A trio of environmental groups warned Monday they would sue the operator of three coal-fired power plants in Maryland for allegedly discharging excessive amounts of nutrient pollution into Chesapeake Bay rivers and trying to mask their violations by transferring pollution "credits" among facilities.

Food & Water Watch, the Patuxent Riverkeeper and the Potomac Riverkeeper contend that NRG Energy has been violating state-imposed pollution discharge limits for the past three years at its Chalk Point, Morgantown and Dickerson power plants.


In 2010, for instance, state documents show that the Chalk Point plant in Prince George's County discharged more than 2,200 times as much nitrogen into the Patuxent River as it was permitted to do, the groups said. All three plants exceeded their limits on nitrogen pollution, the groups contended, and the Dickerson plant in Montgomery County also discharged more phosphorus into local streams than it was allowed. The Morgantown plant in Charles County discharges into the Potomac River.

The groups said they would sue NRG for damages and an injunction if it did not stop its excessive discharges in 60 days, or begin negotiations to settle the matter.

A spokesman for NRG, which is based in Princeton, N.J., emailed that company executives had received the groups' warning letter but need to review it in detail before responding.

Nitrogen and phosphorus from farm runoff, sewage plants and other sources are responsible for the Chesapeake Bay's algae blooms, fish kills and massive "dead zone," where oxygen levels in the water drop so low that fish and shellfish have a hard time surviving.

Samantha Kappalman, communications director for the Maryland Department of the Environment, acknowledged that the three plants have been violating their discharge limits. She said regulators have been conferring with NRG Energy and the plants' former owner, GenOn, which was acquired by NRG last year.

"They're in ongoing discussions right now about the permit limits not being met," she said.

The nutrients discharged by the power plants are contained in wastewater from air pollution control equipment the facilities installed a few years ago to comply with state law, Kappalman said. The power plants treat the wastewater before discharging it, she said, but not enough.

The environmental groups said the alleged violations at the three power plants raise a red flag about efforts by Maryland and other bay states to allow so-called pollution trading.

Maryland regulators permitted NRG to bend the plants' individual pollution caps by taking credit for discharges below the limit at one plant to offset excessive discharges at another. But even with that plan, the company was not able to meet its nutrient limits. So it sought the state's permission to further offset its plants' pollution by paying farmers to apply more conservation practices on their lands.

"It's a shell game," said Michele Merkel of Food & Water Watch. Her Washington-based environmental group has filed suit as well against the U.S. Environmental Protection Agency, contending the federal agency is violating the Clean Water Act by allowing bay states to use trading to clean up the Chesapeake.

The states are developing programs in which, for example, a sewage plant discharging too many nutrients into the bay could pay farmers to reduce the nutrients washing off their fields by planting trees or converting croplands into wetlands.

Proponents of trading say it can help reduce the staggering costs of restoring the bay, estimated in the tens of billions of dollars, since reducing farm runoff by planting trees or "cover crops" is far less expensive than upgrading a sewage treatment plant. But Merkel and other critics argue trading will allow polluters to evade their legal responsibilities and likely could leave poor and minority communities with degraded waterways.

Kappalman said the pollution juggling NRG was doing did not constitute trading since no money changed hands. Because the company owned all three plants, it was permitted to shift nutrient "credits" among the facilities, she said. The environmental groups said such internal swaps are illegal.

NRG's request to buy pollution credits from Maryland farmers has not been approved, the MDE spokeswoman said, because state officials are still studying how to oversee such trades. Pollution washing off land is not as easy to measure and monitor as when it comes out of a pipe.