ActiveRemediation: The Search for Lead Pipes in Flint, Michigan

Jacob Abernethy, Alex Chojnacki, Arya Farahi, Eric Schwartz, Jared Webb, ActiveRemediation: The Search for Lead Pipes in Flint, Michigan, KDD 2018.

We detail our ongoing work in Flint, Michigan to detect pipes made of lead and other hazardous metals. After elevated levels of lead were detected in residents' drinking water, followed by an increase in blood lead levels in area children, the state and federal governments directed over $125 million to replace water service lines, the pipes connecting each home to the water system. In the absence of accurate records, and with the high cost of determining buried pipe materials, we put forth a number of predictive and procedural tools to aid in the search and removal of lead infrastructure. Alongside these statistical and machine learning approaches, we describe our interactions with government officials in recommending homes for both inspection and replacement, with a focus on the statistical model that adapts to incoming information. Finally, in light of discussions about increased spending on infrastructure development by the federal government, we explore how our approach generalizes beyond Flint to other municipalities nationwide....

The overall accuracy of the best performing XGBoost model, based on a holdout set of 1,606 homes (25% of available data), is 91.6%, with a false-positive rate of 3% and false-negative rate of 27%. ...

The most informative home features relate to its age, value, and location, suggesting that the context (place and time) in which the home was built, as expected, is strongly correlated with service line material. For instance, homes built during and before World War II and those that are lower in value are more likely to contain lead in their public service line....

One source of inefficiency in spending is unnecessary service line replacement (SLR) visits (the false-positive error rate). Therefore, our key performance metric is the SLR hit rate, i.e. the percentage of homes visited for replacement that required replacement. 

The proposed approach greatly improves the hit rate. Our key finding from the simulation shows that we predict a reduced rate of costly unnecessary replacements visits from 18.8% (actual) to 2.0%(proposed).... 

Across 18,000 total planned service line replacements, this would extend to an expected savings of about $11M out of current spending.