In March, residents of Chester County’s West Whiteland Township pressed pipeline regulators for answers on Sunoco’s Mariner East construction after it produced sink holes behind some local homes.

Pennsylvania’s Department of Environmental Protection will hold a public hearing on plans by Sunoco Pipeline to modify its construction of the controversial Mariner East pipelines at two sites in Chester County’s West Whiteland Township.

The DEP said Monday that Sunoco proposes to change its construction method for the pipelines from horizontal directional drilling (HDD) to a conventional bore at one site and from HDD to a combination of conventional bore, open trench and HDD at the other sit

The changes would mean “major modifications” to the company’s permits under the DEP’s Chapter 105 water obstruction and Chapter 102 erosion control regulations, and so require DEP approval after a public hearing, the department said in a statement.

The meeting will be held on April 30 from 6:30 pm to 9:30 pm at the EN Peirce Middle School in West Chester. The DEP also extended a public-comment period from April 21 until May 11.

The statement said one of the affected sites is on East Swedesford Road, where the local water utility, Aqua America, has raised concerns about a well at Hillside Drive. The other location is along North Pottstown Pike, where the new work plan has been prompted by hydrogeological analysis and seismic testing, DEP said. Sunoco submitted both plans last October.

The sites are among about 60 along the cross-state pipeline route that have been subject to a court-ordered “re-evaluation” of local geology after a string of drilling-fluid spills.

Sunoco sought the change “to ensure Aqua America’s water supply would not be impacted,” spokesperson Lisa Dillinger wrote in an email. The change would allow construction to continue “in the most efficient manner possible while keeping safety as our first priority.”

In early March, the Public Utility Commission shut down operation of the parallel Mariner East 1 pipeline at Lisa Drive in the township because of concerns that building Mariner East 2 and 2X pipelines through limestone geology might compromise the safety of the existing line. The PUC’s action was triggered by the appearance of sinkholes near two suburban developments.

In August 2017, a state court temporarily halted drilling at nearby Valleyview Drive after HDD punctured an aquifer, causing some private water wells to turn cloudy and leading Sunoco to pay for affected homeowners to be connected to public water.

David Mano, a resident of Valleyview Drive whose well water was affected, said he has no more confidence in the company’s new plans than in the previous construction because both proposals have been made by the same contractor, Tetra Tech.

“They still don’t know what they’re doing,” Mano said, referring to Sunoco. “They are going by Tetra Tech which is the company that did the first evaluation for this area, and they said, ‘It’s OK go ahead and drill.’ You saw what happened with that.

“Now, the same company is saying, ‘You can drill but not so deep,’” he said. “How can we trust them?”

Sunoco did not respond to a request for comment on Monday evening.

The Middletown Coalition for Community Safety, an anti-pipeline group in neighboring Delaware County, said DEP staff and some 30,000 public commenters had recognized the risks to public safety from a pipeline carrying highly volatile liquids through some of Philadelphia’s densely populated western suburbs when Sunoco’s original plan was approved.

The group said in a statement that it “trusts that this time around, Gov. Wolf and his Department of Environmental Protection will fully consider the public and school safety risks and economic downsides of Sunoco’s ‘major modification’ proposal for the Exton area.”

Tetra Tech said in a letter published on the DEP’s website that the new construction would avoid problematic geology. By using the new installation methods, it said, “SPLP is able to avoid geology which would make a HDD installation difficult while maintaining the avoidance of impacts to resources and sensitive areas.”

The DEP set a three-minute limit for individual speakers at the April 30 hearing, and imposed a limit of one speaker per organization. Speakers were also asked to submit their comments in writing.

Mariner East 2, which has been under construction since February 2017, is scheduled to begin operation by the end of June. Dillinger said the change in construction method, if approved, would not affect that timeline.

When complete, the line will carry ethane, butane and propane some 350 miles from western Pennsylvania to a terminal at Marcus Hook near Philadelphia where most of it will be exported.