Victoria (Tori) Byers Lisa R. Fogarty Hayden A. Lockmiller 2026 <p>Lake St. Clair Metropark Beach in Michigan has a history of closures because of elevated <i>Escherichia coli</i> (<i>E. coli</i>) concentrations in its recreational waters. To reduce closures, restoration projects were implemented in 2021 to deter waterfowl from congregating on the beach. In this study, the U.S. Geological Survey, in cooperation with the Michigan Department of the Environment, Great Lakes, and Energy and in collaboration with Huron- Clinton Metroparks and the Macomb County Health Department, monitored <i>E. coli</i> from 2022–23 in surface water, shallow groundwater, and sediment at Lake St. Clair Metropark Beach. Results were compared to data from a prerestoration (2018–19) study. A significant decrease in daily geometric mean <i>E. coli</i> concentrations in surface water was observed postrestoration, but the number of high concentration events increased. This resulted in more frequent beach closures postrestoration. Surface- sediment <i>E. coli</i> concentrations significantly decreased after restoration, and waterfowl populations generally decreased from 2021 to 2023, suggesting that the deterrence measures could be influencing <i>E. coli</i> concentrations in surface sediments and surface water. Groundwater <i>E. coli</i> concentrations were orders of magnitude higher than those in surface water and revealed no change correlated with restoration. Seepage measurements indicated that groundwater occasionally discharges into surface water, potentially providing a transport mechanism for <i>E. coli</i> to reach the lake. Continued monitoring and consideration of environmental factors could help to better understand the beach system.</p> application/pdf 10.3133/sir20265134 en U.S. Geological Survey <i>Escherichia coli</i> monitoring and assessment in 2022 and 2023 after beach restoration at Lake St. Clair Metropark Beach, Macomb County, Michigan reports