The U.S. Environmental Protection Agency has proposed new emissions standards for five chlorine factories -- including the Olin Corp. plant in Augusta -- that use large amounts of toxic mercury.

The proposal would raise the maximum achievable control technology level for mercury cell rooms at the plants to 90 percent, up from 75 percent. Those levels are the point at which a washdown is required in the area where mercury cells are used for chlorine production.

The proposed new rule also would require that a mercury monitoring system be used to reduce fugitive emissions in the cell room, and that each plant develop a cell room monitoring plan, according to Tonya Bonitatibus, an Augusta-based field organizer for the environmental group Oceana.

"The fugitive emissions from the cell room are by far their largest source of emissions at the plant, and because of the difficulty in monitoring the escaping mercury the reported emissions are only an estimate," she said.

Oceana, which has lobbied for years to get Olin to switch to a mercury-free manufacturing process, believes the proposed new rules have both positive and negative aspects.

"We are disappointed that EPA would want to back off of the trigger values requiring a washdown of the cell room, but are encouraged by the requirements of installing a mercury monitoring system that would allow Olin to get a better handle on their fugitive emissions leaving their cell room," Ms. Bonitatibus said. "But they could eliminate the increased cost of continuing to operate using mercury by switching to a mercury-free process."

In an e-mail, Plant Manager David Blair said Olin -- which has no plans to convert to mercury-free technology -- is "currently evaluating the new EPA proposal" and remains in compliance with current standards.

"At the end of 2006 we installed new technology and adopted additional procedures and practices. As a result, we have reduced our 2007 air emission by over 85 percent. We discharge only one-third of what the government allows for water. Our system is designed to recycle mercury, and all emissions are accounted for in an annual audit conducted by independent experts."

There are five mercury cell chlor-alkali plants in the country that produce about 5 percent of the chlorine made in the U.S., according to the EPA.