Frequently Asked Questions

The information below is reprinted from the U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration’s frequently asked questions (FAQ) section as of 11/12/10.

1. How safe are pipelines? What are the statistics?

Pipelines are the safest and most cost-effective means to transport the extraordinary volumes of natural gas and hazardous liquid products that fuel our economy. To move the volume of even a modest pipeline, it would take a constant line of tanker trucks, about 750 per day, loading up and moving out every two minutes, 24 hours a day, seven days a week. The railroad-equivalent of this single pipeline would be a train of seventy-five 2,000-barrel tank rail cars everyday. These alternatives would require many times the people, clog the air with engine pollutants, be prohibitively expensive and — with many more vehicles on roads and rails carrying hazardous materials — unacceptably dangerous.

Relative to the volumes of products transported, pipelines are extremely safe when compared to other modes of energy transportation. Oil pipeline spills amount to about 1 gallon per million barrel-miles (Association of Oil Pipelines). One barrel, transported one mile, equals one barrel-mile, and there are 42 gallons in a barrel. In household terms, this is less than one teaspoon of oil spilled per thousand barrel-miles.

Pipelines also generally have a better safety record (deaths, injuries, fires/explosions) than other modes of oil transportation. For example, compared to the pipeline record, there are 87 times more oil transport truck-related deaths, 35 times more oil transport truck related fires/explosions, and twice as many oil transport truck-related injuries.

Pipeline statistics for calendar year 2002 report 139 liquid pipeline accidents resulted in the loss of about 97,000 barrels and about $31 million in property damage, but no deaths nor injuries. Natural gas transmission line accidents in 2002 resulted in one death and five injuries.

Click here for more statistics.

2. What is done to keep pipelines safe?

Pipelines are operated under a variety of Federal and state regulations and industry standards intended to ensure public and environmental safety and health. These regulations and standards address all aspects of pipeline operations, including where they are built; how they are built, operated and maintained; how they are tested; and what programs and procedures operators must use to ensure the integrity of their pipelines and their operation.

Pipeline operators are inspected by both Federal and state pipeline safety inspectors to ensure they meet or exceed these regulatory requirements and standards. Additionally, there are various government organizations, such as the National Transportation Safety Board (NTSB) and private citizens groups that monitor the operation of pipelines and make recommendations for improvements and changes.

Ultimately, it is the responsibility of the pipeline operator to ensure the safety of its pipelines. Pipeline operators follow regulatory guidance and industry standards in maintaining and operating their pipelines.

3. I understand a major cause of pipeline accidents is careless digging. What is being done to solve this problem?

PHMSA and the pipeline industry have made significant progress in prevention of damage to pipelines by careless digging and other construction activity. Working together, we formed and support a non-profit organization to represent those with interests in underground rights-of-way. The Common Ground Alliance (CGA), comprised of underground utility industries implemented the “Dig Safely” campaign, to create awareness of the vulnerability of pipelines to such activity as construction and the damage that can result from careless backhoe operations, for example. CGA is continuing the awareness and education campaigns, see

Since the “Dig Safely” campaign and establishment of CGA, and during a period of years when new construction was significantly increasing, the number of accidents caused by outside force has decreased.

The Pipeline Safety Improvement Act of 2002 provides authority for the establishment of a national “one-call” system which was implemented as the Call 8-1-1 program in 2007. The centralized center gives construction and utility crews one place to call before they dig, to coordinate and ensure that they will not damage the various underground utilities. Read more about it at the Call 8-1-1 website.

4. What other things are in the future to improve pipeline safety?

Even though pipeline transportation is the safest and most economical means of transportation for our nation’s energy products, PHMSA and pipeline operators are engaged in research to identify and develop more effective means of ensuring the safety of energy pipelines. Research and development (R&D) efforts are looking at: damage prevention and leak detection technologies, enhanced operations, controls, and monitoring, and improved material performance.

Read more about Pipeline R&D.

5. What can I do to help keep pipelines safe?

Become aware of the presence of pipelines in your area. Know what to look for to recognize a pipeline emergency or unusual pipeline condition. Know what to do and who to contact in the event of a pipeline emergency. Anyone planning to dig, especially in an area that appears to be a pipeline right-of-way or where the presence of a pipeline is suspected, should call 8-1-1 at least 72 hours in advance of beginning the excavation.

These calls are extremely important as they can help avoid pipeline ruptures resulting from digging which is a major cause of pipeline accidents. Based on the excavation location information provided in the call to the one-call center, the pipeline owner (and the owners of other nearby underground utilities) will be notified. The pipeline operator will locate and mark the specific location of the pipeline relative to the location of the planned excavation.

Read more about it at the Call 8-1-1 website.

6. What is a pipeline right-of-way?

A pipeline right-of-way is a strip of land over and around pipelines where some of the property owner’s legal rights have been granted to a pipeline company. A right-of-way agreement between the pipeline company and the property owner is also called an easement and is usually filed in the public records with property deeds.

Rights-of-ways and easements provide a permanent, limited interest in the land that enables the pipeline company to operate, test, inspect, repair, maintain, replace, and protect one or more pipelines on property owned by others. The agreement may vary the rights and widths of the right-of-way, but generally, the pipeline company’s right-of-ways extend 25 feet from each side of a pipeline unless special conditions exist.

7. How can I tell where a pipeline is located?

Since pipelines are usually buried underground, line markers and warning signs like the ones shown below are used to indicate their approximate location along the pipeline route. The markers and warning signs are in high-visibility colors (yellow or orange) and are located at frequent intervals along the pipeline right-of-way. The markers can be found where a pipeline intersects a street, highway, railway, or waterway, and at other prominent points along the route. The markers display the material transported in the line, the name of the pipeline operator, and a telephone number where the operator can be reached in the event of an emergency. Pumping stations, tank farms, and cleared rights-of-way also help signal that a pipeline is located nearby.

Yellow pipeline marker showing the words: "WARNING PETROLEUM PIPELINE" Rectangular orange pipeline marker showing the number "4". Yellow pipeline marker with a red top showing the words "WARNING PETROLEUM PIPELINE" on a white pole. Round yellow and red sign showing drilling equipment and the words "WARNING PETROLEUM PIPELINE" Yellow pipeline marker in the shape of a backwards 7 with a red tip. No words are on this marker.

Pipeline right-of-ways are well marked to help prevent damage from digging, the most common cause of pipeline accidents. Anyone planning to dig, especially in an area that appears to be a pipeline right-of-way or where the presence of a pipeline is suspected, should contact the 8-1-1 one-call center at least 72 hours in advance of beginning the excavation.

These calls are extremely important as they can help avoid pipeline ruptures resulting from digging which is the largest single cause of pipeline accidents. Based on the excavation location information provided in the call to the one-call center, the pipeline owner (and the owners of other nearby underground utilities) will be notified. The pipeline operator will locate and mark the specific location of the pipeline relative to the location of the planned excavation.

8. Are pipeline markers always placed on top of a pipeline?

No. Markers and warning signs only indicate the general location of a pipeline. They cannot be relied upon to indicate the exact position of the pipeline they mark. Also, the pipeline may not follow a straight course between markers. And, while markers are helpful in locating pipelines, they are limited in the information they provide. They provide no information, for example, about the depth or number of pipelines in the vicinity. Contact the pipeline operator or the 8-1-1 one-call center for help in determining the specific location of a pipeline prior to beginning any excavation.

9. How does a pipeline operator determine if a leak or rupture has occurred?

Many leak detection systems and methods are used in the operation of pipelines, and, generally, a single pipeline will employ several of these. For example, sensitive instruments are monitored to detect conditions such as a drop in pressure or a change in the flow rate that might indicate a rupture. Also, lines are frequently inspected on foot, by car, or from aircraft.

Leaks rarely occur but many that do are the result of damage caused by someone digging near the pipeline. Most of these damages can be prevented by notifying the pipeline operator or by calling the national 8-1-1 one-call system before beginning an excavation to determine the location of nearby pipelines. The pipeline operator will determine and mark the specific location of the pipeline relative to the location of the planned excavation.  Remember, there may be numerous pipelines in the vicinity of a pipeline marker at different depths.

10. At what temperature do Natural Gas Pipelines freeze?

Natural gas pipelines don’t freeze, at least not on Earth. At minus 260 F and a few psi, natural gas becomes LNG (Liquefied Natural Gas). If a gas pipeline contains a significant amount of water, it may freeze and cause problems in the pipeline, but the gas itself will not freeze.

11. Since a Natural Gas Pipeline won’t freeze unless there is a large quantity of water involved, what should someone do if a Natural Gas Pipeline freezes?

Water freezing in pipelines is only a possibility for services on gas distribution systems. Pressures and flow are too high on gas distribution mains and gas transmission systems. Freezing would only be discovered when it obstructs gas flow, which would result in a no-gas call to the operator. The operator would need to remove or melt the ice to restore gas flow.

You can find more information about pipelines, gas distribution systems, and operations at our Stakeholder Communication site.

12. How are routes for new pipelines determined?

Natural Gas Pipelines

For natural gas pipelines, project planning begins with the basics of supply and demand. Generally, if there is a demand for natural gas, pipeline companies conduct a market analysis to estimate the size of the market. This gas supply requirement is typically expressed in terms of million cubic feet of gas per day. With this information engineers can begin to estimate the facilities required to transport the required volumes of gas and the cost to construct the pipeline facilities.Engineers initially identify preliminary pipeline routes that will minimize impact to the public, public landowners and the environment. The pipeline company typically will go through a process of reviewing available maps of the region to be traversed, and available published environmental data to determine a number of possible alternatives, depending on the characteristics of the region. This desktop work will then be augmented by use of aerial and ground reconnaissance, to identify and select a preferred route.

Once a preferred route is identified, the pipeline company will begin contacting landowners to discuss the project and seek permission to conduct civil and environmental surveys. These surveys are required for use in the detailed pipeline design and for preparing local, state and federal permit applications. Even though pipeline officials may begin discussions with landowners at this point, it is important to remember that the project is undergoing a feasibility analysis, and neither the project nor the pipeline route is finalized at this time.

Selecting a pipeline route often involves discussing and evaluating options with landowners, environmental agencies and regulatory officials. If the market analysis ultimately justifies the cost of pipeline construction, only then will the pipeline company begin seeking permits and preparing a detailed project application for the Federal Energy Regulatory Commission (FERC).

Oil Pipelines

For oil pipelines, potential routes are also initially suggested by demand patterns, including:

  • The predicted required flow of crude oil from a producing field to a refinery complex
  • The expected flow of refined products from a refinery complex to population centers or markets.

Oil pipeline route alternatives are then determined on the basis of studies of the cost of construction, projected growth in population centers, demand for transportation service over a period of time, and rates that are competitive and provide a reasonable return on investment.

Once alternatives have been analyzed, an environmental study helps to select the most feasible option in terms of protecting the safety of the environment and the safety of those who live in the vicinity of the proposed pipeline right-of-way. These environmental studies generally follow procedures set out by federal and state law, sometimes resulting in Environmental Impact Statements or Environmental Assessments that are published in draft form for public comment.

Finally, permissions must be obtained to use an easement corridor, the pipeline right-of-way. Owners of private and public property negotiate with the pipeline companies and sign leases for the use of their land.

Review an expansive discussion of pipelines or read more Pipeline FAQs.