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GENERAL MECHANICAL MATERIALS AND METHODS <br />Section 15050 <br />15-1207 <br />3.12 CONCRETE <br />A. Where specifically indicated on the Drawings or specified as part of Mechanical Work, this <br />Contractor shall furnish and install concrete work, such as thrust blocks or spring isolator <br />bases. <br />B. Concrete and reinforcing steel shall be equal to that specified for General Construction. <br />C. Except as noted above, concrete work will be furnished and installed under General Work. <br />This Contractor shall coordinate requirements accordingly. <br />3.13 EXCAVATING AND BACKFILL <br />A. Perform all excavating required for work of this Section. Do excavating required for <br />installation of piping and service lines and other work that applies as indicated on Drawings. <br />Verify location and elevation of all existing utilities prior to excavation for installation of new <br />piping. Provide the services of a pipe/cable locating service prior to excavating activates to <br />determine location of existing utilities <br />B. Excavations shall be of open vertical construction of sufficient width to provide free working <br />space at both sides of trench and around pipe as required for caulking, joining, backfilling, <br />and compacting. Unless shown otherwise, provide a minimum of 2'-6" cover above top of <br />pipe to finished grade for all service piping unless otherwise noted. Trim trench bottom by <br />hand or provide a minimum of 4" deep sand bed to provide a uniform grade and firm support <br />throughout entire length of pipe. For PE gas pipe, bed the pipe in a 4" sand bed. <br />C. Dig trenches straight and true to line and grade with holes for bells for bell -and -spigot pipe. <br />Evenly support piping for its entire length upon outside periphery of lower one-third of pipe. <br />Where rock is encountered, undercut trenches 3 inches and fill with well -tamped, clean sand <br />and pea gravel to correct pipe elevation. <br />D. After pipe lines in excavation have been installed and tested, backfill excavation to point 6 <br />inches above pipe using sand, fine earth, or other materials free of rocks and large lumps. <br />Proceed evenly on both sides of pipe and continuously tamp. Except as hereinafter noted, <br />backfill above 6 inches above top of pipe shall be made by using earth from excavation <br />placed in layers of 8 -inch maximum depth. Compaction of each successive layer will be <br />made with mechanical compactor. <br />E. Take special care in backfilling over wrapped piping to prevent damage to protective <br />wrapping. <br />F. Bed sewers under pavements, wrapped piping, and PVC piping in sand prior to backfilling. <br />Backfill to point 6 inches above pipe with sand. <br />G. This Contractor shall replace sod, concrete, asphalt paving, curbs, pavement, walks, and <br />any other type of existing work or surface disturbed by excavation, using workmen skilled in <br />trade involved. <br />H. When pipe or underground conduit with a protective wrapping is to be placed in the trench, <br />sand only shall be used for bedding the pipe or conduit. The sand used shall be certified to <br />have a minimum resistance of 5000 ohms per cubic centimeter when wetted to any moisture <br />12 <br />