The $2.6 billion is just the latest round of funding for this. Generally every once in a while, you’ll see one or two billion in funding announced for lead pipe removal.

Edit: I just looked it up, and the state with the second-most lead pipes, Illinois, estimates $11.6 billion to get rid of their 667,000 known lead pipes, and there are over 800,000 whose material is unknown.

Edit 2: it looks like $20 to $30 billion is the overall estimate.