A state senator from Chester County lacks legal standing to challenge the construction and operation of Sunoco’s contentious Mariner East pipeline system, a Commonwealth Court panel ruled Monday.

The court ordered the Public Utility Commission to dismiss a complaint filed by Sen. Andrew E. Dinniman, a Democrat who has battled Sunoco Pipeline LP over its 350-mile pipeline project, which weaves its way through densely developed parts of his district. In an opinion by President Judge Mary Hannah Leavitt, the three-judge panel ruled that Dinniman lacked both personal and legislative standing to challenge the project, and ordered the PUC to dissolve an interim emergency injunction blocking construction of parts of the pipeline.

Dinniman filed the complaint in April 2018, contending that Sunoco’s construction of the Mariner East 2 pipeline caused sinkholes to develop in West Whiteland Township, undermining the integrity of the older Mariner East 1 pipeline. The pipelines are part of a system that Sunoco Pipeline is building to transport natural gas liquids, such as propane, from the Marcellus and Utica Shale regions to an export terminal in Marcus Hook, Delaware County.

Sunoco Pipeline is owned by Energy Transfer Partners LP, of Dallas.

The court’s ruling will allow Sunoco to complete construction of the Mariner East 2 pipeline in several parts of Chester and Delaware Counties, which was blocked by the PUC’s decision. Sunoco was able to work around the incomplete sections by routing fuel flows through a 24-mile section of smaller pipeline that it repurposed for gas liquids.

The Commonwealth Court limited its decision strictly to the issue of Dinniman’s legal standing. The court overruled the PUC’s decision that granted Dinniman personal standing to intervene because he lives in West Whiteland Township. The court said there was no evidence or allegation that the project posed a harm to Dinniman’s property or his person.

Dinniman’s lawsuit is one of several ongoing legal challenges filed by residents and advocacy groups that are working their way through the courts. State environmental regulators have fined the company about $13.5 million for construction violations since 2017. And Dinniman and state Sen. Tom Killion (R., Delaware) have introduced a package of legislation aimed at reforming Pennsylvania’s pipeline oversight.

Dinniman, in a statement Monday, said the court ruling shows how difficult it is “to fight for public safety and environmental protection when a poorly planned and potentially dangerous pipeline project is thrust into our neighborhoods and communities and within feet of our schools and homes. To say it is an uphill battle is an understatement.”

Energy Transfer, in a statement, said it was pleased with the decision and urged the PUC to swiftly “take care of the matter.”

The company also said that because Dinniman did not have legal standing to bring the complaint, he “inappropriately used public funds to pay his legal fees for this case, which should result in him having to pay the money back to the commonwealth.”

Dinniman, through a spokesperson, said that the PUC hearing examiner initially had granted him legislative standing to challenge the project’s safety, and said the company “typically … is trying to distract from the facts.”