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A. Backfill Materials: All backfill materials used after any street cut shall be free from cinders, ashes, refuse, organic and frozen material, boulders, or other materials that are unsuitable. From one foot (1') above the top of pipe to six inches (6") below the ground surface, or to the subgrade elevation for streets or paved surfaces, material containing stones up to eight inches (8") in the greatest dimension may be used. Trench backfill from the top of the pipe to ground surface or to the subgrade of street surfacing is separated into two (2) classifications. Type A trench backfill refers to compacted backfill in streets or paved areas, while type B backfill is designed for alleys, fields, borrow pits, unimproved streets or other unsurfaced areas where special compaction of the trench backfill is not required. Location of the types of backfill required shall be as shown on the plans or as designated in the special provisions.
B. Type A Trench Backfill: Materials used for bedding and backfill should be carefully deposited in layers suitable to the equipment used for compaction, wetted to optimum moisture content and compacted to at least the density of the surrounding material. The upper layer forming the subgrade for pavement which is to be replaced shall be compacted to a density of at least ninety percent (90%) of maximum standard proctor density, as determined by AASHTO designation T-180 method A or C. Compaction by flooding will only be permitted by approval of the Town Engineer. Wherever the trenches have not been properly filled, or if settlement occurs, they shall be reopened to the depth required for proper compaction and refilled and recompacted.
C. Type B Trench Backfill: Materials used for type B trench backfill shall not require special compaction. However, the material shall be placed in layers to achieve a density approximately equal to the density of the existing soil. The person doing the work may be required to mound excess earth over the top of the trench so that depression will not be formed after the trench settles. In cultivated areas, the stripped topsoil shall be placed uniformly over the backfilled trench. The topsoil shall not be compacted but shall be graded to provide a smooth surface conforming to the adjoining ground surface. (1993 Code § 12.08.090)