Four piers on the old Fuller Warren Bridge will be demolished with explosives today, with traffic on the new Fuller Warren being shut down for about 20 minutes during the blasting process.

The blasting has been in the works for more than half a decade, with demolition work on the old span being halted in 2002 before resuming earlier this year.

Since the summer, workers have been chipping off the upper level of the bridge, which was opened to traffic more than 50 years ago.

Now, with the piers down to about 6 to 8 feet above the water, contractor Balfour Beatty Inc. can move ahead with blowing up the structure.

The piers extend 20 feet under the water, where the explosives will be placed. "It will be a bubble in the water," state Department of Transportation spokesman Michael Goldman said.

Ramps leading to the highway will be closed around 1:15 p.m., shortly before the scheduled 1:31 p.m. explosions, and reopened moments after the explosives are set off.

A variety of state and local agencies will be on hand starting about 12:30 p.m. to keep a watch out for manatees, which cannot be in the area while the blasting takes place.

If that happens, Goldman said, traffic would be allowed to resume on the new Fuller Warren until the water is clear.

Demolition of the bridge began back in 2001, after the new span was built, but was quickly stopped when the Department of Transportation discovered the contractor was illegally dumping tons of concrete rubble into the river.

Since the work was halted, the state and Balfour Beatty have wrangled over continuing the project, at odds particularly over the cost of the project.

The company won the contract to build a new Fuller Warren Bridge with a low bid of $81.3 million, which included $360,000 to cover the cost of demolishing the old bridge.

The cost of construction rose to $101.4 million, and Balfour Beatty has asked for more money to do the demolition, saying the situation has changed.

Although work began earlier this year, the company has not requested additional funds, Goldman said, although there is an expectation that money issues will be discussed once the project is completed.

Another four days of blasting will be needed to bring down the rest of the piers, the state said. The work is scheduled for January.