BP Plc (BP) oil spill workers in the Gulf of Mexico prepared for a possible evacuation Thursday as a brewing tropical storm threatened more delays in efforts to end the biggest environmental disaster in U.S. history.

Some oil-skimming vessels came ashore as Gulf seas grew more choppy, and U.S. officials evaluated the growing threat from a tropical storm forming in the Caribbean near the Bahamas.

Weather models project the storm will swirl across the Gulf near the site where crews are working to plug the spill before hitting the Louisiana or Texas coastline.

Ships collecting seismic and acoustic data while the leak remains capped during a well pressure test and two rigs that had been drilling a pair of relief wells remain on site, BP said.

"There has been no evacuation of equipment, but that could change. Some skimmers have been coming in," command center spokeswoman Mary Kahn said.

An evacuation could force a delay of 10 to 14 days in operations to end the spill, retired Coast Guard Admiral Thad Allen said on Wednesday. Ships in the region need several days to disengage from the spill operation and head to safety.

The spill, triggered by an April 20 explosion that killed 11 workers, unleashed an environmental disaster in the Gulf, devastating the region's tourist and fishing industries.

BP capped the blown-out well last week, choking off the flow of oil for the first time since the explosion. The company is conducting pressure tests to ensure the seal can hold, but those would be halted by an evacuation.

Workers were close to completing a relief well designed to permanently plug the leak, but work has stopped to wait out the weather. BP also had been close to launching a "static kill" operation to pump heavy drilling mud and possibly cement into the well.

Vice President Joe Biden was traveling to Alabama on Thursday to assess BP's efforts to counter the spill. He will meet with fishermen and small business owners from the area.

The spill has sparked a crisis for British energy giant BP, which created a $20 billion fund to compensate victims of the disaster. Company shares were up about 1.5% in morning trading in New York.

A New York Times report on Thursday said workers on the doomed Deepwater Horizon drilling platform in the Gulf expressed concern about safety practices in a confidential survey conducted a month before the oil rig exploded.

In a survey commissioned by rig owner Transocean, workers said they "often saw unsafe behaviors on the rig" and indicated they feared reprisals if they reported mistakes or other problems, the Times said.

The equipment assessment report cited at least 26 components and systems on the rig that were in "bad" or "poor" condition, the Times said.