* Tropical storm forms, threatens spill workers
* Louisiana declares state of emergency
* U.S. officials evaluating whether to evacuate area
* Some nonessential workers leave, spill sites unaffected (Adds details, background throughout)
By Kristen Hays and Anna Driver
HOUSTON, July 22 (Reuters) - BP Plc (BP.L) (BP.N) oil spill workers in the Gulf of Mexico prepared for a possible evacuation on Thursday as a tropical storm threatened more delays in attempts to end the environmental disaster.
The U.S. National Hurricane Center said Tropical Storm Bonnie, the second named storm of the 2010 Atlantic hurricane season, was packing maximum sustained winds of 40 miles (65 kph) per hour.
It formed near the Bahamas on Thursday on a track that could take it over BP’s oil spill site in the Gulf of Mexico.
Before it became a named tropical storm, U.S. officials said they would decide on Thursday night whether to unhook surface ships and evacuate the site. But the blown-out well would remain capped even if an evacuation forces a temporary halt to undersea surveillance.
Louisiana Gov. Bobby Jindal, who declared a state of emergency because the storm is forecast to hit the state’s coast on Sunday, said the storm could delay efforts to permanently seal the well by up to two weeks.
“Obviously that’s a concern,” Jindal said.
For full spill coverage link.reuters.com/hed87k
Special report on US spill response chief [ID:nN21101035]
Insider TV link.reuters.com/ruh58m
Graphic on BP assets link.reuters.com/byn78m
Some oil-skimming ships came ashore as Gulf seas grew more choppy with high winds and rain moving northwest out of the Caribbean near the Bahamas.
“We have determined that if we have to evacuate the site, we are prepared to leave the well capped,” retired Coast Guard Admiral Thad Allen told reporters at a briefing earlier in the day. “It’s very possible that we could have wave heights that could exceed the operational envelope for all platforms.”
BP has already evacuated nonessential workers from eight offshore Gulf facilities, but the evacuations did not affect operations at the spill.
The largest offshore oil spill in U.S. history, triggered by an April 20 explosion that killed 11 workers, has unleashed an environmental disaster in the Gulf and devastated the region’s tourism and fishing industries.
BP capped the well last week, choking off the flow of oil for the first time since the explosion.
Workers also had been close to completing a relief well designed to permanently stop the spill and launching a “static kill” operation to pump heavy drilling mud and possibly cement into the well.
BP has received approval to prepare for the “static kill,” but final approval to go is yet to come.
“It’s sort of that one last check before you start to execute,” Kent Wells, BP’s senior vice president of exploration and production, told reporters at a briefing.
Surplus boom and other equipment was being moved inland to prevent storm-related damage. An evacuation could force a delay of 10 to 14 days in operations.
The spill has sparked a crisis for British energy giant BP, which created a $20 billion fund to compensate victims of the disaster and still faces mounting costs.
BP shares remained relatively steady in New York trading, climbing 0.3 percent as the overall market rose. It is due to report quarterly results next week.
President Barack Obama, who has been under political pressure for his handling of the spill, will spend the August 14 weekend along the hard-hit Florida Gulf Coast, the White House announced.
Vice President Joe Biden visited Theodore, Alabama, on Thursday to assess BP’s efforts, and he met with fishermen and small business owners from the area.
“We are preparing for a short-term evacuation. Once the weather passes, we will be back out there,” Biden told reporters. “We are ramping up and looking a lot better. We will resume as soon as possible.”
Still, the well could go unwatched for days. BP executive Doug Suttles told CBS News engineers may have some data on the well, but not until after the storm is gone.
“We’re trying to have some capability to do things like take stored images, photographs, video, other things that we can actually collect after the storm passes. But right now we couldn’t do live monitoring,” Suttles said.
The government announced it was reopening 26,388 square miles of Gulf waters to commercial and recreational fishing after tests and U.S. Coast Guard flights showed no oil in the area and fish showed no signs of contamination.
In a report to a federal judge in New Orleans, the Obama administration said it had complied with his order blocking the government’s original six-month ban on deepwater drilling. But it also argued the case was moot because a revised suspension order has been issued.
The new moratorium, which lasts through November and bars new projects that use blowout preventers similar to the one used on the BP well, has already been challenged by one drilling company, Ensco Plc ESV.N.
In a separate case, a federal judge ruled on Wednesday that all activity on oil and gas leases in the Chukchi Sea off Alaska must stop until regulators complete a more thorough review of how drilling there would impact the environment.
In a lawsuit filed by environmental and Alaska Native organizations, the judge said the U.S. government failed to abide by federal law when it sold $2.66 billion worth of leases in the Chukchi in 2008, mostly to Royal Dutch Shell (RDSa.N).
Workers on the doomed Deepwater Horizon drilling platform expressed concern about safety practices in a confidential survey conducted a month before the oil rig exploded, according to a survey commissioned by rig owner Transocean.
In the survey, workers said they “often saw unsafe behaviors on the rig” and indicated they feared reprisals if they reported mistakes or other problems. (Additional reporting by David Alexander, Jeremy Pelofsky and Xavier Briand in Washington, Chris Baltimore in Houston, Tom Brown in Miami and Verna Gates in Alabama; Writing by John Whitesides and Ed Stoddard; editing by Todd Eastham)