UPDATE: Tides burying oil under sand at Pensacola Beach // PHOTOS

PENSACOLA BEACH - Despite intensive efforts by more than 1,100 workers and heavy equipment to clean thick tar from Pensacola Beach overnight Wednesday, massive sheets of oil remained buried in the sand.

An 8-mile stretch of Pensacola Beach that was covered with gooey oil Wednesday appeared to be clean when the sun came up Thursday. But researchers from the University of South Florida and news reporters discovered that oil is buried from about 1 inch to 8 inches deep.

Mark Bowen, Bay County's emergency services director, said there's "certainly a possibility" tides also are burying tar balls on Panama City beaches. He doesn't know whether tar balls adhere to sand the same way oil does or are more likely to move out with the tides but, he said, he's looking into it.

"Again, we're learning from (Pensacola)," Bowen said. "Time is on our side. All we have to do is look to the west to know what we're going to see next."

Thursday evening, a Pensacola News Journal reporter visited the "clean" section of Pensacola Beach near Peg Leg Pete's off Fort Pickens Road.

At a glance, it appeared at least 90 percent of the oil was gone. Scattered tar balls and a few bigger chunks of fresh crude were all that remained on the surface.

But when the reporter dug about an inch into the wet sand near the high tide line, his fingers sank into thick sheets of tar.

Rip Kirby of USF's research lab and his partner, associate professor of geology Ping Wang, said tides Wednesday night were responsible for burying the oil.

"The oil gets brought in on the incoming tide, it comes in contact with the sand and adheres to it as the tide goes out," Kirby said. "The tide drags sand from the higher elevation on the beach and buries the oil."

A major concern is that a heavy tide can unearth the hidden oil and redistribute it to the cleaner, higher elevated portions of unaffected beach.

Kirby and Wang spent Thursday digging short trenches in intervals from Fort Pickens to Casino Beach to survey the buried oil.

The researchers' efforts at Pensacola Beach mirror earlier examinations of Dauphin Island in Alabama.

Wang said the buried tar on Dauphin Island was more sporadic than on Pensacola Beach, which had a long, consistent path of hidden oil.

"They were buried at Dauphin Island, but not like this. Those were tar balls getting buried," Wang said. "This is a very substantial patch of oil getting buried."

John Temperilli, Escambia County's contracted response operations specialist, said three things are taking the oil on Pensacola Beach out of sight: It's getting cleaned up, pulled back out by the surf or covered up by more sand on the incoming tide.

"There is some oil, particularly the more liquid oil, that will percolate into the sand," Temperilli said.

Escambia officials said they're still working to perfect mechanical cleanup methods to get at oil that's buried.

"They will filter and clean it and it will be lab certified that it's safe," Temperelli said.

He said county officials discussed with Unified Command representatives Thursday morning the protocols that should be followed for sifting sand and returning it to the beach.

So far, efforts to use mechanical rakes to clean up the mess have been unsuccessful.

"The result was mixing the oil into the sand which was the last thing we want to do," Escambia County Commissioner Gene Valentino said.

Keith Wilkins, deputy chief of neighborhood and community services for Escambia, said high tide and an incorrect screen size on the rakes made the work fail.

Four mechanical rakes were to be tested Thursday night, Wilkins said.

News Journal reporters Kris Wernowsky and Paul Flemming contributed to this story.