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• An important characteristic of good backfill material is hardness 1.2.4.2.Geotextile helps preserve the integrity of the select backfill orstabiIitywhen exposed to water or loads.Most materials have envelope that surrounds and supports the tank. no problem meeting the hardness requirement. • Geotextile fabric allows the passage ofwaterin and outofthe excavation • Materials like soft limestone,sandstone,sea shells orshale should but prevents the migration and mixing of in-situ soil and the select not be used as backfill because they may break down overtime. backfill material. • When using select rounded stones,they must conform • Polyethylene film is notconsidered an effective geotextile material to the specifications of ASTM C 33,size numbers 6,67 because it may tearer degrade while in service. or 7.See Primary Backfill Requirements(Appendix C) • If geotextile is used,install geotextile before placing bedding material. for additional information on backfill material specifications. • The tank ownerorthe owner's technical representative is responsible • When using select crushed stones,they must conform to the for determining whether a geotextile or an alternate filtering specifications of ASTM C 33,size numbers 7 or8.See Primary technique is appropriate for a specific installation. Backfill Requirements(Appendix C)foradditional information 1.2.4.3.Where both primary and secondary backfill are used, on backfill material specifications. a layer of geotextile filterfabric must be installed overthe entire 1.2.2.2.We recommend thatthe supplier of backfill material provide surface of primary backfill material before secondary backfill the tank installerand tank owner with written certification is placed.Note the following instructions: that the material conforms to ASTM C 33,ASTM D 448,AASHTO M 43, • All joints in the filterfabric must be overlapped a minimum and any other applicable specifications. of 12 inches[30 cm]. 1.2.2.3.If primary backfill material which meets these specifications • Geoitniextilefabricmust overlap onto the tank and excavation surface a mmum of 12 inches 130 ml]. is not available,contact technical support(eea.su000rt@zcl.com)for . See Split Backfill Instructions(Appendix D)for more information information on alternate materials,installation instructions foralternate regarding this installation situation. materials and the process for approval. 1.2.3.SECONDARY BACKFILL 1.3.EXCAVATION REQUIREMENTS 1.2.3.1.When used(see Appendix D),secondary backfill material A WARNING must meet the following specifications: Consult OSHA's regulations,and/or applicable Canadian federal, • Material is to be clean,free-flowing,and free of large rocks, provincial and municipal safety codes and operational regulations, roots,organic materials,debris,ice and snow. whichever are relevant.Collapse of excavation walls could result • Backfill material shall not be frozen or contain lumps of frozen in death or serious injury. material at any time during placement and compaction. 1.3.1.GENERAL • Material must be compacted to achieve a minimum of 85 percent standard proctor density. I.3.I.I.Theinstalling contractor must take all necessary precautions • 100%of all backfill material must pass through a 1-inch[25-mm]sieve. in or neara tank excavation.These precautions should include but are not limited to the following: 1.2.3.2.Material must be installed in 12-inch to 24-inch[30-cm • Locate and protect any utility installations nearthe excavation before to 61-cm]lifts compatible with the compaction equipment used. opening the excavation. 1.2.3.3.In some conditions,frost heave may be encountered when • Secure the walls of the excavation. using secondary backfill.Therefore,consider any frost-related problems • Take appropriate precautions to protectagainst exposure to hazardous that may occur. vapors from the excavation. • Avoid hazards associated with water accumulation in the excavation. 1.2.3.4.Specifications for secondary backfill material and compaction • Erect barricades,etc,to prevent unauthorized vehicle or pedestrian traffic above the filter-fabric layer may be determined by the requirements of the • Inspect,a minimum of once a day,the excavation and surrounding piping,surface slab or roadway. area during the entire installation process. 1.2.3.5.Refer to applicable codes or standards for base course 1.3.1.2.For additional information on excavation,trenching and shoring and sub-base cou rse material and compaction requirements. safety practices,consult OSHA'sregulations,and/or applicable Canadian 1.2.3.6.Thefollowing are examples of acceptable secondary backfill material: federal,provincial and municipal safety codes and operational regulations, • clean native backfill whichever are relevant. • coarsesand A WARNING • gravel Follow OSHA regulations or consult your local Canadian regulations 1.2.4. GEOTEXTI LE concerning tank excavations,whichever are relevant.Collapse of excavation walls could result in death or serious injury. 1.2.4.I.Usinggeotextilefabricisconsideredgoodinstallationpractice .1.3.The minimum clearance dimensions given in this section and using it in any installation is recommended,especially when the tank are1.3.1.3. Timportantto the successful installation of a tank. is installed in the following conditions: • areas with frequently changing groundwater conditions or areas 1.3.1.4.Additional clearances maybe necessary due to regulations, subject to tidal fluctuations safety requirements or operational requirements of governmental • unstable soils such as those cited in section 1.3.5.3 agencies.Follow all applicable regulations and safety practices. • water conditions with silty in-situ soil I: PLANNING FOR INSTALLATION 05