State says computer model for bay cleanup has problems

People across Virginia are trying to save the Chesapeake Bay, but residents of Charles City County must be working really, really hard.

Estimates before this summer showed that Charles City needed to reduce sediment pollution — the amount of dirt that flows into streams leading to the bay — by 48 percent.

But according to revised figures, Charles City's work is done. In fact, the county gets a credit — it could increase pollution 406 percent.

At least, that's the way it works out in a computer.

Strange new numbers such as Charles City's came from a computer model, or simulation, that the federal Environmental Protection Agency relies upon to help guide the six-state bay cleanup.

Officials in Gov. Bob McDonnell's administration say so many of the new figures for localities, which came out in August, are wrong that it's tough to know what to do.

"It's going be difficult for the localities to put together a good (cleanup) plan when they are using inaccurate numbers," said Anthony Moore, Virginia's assistant secretary of natural resources.

But Jeff Corbin, the EPA's senior adviser on the bay cleanup, said Virginia is fixating needlessly on the model — and on a set of numbers the EPA isn't even enforcing.

The causes of the bay's problems — pollution from farms, suburban yards and other sources — are well-known, and Virginia should be working to make those places cleaner, Corbin said.

"Unfortunately, they have been using the model, the model, the model," Corbin said, "when this is really about putting practices on the ground."

What sounds at first like a geeky argument over a computerized tool takes on a different light when you consider the stakes — the health of a beloved waterway, as well as some serious money. The cleanup is estimated to cost $8 billion in Virginia alone.

The model has been an issue with some critics for years. This year, groups representing farmers and builders challenged the bay cleanup in federal court, arguing in part that the model is flawed. A decision is expected in 2012.

The model was developed in the 1980s by experts with the EPA, other federal and state agencies and academia. Maintained at an EPA office in Annapolis, Md., it is run by the EPA and by academics funded by the EPA.

Scientists plug in land uses — a forest here, a farm there — that represent the six-state bay watershed. The model estimates the amount of pollution flowing toward the bay by what's on the ground — for example, a farm that lets cattle wade into streams pollutes more than a farm that fences cattle out.

Ultimately, the model comes up with estimates of how much pollution flows to the bay and how much should be cut.

Relying largely on the model, the EPA sets pollution limits — a "pollution diet," some call it — for each state and for major-river basins such as the James River region. The model is good at estimating pollution over such broad areas, the EPA says.

Everyone agrees that the model is much less accurate when it comes to estimating pollution cuts at the local level. And Corbin said the EPA is not requiring anyone to meet local-level figures such as those for Charles City.

The model is "sort of like a big-screen TV," said Beth McGee, senior water-quality scientist with the Chesapeake Bay Foundation, an environmental group, "When you look at the individual pixels, they aren't very clear, but it does a good job at the big scale."

The farmers' and builders' groups are using the model as an excuse to resist the cleanup, said McGee. "It's a smokescreen, in our opinion."

But Wilmer Stoneman, a lobbyist for the Virginia Farm Bureau, said farms, homes and other sites are so varied that the model simply cannot reflect all those differences.

"We are basing hard legislative requirements on an incomplete data set," Stoneman said.

Maryland and Pennsylvania are also expressing concerns about the model. For one thing, it appears that the model doesn't always reflect the benefit of individual farm plans designed to limit the use of manure and fertilizer.

The model will be revised over the next few years, Corbin said.

The EPA is requiring bay states to prepare by Dec. 15 a draft report showing the states' latest plans for cleaning the bay.

Virginia's Moore said it makes no sense to rush for that deadline if you are basing your plans on inaccurate numbers.

"Why not stop the process, fix the model, make sure that it's accurate and works correctly, and then continue on with the process?" Moore asked.

Corbin said this is no time to delay the cleanup, which has gotten serious under President Barack Obama after poking along since the 1980s with little improvement to the bay.

"We have got to keep moving on this," Corbin said. "Any time we build in another delay, it endangers the entire process."