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O DEPTH OF EXCAVA � � ���A� �3 � <br /> The hole must be dee O <br /> p eno to provide sufficient Stable ®il diti®ns <br /> bedding and cover depth as determined by the type of <br /> surface pavement and loading. NFPA 30 and 31 should Where shoring is not required to maintain a vertical wall <br /> be consulted as well as local codes. from top to bottom of the excavation, the minimum <br /> Tanks subjected to -,- g1cri <br /> spacing between the sidewall or endcap of the tank and <br /> traffic loads must have 6" ` side of excavation must be 24 inches(60cm). <br /> a cover depth of at I 0- 61, If more than one tank is to be installed in the same hole, <br /> least 30 inches(75cm) there must be at least 24 inches (60cm) between the <br /> of backfill plus 6 inches tanks. <br /> (15cm) of asphalt. An (ll <br /> acceptable alternative 30„ T DRY C =18" <br /> is a minimum of 18 _ <br /> CONDITIONS <br /> Stable <br /> inches (45cm) of - Soil <br /> backfill plus 6 inches 12 I <br /> (15cm) of steel re-bar <br /> reinforced concrete. <br /> Tanks subjected to <br /> traffic loads and high <br /> water must have a g" 6" 24' -- 24" <br /> minimum <br /> of 30 inches ,—_ I I -II I I I I I 11 M <br /> EN! <br /> (75cm) of backfill and _ II-lfV either 8 inches (20cm) = -!' - - - -m of asphalt or 6 inches - <br /> (15cm) of steel re-bar 30�' TRAFFIC D `30" <br /> reinforced concrete. L, CONDITIONS 12„ <br /> _,I <br /> Unstable Soil Conditions <br /> If the soil has less than 750 lbs/sq. ft.cohesion as cal- <br /> Tanks not subjected to culated from an unconfined compression test;or in soils <br /> traffic loads must have having an ultimate bearing capacity of less than 3500 <br /> a minimum cover 24" lbs/sq.ft.;or where soil will not maintain a vertical wall, <br /> depth of 24 inches 411- 12" the excavation must allow a minimum space equal to 1/2 <br /> (60cm)of backfill,or 12 a- =y lthe diameter of the tank between the side and endcap <br /> inches (30cm) backfill _ ,; ' ;-,' of the tank and the excavation wall. The spacing be- <br /> plus 4 inches (10cm) II. DRY I tween adjacent tanks, 24 inches (60cm), remains the <br /> of steel re-bar rein- -LII CONDITIONS same. <br /> NO <br /> forced concrete. ' TRAFFIC <br /> Unstable <br /> i 12„ 'h Soil <br /> Tanker_ <br /> Tanks in high water _ I V Dia. <br /> areas not subjected to <br /> traffic loads must have <br /> a minimum of 36 = <br /> inches (92cm) of 36 1/2 Tank <br /> backfill covering. - - Dia WET <br /> --�'' 24" <br /> CONDITIONSNO <br /> TRAFFIC 112" <br /> �V <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 inches <br /> (30cm)beyond tank in all directions. <br /> NOTE:Maximum burial depth is 7 feet(2.1 meters)of cover over top <br /> of tanks up to 20,000 gallons(76 cu.meters)in size. <br />