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11 BACKFILLING Use only approved backfill material (See Section 3). Do not mix approved material with sand or native soil. Do not use native soil as backfill material. All excavated native soil must be replaced with approved material. Place one 12 inch lift of material evenly around the tank. From the hole side or the top of an adjacent tank, work the material by hand completely beneath the tank body and domes to provide full support. Use a nonmetal probe bar long enough to reach beneath the tank and push the backfill in place. Repeat this step with a second 12 inch lift. After the second lift of material has been placed and probed, the backfill can be brought to the top of the tank without further hand work. 0 CAUTION: Do not strike the tank with the probe bar. The tank may be FIGURE 5-1 FIGURE 5-2 When the tank is backfilled to the tank top: • take an intermediate diameter reading as an in -process check. • repeat the 5 PSIG (3 PSIG for 12 foot tanks) air test as outlined in Section 2, soaping all exposed areas of the tank and all fittings. SUMMARY 1. Prepare the tank bed. 2. Set and level the tanks. 3. Measure the tank diameter. 4. Install holddown hardware (if applicable). 5. Place and probe the first two lifts of backfill material. 6. Add backfill to the top of the tank. 7. Measure the tank diameter and repeat the air test. After the air test and measurement of tank deflection are successfully completed, it is recommended that the tank be ballasted until piping installation and final backfilling to grade is completed. When filling the tank, make sure that the tank is adequately vented. The vent must be large enough to allow the displaced air to escape. NOTE: Do not ballast the tank until the backfill is even with the top of the lank. Q WARNING: If product is used as ballast, exercise special care in handling. Safeguard against sparks, fire or product spills. Improper handling of product can cause a fire or explosion, and death, severe personal injury or property damage. 6. WET HOLE INSTALLATION WARNING: Do not use air pressure to test tanks that contain flammable or combustible liquids, or vapors, and do not perform any post installation pressure tests. The fuel and air mixture may explode and cause death, severe personal injury, or properly damage. 0 Q CAUTION: Never allow an empty tank to remain in a wet hole, ora dry hole that may become wet, unless anchoring and backfilling have been completed. Failure to anchor and backfill may damage the tank or surrounding property. NOTE: Deflection readings to be taken in sequence similar to steps described in Section 5. Pump the water from the hole to maintain minimum water level. Add a minimum of 12 inches of well-placed backfill material to the hole, and level the bed to assure uniform bottom support for the tank. Position the tank in the hole. Partially ballast tank until it settles firmly on the prepared bed. Ballast level in a tank must never exceed water level in hole during installation. Use only enough ballast to sink the tank until backfill material is even with the top of the tank. (Q WARNING: If product is used as ballast, exercise special care in handling. Safeguard against sparks, fire or product spills. Improper handling of product can cause a fire or explosion, and death, severe personal injury or property damage. After leveling tanks, the anchoring procedures in Section 7 must be followed. Backfill must be added evenly after anchoring, and remaining dry hole backfilling procedures should be followed as stated in Section 5. NOTE: Cover depth must meet minimum depth specified in Section 4 of these installation instructions. NOTE: h is recommended that the tank be completely ballasted once backfill is even with the top of the tank. FIGURE 6.1 7. ANCHORING TANKS Xerxes recommends that everysite be thoroughly evaluated for the potential to trap water or otherwise subject the tank to a rise in the local water table. Xerxes recommends that all tanks be anchored In installations in which water may enter the hole. Failure to anchor may damage the tank or surrounding property. DEADMAN ANCHOR A deadman is a reinforced concrete beam. The length of the deadman is equal to the length of the tank. A deadman may be fabricated in multiple sections as long as the total length is not decreased and each section contains at least two anchor points. The width and thickness depend on the tank diameter. Refer to Table 7-1 for specific dimensions. NOTE: Tanks of 10 foot diameter and 30,000 gallons or larger may require larger deadman to offset buoyancy. Contact Xerxes' Technical Service Department for further information.