The legal challenge was filed with the New Jersey Department of Environmental Protection's Office of Legal Affairs.

Opponents say it kills billions of fish a year as it draws in water and it has "endangered the Delaware River's indigenous community of aquatic life."

Maya van Rossum, the Delaware Riverkeeper and the leader of the regional environmental organization, the Delaware Riverkeeper Network, said Friday that the filing is the first step in an effort to reverse the permit ruling.

“We are disappointed by the N.J. Department of Environmental Protection’s failure to recognize the ongoing hazards of permitting the continued use of outdated technology at Salem when there are other proven eco-friendly technologies available,”  van Rossum said. “As protectors of the river and the ecosystem it contributes to, we see it as our responsibility to challenge this action in order to prevent the indiscriminate killing of the fish, eggs and larvae that are vital to a healthy economy. We will not allow NJDEP to abdicate its responsibility to protect our river, our fish, and our communities.”

New Jersey environmental officials in early June issued the final permit that allows the Salem Nuclear Generating Station to continue pulling water from the Delaware River to cool turbines and then discharge the heated water back into the estuary.

The permit request was opposed by environmental organizations in both Delaware and New Jersey, who contend the cooling water withdrawn from the estuary sucks in fish eggs, larvae and fry.

PSE&G, which operates the nuclear facility praised the decision when it was made.

"This is a major milestone for Salem station and this permit reinforces the critical role nuclear plays in meeting key environmental goals as well as the local community and economy," said Joseph Delmar Sr., a company spokesman. "New Jersey and America’s clean air goals can’t be achieved without carbon-free nuclear power. Just as important is the economic impact of the 1,800 jobs we supply and the millions of dollars we spend each year on goods and services right here in New Jersey."

In addition, Delmar said, the company has restored 20,000 acres of wetlands along the Delaware estuary. The new permit requires the company to continue the Estuary Enhancement Program.

The permit comes after a decades-long battle over Salem  1 and 2 nuclear plant cooling water demands. The facility is permitted to draw 3 billion gallons of water a day from the Delaware River. The other nuclear reactor on the site – Hope Creek – is equipped with a cooling tower that is visible from the Delaware side of the river.