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' exercises the option to use Class B Bedding at no extra cost to the OWNER . ' C . Unsuitable Bedding Material : If the materials encountered at the normal bottom of the trench excavation are in the sole judgment of the ENGINEER , ' unsuitable to act as foundation for the pipe , such material shall be excavated to the depth necessary to obtain a suitable foundation . ( Refer to paragraph 3 . 4 , " Removal of Muck , Rock and Other Unstable Material . " ) Remove the unsuitable material and replace it with "Type 3 " material as defined in paragraph 2 . 1 . C . ' D . Pipe Trench Backfill : 1 . Place all backfilling in pipe trenches that are below structures , other pipes or paved areas , in horizontal layers not exceeding 6 -inches in ' depth and thoroughly compact each before the next layer is placed . In other pipe trenches , compacted layers shall be 6- inches thick up to the pipe centerline and up to 12 - inches thick thereafter. 2 . Backfill shall be deposited evenly along both sides of the pipe from a maximum height of 2 feet above the top of the pipe . Material shall not be dropped directly on the unprotected pipe surface . ' 3 . Where thrust blocks , encasement , or other cast-in - place concrete items are used , no backfilling shall be placed until the specific items have been observed and accepted by the ENGINEER . ' 4 . Backfill Material : a . In most circumstances , excavated material from the pipe trench should be acceptable as backfill . This backfill material must meet ' the requirements of "Type 2 " material as defined in paragraph 2 . 1 . 13 . Otherwise , use "Type 3 " material as defined in paragraph ' 2 . 1 . C . b . The backfill from the trench bottom to 124ches above the top of the pipe shall not contain rock or stone fragments greater than 1 - ' 1 /2 inches diameter. The maximum diameter of a rock or stone fragment in the rest of the backfill shall not exceed 6- inches . E . Compaction Methods : ' 1 . All backfill to the springline ( centerline ) of the pipe shall be thoroughly compacted with curved end tamping bars under and on each side of ' the pipe and flat tamped between the pipe and the trench wall . This compaction shall be completed before the remainder of the trench is backfilled . Take extra care to adequately compact the haunch area of the pipe without lifting the pipe off the bedding . The remainder of the ' backfill may be compacted by power-operated tampers , rollers , or vibratory equipment . Last revised 9/ 10/02 02220- 18 EAST GIFFORD FAPublic Works\KeithM\stop-nmter Projects\Gfford East\Construction Contract\Technical Specifications\Final Specifications\Division ' 2\02220 - Excavation and Backill .doc