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 NGL’s to flow through the pipeline after their inspectors reported the sink holes did not pose a threat to public safety.

Latest stories


Denise McCarthy told a Department of Environmental Protection hearing that the Mariner East pipelines would endanger her grand nephew, Jack, whose picture she held up as she spoke. DEP held the public meeting in May to hear comment on Sunoco's proposed permit modifications in West Whiteland Township, Chester County.

Full Mariner East pipeline risk assessment report released

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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.
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Sunoco: Mariner East 2 delayed to 2020, so company will join three pipes as substitute

The cross-state natural gas liquids pipeline Mariner East 2 was supposed to begin operation by the end of September. Now, the company has come up with a workaround after acknowledging another lengthy delay in its pipeline project.

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Construction on the Mariner East 2 pipeline has faced myriad problems, including damaged water supplies and sinkholes in a residential neighborhood in Chester County.
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DEP awards water quality-related grants funded by $12.6M penalty against Sunoco

Money will go to efforts in 14 Pa. counties
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Flames erupt during a natural gas pipeline explosion in Greensburg, Pa. in 2016. The explosion, which burned one person, caused flames to shoot above nearby treetops in the largely rural Salem Township, about 30 miles east of Pittsburgh, and prompted authorities to evacuate businesses nearby.

Mariner East 2: What are natural gas liquids, and what happens if they leak?

The pipeline will carry volatile propane, ethane and butane, which has raised fears of many who live near it — even though explosions are rare. As part of StateImpact Pennsylvania’s “Mariner East 2: At what risk?” series, we put together this video to explain what those substances are and how they act both inside the pipeline and if they got out, and how you should respond if there’s a leak.

By Susan Phillips and Tom Downing

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.

‘Regulatory issues’ delay opening of Sunoco’s Mariner East 2 pipeline

The company missed its deadline of opening the line by the end of September. The Public Utility Commission said there are several issues with the project that still need to be resolved.

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Energy Transfer Partners, 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.

Mariner East 2: Sunoco’s incidents, fines and shutdowns fuel residents’ safety concerns

As part of the “Mariner East 2: At what risk?” series, StateImpact Pennsylvania reports how pipeline opponents say Sunoco’s construction makes them worried about the volatile liquids flowing through the line. The data can be useful, but there may be more to the story, two experts said.

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On a tour of the energy facilities in Salem Township, Forbes Road Volunteer Fire Department Chief Bob Rosatti stops at a Mariner East 2 construction site. The Slickville Volunteer Fire Department would have jurisdiction over an incident here, but the Forbes Road department -- just six miles south -- would provide mutual aid, Rosatti said.

First responders near pipeline prep for an unlikely event: ‘One hell of a boom’

As part of the “Mariner East 2: At what risk?” series, StateImpact Pennsylvania reports how firefighters are trained to respond to a pipeline explosion, though shutting the line down would be the company’s responsibility. Energy Transfer Partners says most of Mariner East 2’s valves can be controlled remotely.

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An aerial view of Mariner East 2 pipeline construction, adjacent to the Fairview Golf Course in Lebanon County August 24, 2018.

We’re wired to be wary of certain things. Here’s why pipelines are among them

As part of the “Mariner East 2: At what risk?” series, StateImpact Pennsylvania reports that pipelines are not likely to explode, but sometimes, they do — and that makes a huge impression on our brains.

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The site of an explosion of the Energy Transfer Partners Revolution Pipeline, Center Township, Beaver County.

In Pennsylvania, no oversight of where some pipelines can be built

As part of the “Mariner East 2: At what risk?” series, StateImpact Pennsylvania reports how the lack of siting regulations for pipelines mean they can be built close to homes, for example. “What are you going to do?” said one man who lives near where an explosion of part of a different pipeline occurred recently.

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Mariner East 2 pipeline construction in Lebanon County August 24, 2018

Cumberland County criticizes Mariner East 2 pipeline builder for dodging safety questions

Cumberland County commissioners say the company has turned a deaf ear to residents’ safety concerns

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