Economic forces and the growing might of China are pushing forward the construction of a 170-mile-long, 90-foot-deep canal from the Pacific Ocean to the Caribbean Sea through Nicaragua. The project, if built, would excavate 6.5 billion cubic yards of material, be wider than the expanded Panama Canal and require 50,000 workers. "There's been no civil engineering project of this magnitude -- ever," said Bill Wild, the chief project adviser to HKND Group, which has a 50-year agreement to build and operate the canal. Initial survey work has started, but the social and environmental costs of the project are unknown.