Soon, the U.S. government may -- or may not -- give the final green light to a project on which the artist and his late wife Jeanne-Claude began working in 1992. The proposal, named “Over the River,” is for translucent fabric panels to be suspended above sections of the 42-mile stretch of the Arkansas River in Colorado. An announcement confirming approval is expected to be made, Christo says, in October. Collector members of the ArtKabinett social network are sure to visit and collect some lithographs and photos of this monumental installation. If it goes ahead, “Over the River” will exist for just a fortnight in August 2014. Many of Christo’s most celebrated works are temporary; they have, he notes, “that fleeting quality, the sense that it will be gone after two weeks and will never exist again.” For the moment, he’s not sure it will happen at all. “We’re in that edgy waiting period.” He’s talking at an exhibition in the Annely Juda Gallery in London, devoted to a half century of such wildly ambitious plans. Over the years, Christo and Jeanne-Claude proposed such improbable acts as wrapping large buildings and an entire coastline in fabric. Another -- as yet unrealized -- project is to erect a structure larger than the Great Pyramid in the desert of Abu Dhabi, composed of 410,000 multicolored oil barrels. At 76 -- he and Jeanne-Claude were born on the same day, June 13, 1935, in different countries -- Christo remains driven by energy. Wiry, white-haired and casually dressed in an open shirt, he talks rapidly with an accent that’s part Slavic, part French. Born Christo Vladimirov Javacheff in Bulgaria, he moved to Paris in 1958 where he met Jeanne-Claude. They went to New York in 1964. Christo is used to long waits, and to disappointments. Over the past half century, he and Jeanne-Claude, who died in 2009, have been through that process many times. “We have succeeded in realizing 22 projects and we failed to get permission for 37.” Often, the process is slow, “The Gates,” 7,503 temporary saffron-colored portals along the paths of Central Park in New York, was first conceived in 1979, turned down in the 1990s, and eventually appeared in February 2005. In Colorado, “Over the River” ran into opposition on environmental and safety grounds, but he claims to welcome the debate as part of his kind of art. “Nobody discusses a painting before it’s painted,” says Christo. “But our works of art are discussed for months and years before they exist. Thousands think they look awful, thousands more think they look beautiful.” Christo seems to relish the setbacks as much as the triumphs. In the mid-1960s, he and Jeanne-Claude proposed wrapping an office block on Times Square. “It was the headquarters of a company,” Christo says. “A friend of ours took us to see the CEO. I showed him the model, he thought we were complete lunatics.” Startling as his proposals may seem, Christo is in some respects highly practical. His conversation is full of engineering details -- each project involved unique construction problems -- and peppered with numbers. The initial planning application for “Over the River,” he details, is 2,029 pages long. “It cost us $1.5 million.” All of Christo and Jeanne-Claude’s projects have been financed by selling works, often drawings and plans for the projects themselves. They have never accepted sponsorship or donations, nor executed commissions. No work is ever repeated, though occasionally one suggests another. The inspiration for “Over the River” dates back to 1985 when they were wrapping the Pont Neuf in Paris. “At a certain moment we saw the fabric held horizontally above the River Seine, moving with the wind, the sun passing through it,” Christo says. “That was the genesis.” Possibly, in a few years, rafters and visitors will see something similar over the Arkansas River. “Christo and Jeanne-Claude 40 Years -- 12 Exhibitions” is at Annely Juda Fine Art, 23 Dering St., London, through Oct. 22. Information: http://www.annelyjudafineart.co.uk.