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On April 25, 2014, the city of Flint switched its water source to the Flint River without properly treating it. That damaged thousands of lead and galvanized water pipes which the city is replacing.
In 2016, University of Michigan researchers developed an algorithm to determine the neighborhoods most likely to have lead pipes. The on-again, off-again use of the model has raised concerns about the efficiency of the city's pipe replacement program.
The records for more than a century's worth of water pipe installations at homes in Flint are incomplete and often unreliable, so the algorithm uses whatever data are available, including the parcels, the years homes were built, and any confirmed construction materials in neighboring homes.
U of M professor of marketing Eric Schwartz worked on the project. In an interview with Michigan Radio's Morning Edition host Doug Tribou, Schwartz said the machine-learning model helped the city get its work crews to areas where they would find a lot of lead pipes.
"Early on, we really looked at our success by saying, 'For every 100 homes that the city was going to with the intention of replacing [lead lines], how many of those homes really did need replacing?' And that number was around 80, 82%," he said. "We are trying to do better than just searching randomly across the city."
A change in tactics
The city eventually hired a national construction firm to continue the final stages of the project, but after the transition the company didn't continue using the algorithm. The pipe replacement program in Flint has to meet the terms of a 2017 legal settlement with the Natural Resources Defense Council and the American Civil Liberties Union. In 2018, those organizations asked Schwartz and his colleagues to analyze the data from the newly hired construction firm's work.
"What we found was actually for every hundred homes they were going to with the intention of replacing those lines, they were only finding lead at about 15 of those. So, instead of 80-some-odd percent, it went down to 15% in just a matter of a few months. And that was a bit concerning," Schwartz said.
A goal of efficiency
Now Schwartz and his colleagues are once again working with the city. Flint Mayor Karen Weaver has said that her goal is for the city to fully excavate and check all the water service lines in the city to prove which homes have lead or galvanized steel pipes. Weaver announced that after some pipes were partially exposed and incorrectly identified as being all copper when only a small section of pipes were. Schwartz applauds the plan to check every service line, but says in the meantime, the algorithm still allows Flint to make the most efficient use of the available resources.
When the city stopped using the algorithm to target neighborhoods, the lead lines found in excavations fell from more than 80% to 15.
"If you have a list of homes, which is what we're really providing, that says here's a few hundred homes that almost definitely have lead and here's another set of a few hundred homes or a few thousand homes that almost definitely don't, which ones, if you had to choose just a few hundred homes to go to next month, would you choose?"
City officials say they hope all lead and galvanized pipes in Flint will be replaced by the end of 2019. Schwartz says the data from the end of March is promising.
"It looks like ... a bit more than 2,000 to 2,500 homes will likely have lead service lines. This is out of the several thousand homes that have yet to be inspected. Based on the city's expectations, the targets look like they're on track," he said.
Sharing the system
Schwartz and his colleagues are working on a plan to make all of the data and records of work that's been done since the city's water crisis began available to the public.
"Something that is easy, accessible, mobile-friendly for people to just look on their phones or computers or even just a poster and be able to see exactly where the lead service lines were, where they are now, where they're expected to be," Schwartz said. "Knowing that kind of information really should empower residents to really see what information is out there and and what they ought to be doing about that if they still have lead lines right now."
He also hopes the algorithm can be used across the country.
"I think this is going to be serving as a model nationwide as other cities are starting to really reckon with the fact that not only do they have lead lines, but there are so many homes that just have unknown records. And it's that unknown that we're trying to provide answers to."
To hear the full conversation with Eric Schwartz, click the play button above.
Lauren Talley contributed to this story.
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