COMPLIANCE INFO_1999-2005 - Laserfiche WebLink

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5.2.3.1.If the soil has less than 750 lbs./sq.ft.cohesion as Tank Shadow calculated from an unconfined compression test;or in soils having an ultimate bearing capacity of less than 3,500 lbs./sq. ft.;or where soil will not maintain a vertical wall,the excavation must allow a minimum space equal to half the diameter of the tank between the side and the endcap of the tank,and the excavation wall to enhance lateral resistance. (See FIGURE5-5.) 5.2.3.2.The spacing between adjacent tanks is to be at least 18 inches. (See FIGURE 5-5.) 2 x Width 1/2 Tank Width(See TABLE 6-1.) Dia. �s PHI FIGURE 5-3 5.2.2.STABLE IN SITU(NATIVE)SOIL CONDITIONS 5.2.2.1.Where shoring is not required to maintain a vertical wall from top to bottom of the excavation,and where the soil is 1/2 Tank Dia. 1/2 Tank Dia. stable,the minimum spacing between the sidewall or endcap of the tank and the side of the excavation must be 18 inches unstable soil [24 inches for 12-foot tanks]. 5.2.2.2. If more than one tank is to be installed in the same hole, FIGURE 5-5 allow for at least 18 inches between the tanks.(See FIGURE 54.) 5.2.3.3.A reinforced concrete slab may be required under the tank as a foundation in the excavation where the bottom is unstable. 5.3.GEOTEXTILE 5.3.1.The tank owner or the owner's technical representative is responsible for determining whether a geotextile or an alternate filtering technique is appropriate for a specific installation. 18" 18" 1s° Geotextile allows the passage of water,but prevents the migration and mixing of in situ soil and the select backfill material.Geotextile helps preserve the integrity of the select backfill envelope,which surrounds and supports the tank. 18" 18" 5.3.2.Xerxes recommends that geotextile be used when the stable soil tank is installed in: • areas with frequently changing groundwater conditions or FIGURE 5-4 areas subject to tidal fluctuations, • unstable soils such as cited in SECTION 5.2.3, • water conditions with silty in situ soil. 5.2.3.UNSTABLE IN SITU SOIL CONDITIONS 5.3.3.For further information concerning geotextile specifications ACAUTION and installation procedures,consult the geotextile supplier's installation guidelines or instructions. Xeres recommends that the tank owner seek the advice of a local foundation professional engineer if the in situ soil is 5.3.4.Polyethylene film is not considered an effective geotextile extremely soft or inherently unstable (for example, peat, material.It may tear or degrade while in service. quicksand, muck, landfill, very soft or highly expansive clay, underground stream, etc.). 11