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(7) <br />DEPTH OF EXCAVAlN <br />The hole must be deep enough to provide sufficient <br />bedding and cover depth as determined by the type of <br />surface pavement and loading. NFPA 30 and 31 should <br />be consulted as well as local codes. <br />Tanks subjected to <br />traffic loads must have <br />a cover depth of at F <br />' <br />least 30inches (75cm) 6° <br />of backfill plus 6 <br />inches (15cm) of as- <br />phalt. An acceptable _ <br />alternative is a min- 30" TRAFFIC <br />-18" <br />imum of 18 inchesDRY <br />CONDITIONS <br />(45cm) of backfill plus <br />6 inches (15cm) of <br />steel re -bar reinforced <br />concrete. <br />Tanks subjected to <br />traffic loads and <br />high water must <br />have a minimum of <br />30 Inches (75cm) of <br />backfill and either 8 <br />inches (20cm) of <br />asphalt or 6 inches <br />(15cm) of steel re - <br />bar reinforced <br />concrete. <br />Tanks not subjected <br />to traffic loads must <br />have a minimum <br />cover depth of 24 in- <br />ches (60cm) of <br />backfill, or 12 inches <br />(30cm) backfill plus 4 <br />inches (10cm) of steel <br />re -bar reinforced <br />concrete. <br />Tanks in high water <br />areas not subjected <br />to traffic loads must <br />have a minimum of <br />36 inches (92cm) of <br />backfill covering. <br />llh�j ,: ter: 61' <br />— I a <br />30" -- TRAFFIC ;30" <br />WET <br />CONDITIONS <br />12" <br />24" 12" <br />4" <br />y — `l ` <br />2, rCONDITIONS <br />RY <br />�TRAFFIC <br />IV 12„ <br />36 <br />WET <br />CONDITIONS <br />NO - <br />TRAFFIC 12" <br />NOTE: These depths of cover are MINIMUMS for high water areas <br />without traffic over the tank. <br />NOTE: Asphalt and concrete pads must extend a minimum of 12 <br />inches (30cm) beyond tank in all directions. <br />NOTE: Maximum burial depth is 7 feet (2.1 meters) of cover over top of <br />tanks up to 20,000 gallons (76 cu. meters) in size. <br />% EXCAVAON SIZE <br />Stable Soil Conditions <br />Where shoring is not required to maintain a vertical wall <br />from top to bottom of the excavation, the minimum <br />spacing between the sidewall or endcap of the tank and <br />side of excavation must be 24 Inches (60cm). <br />If more than one tank is to be installed in the same hole, <br />there must be at least 24 inches (60cm) between the <br />tanks. <br />Unstable Soil Conditions <br />If the soil has less than 750 lbs/sq. ft. cohesion as <br />calculated from an unconfined compression test; or in <br />soils having an ultimate bearing capacity of less than <br />3500 lbs/sq. ft.; or where soil will not maintain a vertical <br />wall, the excavation must allow a minimum space equal <br />to 1/2 the diameter of the tank between the side and <br />endcap of the tank and the excavation wall. The spacing <br />between adjacent tanks, 24 inches (60cm), remains the <br />same. <br />xjQj�r�.�. <br />�0,_ _ <br />