The EPA in November announced final rules to ban mixing zones for bioaccumulative chemicals in the Great Lakes — the first volley in a growing effort to curtail the use of areas beyond discharge pipes to dilute pollutants to acceptable levels.

The Bay Program is poised next year to launch its own effort to phase out most mixing zones over the next decade, but officials say their voluntary program will be more sweeping than the mandatory requirements in the Great Lakes.

The Great Lakes regulations affect 22 toxic chemicals, some of which — such as PCBs, DDT and chlordane — are already banned. Also, the Great Lakes rule applies only to chemicals that bioaccumulate in the food chain.

The Bay Program’s phase-out applies not only to bioaccumulative chemicals, but also those that persist in the environment, such as many toxic metals, because they don’t break down over time.

“In a lot of ways, we’re more far-reaching than the Great Lakes region,” said Kelly Eisenman, toxics coordinator with the EPA’s Bay Program Office. She noted that studies around the Bay have shown that several contaminants allowed to have mixing zones have built up to harmful levels in sediments of some Bay tidal tributaries.

Mixing zones are an area beyond the end of a discharge pipe where pollutants are allowed to exceed water quality criteria. By mixing with water in a river, lake or stream, the goal of the mixing zone is to allow the contaminant to become diluted enough to meet water quality standards downstream.

Although mixing zones are allowed under the Clean Water Act, the EPA and environmental groups have increasingly discouraged their use. “The solution to pollution is not dilution,” EPA Administrator Carol Browner said in releasing the Great Lakes regulations in November.

The Bay Program’s mixing zone phase-out for bioaccumulative and persistent chemicals was called for in the Chesapeake 2000 Agreement. Further details for its implementation were spelled out in the Bay Program’s new toxics strategy, which is to be finalized in December. The strategy calls for initially emphasizing areas with known or suspected contamination problems, but ultimately spreading the phase-out to the entire watershed.

The Bay Program plans to complete a list of affected facilities, expected to number more than 100, by early next year, Eisenman said. The full list of contaminants is also being developed.

“Our first approach is to be very targeted, to be focused on the most impacted areas and the chemicals that are causing the greatest impacts first,” Eisenman said, “and then to go watershedwide with a broader list of chemicals.”

The Bay Program is to report on implementation progress in 2003 and 2007.

Facilities will be encouraged to meet the Bay Program’s voluntary goal through pollution prevention efforts, which seek to reduce the amount of pollution created rather than trying to control contaminants after the fact. Although the goal is voluntary, it was endorsed by both environmental groups and industries during a round of “stakeholder” meetings last year.

“We really wanted to pursue a voluntary approach because we feel that gives industries a little more leeway and flexibility to come up with innovative solutions within a reasonable time frame to eventually phase out mixing zones for particular chemicals,” Eisenman said.

In the Great Lakes, about half of the 600 major industrial and municipal facilities with discharge permits have mixing zones for bioaccumulative chemicals, according to the EPA.

The EPA says phasing out those mixing zones over the next decade will eliminate up to 700,000 pounds a year of chemicals that accumulate in fish and wildlife. It estimates compliance could range from $12 million to $35 million a year. The EPA will make exceptions where high cost or technological limitations make it difficult to eliminate the mixing zones.

First proposed five years ago to eliminate toxins in the Great Lakes, the regulation was voided by a 1997 court challenge brought by industry groups. It was proposed again in September by the EPA.

Since then, five Great Lakes states have moved to ban mixing zones for bioaccumulative chemicals. Under the EPA’s new rule, the three others — Pennsylvania, Ohio and New York — will have 18 months to adopt similar regulations.

The EPA has urged other areas to begin phasing out mixing zones as well, but the Bay Program is the only region outside the Great Lakes to put forward a policy.

“We have not heard of any other estuary or any other region that is doing a voluntary mixing zone phase-out,” Eisenman said, “and we have not heard of any program that is including persistent chemicals in the phase-out.”