James Fallows has a very good post (based on an article in The Atlantic) on the decline in the quality, and even operability, of public infrastructure in the US (with an embedded video of a frightening water main break in Baltimore). A key quote:
"Stephen Flynn points out that the physical infrastructure of big East Coast cities was mainly built by the 1880s; of the industrial Midwest by World War I; and of the West Coast by 1960. "It was advertised to last 50 years, and overengineered so it might last 100," he said. "Now it's running down. When a pothole swallows an SUV, it's treated as freak news, but it shows a water system that's literally collapsing beneath us." (Surface cave-ins often reflect a sewer or water line that has leaked or collapsed below.)"
Given the general scholarly consensus that returns to infrastructure investment are quite large, there are significant opportunities here both to improve the quality of life in the US (and particularly in our larger cities) and also to undertake projects with significant job-creation potential.
It's worth pointing out, though, just how much more difficult it is to replace sewers and water and gas lines and buried telecommunications lines than it is to put them in place to begin with. Even modest sewer replacement projects create horrendous traffic problems, and even modest road reconstruction projects can be ruinous for local businesses, which often see 50% or larger declines in sales.
In addition, any coordinated effort at doing infrastructure replacement will almost certainly have to be developed and funded by the federal government. Too many cities--Gary, for example, where I work, or Detroit, or Camden*--cannot do this themselves. Even reasonably prosperous cities (Chicago, Miami, Atlanta) would find the burden very difficult to bear.
But if we don't make the effort, then the ability of our economy to continue to grow and to provide adequate opportunities is likely to be severely undermined.
*If you want to be really depressed, take a look at this book.