Figure 3.
Levels of Escherichia coli in the Milwaukee estuary, which discharges to Lake Michigan, 2001–2007, during base flow (n46); following rain events with no CSO (n70); and following CSO events (n54). Boxes indicate 75% of values, with median values drawn in each. Whiskers are 95% of value and outliers are shown as closed circles. There were significant differences in E coli levels following rainfall and CSOs compared with base flow (P ≤ .05).5 Abbreviations: CFU, colony-forming units; CSO, combined sewer overflow.