ISO 9001:2008ISO 9001
All Categories > APPENDIX > Wire & Cable: Handling and Installation Engineering Guide > EXCAVATING, TRENCHING, BACKFILLING, and SURFACE RESTORATION > View Items  


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Excavated Backfill Materials

  • Backfill shall be free of roots, stumps, rubbish, and stone, concrete and clay lumps larger than one-third cubic foot.
  • Remove and dispose of unsuitable material in backfill.



  • Verify location of existing underground utilities.
  • Protect all existing underground facilities.
  • Protect all existing above ground facilities and structures.
  • Provide for continuance of use of all utilities.


  • Cut existing surfaces to expose area for trenching.
  • Bore below all asphalt surfaces.
  • No classification of excavated material will be made.
  • Strip topsoil and stockpile for replacement/restoration
  • Excavate trench to required line and grade.
  • Keep trench width to a minimum to allow proper jointing of utility and compaction of bedding and backfill.
  • Organize operations to keep time of open trench to a minimum.
  • Excavation by blasting will not be allowed.
  • Trench bottom shall be firm for entire length and width.
  • Remove unstable material from trench bottom and replace with approved bedding.
  • Remove rock, shale and hardpan to one foot below bedding elevation and replace with approved foundation material.
  • Keep trenches free from water.
  • Dispose of excavated material not used or suitable for use as backfill.
  • Stabilize unstable trench walls.
  • Protect bottom of trench from frost. Do not place structures or conduit on frozen ground.

Backfilling and Compacting

  • Do not start encasement backfilling until work which will be covered is completed and areas are free of foreign material.
  • Restore underground facilities interfered with to original condition.
  • Place minimum of two feet of backfill over initial encasement before beginning compaction operations.
  • Compaction by flooding will not be allowed.
  • Level depressions in finished trench.
  • Replace topsoil.
  • Backfill compaction - 85% of standard proctor density unless otherwise specified on drawings.
    • Testing fees will be paid by the Contractor.

Surface Restoration

  • Provide surface restoration to match existing conditions.

Drain Tile Repairs

Contractor shall use good engineering and construction practices to minimize damage to existing drainage tiles and waterways in order to minimize damage to existing drainage. Contractor shall consult with landowners to determine locations of existing tiles, if known, prior to construction.

In the event that Contractor damages drainage tiles or waterways during construction, Contractor shall repair or replace the damaged tiles and restore the damaged waterways, either at their original location or at such other location as will accomplish their original purpose.

Suitable fill material shall be placed under the repaired or replaced tile to minimize settling.

Contractor shall coordinate drainage tile repair such that Landowner’s representative may observe such work by Contractor, provided such representative must be available in accordance with Grantee’s construction schedule.

All underground power lines (including ground cables) shall be installed at least 4 feet below finished ground elevation. During construction, if Contractor encounters underground drainage tiles while trenching for underground lines, Contractor shall install underground lines below the drainage tiles unless the drainage tiles are 6 feet or more below the surface, in which case the underground lines shall be installed above the drainage tiles.

Upon Completion of the work, Contractor shall provide a site map showing the "as built" location of the underground transmission lines on the Property.


Backfill Compaction Test

Compaction tests shall be performed at a depth of one and 1.5 feet above the cables and 3 feet above the cables.

Compaction tests shall be performed every 500 feet for the first mile and every mile thereafter.

Care is to be taken when compacting under, alongside, and immediately above the cable to avoid crushing the insulation and to preserve the trefoil configuration of the cable.

Compaction Test Failure

If the required state of compaction is not obtained, it shall be the responsibility of the Contractor to re-compact or rework the material to the required state of compaction. In cases where there is a failure to achieve the required state of compaction it may be required that the backfill be removed and re-compacted or replaced at the discretion of Engineer and/or Owner.

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