For decades, labor unions, public safety advocates and environmentalists fought to increase funding to quickly replace the oldest, most vulnerable pipes with little success. The Department of Energy released calls to action. Public service and utility commissions would approve funding to repair damage and hook up new customers, but most of the U.S. iron and unprotected steel distribution mains — some a century old — were only slowly replaced.

Then, in late summer 2010, an explosion ripped apart a neighborhood in San Bruno, Calif., just south of San Francisco. A weld on a 30-inch steel pipe ruptured and exploded, sending a thousand-foot fireball into the night sky. The pipe had been installed more than a half-century earlier.

Tragedy followed a year later in Allentown, Pa. — five dead, three injured. The cause: a 12-inch main installed in 1928. In 2014, a gas main break in East Harlem, N.Y., leveled half a city block, killed eight and injured 48. The gas main had been installed in 1887.

The tragedies focused attention on the potential catastrophe beneath many American cities and state after state, with the help of the Obama-era Department of Energy, began to fund multi-billion-dollar programs to accelerate replacement and increase hiring.

In many parts of the country where the IBEW represents gas workers, the result has been increased hiring and overtime for some of the best paid blue-collar jobs in the nation.

"We fought to get this funding and now we are seeing the benefit, for our customers and for our members," said Utility Department International Representative Chris Harris. "Good jobs, better safety. Everybody wins."

The Problem

Nearly half of America's existing natural gas infrastructure was built before 1960 and cast and wrought iron pipes were used extensively in those years. Wrought and cast iron are brittle and reactive. Like older plastics, they can crack and break from frost heaves or other ground movement.

It was only after the 1960s that steel was brought widely into use. The first generation of steel is less susceptible to breaking but faces the same challenge that has always haunted iron alloys: rust. Corrosion resistant coatings were developed later and when combined with running an electric current — called cathodic protection — steel pipes can be highly reliable.

It wasn't until 1971 that federal guidelines required steel pipes to be coated against corrosion and medium- and high-density polyethylene came into wide usage.

Between 1990 and 2010, gas utilities had already replaced about 85,000 miles of vulnerable mains from a total of nearly 200,000. But at that rate, given where the remaining pipe is located, it could take more than 30 years to replace the rest. All the while they are corroding, growing more brittle and leak-prone, and the threat isn't linear. As a pipe ages, problems accelerate.

Main replacement programs are slow because the cost is extremely high: from $1 million to $5 million a mile according to a 2017 report from the Energy Department's Office of Energy Policy and System Analysis. The report goes on to say that even when utilities receive regulatory approval for replacement programs, "a shortage of skilled labor necessary to perform the maintenance can hamper modernization programs."

The good news is that, after decades of work, only 9 percent of the existing gas distribution infrastructure is made of materials that are considered leak prone. But because the system is so massive, that nine percent represents more than 100,000 miles still to be replaced. This is in addition to the thousands of miles of new pipes connecting new customers that every utility is expected to build as gas prices are kept historically low by the fracking boom.

"Anyone who joins a big city gas utility now will have an entire career before the work driving this expansion is over," said Utility Department Director Donnie Colston. "There are many people who say working for a city utility is the last great blue-collar job and they may be right. I can tell you for certain that it will be one of the most reliable blue-collar jobs until far into the future."

Where the Work Is and Will Be

The oldest, most vulnerable pipes are not evenly spread around the country. They are concentrated in a handful of states, and because they were often the places where natural gas infrastructure was first built, primarily in cities.

Four states (New Jersey, New York, Massachusetts, and Pennsylvania) account for half of all the cast iron pipe in the U.S. Similarly, four states (Ohio, Pennsylvania, California, and New York) account for half of all the unprotected steel pipe in the U.S.

Long Island, N.Y., Local 1049 has seen a boost in manpower inside and outside the fence at National Grid since the state Public Service Commission approved $200 million a year to further increase the rate of pipeline replacement.

"We started replacing cast iron about nine years and were only doing about 10 to 15 miles a year. Now it is 200 miles a year," said Local 1049 business representative Jim Brown. Brown said the National Grid Field Operations and Construction group on Long Island, installing mains and services, grew about 20 percent in the last seven years.

"This is not a one-time deal, this is a career's worth. You hire a guy today, he will retire still doing this work, and that is true across the state," he said.

There is so much work that a significant chunk is subcontracted out, but Brown said that work is still being done by Local 1049 members, working for signatory contractors.

To the south, Cranbury, N.J., Local 94 Business Manager Buddy Thoman is seeing a "tremendous" amount of gas construction work since the state passed the Gas System Modernization Program in 2014.

"The American Gas Association said New Jersey had the highest leakage from gas mains in the country," Thoman said. "We have a lot to do."

More than $1 billion has been invested by state utilities, he said, and the results have been prodigious: more than 1,000 miles of iron pipes and 800 miles of unprotected steel have been replaced in the state since 2011.

New Jersey passed a second $1.5 billion program early this year that will keep Thoman's gas utility members busy for decades.

Even though the oldest systems are in East Coast states, replacement programs are also running apace in the Midwest and on the West Coast.

Aurora, Ill., Local 19 Business Manager Mark Klinefelter has seen a nearly 10 percent increase in permanent staffing at Nicor since the state passed the Natural Gas Consumer, Safety and Reliability Act in 2013.

It has been a rousing success.

"As of November, we have no cast iron pipes in our jurisdiction," Klinefelter said.

And while much of the work was done by outside contractors, they are all union contractors.

And not all new union gas utility work is in trenches.

Vacaville, Calif., Local 1245 represents thousands of northern California and Nevada utility workers for Pacific Gas and Electric and NV Energy.

"San Bruno set into motion a whole range of improvements and upgrades," said assistant business manager Anthony Brown.

PG&E built a revolutionary gas oversight and operations hub in San Ramon. From the screen-filled room, operators can keep tabs on what the entire gas infrastructure is doing and remotely control valves and stations to respond to emergencies.

When the center first opened, the workers were outside the 1245 bargaining unit.

"They fought to get IBEW and they won," Brown said.

The Other Driver: the Gray wave.

Springfield, Ill., Local 51 Business Manager John Johnson also saw between a 5 and 10 percent increase in his inside-the-fence workforce and a significant amount of the work subcontracted out.

"It's illegal in Illinois to have it in our contract that the subcontractors be union," Johnson said. "But we have minimum wage and benefit standards that make union workers the best choice for the work."

But for Klinefelter, the hiring from the gas main replacement program is only a small part of the larger story dominating utilities across the country. He worries most about the generational handover as tens of thousands of baby boomers hit retirement eligibility.

"In the next four years we are looking at a 40 to 50 percent turnover," he said. "We are already training nearly 250 people each year. We could use more, but every seat is full."

Baltimore Local 410 Business Manager Eric Gomez said he is seeing the same: lots to do and lots of retirement on the horizon at Baltimore Gas and Electric.

"I was told we have more work than we have employees and contractors. And they don't know where they will get people from," Gomez said.

But, he said, he knows what their best organizing and recruitment tool is: the company parking lot.

"There is row after row of expensive pickup trucks, and not one of them is stock," Gomez said. "How many other people with high school diplomas are making $200,000 a year? We have hundreds and we are looking for more."