All excavations, where a sidewalk, curb, gutter, or paved street has been cut or where new paving (concrete or asphalt) will be placed shall be backfilled using nonshrinkable backfill. The backfill shall be filled to the subgrade of the undisturbed sidewalk, curb, gutter, paving, or earth surface.
The nonshrinkable backfill shall be a mixture of sand, gravel, Portland cement, and water which flows easily around the utility being covered and develops a 28 day compressive strength of from 30 to 200 psi. No nonshrinkable backfill mix designs shall be used without the approval of the Director of Public Works. Fly ash may be approved in the mix if test data are submitted to indicate the above characteristics are met.
The Director may allow placement of excavated fill in six (6) inch lifts at 95% of maximum density where the opening is very large and the cost of nonshrinkable fill would be prohibitive. In those cases the permit holder will be required to hire an independent soil testing laboratory to test separately each six (6) inch lift for density and certify that each and every lift was compacted to 95% of maximum density.
Graveled streets shall be backfilled with dampened excavated or similar material in successive horizontal layers or lifts not exceeding six (6) inches in thickness and mechanically compacted equal to one hundred percent (100%) of that of the adjacent undisturbed soil. In unimproved areas such as easements and alleys the trench or opening may be backfilled with sand which shall be flushed into place with water; provided, the top twelve inches (12") of backfill shall be made of the excavated top soil.
All surplus excavated material shall be removed from the location by the person, firm, or corporation making an excavation in any street, alley, or public ground in the City. Any person, firm, or corporation having made an excavation in any street, alley or public ground shall maintain all trenches or ditches in a safe condition for the public until the excavated material has reached final settlement.