Four teams of federal, state and local damage assessment experts walked onto the remains of the Quail Creek Reservoir dike Tuesday, beginning a process that could bring millions of dollars in federal assistance to the flood-ravaged region.

State engineering officials were also pondering how the troubled dam, which appeared in better shape than ever just 12 days ago, had failed.Tony Hafen, Washington County Emergency Management director, said Tuesday morning that two teams will evaluate damage to public facilities such as the dike and will study the destruction to private property, such as flooded houses. "Each team will have a federal, state and local (official) on it," he said.

The damage was caused when the west side of the reservoir collapsed after midnight Sunday and sent a 40-foot wall of water down the Virgin River. About 1,500 New Year's revelers escaped injury. Some 100 homes and 100 apartment units in Washington, Washington Fields, Bloomington Hills and Bloomington were damaged.

Meanwhile, fewer than 30 people remained homeless. People have brought in food and most of the displaced are staying in others' homes. Some 1,500 people were evacuated late Saturday and early Sunday from areas along the Virgin River in Washington County.

Engineers will begin drilling soon to determine the cause of the dam collapse, but as of Tuesday morning they had not yet arrived.

Louis Ramirez, Denver, an official of the Federal Emergency Management Administration, said that if President Ronald Reagan declares the region a major disaster area, FEMA will set up an office and begin processing emergency assistance. That agency and the Small Business Administration will be available for help.

Standing beside the enormous gap in the dike, Ramirez told the Deseret News Tuesday that if a disaster area is declared - and it's too early to know yet whether that will happen - then up to 75 percent of repair costs could be provided for public facilities.

As he spoke, bulldozers were working the reservoir bed to build a cofferdam to prevent further water from flowing while officials of the Utah Department of Transportation work on the washed-out U-9 highway.

High above the bulldozer hung an intake pipe where water was to be removed for a new treatment plant to provide culinary water to St. George. The plant had not yet been put into service.

Scott Munson, district maintenance engineer for UDOT, Cedar City, said the flood ripped out 1,700 feet of U-9.

"The bridge at Hurricane is damaged to the point probably where it can't be utilized even for temporary traffic," said Munson.

The water moved the bridge slightly and cracked the 50-year-old structure. The Virgin River gouged a new channel beyond the 350-foot bridge dumping gravel, silt and other debris around it. A new embankment will have to be built.

Hafen said the inspection teams will work quickly because the sooner they write their report, the sooner emergency relief money can flow. "We're going to try to get this done in two to two and a half days max."

Hafen added that if the reports are written quickly, relief could arrive within two weeks.

He said there is yet no reliable damage estimate - although the media has invented all sorts of figures.

"They've just come up with some fabulous figures," Hafen said.

"We have no control whether or not it is designated as a disaster area. The FEMA team will turn in a report to Washington. We hope to hear back within two weeks," Hafen said.

While homeowners and farmers cleaned up Tuesday, dam safety officials began asking why the dike failed. As recently as 12 days ago, Utah's director of dam safety, Richard B. Hall walked along Quail Creek Dike and said it seemed in bettercondition than at any time in the previous four years.

"Trouble with dams, you can't see inside of them," Hall said.

He went to Quail Creek Dike in late December because of the grouting that hadbeen done to stop seepage. The dike has seeped off and on since the reservoir filled in 1985.

Grouting is cement pumped under pressure into the foundation material, to fill holes that develop. "They have, to my knowledge, since it was built, moved on the site three or four times to do remedial grouting," Hall said.

Speculation centers on the possibility that gypsum lenses under the dike may have dissolved and collapsed. That could have caused gaps or loose material in the dike.

The grouting was done to fill such gaps.

Gypsum layers are "interbedded in the shale layers of the bedrock in varyingthickness," Hall said.

This mineral, which is a salt, will eventually dissolve if soaked by a reservoir. It is considerably less soluble than, say, table salt or the kind of salt you'd see out in the Great Salt Lake, he said.

"But it can go into solution and create cavities." The dike's fill material or the foundation could become compressed. Eventually this process could cause gaps within the dike.

Hall said he does not know whether the gypsum lenses were the cause of the collapse. He left late Monday to continue the investigation at the dike itself.

The site was part of the Dixie Water Project, which was proposed decades ago, he believes. But the U.S. Bureau of Reclamation decided not to build that project.

"I don't know if they declined to build it because of the geology of the dam or whether it was an economic problem," he said.

The next step is to obtain a report from consultants on the cause of the failure. Most likely, local interests will want to rebuild, he said. That might require a new design.

Who will be liable for money losses due to the failure?

"I haven't got a clue," Hall said. "There are so many parties involved."

Ellis Armstrong, a Salt Lake engineer who once headed the Bureau of Reclamation, said the original plan that the bureau examined was for a site on the Virgin River itself, near where Quail Creek joins the river.

"In fact, I designed it," he said. "We got the project authorized on the basis of that reservoir."

Later, when he was the bureau's commissioner, another site away from the river was considered. About 1962, the authorization was changed to include the new site, he said.

But then another snag developed: the fact that the woundfin minnow, a native fish, was endangered and could be threatened further by the dam.

"Then the bureau kind of gave up on it, I guess," and state officials became interested in the Quail Creek site.