Pennsylvania regulators are monitoring Sunoco Pipeline LP’s efforts to bring the Mariner East (ME) 1 natural gas liquids (NGL) pipeline back online more than three months after it was shut down to address a sinkhole that formed near it in the southeast part of the state.

Ahead of the Easter holiday on Friday, the Pennsylvania Public Utility Commission (PUC) said it received notice from Sunoco that the company planned to bring the pipeline back into service on Monday. Sunoco voluntarily shut down the system on Jan. 20 after a sinkhole formed on Lisa Drive in Chester County’s West Whiteland Township that exposed a small segment of the line. Sinkholes also formed in the same neighborhood early last year, at which time the pipeline was also temporarily shut down.

Since January, the PUC’s Bureau of Investigation and Enforcement (I&E) has been monitoring Sunoco’s stabilization and remediation efforts, including grouting work to shore up soil in the area. The parties have also agreed to additional safety measures as the line returns to service.

Sunoco has committed personnel to walk the Lisa Drive section of ME 1 daily who would submit regulatory reports detailing observations from those inspections. The company has also committed to performing geophysical tests in the right-of-way every six months for two years and will report those findings to I&E. 

The company installed strain gauges in the Lisa Drive area in 2018 that have yet to reveal any movement of the pipeline. Those gauges and elevation surveys will continue to be monitored around the clock from a remote control room, I&E said. Remediation efforts will also continue after the pipeline restarts.

The 70,000 b/d ME 1 entered service in the 1930s to move refined products, but was repurposed and began moving NGLs from one side of the state to the other about three years ago. The ME 2 and 2X projects, which are still under construction and have yet to enter full service, run parallel along roughly the same path as ME 1 for about 350 miles to move liquids from processing facilities in Ohio, Pennsylvania and West Virginia to the Marcus Hook Industrial Complex near Philadelphia.

ME 2 entered partial service late last year using a short stretch of 12-inch diameter pipeline that once carried refined products to bypass two areas in West Whiteland where construction is on hold over other regulatory issues.

The Mariner East projects have repeatedly confronted legal and regulatory issues related to fouled well water, sinkholes, historic fines for construction violations and leaks, and criminal investigations started by Delaware and Chester counties. The setbacks have also forced producers to find costly workarounds during service outages. Most recently, Sunoco reached a settlement with Pennsylvania regulators to address corrosion control problems on ME 1 that would require the company to conduct a rare “remaining life study” of the system.