Three environmental organizations this week released documents provided by the Pennsylvania Department of Environmental Protection (DEP) detailing more than 61 spills reported by Sunoco Pipeline LP during horizontal directional drilling (HDD) operations for its Mariner East (ME) 2 pipeline project.

The documents were filed with the state Environmental Hearing Board by the Clean Air Council, Delaware Riverkeeper Network and the Mountain Watershed Association. The groups are appealing the project’s water quality permits, which were issued by the DEP in February. The groups want the board to suspend construction while their case is under review.

The organizations have also called into question the inadvertent return of drilling mud and groundwater that occurred this week during HDD operations in Delaware County. Sunoco said on Thursday that the spills are not unexpected or harmful to the environment. A company spokesman said it has plans in place to deal with them accordingly.

Sunoco was already facing public scrutiny after more than a dozen families earlier this month in nearby Chester County reported losing water pressure or murky water in an area about 30 miles west of Philadelphia where HDD was underway. It’s believed drilling mud affected groundwater and private wells in the area. Sunoco is working to pay for and connect the affected homes to municipal water supplies. Other landowners in the area have also had discussions with the company about tapping public water.

The Clean Air Council said Wednesday that Sunoco has “unleashed drilling fluid into exceptional value” wetlands, trout streams, reservoirs and groundwater, “endangering both drinking water supplies and our natural environment.”

“Until drilling can be done safely, Sunoco is putting Pennsylvanians at risk,” the Mountain Watershed community advocate Melissa Marshall said. “In their rush to complete the project, Sunoco began construction without knowing all of the locations of water wells along the route. Now the entire state is paying the price.”

Sunoco Spokesman Jeff Shields said the use of drills below the surface is helping to significantly reduce the total wetland area impacted by construction, assisting in bypassing “culturally sensitive areas” and preventing traffic disruption. “As part of Mariner East 2, Sunoco Pipeline identified ways to minimize environmental impacts to wetlands, waterways, wildlife habitats and other sensitive areas,” he said. “And horizontal directional drilling offered the best construction method to do this.”

Democratic and Republican state lawmakers from suburban Philadelphia have sent letters to the DEP and Gov. Tom Wolf asking that construction be stopped until their concerns about the project are addressed. While ME 2 has plodded ahead with construction and remains on track to be completed in two phases this year and next, it had already battled some landowners and environmental groups in courts across the state.

The 350-mile pipeline would transport ethane, butane and propane from processing facilities in Ohio, Pennsylvania and West Virginia to the Marcus Hook Industrial Complex near Philadelphia for distribution to domestic and international markets. It is an intrastate system not regulated by the federal government.

Shields said the permit applications approved by the DEP require compliance with an Inadvertent Return Contingency Plan. “Horizontal drilling is sometimes accompanied by inadvertent returns of drilling mud, which is made of drinking water and non-toxic bentonite clay,” he said. “Any ingredients in the drilling fluid must be approved by the DEP and meet safe drinking water standards, and that is specifically in case the fluid escapes through a seam in the geology and into the environment.”

As part of its DEP permits, Shields said the company has plans to monitor for inadvertent returns, contain any drilling mud or water, and recover it, which he said the company has done.

The environmental groups said a water well in Delaware County is being tested for possible contamination. They urged residents on Wednesday living along the project’s path to quickly have their water tested for a baseline comparison in the event of problems caused by the project.