BACKFILLING =197. Methods.=—Careful backfilling is necessary to prevent the displacement of the newly laid pipe and to avoid subsequent settlement at the surface resulting in uneven street surfaces and dangers to foundations and other structures. The backfilling should commence as soon as the cement in the joints or in the sewer has obtained its initial set. Clay, sand, rock dust, or other fine compactible material is then packed by hand under and around the pipe and rammed with a shovel and light tamper. This method of filling is continued up to the top of the pipe. The backfill should rise evenly on both sides of the pipe and tamping should be continuous during the placing of the backfill. For the next 2 feet of depth the backfill should be placed with a shovel so as not to disturb the pipe, and should be tamped while being placed, but no tamping should be done within 6 inches of the crown of the sewer. The tamping should become progressively heavier as the depth of the backfill increases. Generally one man tamping is provided for each man shoveling. TABLE 70 DIVISION OF COSTS FOR THE CONSTRUCTION OF CONCRETE SEWERS Gillette’s Handbook of Cost Data. ──────────────┬──────────────────────────────────────────────────────── Item │ Location ──────────────┼─────────┬────────┬──────────┬────────────────────────── │ Fond du │ South │ │ │ Lac │ Bend │Wilmington│ Richmond, Indiana ──────────────┼─────────┼────────┼──────────┼────────┬────────┬──────── Diameter in │ │ │ │ │ │ inches │ 30 │ 66 │ 53 │ 54 │ 48 │ 42 Shape │circular │circular│horseshoe │circular│circular│circular Plain or │ │ │ │ │ │ reinforced │ plain │ rein. │ rein. │ rein. │ rein. │ rein. Cubic yards │ │ │ │ │ │ per foot │ 0.11 │ 0.594 │ 0.37 │5″ shell│5″ shell│4″ shell Daily │ │ │ │ │ │ progress, │ │ │ │ │ │ feet │ 47 │24 to 36│ │ │ │ Cost per foot,│ │ │ │ │ │ dollars │ 1.20 │ 4.40 │ 2.97 │ 1.35 │ 1.08 │ 0.91 Per cent of │ │ │ │ total cost: │ │ │ │ Labor │39.0[103]│ 33.5 │ 33.0 │ =17.1= Tools │ 1.5 │ 11.5 │ │ Sand and │ │ │ │ gravel │ 12.4 │ 15.5 │ 18.9 │ =19.3= Lumber │ 0.9 │ │ │ Water │ 0.7 │ 11.5 │ │ Reinforcing │ 0.0 │ │ 14.5 │ =22.3= Cement │ 23.0 │ 20.0 │ 27.5 │ =32.0[104]=