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TANK INSTALLATION <br /> 11.3.9. Eliminate all voids by using along handled Figure 11-6 <br /> probe to push backfill: Third Vertical Diameter Measurement <br /> 11.3.9.1. Completely beneath tank bottom. <br /> 11.3.9.2. Completely between the 5 o'clock and 7 Backfill to <br /> o'clock positions along the entire length of TankTop <br /> the tank between and around all ribs and <br /> endcaps.It is critical to tank performance /?/ <br /> that this area offers full support under the <br /> tank and end caps(see Figure 11-4). <br /> Figure 11-4 <br /> Right Wrong <br /> Measure from the bottom of the tank <br /> to the bottom of the fitting. <br /> NMIBackfill <br /> Void Ic <br /> o not ballast tank until backfill is even with tank top <br /> \yi rtank damage can occur. <br /> 11.3.15. After backfill is even with tank top,CSI <br /> 11.3.10. Repeat this process with a second 12"lift. recommends filling all tank compartments <br /> 11.3.11. After completion of second lift,backfill can with ballast to minimize chance of buoyancy. <br /> be brought to tank top without additional 11.3.16. Additional information on alternate <br /> handwork. installation techniques is available.Refer to <br /> 11.3.12. Special Instructions for a wet hole installation: Supplemental Documents(Section 21)for <br /> 11.3.12.1. Water level in the excavation should be additional information. <br /> maintained at lowest practical level by 11.4. Backfill To Subgrade <br /> using pumps. 11.4.1. When the tank has been lowered into the <br /> r excavation and all testing,backfilling,venting <br /> and piping has been completed;add the <br /> Keep tank vented to prevent pressurization of tank remaining backfill material to subgrade. <br /> when adding ballast.Asthetanknears full,reducethe 11.4.2. Approved pea gravel or crushed stone must <br /> fill rate toprevent pressurization ortank damage may be used to backfill the tank a minimum of 75% <br /> occur.This may result in personal injury or property up the side wall of the tank(s). <br /> damage. 11.4.3. If alternative smaller or finer backfill material is <br /> used to subgrade,geotextile fabric is required. <br /> 11.3.12.2. Ballast the tank if groundwater cannot Refer to Supplemental Documents(Section 21) <br /> be lowered.Ballast the tank per section 10. for additional information. <br /> 11.3.13. Backfill to the tank top. 11.4.4. Once the tank has been backfilled to subgrade, <br /> 11.3.14. Take the Third Vertical Diameter Measurement before placement of concrete pad,take the <br /> and record the value on theTank Installation fourth vertical diameter measurement. <br /> Checklist and verify measurement A does not 11.4.5. Take the Fourth Vertical Diameter <br /> exceed the value in Table 11-1 (see Figure 11-6). Measurement and record the value on the <br /> Tank Installation Checklist(see Figure 11-7). <br /> 20 <br />