Some of the most valuable real estate in the U.S. energy system is hidden in plain sight: the utility corridor. These narrow strips of land carry high-voltage alternating current (HVAC) transmission lines across farmland, suburbs, and industrial parks. They have become increasingly important as it becomes harder to add lines to new land.
Building transmission lines in new corridors can take 10 to 15 years, largely because of permitting tied to land acquisition and environmental review. To increase capacity within existing right-of-way (ROW), utilities are replacing legacy conductors in HVAC systems with advanced ones that can carry far more power on the same towers. This reconductoring and energizing process typically raises a line’s capacity by 50% to 110% in 18 to 36 months. A 2024 GridLab analysis found that, when construction of new energy transmission corridors is constrained, adding reconductoring could deliver nearly four times as much new grid transmission capacity by 2035 as building new lines alone.
COMMENTARY
The approach is already proving itself. In 2024, Salt River Project reconductored an 8.5-mile, 230-kV line near Phoenix, Arizona, raising its continuous rating by roughly 80% in about 18 months while reusing the line’s 1970s-era towers.
Federal policy is set to accelerate the shift to reconductoring. In September 2026, the U.S. Dept. of Energy announced $1.9 billion for 31 projects under its SPARK program. Combined with about $3.4 billion in project sponsor contributions, the planned investment totals approximately $5.3 billion to reconductor or rebuild more than 1,500 miles of HVAC transmission lines and deploy grid-enhancing technologies across nearly 21,000 additional miles. Together, they are expected to add 23 GW of additional transmission capacity on existing right-of-way.
The Corridor Has Multiple Tenants
This is a promising solution, but one potential challenge is that those corridors are often shared. Power lines run overhead, and oil and gas (O&G) pipelines frequently run beneath or alongside them. Co-location makes sense because it limits land disturbance, but it also means different owners may be responsible for what happens above and below ground.
HVAC transmission lines and O&G pipelines may fall under different regulatory requirements and be managed by separate integrity and corrosion engineering teams, whether they belong to different companies or divisions within the same company. Coordinating across those teams is essential when an upgrade changes conditions in a shared corridor. The challenge is adding capacity overhead while addressing the impact it may have on everything else (assets and facilities) in the right-of-way.
How Higher Operating Currents Can Affect Nearby Pipelines
A buried steel pipeline running near an HVAC transmission line can experience alternating current (AC)-induced voltage and current. As reconductoring increases the line’s current-carrying and operating capacity, AC interference on a nearby pipeline will also increase, depending on the configuration of the power line and pipeline and the mitigation already in place.
AC interference presents two concerns: personnel safety and pipeline corrosion. The first is safety. Induced voltage can create shock hazards for crews working on or near the pipeline. Industry practice under the NACE SP0177 standard uses 15 V AC as the steady-state touch-voltage threshold, and IEEE Standard 80 sets criteria for assessing touch and step voltages during fault conditions. The second is corrosion. Pipelines rely on protective coatings and cathodic protection (CP) to keep buried steel from corroding. Where induced AC finds a small coating defect, it can discharge into the soil and accelerate corrosion at that spot. Voltage, in this case, is not the best indicator of corrosion. A 2015 DNV GL report for the INGAA Foundation notes that when the 15 V AC threshold is used, it “considers personnel safety and does not necessarily address corrosion issues.”
Corrosion risk depends more directly on AC current density at coating defects “holidays” than on voltage alone. ISO 18086 provides criteria for evaluating AC corrosion risk on cathodically protected pipelines. An HVAC power load increase can create a corrosion concern even while voltage readings remain within personnel-safety limits.
A Neighbor’s Upgrade Affects Everyone
A pipeline operator may need to respond to changes made by neighboring utilities. Federal regulation anticipates this scenario under 49 CFR 192.473(c), which requires onshore gas transmission operators to conduct interference surveys when new stray-current sources appear. This includes HVAC power lines with “a voltage up-rating, added lines” or additional generation. Operators must develop a remedial action plan when AC interference current density reaches or exceeds 100 A/m², or when interference impedes safe pipeline operation or could adversely affect the environment or the public.
That trigger assumes the pipeline operator knows something has changed. A same-voltage reconductoring isn’t named explicitly in the regulation, but monitoring indicates a significant increase in stray current triggers a requirement for an interference survey. Because reconductoring stays within existing right-of-way, it can often proceed with limited siting review. In this scenario, handoff communication between electric utilities companies and pipeline operators becomes vital to risk mitigation.
Technical guidance exists on both sides, from IEEE 2746 for electric transmission owners to NACE SP0177 and SP21424 for pipeline operators. Early coordination between electric transmission owners and pipeline operators should be part of reconductoring planning.
A related California HVAC power transmission upgrade illustrates how operators can account for a neighboring pipeline. In 2025, Southern California Edison reported that it did not intend to operate the Lugo-Mohave transmission line at the full compensation provided by its Eldorado-Lugo-Mohave upgrade until AC mitigation work on SoCalGas pipelines was complete. The two companies were working together on the scope, schedule and cost of that mitigation.
Planning Beyond the Asset Owners
Utility corridors cross communities, and the stakes extend beyond the asset owners. A related shared-corridor example comes from Puget Sound Energy’s Energize Eastside project, which upgraded a 16-mile transmission corridor from 115 kV to 230 kV through four Seattle-area suburbs. Sharing the corridor with two Olympic Pipe Line petroleum pipelines, the project’s 2016 planning study demonstrated how asset owners can assess safety when major infrastructure systems operate side by side.
Pipeline safety was a concern during the permitting process. A 2016 AC interference study commissioned by Puget Sound Energy evaluated how different transmission line configurations and routes could affect the nearby pipelines. The study recommended selecting a configuration that reduced interference and conducting field monitoring after the line was energized. The project also included continued coordination with the pipeline operator and additional safety measures during design and construction.
Mitigation itself can involve landowners. Installing grounding systems or gradient-control wire can require trenching along the pipeline, so an upgrade within an existing right-of-way may still involve ground disturbance.
Planning For the Whole Corridor
None of these challenges are arguments against reconductoring. It is one of the fastest, most land-efficient ways to add capacity. In any reconductoring project, capacity planning should account for the whole corridor. Planning for the whole corridor also means considering how an incident involving one asset could affect neighboring infrastructure and operations. This includes notifying co-located operators early when a line’s loading or rating will change, sharing load data, jointly modeling interference before re-energizing, budgeting mitigation into project costs, and confirming results with surveys before and after.
Transmission owners and pipeline operators should coordinate early so interference assessment, integrity and corrosion management and any necessary mitigation are part of the upgrade plan.
—Tim Gonzalez is vice president of Energy Integrity Solutions for the Association for Materials Protection and Performance.
