The Mariner East pipeline system transports natural gas liquids (NGL) such as propane, ethane and butane from the Marcellus and Utica shale in Ohio, West Virginia and Pennsylvania to Energy Transfer’s Marcus Hook Industrial Complex located in Delaware County in south-eastern Pennsylvania, US.

Owned and operated by Sunoco Pipeline, a subsidiary of Energy Transfer, it comprises three parallel pipelines, namely Mariner East 1, Mariner East 2 and Mariner East 2X, with a maximum route length of 563km.

The 482km-long Mariner East 1 pipeline, capable of transporting 70,000 barrels of NGL a day (bpd), entered service in 2014. Construction of Mariner East 2 and Mariner East 2X started in phase two expansion of the project in 2017.

The Mariner East 2 pipeline commenced partial operations in December 2018, whereas Mariner East 2X came on stream in the first quarter of 2021.

Mariner East pipeline system is expected to enter full service to transport up to 370,000 barrels of NGL a day with the completion of the 20-in diameter Mariner East 2 pipeline in the first quarter of 2022.

Delay in Mariner East 2 pipeline construction

Construction of one of the final sections of the Mariner East 2 pipeline that runs through Marsh Creek in Chester County, Pennsylvania, was suspended as horizontal directional drilling (HDD) caused spillage of more than 20,000 gallons of mud fluid in the Marsh Creek Lake in August 2020.

The Pennsylvania Department of Environmental Protection (DEP) permitted a new route allowing open trench excavation rather than HDD for the section of the pipeline in December 2021.

DEP also requires Sunoco to dredge the top six-inch sediment from 15 acres of Marsh Creek State Park’s Ranger Cove and replace all fish, turtle, and bird structures impacted by the drilling mud spillage. Dredging is expected to be carried out between April and July 2022.

Mariner East 1 pipeline project details

The Mariner East 1 pipeline project involved the refurbishment of the pre-existing 400km-long and 8in-diameter oil products pipeline and construction of a new 12in-diameter and 80.5km-long pipeline to transport NGL from western Pennsylvania to the Marcus Hook Industrial Complex.

The Mariner East 1 pipeline started transporting propane in the fourth quarter of 2014 and ethane in the first quarter of 2016.

The old pipeline, which was converted to NGL operation as part of the Mariner East 1 pipeline project, previously transported oil products from the former Marcus Hook refinery to markets in western Pennsylvania.

The Marcus Hook refinery had been operational since 1902 and was idled in 2011. Sunoco Logistics, which later merged with Energy Transfer in April 2017, had acquired the refinery in 2012.

The former refinery site was repurposed as a major NGL hub as part of the Mariner East project.

Mariner East 2 pipeline details

The 563km-long and 20in-diameter Mariner East 2 pipeline will transport up to 275,000bpd of NGL including propane, butane and ethane from processing plants in eastern Ohio and West Virginia to the Marcus Hook Industrial Complex in Pennsylvania.

The pipeline traverses 17 counties in Pennsylvania and mostly follows the same pipeline corridor as the Mariner East 1 pipeline.

Mariner East 2X pipeline details

Mariner East 2X is a 16in-diameter parallel NGL pipeline, which runs for 402km from Delmont, Pennsylvania to the Marcus Hook Industrial Complex.

The Mariner East 2X pipeline entered full service in the third quarter of 2021, whereas the 290km-long Delmont to Cornwall section of the pipeline was commissioned in December 2020.

Marcus Hook NGL hub

The Mariner East pipeline system is connected to the Marcus Hook Industrial Complex, which is spread over 800 acres along the Delaware River in the Delaware County of Pennsylvania.

The Marcus Hook site houses facilities to process, store and distribute NGL to domestic and international markets.

The complex has two million barrels (Mbl) of NGL storage capacity in underground caverns, in addition to 3.8Mbl in above-ground refrigerated storage tanks. It can also store 1Mbl of refined products and 1Mbl of crude oil.

The Marcus Hook terminal can export 400,000bpd of NGL from four marine docks at the site. It also supplies NGL through pipelines and trucks.

Pennsylvania Access project details

The Pennsylvania Access project involved the conversion of the existing 8in-diameter Mariner East 1 pipeline section from Delmont in Westmoreland County to Montello in Berks County to transport up to 25,000bpd of refined products including petrol, diesel, heating oil and jet fuel to Pennsylvania from the existing Allegheny Access Pipeline System.

Scheduled to become operational in 2022, the Pennsylvania Access pipeline will connect refineries in the US Midwest to central Pennsylvania, the Lehigh Valley, and Upstate New York.

Contractors involved

Fluor Corporation was awarded a construction management contract for the new terminal facilities at the Marcus Hook Industrial Complex to store, chill, process and distribute NGL as part of the Mariner East 2 project in February 2016.

U.S. Steel fabricated 5,400t of steel pipe for 85.3km new section of the Mariner East 1 pipeline at its McKeesport facility in Pennsylvania. The coating on the pipeline was performed at its Dura-Bond facility in Duquesne, Pennsylvania.