San Francisco-Oakland Bay Bridge eastern span replacement
San Francisco
This ended up being the most expensive public works mega project in California history. The hope was to build an earthquake-proof structure, and it began in 2002, with a $2.6 billion budget.
But, design defects, water leaks, bolt failures and a welding controversy led to an FBI investigation that shut things down for a while. It was finally finished in 2013, with a final bill of $5.4 billion.