the circumference of the pipe will rest firmly on undisturbed soil. d. Excavations for prefabricated sheet metal manholes shall be sufficient to permit of proper installation, and for formed concrete work shall be as required to suitably form the same. e. Depth of trenches shall be as required for Slopes shown on the drawings or as directed by Engineer. Unless otherwise directed the minimum distance from top of pipe to finished grade shall be 2'-6". f. Except at locations where excavation of rock is required, care shall be taken not to excavate below Specified depths. Where rock is encountered during excavating, the rock shall be removed to a minimum over- depth of é inches below the required trench depths. The overdepth rock excavation and all excessive trench excavation shall be backfilled with loose, moist sand, thoroughly tamped to the satisfaction of the Engineer. 4-04, BACKFILL: a. No backfilling of excavations shall proceed until work therein has been inspected and approved by the Engineer. b. Backfill material shall be finely divided material from excavations as approved by the Engineer, Shall be free of debris and organic matter, and shall be dampened to optimum moisture content. Material for backfilling up to a level of 1 foot above top of pipe shall be free of rocks. c. Backfilling of trenches prior to testing of pipe therein shall be the minimum required to maintain position. Pipe joints shall remain uncovered until testing is completed. dad. Backfill for pipe installed or structure completed shall be placed alongside the pipe or structure in layers not exceeding 6 inches in depth. Backfill shall be placed in a Symmetrical manner and care shall be taken to prevent any wedging action or eccentric loading on or against the pipe or structure. permitted and may be required. Water settling will be e. Surface finish shall conform to natural ground contours aS approved by the Engineer. Additional back- 4-2