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0 1 ZE WARNING: In a non-traffic installation,insure that the areas above the If the soil is extremely soft or inherently unstable,(e.g.peat, tanks will never be subject to traffic or other type loads. quicksand,muck,landfill,very soft or highly expansive clay, NOTE:These depths of cover are MINIMUMS in all cases. etc.)Xerxes recommends that the tank owner seek the advice NOTE:Asphalt and concrete pads must extend a minimum of 12 inches beyond of a local foundation professional engineer. tank in all directions. NOTE:Maximum burial depth is 7 feet of cover over top of tanks. FILTER FABRIC NOTE:Unattached manway riser(if present)must not transmit load from the The tank owner or his technical representative is responsible for concrete slab to the tank.There must be a minimum of 6 inch space between the determining whether filter fabric or an alternate filtering technique bottom of the riser and the top of the tank, is appropriate for a specific installation. Filter fabric allows the NOTE:Tanks of 10 foot diameter and 30,000 gallons and larger may require a passage of water but prevents the migration and mixing of native deeper burial or thicker top slab to offset buoyancy.Contact Xerxes'Technical soil and the select backfill material. It helps preserve the integrity of Service Department for further information. the select backfill envelope which surrounds and supports the tank. Xerxes recommends that filter fabric be used when the tank may TANK SPACING be installed in: A NOTE:These are minimum spacings and must be increased as needed to . areas with frequently changing ground water conditions or accommodate deadmen or anchor slabs.Refer to Section 7 on tank anchoring. areas subject to tidal fluctuations, Always allow sufficient clearance to allow the deadmen to be set outside of the • unstable soils such as cited above, tank shadow. ^ water conditions with silty soil. TOP VIEW For further information concerning fabric specifications and installation procedures,consult the filter fabric supplier's installation guide or instructions. To install filter fabric,typically filter fabric manufacturers e recommend that the installer line the excavation sides and bottom with the fabric.Overlap adjoining panels by at least 12 inches. Place backfill material on the panels around the edge of the hole to anchor them in place. $TAB`S Boi11 l In wet-hole conditions,use backfill material to sink and hold the FIGURE 4-5 fabric in place on the hole bottom. NOTE:Polyethylene film is not considered an effective material to prevent STABLE SOIL CONDITIONS migration of pea gravel,crushed stone and native soil;it may tear or degrade Where shoring is not required to maintain a vertical wall from top while in service. to bottom of the excavation,and the soil is stable,the minimum spacing between the sidewall or endcap of the tank and side of ®® • • excavation must be 18 inches[24 inches for 12 foot tanks]. If CAUTION: more than one tank is to be installed in the same hole,there must be at least 18 inches between the tanks. Xerxes recommends that every site be thoroughly evaluated for the potential to trap water or otherwise subject the tank to a TOP VIEW rise in the local water table.Xerxes recommends that all tanks be anchored in installations in which water may enter the hole. Failure to anchor the tank in a wet hole may damage the tank 112 or surrounding property. =111101111IM11111MIN Prepare a smooth level bed, 12 inches thick,of approved backfill material. Place the tank or tanks onto the bed. Do not set Xerxes tanks directly onto a concrete slab or on timbers,cradles or directly onto the hole bottom. 11140111 Leveling: As the tank is being placed,set the tank pitch as shown FIGURE 4-6 on the site plans.Xerxes does not require that a tank be pitched. All pitch is determined by the tank owners specification. If a double wall tank is pitched,the monitor should be at the low end. UNSTABLE SOIL CONDITIONS Use the tops of the ribs to establish longitudinal level. Establish If the soil has less than 750 lbs./sq.ft.cohesion as calculated lateral level by placing the level across the top of a fitting,a from an unconfined compression test;or in soils having an manway or a collar. ultimate bearing capacity of less than 3500 lbs./sq.ft.;or where When the tank is placed,take the first diameter reading soil will not maintain a vertical wall,the excavation must allow a (Deflection reading"A"on the checklist).See Section 13 for minimum space equal to 1/2 the diameter of the tank between the instructions on taking deflection readings. side and endcap of the tank and the excavation wall to enhance If the tank is to be anchored,install the anchoring hardware at lateral soil resistance.The spacing between adjacent tanks, 18 this time(See Section 7). inches,remains the same.A reinforced concrete slab may be required under the tank for the foundation in the pit bottom.