Despite a boom in tank construction since 2009, U.S. facilities are running out of room for more crude. Photo: Associated Press In a world awash in crude, oil producers and traders are facing a billion-barrel conundrum: where to put it all. U.S. crude-oil supplies are at their highest level in more 80 years, according to data from the Energy Information Administration, equal to nearly 70% of the nation’s storage capacity. A key U.S. storage hub in Cushing, Okla., is expected to hit maximum capacity this spring. While estimates are rough, Citigroup Inc. believes European commercial crude storage could be more than 90% full, and inventories in South Korea, South Africa and Japan could be at more than 80% of capacity. The danger of running out of places to stash crude: Some analysts predict prices, already down 50% since June, […]