“(Meeting regulatory goals) economically is even harder to reach than technically,” he said. “We can’t even reach (this standard) technically. There’s no one who’s done research in the field who believes we can meet that goal.”

David Clegern with the State Water Resources Control Board said the Central Coast board had taken farmers’ concerns into account in developing the proposed rules, even implementing some of the input it had received - for example, in its use of a three-tiered approach when evaluating what regulations to apply to different farms based on the risk they pose to the region’s water quality. But he said nitrate contamination of water in the area is a serious environmental and health problem that needs to be addressed. Clegern said application of the drinking water standard to water from farms is necessary to rehabilitate the contaminated land and protect nearby water sources.

But some of the criticisms by farmers of the board’s proposed rules have been backed by a number of researchers. In 2010, academics including Professor Tim Hartz, a specialist in vegetable crop farming at the UC Davis, sent a letter to the water regulators expressing concerns about some of the policies being considered. The drinking water standard was cited as problematic.

“In the context of NO3-N [nitrates] the implication is that the 10 [parts per million] standard [the drinking water standard] would apply to each and every discharge event,” such as irrigation or rainfall that seeps below plants’ roots, the letter said. According to the researchers, this is “an impossible standard to consistently meet in a row crop context.”

The letter also warned the board that its new regulations might be too focused on fertilizers to effectively address the problem of nitrate contamination of the region’s groundwater. According to the researchers, fertilizers from farming in the area are only one source of nitrates.

“While there is ample evidence that nitrate in agricultural waste water originates at least in part from the use of nitrogen fertilizers, there is much less evidence that nitrogen fertilizers are a significant source of nitrate contamination in groundwater,” the letter said.

If farming isn’t the only major contributor, the water board’s rule might be costly to farms, but ultimately fail to achieve the goal of cleaning up drinking water in the region. Nonetheless, despite recent amendments to the proposed regulations, the board hasn’t relented on the rule, or other controversial proposed requirements, such as expensive water quality monitoring. Some farmers, like Chris Darway, a vegetable farmer in San Luis Obispo County, say the new rules as envisioned would likely drive many growers out of business.

“What’s been proposed, I don’t see how we could conform,” he said. “I don’t see smaller farmers continuing.”