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• An important characteristic of good backfill material is hardness or stability when exposed to water or loads. Most materials have no problem meeting the hardness requirement. • Materials like soft limestone, sandstone, sea shells or shale should not be used as backfill because they may break down overtime. • When using select rounded stones, they must conform to the specifications of ASTM C 33, size numbers 6, 67 or 7. See Primary Backfill Requirements (Appendix C) foradditional information on backfill material specifications. • When using select crushed stones, they must conform to the specifications of ASTM C 33, size numbers 7 or 8. See Primary Backfill Requirements (Appendix C) for additional information on backfill material specifications. 1.2.2.2. We recommend that the supplier of backfill material provide the tank installer and tank ownerwith written certification that the material conforms to ASTM C 33, ASTM D 448, AASHTO M 43, and any other applicable specifications. 1.2.2.3. If primary backfill material which meets these specifications is not available, contact technical support (ena.sunoort@zcl.com) for information on alternate materials, installation instructions for alternate materials and the process for approval. 1.2.3. SECONDARY BACKFILL 1.2.3.1. When used (see Appendix D), secondary backfill material must meet the following specifications: • Material is to be clean, free-flowing, and free of large rocks, roots, organic materials, debris, ice and snow. • Backfill material shall not be frozen or contain lumps of frozen material at any time during placement and compaction. • Material must be compacted to achieve a minimum of 85 percent standard proctor density. • 100% of all backfill material must pass through a 1 -inch [25 -mm] sieve. 1.2.3.2. Material must be installed in 12 -inch to 24 -inch [30 -cm to 61 -cm] lifts compatible with the compaction equipment used. 1.2.3.3. In some conditions, frost heave may be encountered when using secondary backfill. Therefore, consider any frost -related problems that may occur. 1.2.3.4. Specifications for secondary backfill material and compaction above the filter -fabric layer may be determined by the requirements of the piping, surface slab or roadway. 1.2.3.5. Refer to applicable codes or standards for base course and sub -base course material and compaction requirements. 1.2.3.6. The following are examples of acceptable secondary backfill material: • clean native backfill • coarse sand • gravel 1.2.4. GEOTEXTILE 1.2.4.1. Using geotextile fabric is considered good installation practice and using it in any installation is recommended, especially when the tank is installed in the following conditions: • areas with frequently changing groundwater conditions or areas subject to tidal fluctuations • unstable soils such as those cited in section 1.3.5.3 • water conditions with silty in-situ soil 1.2.4.2. Geotextile helps preserve the integrity of the select backfill envelope that surrounds and supports the tank. • Geotextile fabric allows the passage of water in and out of the excavation but prevents the migration and mixing of in-situ soil and the select backfill material. • Polyethylene film is not considered an effective geotextile material because it may tear or degrade while in service. • If geotextile is used, install geotextile before placing bedding material. • 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. 1.2.4.3. Where both primary and secondary backfill are used, a layer of geotextile filter fabric must be installed overthe entire surface of primary backfill material before secondary backfill is placed. Note the following instructions: • All joints in the filter fabric must be overlapped a minimum of 12 inches [30 cm]. • Geotextile fabric must overlap onto the tank and excavation surface a minimum of 12 inches [30 ml]. • See Split Backfill Instructions (Appendix D) for more information regarding this installation situation. 1.3. EXCAVATION REQUIREMENTS A WARNING Consult OSHA's regulations, and/or applicable Canadian federal, provincial and municipal safety codes and operational regulations, whichever are relevant. Collapse of excavation walls could result in death or serious injury. 1.3.1. GENERAL 1.3.1.1. The installing contractor must take all necessary precautions in or near a tank excavation. These precautions should include but are not limited to the following: • Locate and protect any utility installations near the excavation before opening the excavation. • Secure the walls of the excavation. • Take appropriate precautions to protect against exposure to hazardous vapors from the excavation. • Avoid hazards associated with water accumulation in the excavation. • Erect barricades, etc., to prevent unauthorized vehicle or pedestrian traffic. • Inspect, a minimum of once a day, the excavation and surrounding area during the entire installation process. 1.3.1.2. Foradditional information on excavation, trenching and shoring safety practices, consult OSHA's regulations, and/or applicable Canadian federal, provincial and municipal safety codes and operational regulations, whichever are relevant. A WARNING Follow OSHA regulations or consult your local Canadian regulations concerning tank excavations, whichever are relevant. Collapse of excavation walls could result in death or serious injury. 1.3.1.3. The minimum clearance dimensions given in this section are important to the successful installation of a tank. 1.3.1.4. Additional clearances may be necessary due to regulations, safety requirements or operational requirements of governmental agencies. Follow all applicable regulations and safety practices. 05