Skip to Main Content View Text-Only

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

More Contact Info

Horizontal Directional Drilling (HDD)

Drill rig entry pointHorizontal directional drilling (HDD), sometimes called directional boring, is a steerable trenchless method of installing underground pipes, conduits and cables in a shallow arc along a prescribed bore path by using a surface-launched drilling rig. Construction contractors use directional drilling when trenching or excavating isn't practical. HDD involves these steps:

  • Excavate an entrance pit and receiving hole.
  • Drill a pilot hole on the designed path.
  • Enlarge the hole by passing a larger cutting tool known as the back reamer.
  • Place pipe in the enlarged hole by way of the drill stem; the reamer pulls pipe into place behind it.

During horizontal directional drilling, a mixture of water and bentonite or polymer is continuously pumped to the cutting head or drill bit to remove cuttings, stabilize the bore hole, cool the cutting head, and lubricate the passage of the pipe.

Used drilling fluid goes into a machine called a reclaimer which removes the drill cuttings and maintains the proper viscosity of the fluid. Drilling fluids hold the cuttings in suspension to prevent them from clogging the bore.

Drill rig receiving pitWhat to Expect During Horizontal Directional Drilling

  • The equipment is loud and causes vibration that you may feel in your home or business. This is standard for this method of construction.
  • Both preparation and post-HDD work can take a few weeks to complete.
  • There may be road closures and lane restrictions.
  • There may be inactivity between some phases of this process.
  • Typical work hours are 7:00 a.m. to 6:00 p.m. Monday through Friday, but the contractor may schedule work during the same hours on Saturdays.