New York City has nearly 7,000 miles of water mains, enough to send water to Seattle and back.

The city also has 97,607 miles of underground electric lines, 4,416 miles of gas mains, 104 miles of steam pipes and thousands of miles of telephone and cable-televison lines.

And then there is a labyrinth of train tunnels and other assorted equipment, all jammed together beneath the streets.

But much of New York’s underground infrastructure, once visionary and widely imitated, has become old and fragile. The average age of water mains is 66 years, making them as old as boomers born when Dwight D. Eisenhower was president.

A reminder of the brittle condition of the city’s infrastructure has played out in several water main breaks in the last month. Two water mains on the Upper West Side broke within days of each other, sending water gushing into the streets, making them impassable.