Manholes – like the one shown above – are a gateway into a labyrinth of unseen infrastructure that lies underneath every city. It is the architecture of the city; not in its most recognized form, but in its most essential. Few people notice it as they engage in their daily routines. However, this network of gas pipelines, water mains, transmission lines, and sewers that our eyes never meet, are all fundamental to a city's health. And in Washington, D.C., this network hides a troublesome truth: most of the infrastructure that allows the city to function has outlived its prime.

This fact came to grace headlines last month when a study conducted by researchers from Duke University revealed that there are nearly 6,000 natural gas leaks in the pipelines running under the District of Columbia, some of which have explosive potential. And the gas pipelines are not alone. When a water main burst in the DuPont Circle neighborhood back in December, causing nightmarish traffic jams and forcing restaurants to close, it was discovered that the average age of water pipes in Washington, D.C. is seventy-seven years old. It happened again in February when a leaking water main underneath a portion of Massachusetts Avenue helped to form a sinkhole, collapsing part of the hill the road was built on. Instances like these raise questions about how the city is going to be able to meet the needs of present and future residents when so much of the infrastructure it relies on was built for a different time.

This brings to light one of the central difficulties of urban planning – planning where a built environment is already in place. The map above provides a glimpse into the complexity of this problem. Each line represents a different piece of unseen infrastructure, buried under layers of roads and buildings. As can be gleaned from this map, it is not as if a team can simply go in and replace all the old cast iron pipelines, or the eighty year old water mains.

And replacing all this infrastructure costs more than money. There are the soft costs of items such as traffic delays caused by digging up roads, and the opportunity costs that arise anytime you choose to spend money on one project over another. But a city that aspires to remain competitive in the twenty-first century must upgrade its outdated infrastructure. The best way to accomplish this would have been through a piecemeal approach with an eye on the long term, but the mismanagement of the city throughout the final decades of the twentieth century has erased this possibility. Now the District is being forced to play catch up.

This isn't the sort of topic that is going to be debated as the Mayoral election draws near. But, without a plan to renovate the aging, unseen infrastructure of Washington, D.C., loftier goals like housing affordability and transit improvements are going to become more difficult as the city is forced to spend its money fixing one broken piece after another.

But how much should a city invest in replacing infrastructure that hasn't failed yet? Is there validity in the approach of "wait until it breaks," as has been the case so far?

Credits: Image by Chase Keenan. Data linked to sources.