Sunoco Pipeline LP has proposed a quarter-mile reroute of its troublesome Mariner East 2 pipeline in Chester County to reduce the chance of drilling mud leaks, which last year polluted Marsh Creek Lake in Upper Uwchlan Township and shut down the much-delayed construction project.

The Pennsylvania Department of Environmental Protection on Thursday posted plans submitted by Sunoco, a subsidiary of Energy Transfer LP of Dallas, for a “major amendment” of its pipeline route near Marsh Creek State Park.

The new plans would avoid a construction method that led to an Aug. 10 spill of about 8,000 gallons of claylike drilling mud that polluted the 535-acre lake, one of the most heavily visited parks in the state, with more than a million visitors a year. The spill enraged residents and environmental groups, and the DEP ordered drilling stopped at the time.

Rather than building the pipeline through a 2,640-foot-long path drilled horizontally underground, as previously approved, Sunoco instead proposes to use an open trench method of construction.

An open trench is more disruptive to the land’s surface, but minimizes the risk of leaks of fluid from underground drilling, an accident known as an “inadvertent return.”

Because of the open trench, Sunoco plans to move the pipeline path away from the front yards of several houses on Little Conestoga Road between Milford and Highview Roads to a new location along the property lines at the rear or sides of the properties.

“This is a slight reroute of 1,400 feet, running south of the original path near Marsh Creek,” Lisa Coleman, an Energy Transfer spokeswoman, said in an email. “This reroute will only add a minimal increase to the pipeline footprint.”

Plans had called for Sunoco to drill under three streams that feed Marsh Creek Lake to create a pathway through which the 20-inch diameter pipe would be pulled.

Sunoco now proposes to cross the streams with open trenches. It would dam each stream temporarily and reroute the flow to bypass the construction, allowing the pipeline to be trenched and buried in a dry stream channel, Sunoco said in its filing.

The new plan requires the approval of the DEP, and it also would require the acquisition of new easements, potentially adding months to the pipeline project, which would carry natural gas liquids such as propane and ethane across Pennsylvania to an export terminal in Marcus Hook.

But it is a far less dramatic reconfiguration than a one-mile detour that DEP last year ordered Sunoco to take, which would have required borings under the Pennsylvania Turnpike at two locations.

Sunoco said that new route would cause more environmental harm, force it to abandon $17 million of work, and add up to $19 million in costs and would delay completion by two years.

Sunoco sued the DEP, saying its order was “arbitrary, capricious, and an abuse of its discretion.” Environmental Hearing Board Judge Bernard A. Labuskes Jr. delivered a mixed decision in December, and Sunoco’s current plan appears designed to address concerns about the project.

The $5.1 billion Mariner East project is a key link in the state’s effort to promote Pennsylvania shale-gas development and has been supported by organized labor and the energy industry. But its construction has provoked sharp opposition from residents and aroused fears about pipelines transporting highly volatile liquid fuel near populated areas.

The DEP has cited Sunoco for numerous violations during construction, including more than 159 leaks of drilling mud during horizontal drilling runs. The state has fined Sunoco about $16 million over four years.

Sunoco and Energy Transfer face more than the wrath of regulators.

A federal judge in Philadelphia on April 6 allowed a securities fraud suit to proceed against Energy Transfer over the Mariner East project.

The Allegheny County Employees’ Retirement System and several other pension funds allege that Energy Transfer and several executives, including chief executive Kelcy Warren, issued a series of false or misleading statements about the project in recent years that kept its stock at an artificially high price.