30th Street Rule 20A Underground Conversion (138kV)

The 30th Street Rule 20A Conversion involved the undergrounding of a 3.5 mile, 138 kV overhead electric transmission line to provide a safer and more reliable energy source. NV5 provided underground route feasibility studies, CYMCAP ampacity analysis, project management, construction inspection, research and analysis of right-of-way maps, boundaries and easements, and topographic and utility surveys for the project. We designed the final plan and profile drawings, performed construction staking, and completed the as-built drawings as the trench was being constructed to ensure the accuracy of the final design.

In addition, NV5’s structural engineering group designed the access openings through the 30th Street Overcrossing Bridge at SR 94 and provided inspection services during the construction to ensure the plans and specifications were compliant and constructed to Caltrans’ standards. Inspection services consisted of monitoring the contractor’s operations inside the cells of the box girder to ensure that the structural integrity of the bridge was not compromised.

NV5 joined this project during a period of intense legal gridlock and found an innovative solution to keep the underground route within existing 20A boundaries. The result was an award-winning project that was completed ahead of the already aggressive schedule, and $10M under budget.


San Diego, CA


Key Facts

  • 3.5 Miles
  • 138 kV
  • CPUC Rule 20A


Outstanding Civil Engineering Project Award for Energy Facilities, American Society of Civil Engineers (ASCE) – San Diego Section