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such equipment provides an installation consistent with the requirements of this standard, <br />minimum trench widths may be reduced, as approved by the ENGINEER. <br />When supports such as trench sheeting, trench jacks, trench shields or boxes are used, ensure that <br />support of the pipe and its embedment is maintained throughout instailation. Ensure that wall <br />sheeting is sufficiently right to prevent washing out of the trench wall from behind the sheeting. <br />Provide tight support of trench walls below viaducts, existing utilities, or other obstruction that <br />restrict driving of sheeting. <br />Unless otherwise directed by the ENGINEER, sheeting shall not be placed in or below the pipe <br />zone to preclude loss of support of foundation and embedment materials. When specifically <br />allowed by the ENGINEER, sheeting may be placed in or below the pipe zone, with the top of <br />sheeting to be cut off 1.5 feet or more above the crown of the pipe. Leave rangers, whalers, and <br />braces in place as required to support cutoff sheeting and the trench wall in the vicinity of the <br />pipe zone. Timber sheeting to be left in place is considered a permanent structural member, and <br />should be treated against biological degradation (for example, attack by insects or other <br />biological forms) as necessary, and against decay if above groundwaYer. <br />Do not disturb the installed pipe and its embedment when using movable trench boxes and <br />shields. Movable supports should not be used below the top of the pipe zone unless approved <br />methods are used for maintaining the integrity of embedment material. Before moving supports, <br />place and compact ernbedment to sufficient depths to ensure protection of the pipe. As supports <br />are moved, finish placing and compacting embedment. <br />If the ENGINEER permits the use of sheeting or other trench wall supports below the pipe zone, <br />ensure that pipe and foundarion and embedment materials are not disturbed by support removal. <br />Fill voids left on removal of supports and compact all materials to required densities. <br />If ledge rock, hard pan, shale, or other unyielding material, cobbles, rubble or debris, boulders, or <br />stones larger than 1.5 in. (40 mm) are encountered in the trench bottom, excavate a minimum <br />depth of 6 in. (150 mm) below the pipe bottom and replace with proper embedment material. <br />The CONTRACTOR shall be responsible for the satisfactory disposal of excess and unsuitable <br />materials of any sort, and shall be responsible for backfilling, tamping, compacting, and refilling <br />after settlement, of all excavated areas and other land, private and public, damaged or occupied <br />by the CONTRACTOR in the performance of the contract, to as good condition as they were <br />prior to the beginning of the work. It shall be his further responsibility to remove all surface <br />obstruction to his work on easements or sites. He shall protect all pipes, conduits, signs, utility <br />poles, wire, fences, building, and other public or private property improvements adjacent to or in <br />the line of the work. <br />Installation and Backfill of Buried Pipe <br />CONTR.ACTOR shall comply with the "Materials", "Installation", and "Inspection, Handling <br />and Storage" sections of ASTM D-2321, except as modified herein. <br />80 <br />