Backfilling & Grading

Compaction Chart

Guidelines

• All excavations shall be backfilled to the original ground surface or to such grades as specified. The backfill shall begin as soon as practical after the pipe has been placed or repairs made and shall thereafter be carried on as rapidly as possible. At no time, however, shall backfill begin prior to inspection of the installation or repairs by the City.
• Complete clean-up shall proceed directly behind the backfilling to accommodate the return to normal conditions. The Contractor shall have sufficient equipment on the job to assure timely backfill and clean-up at all times.
• Backfilling and compacting shall be done as thoroughly as possible so as to prevent after settlement. Depositing of the backfill shall be done so the shock of falling material will not injure the pipe or structures. Grading over and around all parts of the work shall be done as directed by the City.
• Granular material or other suitable material as determined by the City, free from rocks and boulders, shall be deposited in the trench simultaneously on both sides of the pipe for the full width of the trench to a height at least six inches above the top of the pipe, shovel placed and hand tamped to fill completely, all spaces under and adjacent to the pipe. In the event that natural, suitable, granular material is not encountered during the normal excavation of the sewer trench or when the material is determined unsuitable by the City for backfilling around the pipe as required above, the Contractor shall provide and place such approved material. The Contractor shall furnish approved material.
• Succeeding layers of backfill may contain coarse materials but shall be free from pieces or rock, frozen material, concrete, roots, stumps, tin cans, rubbish, and other similar articles whose presence in the backfill, in the opinion of the City, would cause excessive settlement of the trench or damage to the pipe.
• Wherever select material, that exists in place in the upper four feet of the finished grade of the paved or traveled portions of the street or roadway, is removed by the trench excavation, the Contractor shall replace said materials (or material of equal quality) as backfill in the upper four feet of the finished grade. Where select material does not exist on site, the Contractor shall provide and place sufficient select backfill to stabilize the finished grade.
• Backfilling shall be done in lifts of uniform layers not to exceed the depth shown on the compaction chart and each lift shall be completely compacted over the full width of the excavated area. Compacting shall continue until no more settlement occurs. Three feet of material over the top of the pipe shall be required before a vibratory or sheepsfoot roller may be used. The Contractor shall water the soil as necessary to achieve the proper moisture content for compaction.
• Special compaction shall be done around all manholes, catch basins, valve boxes, curb boxes, end of sewer services, other structures, and utilities by the use of pneumatic tampers, plate tampers or plate vibrators with lifts not to exceed that shown in the Compaction Chart.
• No trenches with any street shall be left open overnight. In areas where curb and gutter exists, sufficient curbing shall be removed to allow compaction over the entire disturbed area or special compaction shall be performed around and under the curb as to prevent future settlement.
• If, in the opinion of the City, the compaction is believed to be inadequate, testing will be performed to verify the amount of compaction. All costs for these tests shall be borne by the Contractor.
• All deficiencies in the quantity of material for backfilling the trenches or for filling depressions caused by settlement shall be supplied by the Contractor. Any excess suitable material shall be hauled away.
• No waste material or debris shall be deposited on any public or private property within the municipality’s limits without the written permission of the City. Waste material and debris shall include, but not be limited to, trees, stumps, pieces of pipe, pieces of concrete, pieces of asphaltic concrete, tin cans, or other waste material from the construction operations.
• When any excavation is within the right-of-ways of State or County Highways, the backfilling of the trench, compaction of materials, sub-grade preparation and surfacing shall be done in strict accordance with the requirements and specifications of the State or County Highway Department at no additional compensation.
• In all cases, the Contractor shall blade and compact the roadway after the trench has been backfilled, so that it shall be passable to traffic at all times. The Contractor shall maintain the roadway in an acceptable condition at all times until final acceptance of the entire work by the City. If the excavation lies within a street and the surface cannot be immediately paved or patched, the upper most portion shall consist of a minimum of four inches of compacted Class V.
• The Contractor shall also blade and maintain all detours and bypasses. In addition to the blading and maintenance requirements specified, the Contractor shall provide dust control, as necessary, on all streets after compaction and grading and on all detours or bypasses.