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EXCAVATION GEOTEXTILE FABRIC 6.3. Shoring Removal 6.4.4.3. Equipment creating vibrations must be placed outside the boundaries of the excavation. 7. GEE FABRIC OTEXTILI Removal of shoring can cause backfill to move and 71Geotextile fabric(filter fabric)allows the tank to lose support, resulting in an excessive tank . passage of water but prevents the migration of deflection.Tank and/or property damage can occur. approved backfill into the native soil and native 6.3.1. After the backfill is properly placed completely soil into the approved backfill.Migration may around the tank(s): compromise the backfill support of the tank. 6.3.1.1. Vibrate shoring and pull slowly to top of 7.2. Geotextile Fabrics are re uired for an backfill. o the o owing insta atlons 6.3.1.2. Fill any voids created by the pulled 7.2.1. Areas subject to tidal conditions. shoring with approved backfill. 7.2.2. Areas subject to frequently changing ground 6.3.2. All shoring should be removed and all voids water levels. must be filled using a long handled probe 7,23. Water conditions with silty soil. before continuing installation. 7,2,4. Muck,bo 6.3.3. If side shoring is left in place,the shoring must g•peat,swamp,landfill type areas not degrade over the life of the installation. ior n any other situations where the soil is inany unstable. 6.3.4. Shoring system components cannot be placed 7.2.5. Soils with less than 250 lbs./sq.ft cohesion or under the tank. with ultimate bearing capacity of less than 500 6.4. Tank Location - Nearby Structures lbs./sq.ft. 6.4.1. CSI recommends that the tank owner seek 7,2,6. Alternate installation methods may the advice of a local foundation professional also require geotextile fabrics.Refer to engineer to determine the proper placement Supplemental Documents (Section 21)for of a tank excavation near any slabs or additional information. foundations. 6.4.2. The location of a tank can be affected by 7.3. The tank owner or tank owner's representative the location of nearby structures.When may also specify the use of geotextile fabrics. selecting a tank site,care must be taken to 7.4. Non-degradable geotextile fabric can be either avoid undermining the foundations of new or woven or non-woven and should have the existing structures. following properties: 6.4.3. Ensure that downward forces from loads • Minimum grab tensile strength of 120 lbs carried by the foundations and supports of (ASTM D4632). nearby structures(constructed before or after • Maximum apparent opening size of 0.300 tank installation)are not transmitted to the mm#50 US sieve(ASTM D4751). tanks.(Refer to NFPA 30 for additional details). Minimum flow rate of 18 gallons/min/ft2 6.4.4. The placement of the installed underground (ASTM D4491). tank is not designed for any of the following: 6.4.4.1. Additional static loads on the slab that • Minimum permittivity of 0.28 sec-1 will cause the load at the tank top to (ASTM D4491). exceed 936 lbs/cubic ft. 7.5. Do not use plastic,or any other material that 6.4.4.2. Adjacent slab,footing or foundation that may tear or degrade over time,as a replacement will place loads on the tank top or sides. for geotextile fabric. This is typically accomplished by insuring 7.6. Geotextile Fabric Installation that the tank is not located within the 7,6.1. Line the side and bottom of the excavation load distribution of any adjacent slabs or with geotextile fabric. foundations using 45°as the angle of the projected loads(see Figure 6-3). 7.6.2. Overlap adjoining geotextile panels a Figure 63 minimum 12". Overburden Footing overburden w i Slab or Foundation 7.6.3. Place backfill on top of the geotextile fabric to -- ---- hold it in place. Footing Slab or Foundation 7,6.4. In wet hole conditions,backfill on top of the Shadow of45°Angle geotextile fabric is necessary to sink and hold 5hadowof45°Angle it in place. Tank Tank 13