For two decades now, the Chesapeake Bay cleanup has been guided largely by a computer model. Housed in Maryland, it spits out targets and forecasts and helps officials set goals for what should be done to restore North America's largest estuary.
The states involved in the celebrated cleanup, including Virginia, have a say in how the model works and help set its guidelines, but its operation falls mainly to the U.S. Environmental Protection Agency.
How the modeling is done, and what data are fed into the computer, have been bones of contention for years. Today, they are central to pending lawsuits from farmers and developers who argue that an aggressive push from the Obama administration is based partially on flawed, incomplete science and should be stopped.
Now another wrinkle has surfaced.
Virginia and several other states - including Maryland, Pennsylvania and Delaware - are complaining that a newly tweaked version of the model, known as 5.3.2, is leading to some weird and incomprehensible results for what local governments are expected to accomplish in the coming years to dramatically improve water quality by 2025.
In James City County, for example, data stemming from the previous model urged the county near Williamsburg to reduce nitrogen from farms, streets, storm drains and development sites by 8 percent, phosphorus by 11 percent and sediment by 20 percent. The guidance worried local officials, unsure how they would pay for environmental improvements and controls to hit those targets.
However, computer runs performed by the state using the new model prescribe something completely different: no reductions needed for nitrogen, and a 20 percent surplus of phosphorus and a 350 percent cushion for sediment.
In short, on paper the county went from a polluter to one that doesn't have to do anything.
While the James City County discrepancies are extreme - new data show that most Virginia localities have to do more, not less, to help save the Bay - state and local officials face a quandary: How exactly to proceed in the face of changing targets?
"What do we say to our localities? 'Well, we think that these practices we are asking you to implement might help you reach your goal, but we really don't know what that goal is and we aren't sure the money you spend to implement these practices will make any difference?' " said Doug Domenech, Virginia's secretary of natural resources, Gov. Bob McDonnell's top environmental official.
The EPA, environmentalists and some scientists concede that the modeling is imperfect and will continue to be updated and improved. But they also say the states are not required to be so precise in their calculations, and that no one asked them to break down data county by county, pound by pound of pollutants, for what they need to do to help the effort.
The model, they add, is not designed to be so specific and its main strength is defining what states must do river by river.
"They're getting down into the weeds, and we're telling them they don't need to go there," said Jeff Corbin, the EPA's senior adviser on the Chesapeake Bay. "Use common sense. Let's get on with it."
Carl Hershner, a scientist at the Virginia Institute of Marine Science, said model critics are missing the point of the new push to get serious about restoring the Bay.
"None of this stuff should impede the planning for what everyone knows is needed to be done," Hershner said. "We need to better control nutrients entering the Bay, and every state, county and city has to help do that."
The two main nutrients, nitrogen and phosphorus, are good for the Bay in proper amounts. But in excess, as today, they spark algae blooms that rob oxygen from water, making life difficult for aquatic life. Sediment that washes off the land clouds water quality, shallows creeks and rivers, and smothers key underwater grasses.
In settling a lawsuit years ago, the EPA pledged to clean up the Bay enough to remove it from a national list of dirty waters. In December, the EPA and its partner states agreed to a pollution diet, or TMDL, short for Total Maximum Daily Load, to achieve this goal.
The diet, which the computer model helped to define, called on Bay states to reduce nutrients and sediments through various means and to implement those improvements by 2025, with 60 percent of them complete by 2017. Virginia estimates its part of the deal could cost as much as $8 billion.
Amid economic woes and lean budgets, officials in the McDonnell administration say they have to be precise in how they spend such money, and that the computer model or any other tool should help guide where to get the biggest bang for the buck.
If the model is not precise enough to tell localities what they need to do without fear of penalty from the EPA, it should be refined to do so before moving forward, state environmental officials say.
"Dealing with numbers like this is just ridiculous when you're trying to put together a plan that the EPA will hold you accountable for," said Anthony Moore, an assistant secretary of natural resources overseeing Bay issues.
Moore and other senior officials from concerned states met with EPA leaders at a "modeling summit" last month. Chiefly, the states complained that many computer problems stem from calculating the impact of farm pollution.
One of the primary strategies for curbing fertilizer runoff from agriculture is implementing nutrient management plans on farms. But in many cases, the new model shows that such plans increase nitrogen and phosphorus pollution, not reduce it, Moore said.
In response, the EPA's regional director, Shawn Garvin, sent a letter to Virginia and other states that attended the summit. Garvin wrote that the EPA will correct its model but that the states should continue writing their plans reflecting how local governments will contribute to the effort. The plans are due Dec. 15.
Garvin also stressed that state calculations based on the new model do not have to be so specific.
"EPA does not expect the jurisdictions to express the 'local area targets' in terms... such as pounds of pollutant reductions by county," he wrote.
Instead, Garvin added, the next round of state plans "could identify 'targets' or actions that local and federal partners would take to fulfill their contribution toward meeting the Chesapeake Bay TMDL allocations."
Virginia officials, while disappointed, said they will press on, though they worry local governments may balk at committing to pollution cuts amid shifting targets.
John Carlock, an environmental specialist with the Hampton Roads Planning District Commission, which represents local governments across the region, described the changing models as "extremely frustrating for everyone."
The commission had serious problems with the previous model and threatened to challenge its recommendations in court.
"The states and the EPA are coming to the conclusion that the model works pretty well at the state level, OK at the river basin level, but not so good at the local level," Carlock said. "We absolutely need more consistency."
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