SDG&E Laguna Niguel Reliability Enhancement Project (138kV) smaller

Laguna Niguel Reliability Enhancement Project (138kV)

The Laguna Niguel Reliability Enhancement Project relocated a two-mile section of two 138kV transmission wood pole lines running through steep unstable canyons to an underground system in adjacent city roadways. NV5 provided electrical engineering, design, as well as surveying and delivered a construction-ready package.

Engineering and design was extremely challenging for this highly visible project. Narrow roadways congested with multiple existing wet and dry utilities resulted in complex route selection and extensive underground survey work. Electrical load capacity of the circuit was an important design consideration. The project was required to incorporate high thermal resistive road materials required by the city which were directly in conflict with maintaining the required electrical capacity of the transmission line.

To overcome this challenge, NV5 performed a thermal engineering study to evaluate cable ampacity ratings using CYMCAP. NV5 concluded that a fluidized thermal backfill could be utilized to compensate and regain the required circuit ratings.


Laguna Niguel, CA


Key Facts

  • 2 Miles
  • 138 kV
  • CYMCAP Software