To defend his Dupont Circle art gallery renovation against construction workers unleashed by a city hall paperwork snafu, architect John Reno made a valiant last stand yesterday -- only to be left swimming in concrete up to his ankles.

As wine-sipping couples at the Kramerbooks outdoor cafe laughed and a groaning concrete mixer eased towards his own personal Alamo, Reno stood his ground -- a patch of sidewalk on 19th Street NW in back of Fisher Art Galleries.

At the request of gallery owner Miriam Fisher, Reno had obtained a city permit to build a brick sculpture garden that would extend to the edge of the street. But the permit on file with the Department of Transportation, had not caught up with the concrete mixer and the angry Burno Brothers Construction men who ordered Reno out of the way.

They had a city contract to pour concrete for a sidewalk in back of the gallery and they weren't stopping for anyone, Reno said they told him.

We've been contracted by the District and we're pouring the cement -- you'd better get out of the way," Reno quoted a Burno Brothers construction worker as saying. But Reno refused to budge.

"I'm normally a passive person, someone who would never challenge authority," an infuriated Reno said later. "But in this case, we were in the right. We had the permit. The city had agreed not to pour in back of the gallery."

Only no one told Burno Brothers.

While Fisher tried to contact DOT supervisors to halt the work, Reno pleaded with construction workers and a city hall site supervisor who said he couldn't call off the men without orders from his boss, Stanley Ather.

The concrete mixing truck was five feet away from Reno and pouring as he stood firm at the property line.

One construction worker accused Reno of trying to "cheat" them out of 300 worth of concrete pouring, Reno said, adding that he offered the man $300 cash on the spot to skip the 30 feet in back of the gallery that he planned to brick over "a la Georgetown."

He got no response. The truck poured and several men shoveled concrete over his expensive Italian loafers, up to the ankles of his $90 slacks. He refused to budge.

A crowd gathered. Construction men hooted. He stood firm. A worker grabbed him in a hammerlock and put him on "dry ground," he said. He jumped back into the concrete.

By the time DOT street maintenance engineer Stanley Ather and several city hall officials arrived, Reno was standing in four inches of wet concrete. Ather said that after "we found out he was rational and not a nut," he ordered the men to stop pouring and "block up" the poured concrete, leaving 15 feet of virgin sidewalk.

"We were unaware he had a permit," he said.

"There was a communication breakdown," said Mario Gugliemi, DOT's acting costruction engineer whose files contained Fisher's building permit, dated April 28. Reno's drawings and the permit called for Fisher to brick in the back of her gallery to the street's edge. The city had agreed, said Gugliemi, to skip pouring the portion of sidewalk.