include inventory control, automatic tank gauging, vapor monitoring or groundwater monitoring. 8.3.2. Check with appropriate governmental agency officials for requirements in your area. 8.4. MONITORING DOUBLE-WALL TANKS 8.4.1. A double-wall tank has an interstitial space between the wall of the primary (internal) tank and the wall of the secondary (external) tank for the detection and containment of product from the primary tank. 8.4.2. A double-wall tank, as supplied, will have a minimum of 1 monitoring access fitting that provides access into the interstitial space. 8.4.3. liquid and vapor sensors are installed through the monitoring access fitting. • Most sensors can be installed after the tank has been backfilled to grade. • For ease of installation, the sensor may be inserted into the monitoring access fitting before installing the monitoring riser pipe to grade. 8.5. MONITORING DOUBLE-WALL TANK WITH A DRY INTERSTITIAL SPACE 8.5.1. A safe electronic or mechanical monitoring system should be used to detect product and incoming water. 8.5.2. The monitoring system should detect product and water at the bottom of the interstice. • Use a drawstring to position the monitoring sensor at or near the bottom of the tank. • If a double-wall tank is sloped, the monitor should beat the low end. 8.5.3. For liquid or vapor sensors, the monitoring access fitting maybe vented to atmosphere (independent from the primary tank) or sealed. 26 8.6. MONITORING DOUBLE-WALL TANK WITH A WET INTERSTITIAL SPACE 8.6.1. A double-wall tank may be shipped with a factory -installed TRUCH EK111 monitoring system, which enables the owner to have continuous monitoring or to conduct a tank -tightness test. • TRUCHEK meets the EPA criteria for tank -tightness testing. See the TRUCHEK brochure for more information. • When a double-wall tank is shipped with theTRUCHEK monitoring system, the interstitial space is typically filled with monitoring fluid at the manufacturing facility. • Some tanks with TRUCHEK installed may be shipped with extra monitoring fluid so the monitoring -fluid level can be topped off. • Do not add monitoring fluid until after tank burial is completed and the monitoring system is set up. NOTICE All wet interstitial spaces must be vented to atmosphere. Failure to follow this notice could result in damage to the tank and/or surrounding property. See section 7.3. NOTICE Monitoring fluid should not be present in the standpipe except during a TRUCHEK test. Monitoring fluid in the standpipe could create excessive pressure on the interstitial space and could result in damage to the tank. See the TRUCHEK brochure for more information. 8.6.2. When the tank is delivered and before it is installed, check the monitoring -fluid level and record it on the shipping/receiving paperwork and Tank Installation Checklist. • The required operating level for the monitoring fluid in the reservoir is 112 full. If necessary, add monitoring fluid to meet that level—BUT not until after the tank is buried and the monitoring system is set up. • If monitoring fluid is not in the reservoir, contact the manufacturing facility that shipped the tank. • In a tank with the interstice filled with monitoring fluid, using a nonmetallic standpipe in the reservoir is recommended. • The monitoring -fluid level may fluctuate during shipping and installation. • If a tank is sloped, the reservoir should be at the high end. 8.6.3. During the installation process,the monitoring -fluid level in the reservoirwill rise naturally undervarious conditions: • preinstallation pressure test • rise in groundwater level • backfill compaction • ballasting • temperature increase 8.6.4. Check and record the monitoring -fluid level during the installation process. See theTank Installation Checklist. 8.7. SETTING THE LEVEL OF THE MONITORING FLUID 8.7.1. After completing the backfilling and placing the top slab: • check the level of the monitoring fluid in the reservoir and set the monitoring fluid to the proper level. • Failure to set the monitoring -fluid level properly could lead to false alarms.