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1 . EXCAVATION SIZE <br /> a. WARNING: Determine the location of overhead and underground utilities <br /> before excavating. <br /> b. Excavation for underground tanks should be made with due care to avoid <br /> undermining foundations of existing structures. Distance between tanks <br /> and structures must assure that downward forces from loads carried by the <br /> foundations and supports cannot be transmitted to the tanks. <br /> C. The excavation should provide adequate space for the tanks, piping, and <br /> associated equipment, and for the placement and compaction of backfill <br /> materials, particularly under the circumference of the tank shell and ends. <br /> d. The slope of excavation walls is determined by soil conditions, depth of the <br /> excavation and, if workers are required to enter the excavation, safety <br /> considerations. <br /> e. Sizes stated are minimums required for proper tank installation. Local, <br /> state, and federal regulations may require larger excavation. <br /> f. The excavation size shall extend a minimum distance of 12" around the <br /> perimeter of the tank. <br /> g. Excavations where two or more tanks will be installed require a minimum <br /> of 12" between tanks. <br /> h. The excavation depth shall be sufficient for bedding and cover as <br /> determined by NFPA 30 and 31, local, state, and federal codes and the <br /> owner's engineer. <br /> i. For burial depths exceeding 5'-0, consult with a Trusco representative prior <br /> to installation. <br /> j. The total depth of the tank excavation is determined by the tank diameter, <br /> bedding thickness, holddown pad (if required), depth of cover, and slope of <br /> piping. Much of the tank's support is derived from compacted backfill <br /> material which permits the downward forces present to be dissipated <br /> uniformly over a large area. <br /> 2. EXCAVATION PREPARATION <br /> a. The excavation shall be free from rocks or debris larger than the approved <br /> bedding or backfill materials. Damage to the FRP secondary containment <br /> from materials such as rocks or debris will void the warranty. <br /> Installation Instructions -2- Rev. 8/19/94 <br /> Trusco Tank Inc. . P.O. Box 11925 . Fresno, California 93775 . 209-264-4741 . Fax 209-237-3413 <br />