The Relationship Between Age and Lead Corrosion : a Case Study in Flint, MI

Abstract

The affect of age of water infrastructure on the water quality of a geographic area is understated and under researched. This case study correlates the water infrastructure 5 zip codes within the city of Flint, MI and a set of parts per billion (ppb) water samples from those respective zip codes. The goal was to test relationship between the proportional age and composition of infrastructure and the corrosion that occurs, measured in lead ppb. The expected results were a positive relationship between the age of the infrastructure and ppb and a positive relationship between the proportion of lead infrastructure and ppb. While the results did not show a consistent significance between either materials or the age and lead ppb, there was a trend of reduced lead ppb in zip codes where the infrastructure had higher proportions of unknown age or composition. The analysis interprets the results and explains their significance in terms of the other correlations and economic theory in a larger context. There was scant significance outside certain age groups, although there were patterns of significance that could indicate a positive relationship between pipes built in 1921-1945 and lead ppb. For the age group 1988-2013, unexpected signs were found for in relation to lead ppb, but this was likely due to issues with the data. Correlations were also run with demographics data from these zip codes, but the only significant relationship was an unexpected negative relationship between vacancy rate and ppb.