After saying for several years that underground installation of high-voltage, long distance electrical transmission lines would be too expensive, Pacific Gas & Electric (PG & E) appears to have changed course. Anyone watching the international news lately will have seen the horrendous wildfires that have raged across the western USA. Given the potential for overhead power-cables to get damaged by or even cause such fires, there has always been the argument that such cables should be buried.
On July 22, 2021, PG & E announced plans to bury as much as 10,000 miles (16,100 km) of its electrical transmission lines underground in fire-prone areas of California. The cost is estimated to be US$20 billion over the course of a decade or more. The move was prompted by the catastrophic damages, lawsuits and bankruptcy PG&E suffered after wildfires caused by sparking electrical lines swept through Northern California in 2017 and 2018
The move is not only good news for contractors and residents of California but highlights an apparent change in thinking about the need to reinforce critical infrastructure. The timing of the announcement came just a week before the U.S. Senate agreed to authorise a massive US$1-trillion-dollar infrastructure bill, of which US$73 billion is earmarked to modernise the nation’s electrical grid and US$50 billion is allocated to protecting infrastructure against climate change and cyber-attacks. “Our goal is 10,000 additional miles of overhead lines converted to underground.” said PG&E spokesperson Paul Doherty. “We are starting now, and we will not stop until we have finished.” The state currently maintains approximately 25,000 miles (40,200 km) of overhead transmission lines. “The exact number of projects or miles of transmission line put underground each year will evolve as the utility develops project scopes, estimating and engineering review.” said Doherty.
The utility also said it will partner with natural gas providers and telephone and internet companies to develop joint trenching projects and share costs. “Major underground utility infrastructure upgrades are happening all around the country, but the PG&E project may be one of the largest of its kind.” said Jerry Beyer, director of sales – Infrastructure Group at Vermeer. “It is not uncommon for us to see massive rollouts of projects when it comes to fibre installations.” said Cory Maker, horizontal directional drilling product manager at Ditch Witch. “For an individual project, this is a pretty large given what they want to do and period of time they want to get it all done.”
PG&E initiated a handful of pilot projects to test the feasibility of putting high-voltage power lines and gas infrastructure underground in 2018. Proof-of-concept projects were completed in the high fire threat areas of Alameda, Contra Costa, Nevada and Sonoma counties. Near Oakland the utility put approximately 3,500 ft (1,070 m) of 12 kV distribution line and reinforced the secondary conductor in trenches cut between 36 and 42 in (915 and 1,070 mm) deep and vaults dug to 7 ft 6 in (190 mm) deep. PG&E also converted an overhead transformer to a pad mount. “The goal of these projects was to help evaluate placing overhead conductor underground as a wildfire safety measure, and to better understand the costs and construction requirements associated with undergrounding for system hardening purposes.” said Doherty. “There will be an initial ramp-up period due to limitations in our supply chain and labour force,” Doherty continued. “But within a couple of years, we will be doing ten times the mileage we are doing today. Eventually we will be completing well over 1,000 miles per year. By comparison, this year we are undergrounding about 70 miles.”
PG&E’s 10,000-mile (16,100 km) project aside, HDD and underground infrastructure contractors are in high demand all over the country. “The fibre market is growing tremendously, and there are a number of large electrical projects currently happening with many more projects kicking off in the near future.” said Beyer. This is especially true of electrical utilities on the East Coast from Florida to Washington DC. Multiple regional utilities are taking overhead power lines and burying them underground to better survive hurricanes, ice storms and other destructive weather events.
Maintenance costs driving change
“The historical argument against underground electrical utilities has been that they are more expensive to install, but the thinking on that is starting to change.” said Beyer. “Installation costs are only one part of the equation.” According to a study published by the utility consulting company PDISquared, the maintenance of underground electrical utilities can be three to seven times less expensive than maintenance of overhead utilities. No doubt the increase in catastrophic fires and weather events on both coasts as well and the 2021 winter storm damage to electrical utilities in Texas, Arkansas and Louisiana, have forced utilities nationwide to reconsider their long-term interests when it comes to installation versus maintenance costs.
Busy industry about to get busier
“PG&E’s announcement comes at a time when underground contractors are very busy with just the normal sewer and gas pipeline work.” said Maker. “But the industry is ready to meet the challenge.” “You may see subsidiaries from all over the United States and even some global contractors travelling to California to work on the PG&E project.” said Maker. “It is not uncommon for HDD contractors to travel substantial distances for work especially when they specialise in certain types of jobs.”
Maker continued: “The areas where much of this work will take place have some of the most rugged, mountainous and challenging terrain in the country, and that is the kind of environment where HDD can really shine. Rock saws, trenchers and open cut methods will also be used where they make sense. But HDD work is less invasive than open cut trenching. In HDD operations contractors do not have to manoeuvre and stage large fleets of equipment in the mountains and around obstacles in the terrain.” The size of HDD drills used in the PG&E project will vary on the length of the bore and the terrain and soil conditions.
Maker commented: “A lot of underground electrical work done with rigs in the 40,000 lb (18 t) and under class, where in good soil conditions it is possible to complete 3,000 to 5,000 ft (915 to 1,500 m) per day. But in densely forested areas longer bores and bigger rigs are used to avoid multiple set ups and disturbing the forest.” “Soil conditions also have an impact on equipment decisions.” Said Beyer. “When working in rock, many contractors will use larger drill rigs and/or trenchers paired with tooling designed for those specific conditions to achieve optimal efficiency.
In ground where there may be a mixture of clays, fragmented rock or boulders, a different machine and tooling combination may deliver better productivity.” Andy Bremner, external sales manager-pipeline for Vermeer, said the hard rock formations common in Northern California may require larger rigs in the 100,000 to 200,000 lb (45 to 90 t) class machines depending on the bundle diameter and in some circumstances even up to the 500,000 lb (225 t) size class depending on the length of bore and how it is designed.
In water-parched California, water reclamation will also play a major role in undergrounding PG&E’s electrical lines. HDD contractors often pair midsize and larger rigs with drilling fluid reclaiming equipment to help manage the total volume of water needed. Reclaimers conserve water can also reduce the amount of bentonite and additives needed. Water conversation and project efficiency gains are also driving the use of reclaimers on smaller scale projects.
OEMs ready but labour shortages loom
Both Ditch Witch and Vermeer agree that the industry will not have any problems ramping up the production of machines, HDD units as well as trenching machines and support equipment, for the increased amount of work coming into the underground industry. “We are in constant communications with our dealer and customers, so we can stay in tune with the level and type of support they need today, and in the future.” said Beyer. “We are ready to support this project with equipment, tooling, parts, service and training.” “The biggest problem the industry faces, is the lack of skilled operators who can go out there and drill and locate.” said Maker. “HDD work is significantly more complex than regular earthmoving and heavy/civil construction. Mistakes are expensive and can lay waste to a schedule.” Both manufacturers run their own education classes at various dealerships and both support trade school programmes.
Ditch Witch and Vermeer are support partners with State Technical College of Missouri, and Vermeer has worked several years with the Des Moines Area Community College. Interesting also is that both companies use machine simulators to train prospective operators in trenchless techniques and technology. “With the simulator, operators can learn a lot without having to sit on a rig costing several hundred thousand dollars.” said Maker. “That has been very appealing to the younger generation as they come into the labour force.”