Pennsylvania regulators want Sunoco Pipeline LP to pay a fine and address what they allege is a “statewide concern” about the company’s corrosion control program stemming from an extensive investigation of Mariner East (ME) 1 after a small leak of natural gas liquids (NGL) from the pipeline last year.

In a 16-page complaint filed on Thursday by the Pennsylvania Public Utility Commission’s Bureau of Investigation and Enforcement (I&E), regulators are asking the full commission to order a $225,000 civil penalty. I&E says its investigation, which lasted about a year, found that Sunoco’s corrosion controls were deficient at the time of the leak, failed to monitor corrosion with regular tests and failed to demonstrate adequate cathodic protection, a method used to control the corrosion of metal surfaces, among other violations.

“While the data reviewed was largely specific to the site of the leak, Sunoco’s procedures and overall application of corrosion control and cathodic protection practices are relevant to all of ME 1, and, thus, I&E alleges that there is a statewide concern with Sunoco’s corrosion control program and the soundness of Sunoco’s engineering practices with respect to cathodic protection,” the complaint said.

The investigation was launched in April 2017 after Sunoco reported a 20 bbl leak of an ethane/propane mixture from the 300-mile ME 1. The pipeline entered service in the 1930s to move refined products. It was converted in 2013 with the capacity to transport 70,000 bbl of NGLs from one side of the state to the other.

When the company excavated and exposed the pipeline in the area of the leak, I&E said, corrosion was discovered on the bottom of it.

Lisa Dillinger, a spokeswoman for Sunoco parent Energy Transfer LP, said the company is aware of the complaint and added that some of the issues it raises have since been addressed.

“We look forward to working cooperatively with the PUC to find common ground on the remaining issues,” she said. “Our first priority is the continued integrity of the line, which has been operating safely for years. We are committed to adhering to all of the appropriate regulations that govern the operations of our pipeline.”

I&E is pushing for the company to revise the corrosion control and protection measures that haven’t already been addressed. The bureau also wants PUC to order a “remaining life study” of ME 1 to determine the forecasted retirement age of the pipeline. It also wants the company to conduct more frequent inspections.

PUC spokesman Nils Hagen-Frederiksen said the company has 20 days to respond to the complaint. Sunoco can contest the allegations, which would send the matter to an administrative law judge, or it can pay the penalty and admit to the violations.

The complaint comes at a time when ME 1 and companion projects ME 2 and 2X, which are under construction, continue to face scrutiny. ME 1 has been offline for about three months this year after sinkholes formed near it and the other projects in the southeast part of the state. The pipeline was allowed to return to service after regulators were satisfied with integrity and geophysical testing. But that hasn’t stopped opponents concerned about safety from trying to prevent operations and construction on the other two lines.