Normally, the air at the Library of Congress is hushed and studious, even reverential toward the great ideas and great issues.

But for more than five hours Friday, lighting and thunderbolts intruded. People were arguing such terms as "boondoggle" and "community development" and "Corps of Engineers."

The setting for this give and take was a board meeting of the American Folklife Center, whose members were agonizing over the issue of accepting $480,000 of Army Corps of Engineers' money to conduct a study.

Folklorists will conduct a study at the drop of a banjo, but this one was different. It was to be a cultural impact study on the most expensive and one of the most controversial corps' waterway projects in history.

Some folklorists feared their small center would be used by the more politically astute corps to help justify the costly project.

The project is the $1.8 billion Tennessee-Tombigbee Waterway, a barge canal in Mississippi and Alabama shortening the water route to the Gulf of Mexico for inland shippers.

A federal court decision is pending on the legality of the project and efforts are being mounted in Congress to stop construction, although work is about one-third complete.

The folklife center, an arm of the Library of Congress, became involved with Tennessee-Tombigbee in late 1977, when Department of Interior officials raised the possibility of a folklife impact study.

Interior administers a heritage conservation program, using Corps of Engineers money, to lessen the damage and disruption caused by some water resources projects.

As Interior and Alan Jabbour, folklife center director, interpreted the law, money could be made available for a folklife impact study along the path of the Tennessee-Tombigbee. Negotiations moved ahead apace.

Last November, the board approved a contract for the study and then the first lightning struck. Critics feared the center's participation would imply support of the controversial waterway. Supporters felt the study was necessary.

A leading critic was Archie Green, a folklorist and former shipwright, whose lobbying efforts over many years led to congressional creation of the center in 1975.

At the prodding of Green and others, the board agreed to review its November vote and consider more details about the advisability of doing the study.

Green's prodding found support from board member S. Dillon Ripley, secretary of the Smithsonian Institution, who also called for a reopening of the discussion.

As the discussion surged back and forth Friday, Green, not a board member, urged the center to withdraw from the study. To do otherwise, he said, would be to apply "whitewash" to an engineers' project that is "a crime against society."

"The corps needs us -- they need a bucket of whitewash. They need to buy us because they want surveys that suggest the damage is not as great as it seems," Green said.

Jane Sapp, of Eutaw, Ala., representing blacks in the waterway area, urged the opposite. The waterway will be built whether the center likes it or not, she said, and the folklife study is seen by blacks in the area as an important boost to them.

After the long debate, the board voted again. It was 5 to 4 in favor of doing the impact study, but Green jumped up to remind Raye Virginia Allen, the chairwoman, that the law requires a two-thirds support of the board's 17 members on contract approvals.

There was a question about that, however, and Allen said that while a legal opinion would be sought from the library's lawyers, the center's participation in the study seemed unlikely.

"Yes, I would say it is dead," Allen said yesterday. "We will get the legal officer's opinion, but the board felt the two-thirds requirement would apply."

Green thought the matter was settled. "It is a good symbol that someone can defy the Corps of Engineers," he said.