Evaluation of Bacteria Impacts on Beaches in Milwaukee: The Bacteria Source, Transport, and Fate Study

The Milwaukee Harbor Estuary Modeling Bacteria Source, Transport and Fate (BSTF) Study was launched in 2003 as part of the development of an integrated water quality modeling framework for addressing the water quality issues in the Greater Milwaukee area. A hydrodynamic model and a water quality model were constructed to work together with historical data collected by Milwaukee Metropolitan Sewerage District and the Great Lakes WATER Institute at the University of Wisconsin — Milwaukee. The models were developed to better define the movement and survival of bacteria in Milwaukee's harbor estuary and near shore area of Lake Michigan. In addition, the BSTF Study includes an investigation of possible bacteria sources through the use of genetic markers and antibiotic resistance techniques. Water quality issues, especially those that pertain to the recreational beach areas of Lake Michigan, have received a great deal of attention in Milwaukee over the last few years. There is public perception that beach closures are correlated to combined sewer overflow (CSO) and separate sewer overflow (SSO) events. It has been found that while CSO/SSO events in recent years have occurred only a few times per year, beaches may be closed for a significant part of the recreational season. The BSTF modeling shows that rainfall events with CSOs do not impact the bacteria concentrations of the near shore area more significantly than rainfall events without CSOs. The BSTF Study is on-going and will provide not only a decision-support tool, but also a means to inform the public about beach water quality.