The Pennsylvania Public Utility Commission (PUC) on Thursday partially lifted a suspension on construction of the Mariner East (ME) 2 and 2X pipelines in southeast Pennsylvania.

In a narrow 3-2 vote, the commission authorized Sunoco Pipeline LP to resume construction at eight locations in Chester County’s West Whiteland Township. But an injunction remains at four other locations until the company receives environmental permits from the state Department of Environmental Protection (DEP).

Construction at the locations has been halted since May, when an administrative law judge ordered it stopped. The move came in response to a complaint from state Sen. Andrew Dinniman, which was filed after sinkholes were discovered in a residential area in West Whiteland.

The PUC in June upheld the construction suspension and gave Energy Transfer Partners LP subsidiary Sunoco 20 days to provide inspection and testing protocols, an emergency response plan and the safety training curriculum it uses for employees and contractors, among other things. Sunoco was also required to file the permission it receives from the DEP to continue with construction in the area. The PUC said Thursday that the injunction at the other four locations would remain in effect until Sunoco receives DEP’s approval.

Dinniman, who represents citizens in Chester County living near the ME right-of-way that have staunchly opposed the project, sought to stop construction and clarify the role that the PUC should play in the installation and safety of such pipelines. His broader case is still pending before the PUC’s Office of Administrative Law Judge, with a prehearing conference scheduled for later this month.

ME 2, which is nearly complete, and 2X would run parallel along the same 350-mile route to move ethane, butane and propane from processing facilities in Ohio, Pennsylvania and West Virginia to the Marcus Industrial Complex near Philadelphia.

The projects have faced repeated delays due to regulatory issues and legal challenges.