Abstract
An interdependent relationship exists between localized sources of contamination and coastal processes. With suitable mechanisms of transport, direct and indirect sources of pollution can negatively impact surface water quality. Public concern prompted a comprehensive investigation of factors contributing to bathing water quality failures at Racine, WI, US. From June 2002- October 2004 samples were collected from water (ground, river, storm, surface) and sediments (submerged, foreshore, nearshore, backshore) and analyzed for the presence of Escherichia coli (membrane filtration/m-TEC agar or DST/Colilert-18) and enterococci (membrane filtration/mEI agar and DST/Enterolert). In conjunction with microbial analysis, ambient conditions [wind speed/direction, wave height, surface water temperature, precipitation, presence of seagulls and algae (Cladophora)] were recorded to determine if significant correlation existed between specific events and an influx of bacterial contamination. E. coli as determined by DST was found to be the most relevant indicator for microbial assessment and the compositing of multiple samples increased sampling reliability. The most frequent contamination sources were storm water (direct) and near shore beach sands (indirect). Algae and seagulls, while found to contain significant amounts of E. coli and enterococci, were not significantly associated with bathing water quality failures. The most frequent triggers of bathing water quality failures (E. coli >235/100 ml) were wave height (> 0.3 m), wind direction (vector east), and antecedent precipitation (surface water temperature had no impact). Failures were scrutinized using both the USEPA risk factor and the classification scheme as set forth in the Annapolis Protocol (AP) to compare methods for estimating health risk. While the USEPA risk factor eliminated some unnecessary postings, the AP classification scheme provided the framework necessary to remediate contamination sources. The institution of a US classification system, inclusive of microbial assessment, would allow regulators to craft alternative approaches for beach management that may permanently reduce bathing water quality advisories.