US pipeline safety agency proposes gas utility over-pressurization rule

US pipeline safety officials proposed a suite of regulations to prevent over-pressurization of natural gas distribution systems, aiming to address the root causes of a catastrophic series of explosions and fires that rocked northeastern Massachusetts nearly five years ago.

The US Pipeline and Hazardous Materials Safety Administration (PHMSA) on Aug. 24 proposed a rule that would require gas utilities to update procedures and record-keeping to better address risks that can lead to over-pressurization on low-pressure distribution systems. The agency also mandated new processes for responding to those events.

The Notice of Proposed Rulemaking aims to fulfill rulemaking mandates in the Protecting Our Infrastructure of Pipelines and Enhancing Safety (PIPES) Act of 2020. The US Congress included the over-pressurization provisions in the PIPES Act following the Merrimack Valley disaster in NiSource Inc.'s former Massachusetts territory. The explosions and fires killed one person and displaced about 50,000 people across three communities.

"This proposal incorporates lessons from the 2018 Merrimack Valley tragedy to help ensure something like that never happens again," PHMSA Deputy Administrator Tristan Brown said in an Aug. 24 news release.

The rulemaking also addressed recommendations from the US National Transportation Safety Board (NTSB). The NTSB traced the Merrimack Valley disaster to weak management at NiSource's former Massachusetts subsidiary and its failure to adequately plan a pipeline replacement project. Insufficient over-pressure protection on the low-pressure system also contributed to the disaster, the NTSB said.

In the five years since the incident, the American Gas Association has issued best practices for preventing over-pressurization events, and NiSource has implemented NTSB recommendations across its six-state footprint.

PHMSA's proposed rule seeks to add another layer of protection. The agency noted that NTSB's review of over-pressurization events found that system designs common in older gas grids can allow high-pressure gas to enter low-pressure systems following a single failure, such as an operator error or equipment failure.

Distribution system management programs

The proposed rule requires several updates to distribution system management programs, the frameworks that gas utilities use to proactively identify, rank and mitigate risks to pipeline integrity.

The rule would require all gas utilities to identify risks to their distribution systems presented by certain threats, including leak-prone vintage pipe and the possibility of over-pressurization. Operators of low-pressure distribution systems would additionally have to evaluate risks from abnormal operating conditions and the potential consequences of low-probability events, such as the Merrimack Valley disaster.

To mitigate the risk of over-pressurization, low-pressure system operators would have to identify and maintain pressure control records, which document inspections of over-pressure safety devices. They would also have to implement measures tailored to their distribution systems to prevent and mitigate threats.

Operations and maintenance manuals

The rule also requires several changes to operations and maintenance procedural manuals to reduce over-pressurization risk. All distribution pipeline operators would have to incorporate procedures into operations and maintenance manuals for identifying and responding to indications of an over-pressurization event, including steps to immediately reduce pressure or shut down parts of the system.

These operators would also have to develop and follow a management of change process, which is a plan for identifying and controlling risks during a significant change in operations. In the gas utility sector, managing changes can include modifying pressure regulators and revising any standard operating procedure.

Under the proposed rule, if an operator determines that a management of change introduces a public safety hazard, it would have to analyze and control for that hazard before resuming work. PHMSA also proposed a requirement that qualified personnel review and certify plans associated with managing change for accuracy and completeness before the work begins.

Emergency response

The rule would require all gas pipeline operators to have procedures in place to ensure a "prompt and effective response" to any gas release that involves a fatality or any other "significant" emergency. That procedure must include a plan to "immediately and directly notify emergency response officials" of a fatal gas release.

For gas distribution system operators, those requirements would also apply to any unintended release that cuts off service to 50 customers or more. The agency also sought feedback on whether it should require gas distributors to adopt practices associated with incident command systems, a type of emergency management system.

Distribution system operators would also be required to "establish and maintain communications" with the public as soon as practicable during any emergency covered under federal pipeline regulations, and PHMSA would require these operators to implement a system that gives customers the option to receive pipeline safety status information during emergencies. The agency sought information on the feasibility of sending emergency notifications through text messages and push notifications.

Record keeping

Under the rule, distribution system operators would have to maintain "traceable, verifiable and complete" maps and other records outlining the parts of their systems critical to controlling pressure. Those records must be accessible to anyone involved in system design, construction and maintenance.

PHMSA anticipated that many gas utilities maintain these records. Those that do not must identify any missing documents and implement procedures to produce the records. PHMSA also proposed that operators update records regularly.

The rule would require distribution system operators to identify any activity that could result in an over-pressurization event during a construction project. For any project where the operator cannot remotely monitor pressure and shut off gas flow, a qualified person would have to be on hand at a district regulator station to prevent or respond to an over-pressurization event.

Operators would have to incorporate at least two methods of overpressure protection into any new, replaced or relocated district regulator station serving a low-pressure distribution system. Operators would also have to outfit these stations with devices capable of alerting the company of an over-pressurization event in real-time.

Additional requirements

Under the new rule, PHMSA would expand its annual reporting requirement to include the number and miles of low-pressure service lines on gas distribution systems, as well as methods used to protect them from over-pressurization.

PHMSA would also require states to use its State Inspection Calculation Tool for submitting data showing they have enough safety inspectors within their pipeline safety programs.

Through the rulemaking, PHMSA additionally revived a 2011 proposed rule that would prevent personnel who construct a pipeline from inspecting their own work for compliance purposes. PHMSA indefinitely stayed the rule in 2015 over concerns among state pipeline safety regulators and small municipal gas utilities. The rule would apply to transmission, distribution and gathering line operators.

PHMSA also used the rulemaking to clarify test methods for distribution and service lines and issue a correction for its automatic shut-off valve rule following a federal appeals court decision striking down its application to certain gathering lines.

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