"The Park Service compromised their integrity and violated their own mission which is to protect public lands, not give them away to utilities," said Jeff Tittel, director of the New Jersey Sierra Club.
Tittel said his group planned to challenge the decision in court, adding, "If we allow PSEG and PPL to put this project in our national parks, they can construct polluting power lines anywhere like Yellowstone or Yosemite."
The utilities building the line said about 95 percent of the route will be built along an existing 85-year-old power line in need of replacement.
The National Park Service, which issued its approval for the project late Monday, will require the utilities to pay about $56 million in mitigation fees for the areas that will be impacted.
The agency says the fees are used to purchase or preserve land for public use, compensate for wetlands impacts, and fund cultural and historic preservation activities.