Washington, DC, has done something remarkable: published a granular, house-level map of the city's lead pipes.

The data, released earlier this week, shows that at least 12,000 buildings (primarily private residences), rely on public lead pipes for water service.

It's one of the most detailed and transparent looks at where lead pipes — which can contaminate water, causing a host of health issues — exist in a major urban area. The data set (which is available as an interactive map here) covers 125,390 water service lines in the 650,000-person city.

All the green dots below represent homes that have lead-free pipes. The dark gray dots are those serviced by lead utilities.

In the aftermath of the water crisis in Flint, Michigan, many American cities have started more closely inspecting and monitoring their own piping infrastructure and water sources. A USA Today investigation found nearly 2,000 water systems across the US where testing showed high levels of lead contamination in the water. And the Environmental Protection Agency estimates that at least 10 million Americans still get drinking water from pipes that contain lead.

Part of the tragedy of what happened in Flint was city officials' deliberate obfuscation of data. They claimed that federal tests showed the water was safe and didn’t admit there was a problem until outside researchers from Virginia Tech found elevated lead levels in the water of 40 percent of the homes tested.

Thankfully, DC has taken the exact opposite approach: It's chosen to make public the exact location and magnitude of the problem — which, arguably, is the first step to fixing it.

"Transparency is important to us," George Hawkins, the CEO of DC Water (which is the District's only water provider), told me. "We wanted to be able to inform people about what our records indicate is true for their dwelling and, if there is a potential issue detected, help determine a series of steps to take."

Washington is a city that struggled through its own lead poisoning crisis in the early 2000s. And like many cities, it worked to follow an EPA mandate that required many of the city’s public water pipes to be replaced. This map shows the strides the city has made in reducing lead piping, but also the challenges in removing it entirely.

What DC's map tells us about lead pipes in a major urban area

First of all, it’s important to stress that the majority of homes in the District do not test positive for lead in the water.

DC Water is required by law to monitor the houses that do have lead pipes — Hawkins told me that of the few homes that return positive test results, most have scores in the single digits, safely below the EPA limit of 15 parts per billion.

At the same time, there are still thousands of homes in the District that do have lead pipes, meaning the risk of contamination exists. And lead piping isn't evenly distributed through the city — it's concentrated in certain areas.

A quick word on understanding the DC map. It includes data on two categories of pipes: those that are public (in some instances, delivering water to entire blocks and office buildings) and those that are private (on the property of the individual homeowner). This diagram from my colleague Javier Zarracina helps explain the difference.

In order to ensure that a pipe is lead-free, both the public and private components have to be free of the metal. That said, let’s dive into the map — and start with my neighborhood of Petworth as an example of a place where there are still many lead pipes.

Petworth is a less affluent neighborhood in DC (median household income as of 2013 was $66,343) and has only recently started to gentrify.

Because there hasn’t been a lot of development in the area until very recently, one can clearly see there is still a large prevalence of gray dots, which signify lead pipes. (A two-color dot signifies different things about the private and public pipes — the left half of the dot represents the public pipe, and the right side represents the private infrastructure that belongs to the homeowner).

Compare this same map with an area of DC that is far more affluent. The neighborhood of Cleveland Park, which had a median household income of $104,068 in 2013, has far more green dots than gray.

Household income is obviously not the only factor to consider when weighing the prevalence of lead pipes, but an initial look at the map does suggest it can make a difference.

In some areas of DC, it's still hard to find complete data — the city doesn’t have good information on an estimated 90,000 private water lines (the pipes that service individual houses, which belong to the homeowner).

To see what I mean, let’s look at the neighborhood of Anacostia in Southeast DC. Considered by many as one of the most marginalized areas of DC, it had a median income of $37,684 in 2013. But the area has benefited significantly from the EPA mandate to remove lead pipes from the city — you can see that in all the green in the map below.

One thing you’ll also notice is that many dots here are half green and half white. Nearly all of these are situations where the city knows that the public pipe is lead-free (the green half of the dot) but has no good information about the house’s privately owned pipes (the white half of the dot).

And this is one of the big challenges that DC — or any city — faces in getting its arms around the size of the lead pipe problem: A lot of the data is currently missing and is labor-intensive to get.

DC Water says there are still more than 16,000 public water lines for which it does not have any information, in addition to nearly 90,000 privately owned lines for which the agency has no data.

When I asked Hawkins what he had noticed in the data, he told me that DC Water’s first priority was to make the data available to the public, rather than analyzing trends. But it is something DC Water hopes to tackle soon, especially as it looks for pockets of the city that it can target where lead pipes remain especially prevalent.

DC’s lead pipe data existed on scraps of paper and index cards. Turning it into a map was a big deal.

Spokesperson Pamela Mooring said that other cities like Boston and Charlotte, North Carolina, have also mapped their lead pipes. But DC's map is by far the most granular effort to map lead pipe data, showing metrics on each house in a city with more than 650,000 residents.

But getting there wasn't easy.

Most homes in the District are at least a century old. Much of the pipe data that the city has individual properties was on handwritten index cards and scraps of paper.

Hawkins told me that getting the information digitized was the department’s biggest hurdle. The whole project took roughly three months to complete because of prior digitization efforts undertaken by the organization.

For the data used in the map, DC Water used permit and meter records in addition to maintenance work. When data was missing, the agency used historical records to determine the material of a residence's pipe. In situations where DC Water has verified the pipe material used, an actual inspection date is listed.

Hawkins acknowledges that some of the information may not be up to date or accurate, but he encourages property owners to reach out with updated information so they can adjust their records.

"We want to mobilize customers and residents to help us," he said. "We want to draw in the people we serve and help them understand what the issues are and make them part of the decision-making process."

Hawkins also wants to help other cities build their own maps, because he believes this kind of data needs to be displayed in a way that makes it easy for customers to look up site-specific information.

"It is doable," he said. "And now that we’ve done it, we want to figure out a way to help other cities do something similar."

What to do if you have lead pipes in your home

First of all, don’t panic. Just because your home relies on lead pipes doesn’t necessarily mean you’re at risk for lead poisoning. You can request a free lead test from DC Water, though, just to be safe (more details about that below).

The DC Water department is actively trying to replace all lead piping in the city, although the process does take significant time — and money. The city recently increased its budget from $500,000 to $2 million this year to keep up with increased requests from city residents to replace their homes' pipes.

Hawkins told me the agency has 1,500 requests for lead pipe removal that it's currently processing. While DC Water does the legwork of actually replacing the pipes, homeowners are responsible for paying for the removal of pipe that is privately owned. DC Water covers the cost for removing the public portion of pipe. On average, the process costs a homeowner $2,500.

If you are interested in free lead testing or information about your water service pipe, contact the Drinking Water Division at 202-612-3440.

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