Natural gas and other pipeline operators are being reminded by federal regulators of their safety obligations and how those obligations are affected by the operational status of pipeline assets.

The clarification from the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) is in response to the Protecting our Infrastructure of Pipelines and Enhancing Safety Act of 2016.

PHMSA regulations don’t recognize an “idle” status for hazardous liquid or gas pipelines, the agency reminded operators in a bulletin. Pipelines are either “active” and subject to all relevant safety regulations, or they are “abandoned.” Pipelines that are abandoned are to be purged of all combustibles, and any facilities left in place are to be sealed.

The last owner/operator of abandoned offshore facilities or abandoned onshore facilities that cross commercially navigable waterways must file a report with PHMSA. According to the regulations, “abandoned” means “permanently removed from service,” PHMSA said.

“The physical asset is abandoned in the truest sense of the word; no future use or value is attributed to it, and no attempts are made to maintain serviceability,” PHMSA said. “Pipeline systems or segments that are not abandoned, but only idled, decommissioned, or mothballed, are considered to have the potential for reuse at some point in the future.

“The maintenance and inspection to be performed in these cases is a function of the probability of reuse, the cost and difficulty of remediation which may be required, and the potential impact of the in-place and idled facility on human safety and the environment.”

The agency said it is aware that some operators might properly purge a pipeline with the expectation of using it later. “A purged pipeline presents different risks, and therefore different regulatory treatment may be appropriate,” PHMSA said. “Degradation of such a pipeline can occur but is not likely to result in significant safety impacts to people, property, or the environment. PHMSA will accept deferral of certain activities for purged but active pipelines. These deferred activities might include actions impractical on most purged pipelines, such as in-line inspection.”

The agency said it is considering proposing procedures in a future rulemaking that would address notification requirements relating to purged but active pipelines. “In the interim, owners or operators planning to defer certain activities for purged pipelines should coordinate the deferral in advance with regulators. All deferred activities must be completed prior to, or as part of, any later return- to-service. Pipeline owners and operators are fully responsible for the safety of their pipeline facilities at all times and during all operational statuses.”