FLINT, MI-- The rate of finding lead or galvanized service pipes in Flint has increased 15 to 70 percent while using a predictive model to plan replacements, according to the researchers who built the model.
Flint first used the model in 2016 and utilized it again in 2017. Workers dug at 8,833 homes in 2017 and out of those homes 6,228 had their hazardous pipes replaced -- a 70 percent accuracy rate, according to researchers Jake Abernethy, Eric Schwartz and Jared Webb.
Flint stopped referring to the computer model for planning replacements in 2018 when AECOM, a Los Angeles-based engineering firm took over FAST Start, the city’s pipe replacement program. Of the 10,531 properties that were dug in 2018, Flint found and replaced about 1,567 lead or galvanized pipes--a 15 percent accuracy rate.
Messages left with Flint city officials for comment on this story were not returned.
Through a court-approved amendment, signed by Judge U.S. District Judge David Lawson on March 26, Flint is now required to use the data-driven model to find lead service pipes using a $97 million Concerned Pastors Settlement.
In 2019, before returning to the predictive model in March, Flint found and replaced 276 lead or galvanized pipes out of 1,245 addresses it dug at. After returning to the model for guidance, Flint replaced lead or galvanized pipes at 238 of the 337 addresses it dug at, according to the researchers.
Flint estimates it will replace about 2,500 lead service lines in 2019. Flint has dug up service pipes at 1,582 addresses and replaced 514 lead or galvanized pipes so far.
There are roughly 4,000 homes on Flint’s 2019 excavation list.
This graph shows the number of excavations in Flint alongside the number of lead or galvanized service pipe replacements between 2016 and 2019. Courtesy of Jared Webb, Eric Schwartz and Jake Abernethy.
How it works
Abernethy, of Georgia Institute of Technology, Schwartz, of University of Michigan, and Webb, a data scientist, built a predictive model that analyzes and uses historical data about a city, neighborhood and residence to predict the chance a home has lead or galvanized pipes.
The researchers provide the city with a spreadsheet of homes that, according to the model, have about a 10 percent or higher chance of having lead or galvanized service pipes.
“That means, if a home was predicted to have a 95 percent or if a home was predicted to have even as low as a 9.5 percent chance of having a non-copper service line, either way, we included it on the 2019 Excavation List," Schwartz said.
Flint then uses its own process to assign the addresses to contractors. City Council approved awarding the jobs to WT Stevens Construction for $5.2 million and Lang Constructors for $5.2 million.
Contractors record the material of the pipes they uncover and send the information back to the city, which turns the data back over to Abernethy and Schwartz.
The data that researchers have received so far shows the computer model’s predictions to be accurate, Schwartz said.
“At the higher risk end of the list, there are more homes that had lead/galvanized service lines," Schwartz said. "And on the lower risk end of that list, there are more homes that have turned out to have copper, just as we had expected.”
The map below shows the copper service pipes, green dots, and lead or galvanized service pipes, red dots, Flint found in 2019 before the city began using the model again in March. Information to create the map was provided by researchers.
The map below shows the copper service pipes, green dots, and lead or galvanized service pipes, red dots, Flint found in 2019 after the city began using the model again in March. Information to create the map was provided by researchers.
Flint’s most recommended ward for replacements
Service pipe work in Flint’s ward with the highest predicted hit-rate for finding lead or galvanized pipes is on hold until the city hires an archaeologist to oversee digging.
Flint’s Ward 5 has a 83 percent hit-rate of lead or galvanized pipes, according to researchers. But only 105 of the 734 homes on the city’s 2019 excavation list have been dug at.
An archaeologist is required to be present for excavations by the state because of an ancient Native American burial grounds located within the ward.
A state inspector found Flint did service pipe work at 29 separate addresses within Ward 5 without an archaeologist present, according to a recent letter from a state official.
Researchers predict to find lead or galvanized service pipes at 550 of the 734 homes.
“This is the highest hit-rate out of any ward,” Webb said.
Flint received preliminary approval in February 2018 to use hydrovac, a high pressurized water method of digging, to uncover buried service pipes in Ward 5.
AECOM had its own archaeologist and the contact information for a University of Michigan archaeologist but postponed digging in Ward 5 in 2018.
The engineering firm’s previous project manager, Alan Wong, stated the company was concerned about the burial grounds since the scope of work was changed.
Mayor Karen Weaver banned the use of hydrovacing service pipes in June 2018 over concerns the method of digging wasn’t thorough enough.
The city wanted to wait for a response from Native American tribes associated with burial grounds before digging in the ward last year, Flint’s Public Information Officer Candice Mushatt previously said.
A response from the Native American tribes isn’t required by the state to start digging.