COMPLIANCE INFO_1999-2001 - Laserfiche WebLink

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0 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 stable, the minimum spacing between the sidewall or endcap of the tank and the side of the excavation must be 18 inches [24 inches for 12 -foot tanks]. 5.2.2.2. If more than one tank is to be installed in the same hole, allow for at least 18 inches between the tanks. (See FIGURE 54.) FIGURE 5-4 5.2.3. UNSTABLE IN SITU SOIL CONDITIONS A CAUTION Xerxes recommends that the tank owner seek the advice of a local foundation professional engineer if the in situ soil is extremely soft or inherently unstable (for example, peat, quicksand, muck, landfill, very soft or highly expansive clay, underground stream, etc.). II 9 5.2.3.1. If the soil has less than 750 lbs./sq. ft. cohesion as 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. (SeeFIGURE5-5.) 5.2.3.2. The spacing between adjacent tanks is to be at least 18 inches. (See FIGURE 5-5.) FIGURE 5-5 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. 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. 5.3.2. Xerxes recommends that geotextile be used when the tank is installed in: • areas with frequently changing groundwater conditions or areas subject to tidal fluctuations, • unstable soils such as cited in SECTION 5.2.3, • water conditions with silty in situ soil. 5.3.3. For further information concerning geotextile specifications and installation procedures, consult the geotextile supplier's installation guidelines or instructions. 5.3.4. Polyethylene film is not considered an effective geotextile material. It may tear or degrade while in service. • is