When back-filling is to be done by water settling and before any compacting of the trenches is attempted, the permittee shall cause the loose material to be wetted by forcing a head of water of not less than 30 feet in height, down into the soft material so that the end of the pipe is not more than 3 feet above the bottom of the excavation. The permittee shall allow the water to run until the material is saturated as indicated by the water rising and running out on the surface of the ground around the pipe. After each hole has been saturated the jet pipe shall be moved along the trench line a distance of approximately 4 or 5 feet, but in no case more than 8 feet, and the process repeated for the entire length of the back-fill trench. All work shall be done in such a manner as to obtain a relative compaction throughout the entire depth of the back-fill of not less than existing adjacent to the excavation. Any deviation from the method set forth above shall have prior written approval of the Public Works Director.