Specifications include, but are not limited to: All trenches shall be kept free from water during excavation, fine grading, pipe laying, jointing, and embedment operations. Where the trench bottom is wet or otherwise unstable because of the presence of ground water, and in cases where the static ground water elevation is above the bottom of any trench or bell excavation, such ground water shall be lowered to the extent necessary to keep the trench free from water and the trench bottom stable when the work within the trench is in progress. ; When rock, stones, cobble rock, concrete, masonry or other unsatisfactory material is encountered in the excavation, it shall be removed to provide a clearance of at least 6 inches below and on each side of all pipe. When excavation is completed, a bedding of sand, screened stone, or earth that is free from stones, large clods, or frozen earth, shall be placed on the bottom of the trench to the required depths, leveled, and tamped.