An environmental group that accused regulators of weakening a ban on the dumping of fracking wastewater in the Delaware River watershed has dropped its federal lawsuit, saying its most pressing concerns have been addressed.

Damascus Citizens for Sustainability sued the Delaware River Basin Commission in January, about a month after regulators voted to ban the disposal of drilling wastewater in a vast watershed that includes portions of Pennsylvania, New Jersey, New York and Delaware.

The lawsuit said regulators had quietly issued "extra-regulatory exemptions" after the vote that could have paved the way for the road spreading of contaminated fracking wastewater from so-called "conventional" well sites.

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Conventional wells are traditional vertical wells. Most new natural gas wells are drilled into deeper, "unconventional" rock formations like Pennsylvania’s Marcellus Shale. Energy companies use hydraulic fracturing, or fracking, to stimulate production in both types of wells and must recycle or otherwise properly dispose of the wastewater that results.

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A New York-based activist group has dropped its federal lawsuit against the Delaware River Basin Commission after the agency clarified the terms of its fracking wastewater ban.

The basin commission denied Damascus Citizens for Sustainability's legal claims of a loophole, saying the group had misinterpreted regulatory guidance on the new ban. But regulators agreed to clarify policy language to make clear the ban approved in December includes wastewater from all kinds of fracking sites, not just unconventional gas wells.

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The revisions "dispel any confusion on the part of DCS or others," the basin commission said last month in asking a judge to dismiss the lawsuit.

The environmental group dropped the suit Wednesday, citing the regulatory agency's assurances. The group said in court documents it still expects the basin commission — which is responsible for the water supply of more than 13 million people in the four states — to take action to prevent illegal importation of fracking wastewater into the Delaware River basin.

The agency "has thankfully seen the light," said Barbara Arrindell, the group's director. "We are glad to see DRBC fulfilling its role to proactively protect the Delaware River Basin."

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An agency spokesperson declined to comment.