Combining these sources gave them a rough sense of where to start. McDaniel set out to replace 600 lead pipes each in 10 small zones. “It was a matter of what was efficient and what was equitable across the city,” he said.
When Abernethy and his collaborator, the University of Michigan’s Eric Schwartz, got involved over the summer of 2016, they saw a familiar type of prediction problem: sequential decision making under uncertain conditions. The crews didn’t have perfect information, but they still needed the best possible answer to the question Where do we dig next? The results of each new dig could be fed back into the model, improving its accuracy.
Initially, they had little data. In March 2016, only 36 homes had had their pipes excavated. And even as the crews began to do hundreds of digs, they were looking for lead pipes, which meant that they were creating a decidedly unrepresentative sample of the city. Using just that data, the model was likely to overpredict how much lead existed elsewhere in Flint. So the University of Michigan team asked Fast Start to check lines across the city using a cheaper system called “hydrovacing,” which uses jets of water, instead of a backhoe, to expose pipes. The data from those cheaper excavations went back into the model, allowing the researchers to predict different zones of the city more accurately.
Read: How to prevent the next Flint
As they refined their work, they found that the three most significant determinants of the likelihood of having lead pipes were the age, value, and location of a home. More important, their model became highly accurate at predicting where lead was most likely to be found, and through 2017, the contractors’ hit rate in finding lead pipes increased. “We ended up considerably above an 80 percent [accuracy] for the last few months of 2017,” McDaniel told me.
In late 2017, Weaver announced that the City was awarding a $5 million contract to AECOM, the major national contractor, to run the project. In February 2018, the City held a community forum to “really introduce you to the company that’s going to accelerate Fast Start,” as Weaver put it. Robert Bincsik, Flint’s director of public works, noted at the forum that the City was doing something nearly unprecedented. “There is not anybody else doing this as aggressively as we are,” Bincsik said. “Overall, I think we’ve done a wonderful job.”
AECOM’s published plans said it intended to “efficiently identify and replace 6,000 [lead service lines] per year.” This goal made sense, as the small ragtag and mostly volunteer management team in 2017 had identified and replaced more than 6,000 service lines.
The contractor’s process, as laid out at that community meeting, would consist of two steps. First, it would hydrovac in 10 zones laid out by the contractor. Then, after the nature of the pipes was determined, it would go out and replace the lead and galvanized-steel pipes. Bincsik extolled the virtues of hydrovacing: It was cheaper and faster, less intrusive, and created a lower risk of damaging pipes. Hydrovacing cost $300 or less. Digging up the pipes in a traditional way cost several times more, according to contractor invoices from the 2017 phase of the project—at least $2,500, and as much as $5,000 depending on the type of pipes dug up and replaced.