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


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

Higher operating pressure prompts new safety concerns over Sunoco’s Mariner East 2X pipeline

Documents indicate Sunoco has a new maximum operating pressure for the line, which is under construction. An engineer who conducted a risk assessment of the Mariner East project said a higher pressure increases risk.

By Susan Phillips

Tree-clearing in Delaware County to prepare for the construction of the Mariner East 2 pipeline project. The builder, Sunoco Logistics, rejected an attempt by a township in neighboring Chester County to block the installation of a valve along the line.

State attorney general, Delaware County district attorney launch criminal investigation into Sunoco, Energy Transfer

Chester County’s district attorney is already investigating the Mariner East pipeline project. The company said it will “aggressively” defend itself.

By Susan Phillips

Crews worked on Monday Jan. 21 to stabilize a new sinkhole that opened up at Lisa Drive, a suburban development in West Whiteland Township, Chester County where Sunoco operates its Mariner East pipelines.

Chester County investigation of pipeline builder Energy Transfer now includes grand jury

District attorney's probe of Mariner East project began in December
By Susan Phillips

Workers installing the Mariner East 2 pipeline August 22, 2018 in Lebanon County. Energy Transfer Partners, parent company of Sunoco Logistics, had told investors that the line would be operational by the end of September. But regulatory issues have held it up.

Mariner East 2 construction to restart in area of Chester County where water damage occurred

Drilling for the pipeline along Shoen Road in West Whiteland Township destroyed private drinking water wells nearby
By Susan Phillips

Energy Transfer, the parent company of Mariner East 2 pipeline builder, Sunoco, works at Snitz Creek in West Cornwall Township, Lebanon County after a drilling mud spill during the summer.

Energy Transfer CEO: ‘We’ve made mistakes’ in building Mariner East

The company vowed not to make those mistakes again. But critics of the project in southeastern Pennsylvania said it’s too late for the people who are living near the pipelines.

By Jon Hurdle

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

Drilling on shaky ground: Why Chester County’s DA is investigating the Mariner East pipeline project

StateImpact Pennsylvania reporter Susan Phillips discusses the Mariner East project’s problems, and how a pipeline explosion in western Pennsylvania led District Attorney Tom Hogan to take a hard look at a pipeline in his own backyard.

By Staff

Crews worked on Monday Jan. 21 to stabilize a new sinkhole that opened up at Lisa Drive, a suburban development in West Whiteland Township, Chester County where Sunoco operates its Mariner East pipelines.
Updated: February 13, 2019 | 12:29 pm

Wolf’s support for pipeline-safety bills boosts bipartisan advocates

Continued problems with Sunoco’s Mariner East project, and the company’s failure to fix problems related to a line in western Pennsylvania, have raised the profile of legislation that has stalled in the past.

By Jon Hurdle

The site of the Revolution Pipeline explosion that occurred in September 2018.
Updated: February 8, 2019 | 4:13 pm

PA DEP halts new pipeline permits for Mariner East, cites ongoing violations with Revolution pipeline

The DEP says Energy Transfer, which is the parent company of Sunoco, failed to fix problems after an explosion rocked Beaver County in September.

By Susan Phillips

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

To help deal with Chester County sinkhole, Sunoco removes product from 44 miles of pipeline

No natural gas liquids are flowing in Mariner East 1 anywhere in Pennsylvania, PUC says
By Jon Hurdle

Crews worked on Monday Jan. 21 to stabilize a new sinkhole that opened up at Lisa Drive, a suburban development in West Whiteland Township, Chester County where Sunoco operates its Mariner East pipelines.
Updated: January 22, 2019 | 10:12 am

Sunoco to ‘purge’ part of Mariner East 1 after new sinkhole opens at Lisa Drive

Sinkholes in early 2018 exposed a section of Mariner East 1, prompting a Public Utility Commission administrative law judge to shut down the pipe and halt construction of two new lines, citing an “imminent risk” to the public. 

By Jon Hurdle
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