PG&E plans to bury 10,000 miles of power lines to reduce wildfire risk at an estimated cost of up to $20 billion. In recent years, PG&E has tried to reduce wildfire risk by trimming or removing trees and strengthening its lines to operate safely during periods of high winds in order to reduce the risk of branches flying into live wires. There are over eight million trees near the company’s power lines. PG&E plans to spend $1.4 billion this year to trim over a million trees and remove more than 300,000 of them.
The project constitutes only a fraction of the PG&E’s electrical system, which consist of about 80,000 miles of lower-voltage distribution lines and 20,000 miles of higher-voltage transmission lines. The company will focus initially on burying distribution lines and may later consider burying transmission lines. Currently, the utility has 27,000 miles of power lines underground, but they are generally not in areas at high risk of wildfires.
The announcement prompted questions about how much of the cost would be borne by ratepayers versus shareholders. PG&Es service territory includes 5.5 million electric customers in Northern and Central California. PG&E will submit the plan to the California Public Service Commission for approval.
The project is daunting. This year the company is putting 70 miles of lines underground, so increasing the work to even 1,000 miles a year would be monumental.
Burying Electric Lines is Costly
There are two methods used to bury utility cables underground. The cheapest method is called open trenching, where utility companies dig into the earth, laying down the utility cables as they go and backfilling the trenches later. This often requires rerouting traffic and making other changes to the movement of a community. The other method, directional drilling, is adapted from oil and gas drilling and is less invasive—but more expensive—for undergrounding utilities. From a fixed point, installers drive a pipe through a miles-long subterranean channel and without disrupting street-level activities.
In either case, because electricity wires are very warm from the current, the wires must be insulated—underground wires are wrapped in plastic and surrounded with a conduit such as oil to keep them from overheating. In the open air, the heat can dissipate, but deep in the soil it cannot. The process is much more complicated than many think.
Depending on the density of the local population and the terrain, underground burying of utility wires can cost billions of dollars. In North Carolina, for example, a study found that undergrounding the entire state’s utility wires would take 25 years and would raise electricity prices by 125 percent. The state decided not to undertake that cost. Even in Washington, D.C., undergrounding a portion of its utility wires was expected to cost $1 billion and raise rates 3.23 percent on average after seven years. The D.C. study found that $1.1 billion (in 2006 dollars) would improve the reliability for 65 percent of the customers in the utility’s service territory, but an additional $4.7 billion would be required to improve service for the remaining 35 percent of customers in outlying areas.
Repairing underground systems is often more expensive than repairing those suspended in the air. While smart grid technology is making identification easier to detect the location of a disruption, access to underground systems is still hindered and can require disruptive digging and significant additional time for repairs. Weather issues can make it more difficult with frozen soils resulting from a blizzard or floodwaters that often follow hurricane-force winds. Neither system can protect power in every situation. In 2012, during Hurricane Sandy, underground electrical equipment was flooded and aboveground utility poles were downed. Above ground lines can last 70 to 80 years while underground lines need replacement every 30 to 35 years.
Other Options
Many cities have replaced the old wooden utility poles with frames made of durable metal and added tension ropes, called guy wires, to help anchor poles to the earth. Pruning, watering, and inoculating trees against pests can keep them healthy and better able to endure storms. Also, removing unstable trees could reduce the chance of an old tree destroying neighboring power lines when high winds uproot it.
Many utility companies also deploy drones. Commercial Drones can reduce the response time for customer calls. In some utility districts, data from drones is used to share the latest information with technicians and customers on status and technical details such as the height of utility lines or the functionality of neighborhood storm drains. Drones can also aid in aerial reconnaissance at sites that have been rendered inaccessible by storms.
Smarter grids have helped utilities to get ahead of problems before they arise. In recent hurricanes, Florida’s power providers selectively shut down substations at risk of flooding or other damage and rerouted the energy. Proactive decisions allow power to be restored more quickly and reduce the potential for a single location to default the entire system.
Biden’s Proposal
President Biden’s infrastructure proposal calls for $73 billion to improve the nation’s power grid and to build transmission lines to reach remote locations for wind and solar power. That would only bury 36,500 miles of transmission lines at PG&E cost estimates. The United States has 200,000 miles of high voltage transmission lines and 5.5 million miles of local distribution lines. According to the Edison Electric Institute, about 18 percent of the country’s electric distribution lines are buried, including those for nearly all new residential and commercial developments. Distribution lines are easier to place underground than high voltage transmission lines.
Conclusion
PG&E estimates that it will cost about $20 billion to bury 10,000 miles of its transmission and distribution lines, which will make its grid more reliable and resilient for its customers and reduce the risk of wildfires. It is not clear how long the project will take since it plans to bury just 70 miles this year. Yet, President Biden believes he can transition the entire U.S. electric utility system to be non-carbon by 2035—in just 14 years—and plans to spend just $73 billion on the nation’s power grid, which has to be reconstituted to handle mostly wind and solar power, both of which are inherently intermittent, which cause additional challenges to the grid.
