LOS ANGELES — As officials prepare to finalize a much-heralded plan to combat pollution at the Los Angeles-Long Beach harbor complex, the two ports are gearing up to fortify their dominance of the nation's Pacific Rim trade with long-delayed expansion projects.

The projects call for enlarging terminals and rail yards, building a marine terminal for crude oil and widening roads. An aging Long Beach bridge would be replaced — at the cost of $864 million — to allow larger container ships to dock at what is already the nation's busiest port complex.

If all goes according to plan, the ports hope to begin work on at least four of a dozen high-priority expansion projects by this time next year. All this activity was set in motion last fall when commissioners at both ports approved their $2 billion Clean Air Action Plan, which aims to reduce harbor emissions by 50 percent over five years.

"This is the biggest piece of work this city has undertaken in some time," said Los Angeles Board of Harbor Commissioners President David Freeman. "We're going to grow and we're going to clean up this place or my head will be served up on a silver platter in Los Angeles Mayor Antonio Villaraigosa's office."

Still, it won't be easy convincing port communities that large-scale industrial growth and a healthy environment aren't mutually exclusive goals.

Tensions remain between the fast-growing ports and neighborhoods enduring their side effects: air pollution, industrial blight, heavy truck traffic, excessive noise and light, container terminal projects that consume homes and businesses and higher rates of asthma and cancer.

State air quality and health experts have linked 2,400 premature deaths a year to noxious emissions produced by the ports, which reported an average 10 percent increase in trade in 2006.

A state study released last week showed that residents who live near rail yards face higher cancer risks from soot.

The question being asked harbor-wide, from the working-class neighborhoods of Wilmington and west Long Beach to the Dalmatian-American Club of San Pedro, is this: Will port growth outpace the mitigation efforts?

Tom Politeo, a spokesman for the Sierra Club's Angeles Chapter, worries that some expansion projects could be up and running before the ports' clean-air plan is fully implemented.

"The level of technology being described is not up to the task when you have an industry growing at a rate of 11 percent per year," Politeo said. "Even if everything in the ports is 90 percent cleaner, you'll eventually lose ground on the basis of current growth rates."

Robert Kanter, director of planning and environmental affairs for the Port of Long Beach, disagreed.

"Unless we can clean the air, we're not going to move forward with any of these projects. The community won't allow it," he said. "In fact, I expect that every one of the environmental impact documents for these projects will be challenged and end up in court."

A court challenge has delayed some of the projects for about six years. The Los Angeles City Council approved plans in 2001 for a 174-acre terminal for China Shipping Holding Co., prompting lawsuits by environmental groups.

That suit ended in 2003 with the port and City of Los Angeles announcing a $60 million settlement with environmental groups. Much of the money will fund projects to reduce air pollution.

Although the suit did not directly affect other expansion projects, it had a chilling effect on plans for other efforts. It also helped prompt the drafting of the Clean Air Action Plan.

Officials continue to refine the plan, and in April, approved, as part of it, an overhaul of dockside trucking to reduce diesel pollution from trucks by 80 percent in five years.

Calls to reduce pollution are driven in part by the increase in trade at the port complex over the last decade or so.

The value of containerized trade — led by imported furniture, clothing and shoes, computers and office machines, autos and trucks and motorcycles, and toys — soared from $74 billion in 1994 to $305 billion in 2006. That's an increase of 312 percent.

Port trade, which helps support an estimated 3.3 million jobs from California to New York, is expected to double by 2020, port officials said.

The projects range from a $90 million container terminal expansion plan to the replacement for the Gerald Desmond Bridge, believed to be the only significant bridge in the nation wearing "diapers" — large wire nets that prevent chunks of exfoliating concrete from falling into the water and streets below.