A coalition of wastewater treatment plants has filed a motion to join a lawsuit over pollution trading on the side of the EPA.

The National Association of Clean Water Agencies, which represents 300 sewer and stormwater utilities all over the country, joined state municipal water agencies in Maryland, Virginia, West Virginia and North Carolina in a motion to be intervenors in the pollution trading lawsuit, Food and Water Watch, et al. v. EPA, filed with the U.S. District Court of the District of Columbia.

The parties "seek to intervene to protect and defend the rights of their members to engage in, or continue engaging in, pollutant credit trading pursuant to the federal Clean Water Act for purposes of compliance with their state-issued National Pollutant Discharge Elimination System Permits," the motion stated.

Nutrient trading to meet water quality permits has been controversial for years, and the discussion heated up recently when trading became part of the EPA's plan to meet the pollution reductions required by the Chesapeake Total Maximum Daily Load.

The idea is that regulated sources, such as wastewater plants, could buy credits generated by nonpoint sources, such as farms. Farm pollution, in many cases, is less expensive to reduce than wastewater or stormwater pollution, so the credits that a wastewater treatment plant bought could theoretically provide farms with income and spur additional pollution-reducing practices such as buffers, grass waterways and restored forestland. Regulators also see trading as a way to tackle farm pollution, much of which is exempt from the Clean Water Act.

Some environmental groups, including the Chesapeake Bay Foundation, support trading. The CBF has received grant funding from the U.S. Department of Agriculture to help develop a best management practice credit system. The foundation, which began softening its tone on farm pollution about a decade ago, has said the practice will bring farm families much-needed income to help them stay in business and keep their land from becoming another housing development.

But many other Chesapeake Bay advocates oppose the practice. They argue it will lead to a watered-down effort to clean up the Bay from point sources, and will not provide enough accountability to make sure the nonpoint sources generating credits hold up their end of the bargain. They also worry that it will lead to environmental inequality, with certain areas bearing the costs of pollution while other areas enjoy the benefits of pollution reduction.

In October, Food and Water Watch and Friends of the Earth filed the lawsuit against the EPA, arguing that the trading scheme was illegal under the Clean Water Act and that it undermined efforts to comply with the strict pollution limits outlined in the TMDL.

Chesapeake Bay Riverkeepers, many of whom file lawsuits to protect waterways, are divided on trading. Some, particularly in rural areas, believe in its benefits. Others question both its ability to reduce pollution and its effectiveness in a time of budget cuts in enforcement staffs. But even those who oppose trading did not join the lawsuit over worry that challenging trading could delay the long-awaited TMDL.

"We are, and continue to be against trading, but we will not be part of the lawsuit," said Potomac Riverkeeper Ed Merrifield. "However, I am cheering them on for wanting trading to be removed from the TMDL. It seems to add another layer of problems in a system that is already not working."