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4.9.4.1.This date that the vacuum was applied may be used 5.2.2.Record this measurement as Measurement#1 on the Tank as a reference under this procedure to evaluate the tank's integrity Installation Checklist. prior to installation. 5.2.3.Locate the excavation site according to instructions in section 1. 4.9.4.2.Tanks shipped under vacuum must be under vacuum for 5.2.4.Prepare the excavation according to instructions in section 1 a minimum of 7 days.If this requirement is not met,a pressure soap and the following points: test is required. • When preparing the excavation,allow for an anchoring system 4.9.4.3.The tank shipped undervacuum should be installed (if used)and geotextile fabric(if used).See section 1. and backfilled with the vacuum intact if both of the following • When preparing the excavation,allow for the appropriate depth two conditions are met: of cover as specified in section 1. • installation of the tank is to begin 7 days or more after the factory • If two or more tanks are to be installed in the same excavation application of vacuum(as indicated on the shipping documents hole,follow instructions in section 1. and/or tank labels) • If the tank has a bottom sump or fitting,prepare the excavation • the vacuum gauge shipped with the tank reads 12 inches hole according to instructions in section 1. of mercury[40 kPa]or more 5.2.5.If an anchor slab is needed,install it now.See section 1. NOTE:Under certain field conditions(such as major changes 5.2.6.Where necessary,level the bottom of the excavation using in temperature,barometric pressure and/or altitude)and/or with primary backfill material,filling in any low areas.See section 1 certain equipment failure(such as freezing or sticking of gauge for backfill requirements. mechanism),the vacuum-monitoring method may not be an accurate enough test. 5.2.7.Geotextile fabric,if used,must be placed to separate the primary backfill material from all other in-situ soil and/or secondary 4.9.4.4.When in doubt,or when such conditions occur, backfill material.See section 1. see Pressure-Testing Sidebar for instructions on testing a dry, double-wall tank not under vacuum. 5.2.8.If deadmen are used,see section 1 for information on deadmen placement. 4.9.5.PRESSURE TESTING A DRY-MONITOR, If deadmen are used and they are to be placed so that they are in the DOUBLE-WALL TANK NOT UNDER VACUUM bedding or below the bottom of the tank,place the deadmen before 4.9.5.1.See Pressure-Testing Sidebar for instructions. preparing the backfill bedding. 4.9.6. PRESSURE TESTING A DRY-MONITOR, 5.2.9.Prepare a 12-inch-thick[30-cm-thick]smooth,level bed of DOUBLE-WALL MULTICOMPARTMENT TANK approved primary backfill material on the bottom of the excavation NOT UNDER VACUUM or on top of slab.See section 1 for backfill requirements. NOTICE NOTICE Do not connect pressure source directly to the access fitting for If anchor straps are used,bedding must be carefully leveled. interstitial-space monitoring.Pressurizing the interstitial space by Failure to follow this notice could result in straps being too short itself could result in damage to the primary tank and/ortank failure. or too long,which could result in property damage. 4.9.6.1.See Pressure Testing Sidebar for instructions. NOTE: If the excavation has soft soil conditions or if there might be difficulties controlling water accumulation,it is acceptable to increase the bedding thickness as needed.Set the tank anchors 5: INSTALLING TANKS once the bedding thickness has reached a level 12 inches[30 cm] below the tank bottom elevation. 5.1.GENERAL 5.2.10.See section 2 regarding the use of lifting lugs to hoistthe tank 5.1.1.Take safety precautions throughout the entire installation when unloading and installing it. process.See the Introduction. NOTICE 5.1.2.Use only approved backfill material.See section 1.2. Do not set tanks directly onto a concrete slab,timbers,cradles or in-situ soil.Failure to follow this notice could result in damage to the tank. 5.1.3.Do not mix approved material together with sand or in-situ soil. 5.2.11.Place the tank or tanks onto the bed: • If deadmen are in place,centerthe tanks between them. 5.1.4.Do not use in-situ soil as primary backfill material. • Align the tanks with anchors for proper placement of anchor straps. 5.1.5.Typically,all excavated in-situ soil must be replaced with • Asthetank is being placed,slope the tank according to site specifications. primary backfill material. • Sloping of tanks may affect accuracy of calibration charts. • If a double-wall tank is sloped,the monitor should be at the low end 5.2.DRY-HOLE INSTALLATION in a tank with a dry interstitial space and atthe high end in a tank with 5.2.1.Before beginning tank installation,take a tank diameter a wet interstitial space. measurement.See section 1 for instructions. NOTE: We do not require that a tank be sloped.However,sloping the tank may be required by the tank owner's specifications. 20