(A) As soon as the condition of the pipe will permit, the entire width of the trench shall be backfilled, with moist fine aggregate to a height of at least the elevation of the center of the pipe. The fine aggregate shall be placed longitudinally along the pipe. The elevation of the backfill material on each side of the pipe shall be the same. Special care shall be taken to completely fill the space under the pipe. The fine aggregate backfill material shall be placed in four inch layers, loose measurement, and compacted to the satisfaction of the Engineer by ramming or tamping with tools approved by the Engineer. The fine aggregate used for backfilling shall meet the approval of the Engineer.
(B) The remainder of the trench and excavation shall be backfilled to the natural line or finished surface as rapidly as the condition of the sewer will permit. The backfill material shall consist of the excavated material or trench backfill as herein specified. All backfill material shall be deposited in the trench or excavation in such a manner as not to damage the sewer. The filling of the trench shall be carried on simultaneously on both sides of the pipe in such a manner that injurious side pressures do not occur. The backfill for trenches and excavation made in the sub-grade of the proposed improvement, and for all trenches outside of the sub-grade where the inner edge of the trench is within two feet of the edge of the proposed pavement, curb, gutter, curb and gutter, stabilized shoulder or sidewalk, shall be made with trench backfill material unless the excavated material meets the requirements of § 211 of the Indiana State Highway Standard Specifications.
(C) All backfill material up to a height of 12 inches above the pipe shall be carefully deposited in uniform layers not exceeding four inches thick (loose measure). The material in each layer shall be firmly compacted by ramming or tamping with tools approved by the Engineer, in such a manner as not to disturb or injure the pipe. The backfilling above this height shall be done by Method 1, 2 or 3 below.
(D) When required, trench backfill material or excavated material meeting the requirements of § 211 of the Indiana State Highway Specifications above the first 12 inches above the pipe shall be compacted by either Method 2 or Method 3 specified below, or in accordance with Method 1 except that the compacted lifts shall not exceed four inches in thickness.
Method 1: The material shall be deposited in uniform layers not exceeding twelve 12 inches thick (loose measure) and each layer shall be compacted by ramming or tamping with tools approved by the Engineer.
Method 2: The material shall be deposited in uniform layers not exceeding 12 inches thick (loose measure), and each layer shall be either inundated or deposited in water.
Method 3: The trench shall be backfilled with loose material and settlement secured by introducing water through holes jetted into the backfill to a point approximately two feet above the top of the pipe. The holes shall be spaced as directed by the Engineer, but shall not be any further than six feet apart.
(E) The water shall be injected at a pressure just sufficient to sink the holes at a moderate rate of speed. The pressure shall be such that the water will not cut cavities in the backfill material nor overflow the surface. If water does overflow the surface, it shall be drained into the jetted holes by means of shallow trenches. Water shall be injected as long as it will be absorbed by the backfill material and until samples taken from test holes in the trench show a satisfactory moisture content. The Contractor shall bore the test holes not more than 50 feet apart and at such other locations in the trench designated by the Engineer. As soon as the water soaking has been completed, all holes shall be filled with soil and compacted by ramming with a tool approved by the Engineer.
(F) Backfill material which has been water soaked shall be allowed to settle and dry for at least ten days before any surface course or pavement is constructed on it. The length of time may be altered if deemed desirable by the Engineer.
(G) Where the inner edge of the trench is within two feet of the edge of the proposed pavement, curb, gutter, or curb and gutter, the provisions of this paragraph shall also apply.
(H) At the end of the settling and, drying period, the crusted top of the backfill material shall be scarified and, if necessary, sufficient backfill material added, as specified in Method 1, to complete the backfilling operations.
(I) The method used for backfilling and compacting the backfilling material will be the choice of the Contractor. However, if the method used does not produce results satisfactory to the Engineer, the Contractor will be required to alter or change the method being used so that the resultant backfill will be satisfactory to the Engineer.