November 2021, Vol. 248, No. 11


Highway Traffic and the Effect on Pipelines

By Richard McDonough, U.S. Correspondent 

When the average American drives down a street and their vehicle hits a pothole – a divot, a dip, a depression – sometimes, after a few choice words, the driver may wonder whether a tire will need to be repaired or replaced, or if their vehicle is now out of alignment. If the rest of the trip goes well, the driver typically forgets about the momentary bump.  

Few realize that that jolt may have a far greater impact than a flat tire or an alignment repair.  

On Jan. 27, 1971, explosions rocked West Conshohocken, Pennsylvania. A 16-inch steel pipeline that carried natural gas at 60 psi for the Philadelphia Electric Company (PECO) ruptured in the right-of-way (ROW) of a roadway.  

The escaping gas fueled fires that raged for three hours in the midst of freezing weather. The community in suburban Philadelphia was devastated. Five people died. More than 40 firefighters were injured.   

Portions of the ruptured pipeline were sent for study by the National Bureau of Standards of the U.S. Department of Commerce. In August 1971, a 28-page report was prepared for the Office of Pipeline Safety at the U.S. Department of Transportation.   

The Office of Pipeline Safety indicated in the report, “The fractured pipe was under about two feet of soil and passed under a roadway (very near the site of the fracture) carrying heavily loaded trucks, which were hitting a bump in the road almost immediately over the pipeline.”  

No one in the natural gas industry – businesses, regulators and consumers – wants any pipeline to experience a rupture. Whether the pipelines are used for transmission, distribution or service, everyone in the industry strives for safety.  

That said, natural gas pipeline ruptures occur more frequently than anyone in the industry wants. In many cases, these ruptures take place on a services line and only affect one building or just a few structures.   

In some cases, these events are the result of someone mistakenly hitting an underground natural gas pipeline; others take place because of pipeline corrosion, sinkholes or other subsoil activities.  

Ruptures of natural gas pipelines in ROWs are less common, but when they occur, the devastation can be far more extensive than the more common ruptures.  

Aboveground markers indicate to people driving and walking along this roadway that a natural gas pipeline, owned by Transcontinental Gas Pipe Line (Transco),  is below the ground as it crosses this road in Pennsylvania and other states. Transco brings natural gas from Texas to the northeastern states.  

Regulations, Guidance  

The Pipeline and Hazardous Materials Safety Administration of the U.S. Department of Transportation noted specific wording within the regulations governing the sites where pipelines are in the same ROWs as railroads and roadways:   

“§195.256 Crossing of railroads and highways. The pipe at each railroad or highway crossing must be installed so as to adequately withstand the dynamic forces exerted by anticipated traffic loads.”  

One of the dilemmas with this specific regulation is that “the word ‘anticipated’ is not actually defined within the federal regulations mandating operators to construct a line capable of handling anticipated traffic loads,” according to Rebecca Craven, program director of the Pipeline Safety Trust. “Regulations that use words like ‘anticipated’ and then don’t define what that means are very difficult for an agency to enforce in the absence of an incident where a pipeline failure makes clear that the event should have been anticipated.”   

 This, she added, is a general challenge in enforcing performance-based regulations as opposed to prescriptive regulations, like a speed limit, where both the operator and enforcer know ahead of time if a safety regulation is being broken.  

“Natural gas pipeline companies adhere to strict regulations from the federal government,” said Christina Sames, senior vice president, Safety, Operations and Security of the American Gas Association (AGA). “These regulations include details on how natural gas pipelines should be designed, built, operated, maintained and inspected. In addition, our members utilize the guidance provided by the Gas Piping Technology Committee.”   

Beyond the federal regulations, individual states can impose their own regulations, which, in turn, are followed by AGA members, she said.  

Procedures in place in Pennsylvania are examples of how some states implement their regulations to operate safe roads.  

“All state highways are inspected on a regular schedule,” said Francis Hanney, senior manager of Transportation Services Division, Engineering District 6-0 of the Pennsylvania Department of Transportation (PennDOT). “These inspections are performed by county maintenance managers and foremen who drive all roads in their assigned geographic area.”   

The inspectors look for any conditions that may affect the integrity of the roadway. Hanney said many of the problems result from leaking water pipes and sources of underground water.   

“Federal regulations for natural gas pipelines have detailed definitions for different class locations,” Craven said. “Much of the definitions are based on the density of buildings and the density of people within the surrounding areas.”  

A sliding mile distance is used in these definitions, she said, adding that there are two different concepts involved, both of which are relevant in the regulations.  

One is class location, which controls some construction and design rules; the other involves a moderate- or high-consequence area that triggers  “applications of the integrity management rules.”  

This means the operator must identify and mitigate against threats to the pipeline and that certain assessments are required on a specific time schedule. Operators can choose from two methods under the regulations for identifying high-consequence areas, and those designations determine whether the integrity management rules apply.  

Craven explained that “in high-consequence areas, natural gas pipeline operators not only must assess risks within their rights-of-way, but they have additional obligations to mitigate current and anticipated threats and risks to natural gas pipelines that may come from outside the rights-of-way.”  

These would include landslides or other geologic hazard, a river changing channel or an out-of-control semi-truck.  

Integrity of Pipelines  

Protecting the long-term integrity of the natural gas pipelines not only minimizes the risks of pipeline ruptures, but also reduces the risk of damage to roadways and nearby structures.  

“Natural gas operators practice integrity management to help ensure the safety of their natural gas pipelines,” according to Sames. “Our members need to be aware of any changes in conditions where the pipelines are located. This includes being aware of changes in roadway conditions above pipelines.”  


Among the challenges faced with having natural gas pipelines in roadway ROWs are aspects of coordination among interested parties, as well as maps that do not detail all underground pipelines and facilities.  

“There is no one entity that coordinates the physicality of the ground – what happens above the ground as well as what happens below the ground – in rights-of-way,” said James Anspach of the American Society of Civil Engineers. “We really have a utility and roadway system of systems in our country. There is very little engineering guidance when one system impedes on another system’s turf.”   

In most communities, he added, there is a “systemic lack of communications” among the entities that share ROWs. This leads to problems with construction planning, including that within existing highway rights-of-way.  

“We tried in the late 1990s to have a common ground between all of the entities involved in roadway construction to enhance safety,” explained Anspach. “It was a good idea, but it’s not made much progress.”   

He said some states have focused on better ways to handle aspects of the interactions between roadways and natural gas pipelines, pointing to Colorado as a good example of a state moving toward a more coordinated approach among all entities involved in new roadway construction.  

Anspach also cited mapping as another long-running challenge facing all aspects of the industries that use space within roadway ROWs.   

“We don’t have good records to show where every pipeline is located in highway rights-of-way,” he said. What’s underground is largely hidden, and it’s expensive to find out what actually exists under rights-of-way.”  

Based on his work through the years, he estimated that ROWs include up to 40% abandoned pipelines and other utilities. Many of these pipelines are not noted on any maps of these ROWs.   

Author: Richard McDonough writes on energy infrastructure-related issues in North America. He can be reached at 

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