EXPLAINER | Mariner East: A pipeline project plagued by mishaps and delays
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Mariner East: A pipeline project plagued by mishaps and delays

Jon Hurdle / StateImpact PA

A Mariner East 2 construction site in rural Pennsylvania. The Public Utility Commission lifted a ban on construction of a valve, removing one obstacle to completion of the troubled project.

Sunoco Logistics Mariner East pipeline project includes three lines — the Mariner East 1, the Mariner East 2, and the Mariner East 2X, all of which carry or will soon carry natural gas liquids (NGLs) from the Marcellus and Utica Shale plays in eastern Ohio and western Pennsylvania across the state to a processing and export terminal in Marcus Hook, Delaware County.

In 2014, Sunoco completed its conversion of a gasoline pipeline originally built in the 1930’s to ship gas from Philadelphia area refineries to rural Pennsylvania. Reversing the flow of the 8-inch line, Sunoco’s Mariner East 1 now carries NGLs across Pennsylvania to its suburban Philadelphia facility where it is shipped overseas to manufacture plastics.

The Mariner East 2 would expand capacity to 345,000 barrels of NGLs a day. The 20-inch diameter high pressure pipeline tunnels beneath 17 counties, cuts through 2,700 properties with a 50-foot right-of-way, and crosses more than 1,200 streams or wetlands. The company used eminent domain procedings to secure right-of-ways from reluctant landowners, including one family in Huntingdon County that sat in their trees to protest the pipeline construction. Dozens of landowners are still tied up in litigation with the company and the state Supreme Court could decide to hear the cases.

Construction on the $2.5 billion project began in February 2017, after the Department of Environmental Protection identified hundreds of deficiencies in its water-crossing and earth-moving permits. Since then the DEP has issued more than 60 violations to the company for polluting wetlands, waterways, and destroying about a dozen private water wells. In the summer of 2017, DEP, along with several environmental groups, agreed to a consent decree with Sunoco after dozens of drilling mud spills led to the pollution of high value wetlands and trout streams, and the loss of drinking water for residents of a Chester County community.

In April, 2017 Sunoco Logistics merged with Energy Transfer Partners, the builder of the controversial Dakota Access line. Completion of the line is now about 18 months behind its original schedule. The Mariner East 2X is a 16-inch NGL line that will run parallel to the ME2.

In March 2018 Pennsylvania’s Public Utility Commission ordered a temporary shutdown of the Mariner East 1, saying it could have a “catastrophic” effect on public safety if it leaks. The commission said the pipeline had been exposed by the appearance of sinkholes near the construction of the two other Mariner pipelines. On May 3, 2018 the PUC allowed NGLs to flow through the pipeline after their inspectors reported the sinkholes did not pose a threat to public safety.

In mid-December 2018, Chester County’s district attorney opened a criminal investigation into the pipeline project, saying the sinkholes at Lisa Drive show that the project has endangered life and property. As part of the probe, he impaneled a grand jury. Sunoco called the allegations “baseless” and said it is “confident that we have not acted to violate any criminal laws in the Commonwealth of Pennsylvania.”

A hybrid Mariner East 2 line went into service at the end of December 2018. It was planned as a 20-inch cross-state pipeline. But because the full length of the 20-inch line will not be finished until 2020, Energy Transfer has said, the company will join three different pipelines to create a line through which natural gas liquids will flow temporarily.

In March 2019, the Delaware County district attorney and the state attorney general’s office began a criminal investigation of the pipeline project. Sunoco once again said there is no basis for an investigation.

Latest stories


Ginny Kerslake, an anti-pipeline activist, urged Gov. Tom Wolf to halt construction of the Mariner East pipelines.
Updated: September 19, 2019 | 3:06 pm

Court ruling clears way for Mariner East construction to restart at West Whiteland

PUC will have to lift injunction that blocked work at Chester County site, lawyers say
By Jon Hurdle

Crews work at the site of a sinkhole along the Mariner East pipeline route near the Pennsylvania State Police barracks on Route 1 in Delaware County on Thursday, April 25, 2019. Pipeline builder Sunoco said no pipelines were exposed and that the sinkhole was contained.

Crews work at the site of a sinkhole along the Mariner East pipeline route near the Pennsylvania State Police barracks on Route 1 in Delaware County on Thursday, April 25, 2019. Pipeline builder said there were no leaks and no pipelines were exposed.
Updated: September 3, 2019 | 4:24 pm

Criminal defense counsel represents DEP in Mariner East probe

The firm is among several chosen in 2018 by the state’s Office of General Counsel to provide legal services related to criminal procedures, if needed, to about 30 state agencies. Several environmental lawyers say they’ve never heard of the Department of Environmental Protection using a criminal defense attorney, and wonder why the agency felt the need to do so.

By Susan Phillips

In the distance, construction of the Mariner East 2 pipeline at Raystown Lake Recreation Area in Huntingdon County, Pennsylvania.

Mariner East 2 pipeline construction crews work in the backyards of homes on Lisa Drive in West Whiteland Township, Chester County, on May 2. Sinkholes that opened in the area prompted the state's Public Utility Commission to order that an existing pipeline nearby, the Mariner East 1, be shut down until it could be determined that the sinkholes didn't threaten its safety. PUC on May 3 approved a re-start of Mariner East 1.
Updated: August 28, 2019 | 4:59 pm

PUC’s review of pipeline safety regulation prompts attacks by residents, groups and lawmakers

Some argued for no added regulations, but most urged tighter curbs on the pipeline industry
By Jon Hurdle

Rosemary Fuller, an anti-pipeline activist, urged Gov. Tom Wolf to halt construction of the Mariner East pipelines.
Updated: August 26, 2019 | 10:08 am

Wolf tells pipeline activists he won’t shut down Mariner East

Gov. Tom Wolf met Chester County residents at a pipeline construction site. After one resident expressed concerns about pipeline safety, Wolf said, “I fully agree that we should do a better job but we disagree on whether we should keep doing this or not.”

By Jon Hurdle

Sunoco's Mariner East 2 pipeline construction on Pennell Road in Middletown Township. (Emma Lee/WHYY)

PUC ordered Sunoco to produce its calculations on Mariner East blast zones

Regulator demanded information on how local population would be affected by any pipeline failure
By Jon Hurdle

A sinkhole that opened up in January was surrounded by orange plastic fencing outside a suburban home at Lisa Drive in West Whiteland Township, Chester County.

Chester County DA files charges against two Sunoco security guards

Hogan says constables overstepped their bounds when patrolling a suburban development
By Jon Hurdle

Sunoco's Boot Road station, site of what the company called a 'backfire on a flare stack' Aug. 5 that residents said sounded like an explosion.
Updated: August 9, 2019 | 7:59 am

Pipeline experts say vapor buildup likely led to explosion at Chester County pump station

It looks like pilot light ignited excess hydrocarbons when it was re-lit, experts say
By Jon Hurdle

Sunoco's Boot Road station, site of what the company called a 'backfire on a flare stack' Aug. 5 that residents said sounded like an explosion.
Updated: August 6, 2019 | 5:11 pm

Sunoco says Mariner East 2 system ‘backfired’ during maintenance but no risk to public

Resident reports loud explosion; company says no liquids leaked from line
By Jon Hurdle
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