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The City of Portland, Oregon

Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Ave, Suite 613, Portland, OR 97204

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Horizontal Directional Drilling (HDD)

Horizontal Directional Drilling (HDD) is a trenchless method of sewer construction. It is suitable for soft to hard clays, wet soils, and environmentally sensitive areas. This method avoids having to dig large pits to install jacking and boring machines. Instead, crews dig much smaller sending and receiving pits. They use a drilling rig to drill a pilot hole and cut a path for the new sewer pipe. Crews install the new sewer pipe from the surface through the sending pit and then pull it through the cut path at the receiving pit.

The work involves the following steps:

  • Dig shallow sending and receiving pits to the required depth
  • Drill a pilot hole that will establish the desired line and grade for the new sewer pipe
  • Cut a larger-diameter path through the pilot hole to accommodate the new sewer pipe
  • Install the new sewer pipe from the surface by pulling it through the cut path
  • Connect the new pipe to the existing public sewer
  • Cover open pits with steel plates—or secure the pits with fencing—at the end of each day as needed while work is in progress
  • Backfill pits with sand or gravel and apply temporary asphalt patches
  • Conduct quality control inspections
  • Complete permanent pavement restoration of patched pits after work passes inspections