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b-2 . During initial backfilling the fill shall be deposited evenly along both <br /> sides of the pipe from a height not to exceed 2 feet above the top <br /> of pipe, and fill shall not be dropped directly on the <br /> unprotected pipe surface . <br /> b-3 . Where thrust blocks, encasement, or other cast-in-place concrete <br /> items are below grade, no backfilling shall start until the specific <br /> items have been inspected and approved by the Engineer or his <br /> authorized representative. <br /> b-4 . The backfill to one foot above the top of the utility shall be <br /> thoroughly compacted with curved end tamping bars under and on <br /> each side of the pipe and flat tamped between the pipe and trench wall <br /> and shall be completed before the remainder of the trench is <br /> backfilled . Initial backfill shall be compacted to 100 percent of <br /> maximum density as determined by AASHTO T- 180 . No subsequent <br /> backfill will be permitted until the initial backfill has been <br /> accepted by the Engineer or his authorized representative . <br /> 2) Subsequent Backfill <br /> a. Subsequent backfill is that backfill between the initial backfill and <br /> the finished ground level or bottom of subbase . <br /> b . Subsequent backfill material shall be placed full trench width in <br /> horizontal layers not exceeding 12 inches loose depth and <br /> compacted by power-operated tampers, rollers , or vibratory <br /> equipment to a density equal to 98 percent of the maximum <br /> density as determined by AASHTO T480 for pipe placed under <br /> and adjacent to roadways or paved surfaces , and 95 percent under <br /> areas where no pavement is to be constructed and vehicular traffic is <br /> not to pass over the pipe . Each layer shall be compacted to the <br /> specified density prior to placing subsequent layers . The <br /> thickness of the loose layer may be increased when in-place density <br /> tests show that the specified density can be obtained . <br /> 3 ) Backfill Material <br /> a. Type 2 material shall be used for initial backfill and subsequent <br /> backfill with the following conditions : Initial backfill shall <br /> be predominately sandy material free from rock or stone greater <br /> than 1 1 /2 inches diameter, and the maximum allowable dimension of <br /> a stone or rock fragment for subsequent backfill shall be 6 inches . <br /> If in the opinion of the Engineer the Type 2 material will not provide <br /> adequate and uniform support for load distribution to the pipe, the <br /> Contractor shall obtain and place either Type 1 or Type 3 backfill as <br /> determined by the Engineer. <br /> CADownloadVechspec-02601 .doc SC601 -7 <br />