While it has been nearly two years since the EPA finalized its plan to put the Chesapeake's 64,000-square-mile watershed on a "pollution diet," the question of whether the agency was acting within its authority remains unsettled.

Within weeks of the EPA finalizing what it called a "historic" Chesapeake Bay Total Maximum Daily Load in December 2010, the Pennsylvania Farm Bureau and American Farm Bureau Federation filed suit challenging its legality.

That suit, which was later joined by several other agricultural trade groups as well as the National Home Builders Association, contends that the EPA overstepped its legal authority in developing the cleanup plan, used flawed models to develop the plan and gave inadequate opportunity for public comment.

Those charges are disputed by the EPA and a coalition of interest groups that has joined its side of the case, including environmental organizations and others representing wastewater treatment operators.

After months of arguments and rebuttals in court filings, both sides got to make their case Oct. 4 before U.S. District Judge Sylvia Ramble of the Middle District of Pennsylvania.

And after nearly five hours of presentations by attorneys, it wasn't clear when the complex legal issues would be resolved. "Don't expect a decision soon," Rambo said as the hearing came to an end.

The stakes in the decision are huge. Environmental advocates see the pollution limits established by the TMDL, which are to be achieved by 2025, as their best opportunity to curb the nutrient and sediment pollution that continues to foul the Bay's water nearly three decades after the EPA and states first vowed to clean it up.

Critics, especially agricultural groups, fear the Bay TMDL would be a template for other regions and lead to increased regulation of farm runoff.

Attorneys on both sides of the case presented sharply different interpretations of both the Clean Water Act, and the process leading to the development of the Bay TMDL, which established the maximum amount of nitrogen, phosphorus and sediment that can reach the Bay from each state and tributary and still have water quality good enough to support healthy populations of fish, shellfish, underwater grasses and other resources.

The TMDL also allocates the pollutant loads to various pollution source categories within the states, such as wastewater treatment plants, stormwater, large animal feeding operations, other types of agriculture, forests, air deposition and septic systems.

Attorneys for the agricultural groups, in both their briefs and presentations, took issue with that detailed allocation, and instead offered a narrow interpretation of EPA's authority in the section of the Clean Water Act dealing with TMDLs.

Richard Schwartz, an attorney for the plaintiffs, said the EPA may have the authority to establish the overall load that can reach the Bay, but that it overstepped its authority when it allocated nitrogen and phosphorus limits to various pollution sectors.

He said the TMDL figure is simply the total load of a pollutant that can be allowed to reach a water body. It was, he said, "primarily an informational tool" intended to help guide state water protection planning.

He contended that the planning and implementation of water cleanup programs were delegated to the states under the Clean Water Act and that the EPA had encroached on state planning and implementation roles by allocating nutrient loads to specific sectors.

"Meeting the load is a social and economic decision" which affects growth, how much people have to pay for the cleanup, and who pays, Schwartz said. Those are "intensely local and intensely expensive" decisions which Congress delegated to the states, he said.

While the Clean Water Act gives the EPA authority to regulate point sources of pollution, such as wastewater treatment plants discharges as well as some stormwater and certain large animal feeding operations, the act does not give EPA authority to regulate more diffuse nonpoint source runoff, such as fertilizer from crop lands.

Schwartz acknowledged that meeting a TMDL might require pollution reductions from agriculture and other nonpoint sources, but said it was up to the states to make the "logical division" about who should achieve those reductions. In the Chesapeake Bay TMDL, he said, the EPA was "federalizing" state roles by establishing specific pollution reduction amounts that should come from agriculture, which it does not have direct authority to regulate. "What EPA has done is put itself in the driver's seat for allocations," Schwartz said.

But Kent Hanson, a Justice Department attorney representing the EPA in the case, depicted a sharply different picture of the TMDL development process, in which the nutrient reduction goals set forth in the final document, were developed over several years of meetings that involved EPA, state officials and various stakeholders, and which were open to the public.

"The Bay partnership did most of the work, and reached a consensus," Hanson said. The allocations in the TMDL, he said, were primarily developed by the states, in consultation with the EPA. In three instances, he said, the EPA changed allocations where the agency determined states had provided inadequate evidence they could achieve nutrient reductions from certain sources.

Hanson, though, insisted even those altered allocations were not necessarily binding on the states. States may suffer some ramifications if they unilaterally changed allocations — for instance, the EPA could opt to withhold grant money or require more reductions from wastewater discharges, which it has authority to regulate — but the agency could not prevent the state from making the change, Hanson said. "There may be ramifications, but those are ramifications allowed by law," he said.

Jon Mueller, an attorney with the Chesapeake Bay Foundation, one of several environmental groups that intervened in the case on the side of the EPA, recounted the long history of past multi-state Bay agreements that failed to restore the Chesapeake.

Those agreements, he said, constituted interstate contracts that bound the EPA and bound it to come up with a cleanup plan for the Bay when those efforts failed, noting that the Chesapeake 2000 agreement, signed by the EPA and states, specifically called for developing a TMDL by the end of 2010 if cleanup plans failed.

The development of the TMDL was discussed for years at high-level Bay Program meetings that involved state and federal agency leaders, who were heavily involved in planning the document, Mueller said.

"What we see here is debate. What we see here is compromise. What we see here is democracy," he said. "There is no undue coercion here. There is no slapdash rush to judgment."

Mueller read off notices for publicly announced meetings, hearings and webinars related to the development of the TMDL, and commented, "This wasn't done in a dark room behind closed doors."

He also said the failure to meet past goals had taken a toll on people, such as watermen who have seen their catches decline over the years. "That's what this TMDL is really about — the impact on people," Mueller said.

Christopher Pomeroy, an attorney representing municipal wastewater agencies, said many treatment plant operators had concerns about the TMDL, but still opposed the agriculture and home builder's position. Reducing pressure on nonpoint sources, as their suit suggests, would likely increase regulation of regulated wastewater dischargers.

"Their alternatives just won't work in the real world," Pomeroy said. Even if wastewater facilities stopped discharging altogether, it would not achieve cleanup goals, he said. He also disputed the view that allocations were driven by the EPA. "The allocations were largely determined by the states," he said.

Schwartz acknowledged that allocations in the TMDL were largely developed by the states in Watershed Implementation Plans they developed to achieve cleanup goals. But, he contended, states were coerced to participate in the TMDL process, noting that the EPA had threatened to "go it alone" if states did not cooperate. The states "did it under some duress."

And, he noted that at various times during the TMDL development process, New York, Pennsylvania and West Virginia had all disputed some aspects of EPA's authority in the process.

While much of the argument was focused on the scope of the TMDL and allocations, the two sides also debated other issues, including the validity of the models used to help establish nutrient loads in the TMDL, and whether outside groups were given adequate opportunity to comment on the TMDL.

Plaintiffs questioned the capabilities of the computer models used by the EPA, especially the accuracy of their numbers at local levels. They also contended that the models in some cases did not incorporate up-to-date information about the watershed, especially conservation practices implemented by farmers.

They also said the 45-day comment period allowed for the TMDL was too short, and that the EPA had failed to make some key information available, especially relating to its computer models, until late into the comment period.

Attorneys for the defendants responded by defending the quality of the modeling, and said that all meetings where model issues — including the information going into the models — had been open to the public for years, and that a number of public briefings had been made. Similarly, they argued that the comment period was adequate as meetings leading up to the TMDL development were open to the public.

Farmers and environmental advocates filled the benches in the courtroom, each worried about the implications of the outcome, both for the region — and beyond.

Will Baker, president of the Chesapeake Bay Foundation, said in an e-mail to supporters on the morning of the hearing that the TMDL was "our last and best chance to leave a legacy of clean water for future generations."

Martin Barbre, first vice-president of the National Corn Growers Association, emphasized the impact the case could have on the nation. "This lawsuit is extremely important to America's farmers because the outcome could affect EPA's future handling of water quality regulations throughout the country," he said.

Part of the lack of clarity stems from the history of TMDLs. Although included as section 303(d) in the original 1972 Clean Water Act, the reference is short and remarkably vague, directing that states identify all of the waters that do not meet water quality standards and report them to the EPA. The act doesn't say how often this should occur — its exact phrase is "from time to time."

For those waterways, the law says states should determine the maximum pollution "load" a water body can receive and still achieve its water quality standard. It says that load should then be allocated among contributing sources. The allocations are to include a margin of safety and account for seasonal variation.

The EPA has since sought to clarify the law through regulations. For example, "from time to time" now means every two years.

Nonetheless, all of this was largely overlooked until the 1990s when environmental groups filed a spate of suits against the EPA for failing to ensure that states were writing TMDLs.

Since then, roughly 40,000 TMDLs have been completed across the United States; the Chesapeake Bay TMDL is by far the largest and most complex one.

The Bay case is one of several suits in recent years which have sought to clarify the authority of TMDLs, and the EPA's role in enforcing them.