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2 . If a concrete arch is required, the pipe shall be embedded in carefully <br /> compacted Type 1 material having a minimum thickness equal to 1 /4 the <br /> outside pipe diameter or to a minimum of four inches under the barrel, <br /> which ever is greater, and extending up the sides for a height equal to 1 /2 <br /> of the outside pipe diameter. The top half of the pipe shall be covered with a <br /> monolithic Class C concrete arch having a minimum thickness equal to 1 /4 <br /> the outside diameter of the pipe or a minimum of four inches over the <br /> crown of the pipe, whichever is greater, and extending down the sides for <br /> a depth equal to 1 /2 of the outside pipe diameter. The arch shall have an <br /> over all width equal to 1 1 /4 of the outside diameter of the pipe or a <br /> minimum width equal to the outside diameter of the pipe plus eight inches , <br /> whichever is greater. <br /> B . CLASS B (FIRST-CLASS BEDDING) <br /> 1 . Where Class B Bedding is required, the trench shall be excavated <br /> below the planned bottom of the pipe to a depth equal to 1 /4 the <br /> nominal diameter of the pipe, or 6 inches, whichever is greater. The over <br /> excavated depth shall be backfilled using either Type 1 or Type 3 materials <br /> carefully compacted and shaped using hand tools so as to provide a <br /> uniform support for the lower portion of the pipe barrel . Shaping under <br /> the pipe bells shall be so that the bell does not support the pipe and joints can <br /> be made without bedding material interference . <br /> 2 . At the option of the Contractor, Class B Bedding may be used in place of <br /> Class C (Ordinary Bedding) provided that the exercise of this option shall <br /> create no additional expense to the Owner. The Contractor shall notify the <br /> Engineer in writing of those portions of the project on which he proposes to <br /> exercise this option. <br /> C . CLASS C (ORDINARY BEDDING) <br /> 1 . The bottom of the trench shall be hand shaped to provide a firm <br /> bedding for the utility pipe . The utility shall be firmly bedded in <br /> undisturbed firm soil . The bedding shall be shaped so that the pipe will be in <br /> continuous contact therewith for its full length and shall provide a minimum <br /> bottom segment for the pipe equal to 0 . 6 of the outside diameter of the <br /> barrel . Excavation under the bell shall be sufficient so that the bell does <br /> not support the pipe and the joint can be made without interference . <br /> D . UNSUITABLE BEDDING MATERIAL <br /> 1 . Class C Bedding shall be used for all pipeline construction unless <br /> otherwise shown on the Drawings or unless unsuitable material is <br /> encountered at the bedding surface . In the event that the materials <br /> encountered at normal bottom of trench excavation are , in the <br /> judgment of the Engineer, unsuitable to act as foundation for the pipe, such <br /> material shall be excavated for the full width of the trench to the depth <br /> C : \ Down1oad \ techspec - 02403 . doc 02403 - 4 <br />