NTSB Preliminary Report Points Finger at Cast Iron Pipe in Massachusetts Explosion

A National Transportation Safety Board (NTSB) preliminary report published on Oct. 11, regarding the Massachusetts gas pipeline explosion in September, where one person was killed, is likely to spur renewed attention to the safety of cast iron distribution lines.

Columbia Gas of Massachusetts, a subsidiary of NiSource, is now in the process of replacing the 48-mile, cast iron and bare steel distribution system in three communities with state-of-the-art infrastructure and safety features such as excess flow valves. The cast-iron, low-pressure distribution system was installed in the early 1900s and had been partially improved with both steel and plastic pipe upgrades since the 1950s.

The explosion was caused by a loss of pressure in a line being abandoned, related to regulator sensing lines, leading to a full flow of high-pressure gas released into the distribution system supplying the neighborhood, that exceeded the maximum allowable pressure, according to the NTSB preliminary report. The system over-pressure damaged 131 structures, including at least five homes destroyed in the city of Lawrence and the towns of Andover and North Andover. In addition to the one death, at least 21 individuals, including two firefighters, were transported to the hospital.

The safety of cast iron pipe in gas distribution systems has been a significant safety concern for some time. In 2012, President Obama signed the Pipeline Safety, Regulatory Certainty and Job Creation Act which required a survey by the Pipeline and Hazardous Materials Safety Administration of the nation’s progress in replacing cast iron gas pipelines. That provision was inspired, in part, by the death of five people in a 2011 gas explosion in Allentown, Pa., where cast iron pipe was the culprit.

For the most part, the safety of the distribution lines is a matter for state officials, not the Pipeline and Hazardous Materials Safety Administration, which did issue a 2012 Advisory Bulletin to owners and operators of natural gas cast iron distribution pipelines and state pipeline safety representatives. The advisory urged owners and operators to conduct a comprehensive review of their cast iron distribution pipelines and replacement programs and accelerate pipeline repair, rehabilitation and replacement of high-risk pipelines.

According to statistics PHMSA has assembled in compliance with the 2012 pipeline act, 20 states have totally eliminated cast iron pipeline from distribution systems. Approximately 97 percent of natural gas distribution pipelines in the U.S. were made of plastic or steel at the end of 2017. The remaining 3 percent is mostly iron pipe. Nationally, cast and wrought iron distribution main mileage has decreased by almost 38 percent from 2005 to 2017. The number of cast or wrought iron service lines has decreased by almost 77 percent over the same time period.

According to Jake Rubin, a spokesman for the American Gas Association, the AGA supported a July 2013 National Association of Regulatory Utility Commissioners resolution encouraging state regulators and industry to consider sensible programs aimed at replacing the most vulnerable pipelines as quickly as possible. It also encouraged them to explore, examine and consider adopting alternative rate recovery mechanisms in order to accelerate the modernization, replacement and expansion of the nation’s natural gas pipeline systems.

Significant Opposition to Class Location Rules

Citizen organizations and state regulators are opposing interstate pipeline efforts to convince federal regulators to provide an alternative to the class location system, which requires steps be taken there is population growth around a pipeline. The Interstate Natural Gas Association of America (INGAA) wants the Pipeline and Hazardous Materials Safety Administration (PHMSA) to in effect expand class location safety requirements, which it considers outdated, by allowing an integrity assessment option for instances where class locations change from class 1 to class 3, and class 2 to class 4.

PHMSA raised the possibility of either eliminating or altering class location requirements in August via an advanced notice of proposed rulemaking (ANPR). Pipelines have been pressing for changes to the class location requirements for decades because they require replacing pipe in areas where population growth may be minimal and where the cost of replacement is both expensive and, in some cases, unnecessary.

Increases in population around a pipeline – and that can be as few as 500 people – force a pipeline to confirm safety factors and recalculate the maximum allowable operating pressure (MAOP) of the pipeline. If the MAOP per the newly determined class location is not commensurate with the present class location, current regulations require that pipeline operators: reduce the pipe’s MAOP to reduce stress levels in the pipe; replace the existing pipe with pipe that has thicker walls or higher yield strength to yield a lower operating stress at the same MAOP; or pressure test at a higher test pressure if the pipeline segment has not previously been tested at the higher pressure and for a minimum of eight hours.

INGAA understands that any action on the new ANPR awaits a final rule based on a 2016 proposal that would require interstate pipelines to expand integrity management to areas beyond high-consequence areas (HCA). The final rule, ostensibly modified by suggestions from a PHMSA advisory committee, is theoretically due to be published in March 2019. Because that final rule will expand IM requirements, INGAA believes that it is now time to provide the pipelines with an IM option for dealing with class location changes.

PHMSA opens that door in the form of the ANPR. A number of citizen groups and the state pipeline safety organization oppose an IM option to the class location requirements. But C.J. Osman, INGAA director of operations, safety and integrity, hopes that as ANPR is discussed, including in the forum of the advisory committee meetings, opponents can be convinced of the merits of the INGAA-sought option.

Pipelines can apply for and receive special permits which allow the circumventing of class location requirements in certain situations.

Lynda Farrell, executive director, Pipeline Safety Coalition, a Pennsylvania group, refers to a National Transportation Safety Board study and a PHMSA advisory bulletin to underpin her statement that the “ANPRM is premature and that allowing a relaxation of class location strength requirements is ill advised.”

Farrell also refers to the following comments from the National Association of Pipeline Safety Representatives to buttress her opposition to any changes in class location requirements.
“Class locations are primarily a design safety measure. Replacing a design measure with an operation measure does not improve safety. Integrity management strategies have been critically important to pipeline safety success, but we feel that the reliability of these measures have not evolved to a level where their total dependency would be practicable. We have observed some recent accidents resulting from misapplication in managing ILI technologies especially when managing cracks and interactive defects. There are too many accidents related to mismanagement of integrity management issues to justify eliminating class locations in lieu of integrity management.”

The Pipeline Safety Trust acknowledged the importance of the upcoming IM changes in the finalization of the 2016 proposed rule and said any modifications to the class location requirements should wait until “the gas safety rule, now in the works for seven years, is complete and the ‘IVP’ process for identifying and verifying operator system records is in place and shown to be working to improve operator assessments of their systems.”

Osman agrees that some of the comments to the ANPR oppose INGAA’s position based on technical concerns. He acknowledges, “The onus is on us to prove this is the right change to make, to explain why the integrity management program offers not just equal protection but a safer alternative to the current class location method.”

Related Articles

    Find articles with similar topics