PORTLAND – After years of delay, an $82 million U.S. Postal Service mail distribution center that became the focus of tough competition between Lewiston-Auburn and Greater Portland will open July 8 in Scarborough.

The 429,000-square-foot facility, equal in size to about 71/2 football fields, will handle all mail for southern and central Maine, with a work force of more than 600 assigned to three eight-hour shifts.

The plant, built on a 51-acre site, was designed to consolidate the area’s mail processing and distribution. It brings together operations from the 275,000-square-foot Forest Avenue facility in Portland and satellite operations. The Forest Avenue site will be renovated for district administrative offices and letter carriers.

The project began in 1996 after a report found that the existing facility was 40 percent too small. Three sites in Greater Portland were announced as finalists the next year, but the Lewiston-Auburn area emerged by 1998 as a contender as well.

The Postal Service announcement in 1999 that it would build the plant in Lewiston or Auburn triggered complaints from employees who faced the prospect of a longer commute. After saying it would consider new sites between Scarborough and Lewiston, postal officials announced in 2000 the selection of the Scarborough location.

“I think it’s been a good process. We should all be proud of what’s opening in our backyard,” said Godfrey Wood, chief executive officer of the Portland Regional Chamber, which fought to keep the center in the Portland area. “I think it’s good for the entire region.”

Work on the project was delayed for several years because of budget constraints and security issues after the Sept. 11, 2001, terrorist attacks.

Sen. Susan Collins, who chairs the Senate Homeland Security and Governmental Operations Committee, which has jurisdiction over the Postal Service, said that amid the delays she was assured by Postmaster General John Potter that the facility remained a top priority.

“I am pleased that that promise will soon be fulfilled when the Scarborough facility is finally on line,” said Collins, R-Maine.

Construction jobs already have boosted the local economy, she said, and the Postal Service is expected to award about $6 million a year in contracts to local vendors.

The Forest Avenue facility, which handled about 1.1 billion pieces of mail last year, was built in 1933 and nearly tripled in size 30 years later. Satellite locations were added in the early 1990s, said Tom Rizzo, a spokesman for the district of Maine.

Consolidation allows a more efficient layout of current and anticipated equipment, which will smooth mail flow and hold down mail processing costs, he said. The relocation also is expected to relieve traffic congestion around the Forest Avenue facility, Rizzo said, while the new site near major highways should reduce weather-related transportation delays in mail delivery.