Four environmental advocacy groups filed to intervene formally in Sunoco Pipeline L.P.'s application for public utility corporation status, which would exempt its 299-mile Mariner East pipeline to Marcus Hook from local zoning codes.

The Delaware Riverkeeper Network, the Clean Air Council, the Pipeline Safety Coalition and the Mountain Watershed Association filed requests by Monday's deadline with the Pennsylvania Public Utility Commission to intervene in the case.

The advocacy groups argue that Sunoco does not meet the legal standard for classification as a public utility corporation and should not be exempt from the Pennsylvania Municipalities Planning Code.

The groups also argue that overriding local zoning interests would conflict with a state Supreme Court decision in December that threw out sections of the state's oil and gas law that superseded local zoning.

Sunoco Pipeline, a subsidiary of Sunoco Logistics Partners L.P., is converting an old refined-fuel pipeline to transport natural gas liquids, primarily ethane and propane, from Marcellus Shale fields to a new energy hub being built at the former site of the Sunoco Marcus Hook refinery.

Sunoco's application involves building pump and valve stations in 31 municipalities across the state. Only two local governments - West Goshen and East Goshen Townships in Chester County - filed to intervene in the PUC case.

About three dozen parties filed letters supporting or opposing the granting of public utility corporation status - 19 in support and 16 opposed.

Senate Majority Leader Dominic Pileggi (R., Delaware), a supporter of shale-gas development, was among those opposed to granting Sunoco the zoning exemptions.

"The economic benefits of the Marcellus Shale industry must be carefully balanced with the potential burdens to our communities and the environment," Pileggi wrote. "Requiring Sunoco to respect local ordinances related to pipeline construction will help to achieve this balance."