Directional Drill Under a Refinery


Bath Engineering provided the engineering design services to connect 69kV Substation 1 to 69kV Substation 3 at a South Texas Refinery. The project was a high priority after a lightning strike caused a chain reaction that destroyed the existing 69kV cable interconnect. Five options were considered, two were ruled out the other three were thoroughly investigated.  One was a conventional cable tray routing causing the least disruption to operations but requiring a length of 7500 ft and costing $7 million. A 5000 ft cable tray route was also considered costing $4 million with more disruption to plant operations. The final decision was made to use a 3500 ft directional bore underneath the plant with a 30 in. schedule 20 casing at a cost of $3.5 million. Environmental precautions included air sampling and soil sampling was involved.

  • 750kCM compact copper, 105C, shld, 69kV cable
  • Casing lengths of 1000 ft and 200 ft used
  • Boring depth to 35 ft
  • Reamers 1.5 times casing diameter
  • 3500 ft directional bore