In the aftermath of the lead contamination crisis that plagued the water system in Flint, MI, more than 35,000 water samples were collected from the city’s premises. The majority of these samples (>85%) were collected through a voluntary crowdsourced sampling campaign. The samples were analyzed for lead concentrations by the Michigan Department of Environmental Quality (MDEQ), and the results were posted online on a periodic basis. 

In this study, the crowdsourced sampling data were analyzed by means of spatial autocorrelation analysis to reveal the locations of statistically signiﬁcant hotspot regions of high water lead levels (WLLs), and to track the spatiotemporal evolution of WLLs as the system recovered from lead contamination. The results showed that hotspot regions that experienced high WLLs were consistent with the areas where lead service line (LSL) density was the highest. Additionally, galvanized service lines and other lead-containing plumbing components appeared to have also contributed to lead release in hotspot regions. The temporal trend exhibited by the crowdsourced sampling data did not reﬂect a consistent decrease in WLLs despite the interventions implemented by MDEQ and EPA. Instead, sampled WLLs remained high for several months after boosting the orthophosphate dose and launching a city-wide residential ﬂushing campaign. The ﬁndings of this study revealed that this could be partially attributed to disproportionate sampling from premises in hotspot regions of high WLLs and LSL density. The results suggested that homeowners of high-risk premises were more likely to repeat the sampling, which highlighted the kind of biases that may exist in crowdsourced sampling data. With the increasing interest in citizen science and crowdsourcing water quality data collection, the utility of the proposed geospatial analysis generalizes well beyond the lead contamination crisis in Flint.

Crowdsourced Water Sampling Reveals the Spatiotemporal Trends of Recovery from Lead Contamination in Flint, MI

Created in 1999, the Environmental & Water Resources Institute (EWRI) is the recognized leader within ASCE for the integration of technical expertise and public policy in the planning, design, construction, and operation of environmentally sound and sustainable infrastructure impacting air, land and water resources.

[Paper Proceedings](https://doi.org/10.1061/9780784483466)

Conference DOI: https://doi.org/10.26226/m.6329c39b68fb0e00131f77d2