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i 550ILE • iB Ie' 1e" 24.1 DRY I1"e CONDITIONS If36' 1611 II No TRAFFIC _ NOTE:Numbers in brackets I] 1 a" 18, II Ir_ I referto12'tanks. Tanks not subjected to traffic loads must have a minimum cover depth of 24[481 inches of backfill,or 12[36]inches backfill plus STABLE SOIL CONDITIONS 4 inches of reinforced concrete or 6 inches of asphalt. Where shoring is not required to maintain a vertical wall from.top to bottom of the excavation,the minimum spacing between the sidewall or endcap of the tank and side of excavation must be 18 inches(24 inches for 12'tanks).if more than one tank is to be installed in the same hole,there must be at least 18 inches between the tanks. u I _I 36•� uEr gl 1/2 TA I18 CONDITIONS DIA!TANK NO �� B" TRAFFIC NOTE:Numbers in brackets I I referto 12'tanks. Tanks in high water areas not subjected to traffic loads must have a 1/2 TANK DIA. minimum of 36[48]inches of backfill covering. WARNING:In a non traffic installation,insure that the areas above the tanks will never be subject to traffic loads. NOTE:These depths of cover are MINIMUMS in all cases. NOTE Asphattand concrete pads must extend a minimum of 12 inches beyond UNSTABLE SOIL CONDITIONS tank in all directions. If the soil has less than 750 lbs./sq.fL cohesion as calculated from NOTE Maximum burl)depth Is 7feet of cover over top of tanks. an unconfined compression test;or in soils having an ultimate NOTE Unattached maI riser if present)must not transmit load from the slab bearing capacity of less than 3500 lbs./sq,ft.;or where soil will not to the tank There must be a minimum 6 inch space between the bottom of the I maintain a vertical wall,the excavation must allow a minimum and the top of ft tank space equal to 1/2 the diameter of the tank between the side and endcap of the tank and the excavation wall.The spacing between TANK SPACING adjacent tanks,18 inches remains the same. NOTE These are minimum spacings and must be increased as needed to accommodate deadmen or anchor slabs.Refer to Section 7 on tank anchoring. FILTER FABRIC Always allow sufficient clearance to allow the deadmen to be set outside of the The tank owner or his technical representative is responsible for tank shadow. determining whether filter fabric or an alternate filtering technique is appropriate for a specific installation.Filter fabric allows the passage of water but prevents the migration and mixing of native soil and backfill material.It preserves the integrity of the backfill envelope which supports the tank. Polyethylene film is not considered an effective material to prevent migration of pea gravel and native soil;it may tear or degrade while in service. Xerxes recommends that filter fabric be used when the tank may be installed in: •areas with frequently changing ground water conditions or areas subject to tidal fluctuations, •unstable soils such as bog,swamp,landfill or mud, •water conditions with silty soil.