Sunoco Pipeline LP is challenging a recent directive from state regulators to suspend work on a horizontal directional drill (HDD) in Chester County, PA, needed to complete parts of its embattled Mariner East pipeline system.

Mariner East

A prolonged construction stoppage at the site in West Whiteland Township, dubbed HDD 360, creates “a significant risk of adverse consequences at this work location” including “a complete loss of the HDD over 2,800-foot borehole, and the continued discharge of groundwater through the existing pilot hole,” Sunoco’s legal representation wrote in an appeal filed Sunday with the Pennsylvania Environmental Hearing Board.

The appeal seeks to overturn a Notice of Violation (NOV) issued last Thursday by the Pennsylvania Department of Environmental...