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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, carry 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 /> 3 . 04 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 — Excavation and Fill <br /> 02302 - 6 <br />