Cost overruns and construction problems have either delayed or scuttled most of those projects. Last week, a report from the national auditing office found that nearly all of the public-works projects are behind schedule and the costs have increased between 7 and 122 percent above their original forecast. Some sites haven't even broken ground, and construction at Deodoro, the venue which will host events like BMX biking and rugby, won't start until later this year.
A more literal example can be found in Guanabara Bay, the site of the Olympic sailing competition. Rio had promised to clean up the water—which is fouled with debris, sewage, and even fish corpses—but Mayor Eduardo Paes conceded last month that goal wouldn't be met.
"I am sorry that we didn't use the games to get Guanabara Bay completely clean, but that wasn't for the Olympic Games—that was for us," he said.
During an April visit, International Olympic Committee Vice President John Coates said during an April visit that the preparations were "the worst" he had seen.
Rio is far from the only host of an international sporting event to overpromise and under-deliver. The possibility that any such so-called mega-event could be sustainable is a long shot at best, but that hasn't stopped countless cities from making the promise.
The optimistic environmental promises are a product of a misaligned incentive system. Countries' hosting bids are greatly bolstered when they include major green pledges. But once the event is awarded, there are few, if any, consequences for countries if they don't follow through.
"The IOC and FIFA understand that one of the big objections to these mega-events is that they destroy the environment, so they put in these requirements. But then what do they do?" said Jay Coakley, professor emeritus at University of Colorado (Colorado Springs). "They can't enforce them. There's no accountability after the fact."
Plus, he added, the high cost of building and hosting the events leaves little money in the end for projects that were extraneous to the games themselves.
"If the money hasn't been allocated up front, what can happen is a city or region goes so deeply into debt and there's so little money and energy left to complete those projects," said Coakley, who has studied the impact of mega-events. "Sustainability goals usually get shoved to the side. It's difficult to have an event with the footprint of the Olympics and make any improvements that have a net sustainability impact."
The problem of unmet sustainability promises also plagues Brazil's hosting of the World Cup, where all 12 host cities talked up varying degrees of improvements. As the $10 billion-plus preparations for the Cup ran increasingly behind schedule and over budget, attention turned away from legacy projects and onto triage for the stadiums.