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3.04 <br />A. Pipe Trenches <br />Excavate trenches to uniform width, sufficiently wide to provide ample working room and <br />a minimum of 9 to 12 inches of clearance on both sides of the pipe or conduit. Grade <br />bottom of trenches to provide uniform support for each section of pipe after pipe bedding <br />placement. <br />B. Excavate trenches to depth indicated or required to establish indicated slope and invert <br />elevations and to support bottom of pipe or conduit on undisturbed soil. <br />1. Where rock is encountered, cavy excavation 6 inches below required elevation and <br />backfill with a 6 -inch layer of tamped sand or gravel prior to installation of pipe. <br />2. For pipes or conduit less than 6 inches in nominal size, and for flat-bottomed, multiple - <br />duct conduit units, do not excavate beyond indicated depths. Hand -excavate bottom <br />cut to accurate elevations and support pipe or conduit on undisturbed soil. <br />3. For pipes and equipment 6 inches or larger in nominal size, shape bottom of trench to <br />fit bottom of pipe for 90 degrees (bottom 1/4 of the circumference). Fill depressions <br />with tamped sand backfill. At each pipe joint, dig bell holes to relieve pipe bell of <br />loads and to ensure continuous bearing of pipe barrel on bearing surface. <br />FILLING AND BACKFILLING <br />Fill and backfill to contours, elevations, and dimensions indicated. Compact each lift before placing <br />overlaying lift. <br />B. Unsuitable Material Replacement <br />Fill material shall be placed and spread evenly in layers not to exceed twelve inches before <br />compaction. All fill material shall be free from vegetable matter, wood, and other <br />deleterious substances, and shall not contain rocks or clods having a diameter of more than <br />three inches. <br />B. Pre -fill Compaction <br />Should the pre -fill surface elevation be below that required for the base of proposed <br />building foundations or paving subgrade, the areas within road rights -of -ways, under <br />parking areas, and the areas under and within five feet of proposed buildings shall be <br />precompacted. This precompaction shall be performed equally on existing ground and on <br />surfaces which have been excavated to remove unsuitable material. The top one foot of <br />said areas shall be compacted to a minimum density of 95% of maximum as determined by <br />AASHTO T-180. The maximum spacing between density tests shall be 150 feet. <br />B. Compaction <br />Backfill material shall be compacted to 95% of maximum density per AASHTO T-180. <br />Equipment suitable and adequate for uniform compaction to the specified density shall be <br />used for backfill operations subject to the approval of the Engineer. All compaction <br />equipment shall be in good working order and any worn or defective equipment shall be <br />immediately replaced or repaired. <br />02302 - 6 <br />02302 — Excavation and Fill <br />