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Testimony before the Committee on Commerce, Science, and Transportation Subcommittee on Transportation and Safety United States Senate on Pipeline Safety: Federal Oversight and Stakeholder Perspectives
Robert L. Sumwalt
United States Senate, Washington, DC

Download the Testimony and Appendix

Good morning Chairman Fischer, Ranking Member Duckworth, and Members of the Subcommittee. Thank you for inviting the National Transportation Safety Board (NTSB) to testify today.

The NTSB is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents and incidents in other modes of transportation―railroad, highway, marine and pipeline. We determine the probable cause of accidents and other transportation events and we issue safety recommendations aimed at preventing future accidents. In addition, we conduct special transportation safety studies and coordinate the resources of the federal government and other organizations to assist victims and their family members who have been impacted by major transportation disasters.

Our Office of Railroad, Pipeline and Hazardous Materials Investigations investigates pipeline accidents involving the release of natural gas, hydrocarbon liquid, ammonia, or carbon dioxide in which there are fatalities or substantial property damage. Pipeline accident investigations focus on the cause of the release, the emergency response, and in the case of hydrocarbon pipelines, the actions taken to mitigate the spill. Based on these accident investigations, the NTSB issues safety recommendations to federal and state regulatory agencies, industry and safety standards organizations, pipeline operators, and emergency response organizations.

Pipeline Safety in the United States

More than 2.5 million miles of pipelines crisscross the nation, delivering important resources such as natural gas, oil, and other hazardous liquids, to consumers. Pipelines are integral to our economy, providing the fuel that powers our homes and industries.[1]

Pipelines are one of the safest and most efficient modes of transportation, but when their integrity is compromised, the consequences can be devastating, especially when safety standards are not observed or implemented.

The NTSB has completed more than 120 investigations of hazardous liquid pipeline ruptures and natural gas pipeline explosions since 1967, which have demonstrated the potential for loss of life and property damage. Additionally, NTSB has eight open pipeline investigations – including Tekamah, Nebraska; Firestone, Colorado; Minneapolis, Minnesota; and Merrimack Valley, Massachusetts – in which lives were lost, homes destroyed, and communities severely affected.[2] In addition to these tragic events, on April 23, the Board will hold a Board Meeting to deliberate and complete the investigation of an apartment building explosion and fire as a result of a natural gas accumulating in a utility room and exploding. This 2016 accident, occurred in Silver Spring, MD, and tragically claimed seven lives.

In response to these accident investigations, the NTSB has issued more than 1,300 recommendations to federal, state, and local agencies, and industry. More than 80 percent of these recommendations have been closed favorably, meaning they have been adopted by their recipients, mandated by Congress, or implemented through federal agency action, resulting in significant improvements in pipeline safety.

For example, in 1998, the NTSB investigated a natural gas pipeline explosion and fire in the South Riding community of Loudon County, Virginia. A family consisting of a husband and wife and their two children were spending their first night in their new home at the time of the explosion. As a result of the accident, the wife was killed, the husband was seriously injured, and the two children received minor injuries. The NTSB found that had an excess flow valve been installed on the line, the accident would never have occurred. Excess flow valves automatically close and restrict gas flow when there is an excess flow of gas in the pipeline. At the time of the South Riding accident, the NTSB had been recommending the installation of excess flow valves for nearly 30 years. In 2006, Congress enacted the Pipeline Inspection, Enforcement, and Protection Act which required the installation of excess flow valves on all new and replaced single-family residential service lines.[3] In 2012, Congress enacted the Pipeline Safety, Regulatory Certainty, and Job Creation Act of 2011 which expanded that requirement to multi-family residences – including apartment buildings – and small commercial facilities.[4] The NTSB closed the South Riding recommendation on December 5, 2016, following issuance of a final rule.

However, there are provisions in current law related to NTSB pipeline safety recommendations that have not been implemented, such as automatic or remote-control shutoff valves, and other recommendations that have not been acted upon. We continue to see accidents and incidents that remind us of the need to be ever-vigilant in improving safety.

Merrimack Valley, Massachusetts

On September 13, 2018, a series of explosions and fires occurred throughout the northeast region of the Merrimack Valley after high-pressure natural gas was released into a low-pressure distribution system, resulting in one fatality and injuring at least 21 individuals, including two firefighters. Seven other firefighters received minor injuries. The distribution system was owned and operated by Columbia Gas of Massachusetts, a subsidiary of NiSource, Inc. The system overpressure damaged 131 structures, including at least five homes that were destroyed in the city of Lawrence and the towns of Andover and North Andover. Most of the damage was a result of structure fires ignited by gas-fueled appliances.

While this investigation is ongoing, NTSB has issued five interim safety recommendations, including four which are classified as “urgent.” We only issue urgent recommendations when we determine that the course of action requires immediate attention to avoid imminent loss due to a similar accident.

One recommendation calls upon the Commonwealth of Massachusetts to eliminate existing professional licensure exemptions and require the seal of a professional engineer (PE) on all public utility engineering drawings.[5] The NTSB believes that it is critical that an engineer with appropriate qualifications and experience review engineering plans for a gas company, if not develop them. Massachusetts’ exemption for the requirement of PE licensure to perform “industrial” and public utility work forecloses an opportunity to detect this design oversight. The seal of a PE should be required on all public utility engineering plans to reduce the likelihood of an accident. On December 31, 2018, Gov. Charlie Baker signed into law legislation requiring such; the Massachusetts Department of Public Utility is in the process of promulgating regulations.[6]

The four urgent safety recommendations issued to NiSource were: (1) revise the engineering and constructability review process to include all internal departments and require plans to be sealed by a PE prior to construction; (2) ensure that all natural gas systems records are complete and readily available; (3) incorporate risk assessments into project development; and, (4) while any modifications are being made to gas mains, actively monitor pressures and require personnel to be in place to immediately respond to any abnormal changes in the pipeline system. As this investigation progresses or following the Board’s adoption of the final report, the NTSB may issue additional safety recommendations to improve pipeline safety and prevent occurrence of a similar tragedy.[7]

Most Wanted List of Transportation Safety Improvements

On February 4, 2019, we announced our Most Wanted List of Transportation Safety Improvements for 2019–2020.[8] This list identifies 10 focus areas for transportation safety improvements based on issues identified through our investigations. Many of the issues on the Most Wanted List address multimodal challenges for improving safety, including alcohol and other drug impairment and fatigue. One issue area is specific to pipeline safety: Ensuring the Safe Shipment of Hazardous Materials.

There are currently 36 open pipeline safety recommendations, 32 of which are on our Most Wanted List: 24 to the Pipeline and Hazardous Material Safety Administration (PHMSA), [9] to industry, and 3 to state regulators.9 Three of the Most Wanted recommendations to PHMSA are designated as “Open – Unacceptable Response.” While the NTSB appreciates progress made by PHMSA on many of our recommendations, they cannot lose focus and must see all safety recommendations through to completion.

Automatic Shutoff and Remote Control Valves

One significant NTSB recommendation urges the use of automatic shutoff or remote control valves in high consequence areas (HCAs) based on an investigation in San Bruno, California.[10]

On September 9, 2010, a 30-inch-diameter segment of an intrastate natural gas transmission pipeline owned and operated by the Pacific Gas and Electric Company (PG&E) ruptured in a residential area in San Bruno. In the 95 minutes it took PG&E to stop the flow of natural gas, an estimated 47.6 million standard cubic feet of gas was released. The released natural gas ignited, resulting in a fire that destroyed 38 homes and damaged 70. Eight people were killed, many were injured, and many more were evacuated from the area.

The NTSB found that the 95 minutes it took PG&E to stop the flow of gas was excessively long and contributed to the extent and severity of property damage and increased the life-threatening risks to the residents and emergency responders. Use of automatic shutoff or remote control valves would have significantly reduced the amount of time taken to stop the flow of gas and to isolate the rupture.

The NTSB recommended that PHMSA amend Title 49 Code of Federal Regulations 192.935(c) to directly require that automatic shutoff or remote control valves in high consequence areas and in class 3 and 4 locations be installed and spaced at intervals that consider the factors listed in that regulation.[11] Current PHMSA regulations leave the decision of whether to install an automatic shutoff or remote control valve up to operators, based on their evaluation of certain factors. The NTSB believes the requirement should be mandatory.

This was not the first time that the NTSB recommended the installation of automatic shutoff or remote control valves. Several nearly identical recommendations were issued in the 1980s, 1990s, and early 2000s to the Office of Pipeline Safety of the Department of Transportation and the Research and Special Programs Administration – the predecessors of PHMSA – and the industry that were closed and designated as “Unacceptable Action” because of their failure to implement the recommendation.

Three months after NTSB issued its San Bruno recommendations, Congress passed the Pipeline Safety, Regulatory Certainty, and Job Creation Act of 2011 (2011 Act) requiring the use of automatic shutoff or remote control valves within two years. PHMSA has initiated but not completed the rulemaking process for this Congressional mandate. PHMSA’s last communication with NTSB stated: “Publication of the proposed rule was initially expected to publish in spring 2017. Like many other issues before us, this is part of an ongoing regulatory review pursuant to the executive order issued by the President.”

There are additional open recommendations from the San Bruno investigation to PHMSA that Congress addressed in the 2011 Act, including requirements that (1) all operators of natural gas transmission and distribution pipelines equip their systems with tools to identify and pinpoint the location of leaks; (2) all gas transmission pipelines constructed before 1970 be subjected to a hydrostatic pressure testing; and (3) any manufacturing- and construction-related defects be tested by a postconstruction hydrostatic pressure test of at least 1.25 times the maximum allowable operating pressure.[12] These recommendations remain on the NTSB’s Most Wanted List of Transportation Safety Improvements and should be implemented by PHMSA expeditiously.

Leak Detection

The NTSB has investigated a number of accidents where operators failed to detect a leak, significantly impacting response time. In San Bruno, control center staff had difficulties determining that there had been a pipeline break and quickly pinpointing its location. Accordingly, the NTSB recommended that PHMSA require that all operators of natural gas transmission and distribution pipelines equip their supervisory control and data acquisition systems with tools to assist in recognizing and pinpointing the location of leaks, including line breaks.[13] The recommendation remains on the NTSB’s 2019-2020 Most Wanted List of Transportation Safety Improvements.

The NTSB’s investigation of one of the largest inland oil spills in U.S. history found deficiencies in the operator’s detection of a leak which led to significant delays in stopping the flow of crude oil. On July 25, 2010, a segment of a 30-inch-diameter pipeline, owned and operated by Enbridge Incorporated (Enbridge) ruptured in a wetland in Marshall, Michigan. The rupture was not discovered or addressed until Enbridge was notified by an outside caller more than 17 hours later. The oil saturated the surrounding wetlands and flowed into the Talmadge Creek and the Kalamazoo River; the total release was estimated to be 843,444 gallons of crude oil. Local residents self-evacuated from their houses, and the environment was negatively affected. Costs exceeded $1.2 billion. About 320 people reported symptoms consistent with crude oil exposure. Fortunately, there were no fatalities.

Similarly, the NTSB’s investigation of a pipeline release near Centerville, Virginia, on September 21, 2015, found significant deficiencies in the ability of Colonial Pipeline Company (Colonial) to detect a leak in their large diameter pipeline that transports gasoline and other refined petroleum liquids. The incident was initially reported by an employee of a restaurant in Centerville who called the Fairfax County 911 Center to report a gasoline odor. Colonial confirmed the pipeline leak two days later, after their inspectors and control room center personnel reported that there were no abnormalities on the pipeline and that all line pressures were normal.

The leak occurred in an HCA. Fortunately, no fatalities or injuries resulted from the release. Colonial estimated that 4,000 gallons of gasoline were released from the pipe; flammable vapor in storm drains was as high as 100 percent of the lower explosive limit (potentially explosive if an ignition source is present).

The Pipeline Safety, Regulatory Certainty, and Job Creation Act of 2011 included measures to improve leak detection capabilities; PHMSA has not yet implemented those measures. Leak detection remains on the NTSB’s Most Wanted List for Transportation Safety Improvements. The NTSB recommendation stemming from the Colonial Pipeline incident is designated as “Open – Unacceptable Response.”[14]

Integrity Management Programs

In the last eight years, the NTSB has completed three major gas transmission pipeline accident investigations in which deficiencies with the operators’ integrity management (IM) programs and PHMSA oversight were identified as a concern.[15] These three accidents—located in Palm City, Florida; San Bruno, California; and Sissonville, West Virginia—resulted in 8 fatalities, more than 50 injuries, and 41 homes destroyed, with many more damaged. As we have learned from these investigations, ensuring adequate IM programs and oversight of pipelines transporting natural gas and hazardous liquids remains critically important.

Since 2004, PHMSA has required the operators of these pipelines to develop and implement IM programs to ensure the integrity of their pipelines in HCAs to reduce the risk of injuries and property damage from pipeline failures.[16] An operator’s IM program is a management system designed and implemented to ensure the operator’s pipeline system is safe and reliable. It consists of multiple components, including procedures and processes for identifying HCAs, determining likely threats to the pipeline within the HCA, evaluating the physical integrity of the pipe within the HCA, and repairing or remediating any pipeline defects found. These procedures and processes are complex and interconnected. Effective implementation of an IM program relies on continual evaluation and data integration. The IM program is an ongoing program that PHMSA and state regulatory agencies periodically inspect to ensure operator compliance with regulatory requirements.

In January 2015, the NTSB’s Safety Research Division conducted a safety study using the results from the completed investigations and additional research to identify weaknesses in the implementation of gas transmission pipeline IM programs in HCAs. The study, Integrity Management of Gas Transmission Pipelines in High Consequence Areas, found that, although PHMSA’s gas IM requirements have kept the rate of corrosion failures and material failures of pipe or welds low, no evidence exists to show that the overall occurrence of gas transmission pipeline incidents in HCA pipelines has declined.[17] Rather, the study identified areas where improvements need to be made to further enhance the safety of gas transmission pipelines in HCAs.

We recognize that IM programs are complex and require expert knowledge and integration of multiple technical disciplines including engineering, material science, geographic information systems, data management, probability and statistics, and risk management. This complexity requires pipeline operator personnel and federal and state pipeline inspectors to have a high level of practical knowledge and skill to adequately perform their functions. This complexity can make IM program development and implementation, and the evaluation of operators’ compliance with IM program requirements, difficult. The study illustrated the need to expand and improve PHMSA resources in guiding both operators and federal and state inspectors.

The effectiveness of an IM program depends on many factors, including how well threats are identified and risks are estimated. This information guides the selection of integrity assessment methods that discover pipeline system defects that may need remediation. The study found that aspects of the operators’ threat identification and risk assessment processes require improvement. Further, the study found that of the four different integrity assessment methods (pressure test, direct assessment, in-line inspection, and other techniques), in-line inspection yields the highest per-mile discovery of pipe anomalies, and the use of direct assessment as the sole integrity assessment method has numerous limitations. Compared to their interstate counterparts, intrastate pipeline operators rely more on direct assessment and less on in-line inspection.

As a result of the safety study, the NTSB issued 28 new recommendations. Of these, 22 were issued to PHMSA and 1 previous recommendation issued to PHMSA was reiterated.[18] These include improvements to the training of state inspectors, the National Pipeline Mapping System, and the current process for identifying HCAs; requirements for in-line inspection of natural gas pipelines; and, eliminating the use of direct assessment as the sole integrity assessment method for gas transmission pipelines.

Nine of the recommendations to PHMSA resulting from the safety study are classified as closed with an acceptable action or reconsidered. The remaining 13 are open; 10 of them are listed on the NTSB’s Most Wanted List of Transportation Safety Improvements. The remaining six recommendations, issued to industry, are all classified as “Closed – Acceptable Action.”

“Open – Unacceptable Response” Recommendations to PHMSA

The NTSB would like to highlight three recommendations to PHMSA stemming from our investigations in Marshall, Michigan, Sissonville, West Virginia, and Centreville, Virginia that are designated as “Open – Unacceptable Response”: P-12-3, P-14-1, and P-17-2. All three of these recommendations are included in the NTSB’s Most Wanted List of Transportation Safety Improvements.

P-12-3 recommended PHMSA revise existing federal regulations to clearly state: (1) when an engineering assessment of crack defects, including environmentally assisted cracks, must be performed; (2) the acceptable methods for performing these engineering assessments, including the assessment of cracks coinciding with corrosion with a safety factor that considers the uncertainties associated with sizing of crack defects; (3) criteria for determining when a probable crack defect in a pipeline segment must be excavated and time limits for completing those excavations; (4) pressure restriction limits for crack defects that are not excavated by the required date; and (5) acceptable methods for determining crack growth for any cracks allowed to remain in the pipe, including growth caused by fatigue, corrosion fatigue, or stress corrosion cracking as applicable.[19]

This recommendation was issued following an investigation of the Enbridge pipeline rupture in Marshall, Michigan, which found that five years prior to the rupture, in 2005, Enbridge identified crack defects during an in-line inspection of the pipeline ranging up to 51.6 inches that were left unrepaired.

While PHMSA published a notice of proposed rulemaking (NPRM) in October 2015 to address our recommendation, the changes proposed to requirements for scheduling crack defect remediation only addressed indications of significant stress corrosion cracking (SCC). We reiterated that the recommendation refers to all forms of crack defects, not just SCC. By only addressing crack indications identified as SCC colonies, the proposed regulation does not limit or otherwise describe requirements for remediating other types of crack indications, including the indication associated with the crack that led to the rupture in Marshall, Michigan.

P-14-1 recommended PHMSA revise existing federal regulations to add principal arterial roadways to the list of “identified sites” that establish an HCA.[20]

This recommendation was issued following an investigation into an explosion and subsequent fire from a 20-inch natural gas transmission pipeline in a sparsely populated area along Interstate 77 near Sissonville, West Virginia on December 11, 2012. About 76 million cubic feet of natural gas was released and burned. While there were no fatalities or serious injuries, three homes were destroyed. The Board determined the probable cause of the pipeline rupture was (1) external corrosion of the pipe wall due to deteriorated coating and ineffective cathodic protection and (2) the failure to detect the corrosion because the pipeline was not inspected or tested after 1988.

PHMSA published an NPRM in April 2016 proposing an alternate approach by creating a “moderate consequence area (MCA)” that included a highway-size threshold. We disagreed with this proposal because it limited highway coverage to only four-lane configurations, which would exclude principal arterial roadways wider than four lanes. Although wider divided highways most likely coincide with the existing HCA criteria, we are concerned that some wider highways may not. While PHMSA has stated they are considering revising the definition, no formal action has been completed.

P-17-2 recommended PHMSA require operators to either (a) repair all excavated dent defects, or (b) install a local leak detection system at each location where a dent is not repaired, continuously monitor for hydrocarbons, and promptly take corrective action to stop a detected leak.[21]

This recommendation was issued following the NTSB’s investigation into a release of the 2015 Colonial Pipeline release of about 4,000 gallons of gasoline in an HCA near Centerville, Virginia. As stated earlier, the leak was not identified by the pipeline operator, Colonial Pipeline Company, for two days after initial report of gasoline odor. The Board determined the probable cause of the release of gasoline from the pipeline was a through-wall corrosion fatigue crack that developed at a dent in the pipeline due to residual and operational stress and exposure to the underground environment. Contributing to the accident were PHMSA regulations that allowed the dent to remain in the pipeline.

PHMSA regulations do not specifically require dents having depths less than six percent of the pipeline diameter to be repaired unless there is an indication of metal loss, cracking, or a stress riser, or unless the dent affects pipe curvature at a girth weld or a longitudinal seam weld. The dent at the leak location was about 1.6 percent of the outer pipe diameter and the upstream dent was 1.57 percent of the outer pipe diameter. Colonial did not repair either dent because they did not meet PHMSA’s repair criteria. During the investigation, Colonial reported to the NTSB that pipelines in Pelham, Alabama, Felixville, Louisiana, and Simpsonville, South Carolina, also developed through wall-cracks in dented pipe. The depths of these dents were less than two percent of the pipe outer diameter.

The NTSB recommended that PHMSA require operators to either (a) repair all excavated dent defects, or (b) install a local leak detection system at each location where a dent is not repaired, continuously monitor for hydrocarbons, and promptly take corrective action to stop a detected leak. The recommendation remains “Open – Unacceptable Response.”

PHMSA has communicated that compliance with current regulations, improved operator guidance, focused inspections, and an advisory bulletin would address the safety risks of dent defects and would be more cost- and safety-efficient than requiring leak-detection systems. However, existing regulations, guidance, and bulletins are inadequate. Pipeline operators should be required to act on all excavated dent defects, but PHMSA proposed wording gives pipeline operators a choice about whether and how to act on defects. Installing a leak-detection system at each location where a dent is not repaired should be the pipeline operators’ only alternative when not repairing an excavated dent defect.


Over the last 52 years, our investigations have found that safe operation of pipelines is a shared responsibility among operators, government oversight agencies, and local communities.

Pipelines remain one of the safest and most efficient means of transporting vital commodities used to power homes, businesses, and vehicles in all modes of transportation. However, the consequences are tragic when there is insufficient safety planning and oversight. To that end, the NTSB urges expeditious implementation of all outstanding safety recommendations issued to operators and government agencies – especially PHMSA.

We recognize the progress that has been made; yet, there will always be room for improvement. The NTSB stands ready to work with this Subcommittee to continue improving the safety of our nation’s pipeline systems.

Thank you again for the opportunity to testify today. I am happy to answer your questions.

  1. Public Law 109-468.
  2. National Transportation Safety Board, Safety Recommendation P-18-005.
  3. An Act Further Providing for the Safety of the Commonwealth’s Natural Gas Infrastructure. Mass. Gen. Laws ch. 339 (2018).
  4. National Transportation Safety Board, Safety Recommendations: P-18-006, P-18-007, P-18-008, P-18-009. Each of these safety recommendations are currently classified as “Open—Acceptable Response.”
  5. National Transportation Safety Board, 2019–2020 Most Wanted List.
  6. HCAs are defined by federal regulation and are areas where a release could have the most significant adverse consequences, including populated areas, areas with a number of structures, drinking water sources, and unusually sensitive areas.
  7. National Transportation Safety Board, Safety Recommendations: P-11-011
  8. National Transportation Safety Board, Safety Recommendations: P-11-010, P-11-014, P-11-015.
  9. National Transportation Safety Board, Safety Recommendation P-11-010.
  10. National Transportation Safety Board, Safety Recommendation P-17-002.
  11. National Transportation Safety Board, Columbia Gas Transmission Corporation Pipeline Rupture Sissonville, West Virginia on December 11, 2012, Rpt. No. NTSB/PAR-14/01 (February 19, 2014); Rupture of Florida Gas Transmission Pipeline and Release of Natural Gas Near Palm City, Florida, Accident Brief No. NTSB/PAB-13/01 (August 13, 2013); Pacific Gas and Electric Company Natural Gas Transmission Pipeline Rupture and Fire San Bruno, California on September 9, 2010, Rpt. No. NTSB/PAR-11/01 (August 30, 2011).
  12. Title 49 Code of Federal Regulations (CFR) Part 192, Subpart O.
  13. National Transportation Safety Board, Integrity Management of Gas Transmission Pipelines in High Consequence Areas, No. NTSB/SS-15/01 (January 27, 2015).
  14. National Transportation Safety Board, Safety Recommendation P-12-003.
  15. National Transportation Safety Board, Safety Recommendation P-14-001.
  16. National Transportation Safety Board, Safety Recommendation P-17-002.