Here in this age of austerity, it’s fashionable to point out that the world just doesn’t work the way it did when John Maynard Keynes was the talk of the town. You just can’t find any shovel-ready projects, so weighted are they by environmental impact reports and the other red tape of 21st century life. But this neglects an entire area where construction work is needed: maintenance. I know from living in Los Angeles that there are enough potholes to keep a small army of workers in business year-round. Similarly, century-old water pipes that need to be replaced would not take the moving of heaven and earth to get processed:

A major water supply line in the Bronx burst on Wednesday morning, flooding Jerome Avenue for several blocks near 177th Street, halting traffic, disrupting subway and bus service and damaging two nearby gas mains.

The burst happened just before 6:30 a.m., and officials said the water flow was capped by 9:20 a.m.

Mayor Michael R. Bloomberg said it was not clear why the pipe, which was installed in 1903, had burst. “It has been doing yeoman’s work, but unfortunately, after 108 years, it’s not,” Mr. Bloomberg said in a news conference.

I’d say that it’s fairly clear why a pipe installed in 1903 would go ahead and stop working. There are pipes like this all over America, and we could employ a million people to fix them. We could employ a million more to fix crumbling schools, or roads, or bridges. To say that this is too expensive neglects how much we pay in the long run for infrastructure failure.

New tires add up. That’s the finding of a report issued Wednesday by the American Society for Civil Engineers, which tallies up the cost of our decaying surface transportation infrastructure, from potholes to rusting bridges to buses that never come.

The engineers found that overall, the cost of failing to invest more in the nation’s roads and bridges would total $3.1 trillion in lost GDP growth by 2020. For workers, the toll of investing only at current levels would be equally daunting: 877,000 jobs would also be lost. Already, the report found, deficient and deteriorating surface transportation cost us $130 billion in 2010.

By and large those costs would not come from the more dramatic failings of America’s transportation system — like the collapse of the I-35W Bridge in Minnesota — but more mundane or even invisible problems. The minivan that hits a pothole chips away at a family’s income. The clogged highway that drains away an extra half hour of a trucker’s day also drives up the cost of shipping for businesses.

Investing in maintenance now would save trillions over time, and put enough people back to work to increase consumer spending, grow the economy and lower the deficit through increased tax revenues.

So of course, we won’t be doing it.