(A) Backfill shall consist of sound earth material (other than open graded rock) free from concrete, timber, asphalt pavement or other debris. When select material, or A.B.C. material, is substituted or specified, it shall conform to the applicable specifications for construction of highways of the M.A.G. Specifications.
(B) Compaction of backfill materials shall be governed by the following:
(1) That portion of the backfill from the bottom of the trench to eight inches, compacted depth, over the top of the pipe shall be back-filled with uniformly graded material with maximum size passing a one and one-eight-inch screen. This material shall be uniformly jetted to ensure proper bedding of pipe. Backfill around underground electric lines must meet the specification of the responsible electrical utility.
(2) For the purpose of these special provisions, WATER SETTLING is defined as the addition of water to backfill material in an excavation in such a quantity as to make the water content of the material higher than the optimum moisture as determined by Standard Proctor Test (AASHO T-99). Water settling is not permitted where the excavation is in an existing pavement or where any portion of the excavation falls within a distance from the edge of existing pavement or back of curb equal to one- half the depth of the trench, measured from the edge of pavement or gutter line.
(3) Water settling is permitted in new subdivisions under the following conditions:
(a) Fill material in lifts not exceeding eight feet in depth shall be leveled, the trench flooded and the material jetted to within one foot of the pipe with sufficient water to ensure filling of all voids with backfill material.
(b) No paving will be permitted over water settled trenches until compaction test results have been approved by the Director of Public Works. Water settling is permitted beyond the limits of division (B)(2) above with a required compaction of 85%, or the natural compaction of the native material, whichever is higher.
(C) Where an excavation meets the criteria of division (B)(2) above, the excavation shall be filled with A.B.C. or granular select material, placed at optimum moisture in lifts sufficiently thin to ensure required compaction for the full depth of the lift, and in no case greater than 30 inches compacted depth, unless previously approved in writing by the Director of Public Works. Granular select material shall not exceed three inches in diameter and shall be graded in such a manner as to ensure the exclusion of any and all voids in the backfill. The upper two feet is to be mechanically compacted to not less than 95% of maximum density. Sufficient water may be added to raise the moisture content to optimum only. Below these two feet, the material shall be compacted to not less than 85% of the maximum density for the backfill material as determined by AASHO Test T-99. Field determination of density shall be made in accordance with AASHO Test T-147 or other test procedure previously approved in writing by the Director of Public Works.
(D) The minimum cover for utility lines shall be 36 inches, other than direct burial cable which shall be 24 inches. The minimum cover for storm drainage or irrigation pipe shall be 18 inches. COVER is defined as the difference in elevation between the top of the line or pipe and the ultimate gutter grade of the roadway. If paving is not completed within 30 days after installation of the underground facilities, a temporary earth cover sufficient to meet the above requirements must be placed and maintained.
(E) For facilities outside the area defined in division (B)(2) above, COVER is defined as the difference in elevation between the top of the line or pipe and the natural or regraded ground surface, whichever is lesser.
(Prior Code, Ch. 16, Art. II, § 16-35) (Ord. 55, passed 12-15-1983)