Beneath Our Feet

Underground infrastructure in America run for millions of miles. These make possible the basics of modern American life, carrying water, energy resources, electricity, cable, Internet, and phone service. Often we see utilities over our heads, like electrical lines, or even along the sidewalk, like pad-mounted transformer boxes.

What we don’t see is the underground infrastructure. Pipelines, cables, wires, and more just beneath the surface. By some estimates, they run for over 20 million miles under our feet.

This is an often-cited statistic that is beyond question. It comes, ostensibly, from the Common Ground Alliance (CGA). If you read about damage prevention or excavation, you are bound to come across it. It has been cited by nearly every major utility and One-Call center during awareness campaigns, in blogs, and through infographics. The same number has been highlighted for years.

There are more than 20 million miles of underground utilities in the United States, per data compiled by CGA from various industry groups. That figure equates to more than one football field’s length (105 yards) of buried utilities for every man, woman and child in the U.S. -CGA

The line directly above comes from a press release issued in 2018, though an earlier release from CGA in 2014 cited the same line. We know more utilities were laid underground in the four years between; perhaps not enough to update the statistic meaningfully, but the rate of undergrounding suggests it may be worth it to keep awareness campaigns as accurate as possible.

But if we look earlier, we find that the 20 million-mile statistic was born long before a 2014.


An Earlier Estimate

In 1994, the National Transportation Safety Board (NTSB) hosted a damage prevention workshop during which Bell Communications Research presented an estimate for total underground utility mileage. In 1997, the NTSB produced a Safety Study entitled “Protecting Public Safety Through Excavation Damage Prevention.” That study continued to rely on the estimate from three years earlier.

The estimate? 20 million miles.

Noted in the paper is that the mileage is difficult to verify, but that this number was sufficient for the NTSB workshop in 1994. While it was difficult to verify, it was the product of serious research by an industry group, accepted by industry and federal government experts, and used to discuss public safety and regulation at a high-level workshop and thereafter for years in government reports. There is good reason to trust the estimate.

In 1999, the Common Ground report, Study of One-Call Systems and Damage Prevention Best Practices, was initiated by the U.S. Department of Transportation. Over 160 individuals poured into it, and they cited the well-accepted 20 million miles of underground utilities and added: “This figure has likely dramatically increased in the years since.”

In 1994, the experts agreed on 20 million miles, continued to trust it in 1997, and in 1999, more experts validated the statistic while suggesting a dramatic increase in underground utility mileage in the meantime.

Perhaps CGA, in compiling various industry group data in recent years, came to 20 million miles independently or asserts that the 1994 statistic was an overestimate. If so, the industry did then or does now lack accurate data in a field we would hope has detailed and accurate records of its subterranean hazards.

If the number was close to correct 26 years ago, what might it look like now?

A Peek At The Data

We should consider some other estimates. From 1994 to 2018, total gas lines increased from 1,335,530 miles to 1,627,364 miles. Between 2001 and 2018, total oil pipeline mileage increased from 158,248 miles to 218,956 miles.

According to an Edison Electric Institute (EEI) study, “nearly all new residential and commercial developments in the United States are served with underground electrical facilities.” It further concludes that the growth rate of miles-of-lines and investment for underground facilities outpaces overhead lines.

The Internet obviously saw dramatic changes in performance and accessibility in the 1990s alone, and we can only assume that in the last 26 years, the miles of Internet, phone, and other telecommunication lines added are significant. It is common sense that the underground infrastructure network needed for population growth alone is substantial, but factoring in technological innovation and resilience techniques to protect infrastructure underground means far more is likely buried than we currently think.


What To Make Of It

With a dramatic increase between 1994 and 1999, and at least an equally (though in all likelihood a far more) dramatic increase since 1999, how are we still citing 20 million miles of underground infrastructure? And does it matter?

We almost always see the statistic with the qualifier “over.”  This means the statistic will never technically expire or be invalid. If it were truly 50 million miles, it would still be “over” 20 million. It is also probably true that 20 million miles is incomprehensible or at least an abstract number to most people. Perhaps updating to 22 million miles (which I do not assert is correct) would be meaningless to most people. It seems, however, that no one would care less about a higher number, and some may be more cautious with a higher number, so it would be worth it to warn homeowners and excavators with the biggest, best data possible.

An out of date estimate speaks to the lack of attention paid to something so critical – not only critical in providing the services of modern life, but critical in how dangerous it can be to damage these facilities.

We should expect robust and accurate records kept by companies and facility operators, especially in the digital age. It might be time to update the statistic and launch an even stronger campaign for calling 811.

‘If you thought 20 million miles was a lot, it now looks like there are 25 million? 30 million? more? miles of underground utilities just beneath your feet! In almost any – or every – place you could be, it is imperative to call 811 because odds are there’s something near your dig site!’

The more and better information we have, the better we can work to reduce damage. Perhaps the 20 million-mile statistic is not the top priority, but it would be great to freshen up the data. Awareness and education are most effective with accurate information. It might finally be time to upgrade from 20 million miles.


Written by Benjamin Dierker, Director of Public Policy


The Alliance for Innovation and Infrastructure (Aii) is an independent, national research and educational organization. An innovative think tank, Aii explores the intersection of economics, law, and public policy in the areas of climate, damage prevention, energy, infrastructure, innovation, technology, and transportation. (