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1.3.7.6. ANCHOR SLABS NOTE: The tank owner is responsible for the design of anchor slabs. 1.3.7.6.1. An anchor slab is a reinforced concrete base and should be designed according to the applicable American Concrete Institute code or the applicable Canadian Standards Association (CSA)standard, whichever is relevant. 11.3.7.6.2. The total length of the slab must be at least the same as the length of the tank. 1.3.7.6.3. The minimum slab thickness is 8 inches [20 cm]. 1.3.7.6.4. The width of the slab depends on the tank diameter. The slab must extend a minimum of 18 inches [46 cm] (12 inches [30 cm] for 4 -foot -diameter tanks) beyond each side of the tank. 1.3.7.6.5. Provide a separate anchor point for each anchor strap. 1.3.7.6.6. All anchor points must be engineered to withstand the tank's buoyancy forces. 1.3.7.6.7. Refer to Figure 1-12 for anchor -point height. Refer to Table 1-4 for other anchor -point dimensions. 1.3.7.6.8. When using a concrete anchor slab, allow sufficient depth in the excavation for 12 inches [30 cm] of bedding material between the tank and the anchor slab. See Figure 1-12. 1.3.7.6.9. When using our straps and turnbuckles, anchor points must extend at least 3 inches [7.6 cm] above the bedding. With a 12 -inch [30 -cm] bedding, the anchor point is 15 inches [38 cm] above the slab. 1.3.7.7. TAKING DIAMETER MEASUREMENTS GENERAL 1.3.7.7.1. Diameter measurements must be taken at various stages of the installation process to verify that the process is proceeding correctly. 1.3.7.7.2. It is important that these measurements are taken and, if needed, appropriate action is taken so that tank deflection is within allowable limits. 1.3.7.7.3. Diameter measurements of the tank must be taken at one or more locations on each tank or tank compartment. It is preferable to take the measurement near the center of a tank or compartment if possible. 1.3.7.7.4. An initial measurement must be taken before installation of the tank begins.This first measurement is used as a comparison reference for subsequent measurements in order to check proper backfill placement. 1.3.7.7.5. Additional measurements must betaken: • after applying anchor straps (if used) • after backfilling is brought to the top of the tank • after backfilling is brought to subgrade 1.3.7.7.6. Described here are two methods using a dipstick to measure the internal diameter of the tank—one not using a standpipe and one using a standpipe. 1.3.7.7.7. Similar methods can be used, such as using a tape measure, for example. 1.3.7.7.8. Both methods fortaking deflection measurements will give the same result. 1.3.7.7.9. For both methods, drive a small -headed, nonsparking nail (for example, brass) halfway into a wooden dipstick 1 inch [2 cm] above its base. DIAMETER MEASUREMENT WITHOUT A STANDPIPE 1.3.7.7.10. Place the dipstick into a service fitting 1.3.7.7.11. Measure the distance from the tank bottom to the top of the fitting and record this measurement. 1.3.7.7.12. Pull the dipstick up until the exposed nail catches on the inside top of the tank. 1.3.7.7.13. Measure the distance from the tank top (inside) to the top of the fitting. Subtract the distance from the nail to the base of the dipstick and record this measurement. 1.3.7.7.14. Subtract the second measurement (inside tank top to top of fitting) from the first measurement (tank bottom to top of fitting)to calculate the diameter measurement. 1.3.7.7.15. Record this diameter measurement atthe appropriate place (as Measurement #1, #2, #3 or #4) on the Tank Installation Checklist. DIAMETER MEASUREMENT WITH A STANDPIPE 1.3.7.7.16. Place the dipstick into a service fitting with a standpipe. 1.3.7.7.17. Measure the distance from the tank bottom to the top of the standpipe and record this measurement. 1.3.7.7.18. Pull the dipstick up until the nail catches on the inside top of the tank. 13