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