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4O DEPTH OF EXCAVSl O EXCA\BION SIZE <br /> The hole must be deep enough to provide sufficient Stable Soil Conditions <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 - _ spacing between the sidewallorendcapofthe tank and <br /> *7 side of excavation must be 24 inches(6Ocm). <br /> traffic loads must have 6"' h-�-� <br /> tr cover depth of at 8-- 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 (6Ocm) between the <br /> of backfill plus 6 inches tanks. <br /> (15cm) of asphalt. An Ri =� <br /> acceptable alternativeTRAFFIC -18° <br /> is a minimum of 18 30"� DRY Stable <br /> _ CONDITIONS Soil <br /> inches (45cm) of - 12" <br /> backfill plus 6 inches <br /> (15cm) of steel re-bar �- <br /> reinforced concrete. <br /> Tanks subjected to ISE ��2 �J � <br /> traffic loads and high —� <br /> water must have a 8„ ', g' 24', 24" 24rf <br /> minimum of 3O inches III-III <br /> - ' - - <br /> (75cm) of backfill and -IIG-IIII- <br /> either 8 inches (2Ocm) - - <br /> of asphalt or 6 inches TRAFFIC <br /> (15cm) of steel re-bar 10 WET 30" <br /> reinforced concrete. �jlnl- - CONDITIONS <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 cover24 lbs/sq. ft.; or where soil will not maintain a vertical wall, <br /> depth of 24 inches _ 4„ 12" the excavation must allow a minimum space equal to 1/2 <br /> (6Ocm)of backfill,or 12 = - _ the diameter of the tank between the side and endcap <br /> inches (3Ocm) backfill yT of the tank and the excavation wall. The spacing be- <br /> plus 4 inches (1Ocm) (DRYToNstween adjacent tanks, 24 inches (6Ocm), remains the <br /> of steel re-bar rein- - �1 same. <br /> NOforced concrete. AFFIC <br /> Unstable <br /> y2 Soil <br /> Tank.—_ <br /> Tanks in high water I II Dia. <br /> areas not subjected to <br /> traffic loads must have <br /> a minimum of 36 <br /> inches (92crn+ of 36" _ 1/2 Tank 24„ <br /> backfill covering. Dia. <br /> WET <br /> CONDITIONSNO <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 inches <br /> (30cm)beyond tank in all directions. <br /> NOTE:Maximum burial depth is 7 feet(2.1 meters)of cover over top <br /> +CG' of tanks up to 20,000 gallons(76 cu.meters)in size. <br />