A. Excavation: Trenches shall not be excavated more than three hundred feet (300') in advance of pipe laying, nor left unfilled for more than seven hundred feet (700') where pipe has been laid, except by special permission from the city engineer. The length of the trench that may be opened at any time shall not be greater than the length of pipe and the necessary accessories which are available to the site ready to be put in place.
B. Completed Trench: The completed trench shall be kept not less than thirty feet (30') ahead of the pipe layers. Trenches shall be at least six inches (6") wider on each side or a total width of twelve inches (12") more than the exterior diameter of the pipe, except where pipes are four inches (4") or less in diameter. Where excavation is made in rock, a minimum of six inches (6") of noncorrosive soil, sands or fine existing spoils shall be used as a padding beneath the pipe and an additional six inches (6") above the pipe.
C. Manholes And Other Structures: Excavation for manholes and other structures shall be sufficient to leave at least twelve inches (12") between their outer surfaces and the sides of the excavation. (1959 Code § 4-7-9)