Although some local beach officials can predict beach pollution through the use of computer models or other information, most local officials must wait for test results before they can take action, potentially exposing the public to disease causing organisms. EPA is sponsoring research to develop and validate models that enable government officials to predict pollution before the public is exposed. These models will identify, in advance, when closure of a specific beach is necessary (to protect public health). Predictive models use data such as rainfall rate, duration of pollution, and historical severity of pollution to calculate potential adverse water quality conditions. They are an effective initial warning device that local officials can use to alert beach goers of potential problems during and immediately following a rain storm.

Typically, pollutants washed into rivers, lakes, and streams eventually make their way to recreational beaches. Local officials collect samples of water at down-stream beaches and test them for the presence of contaminants. However, people swimming during the time between sample collection and test results may be unnecessarily exposed to microbial pollutants at peak contamination times. Predictive models are intended to reduce such exposures. EPA has begun an evaluation of existing models and will begin collecting modeling data from new sites in 1998. Once complete EPA will provide copies of the models and training in their use.

Delaware Uses Predictive Models

The State of Delaware monitors approximately 50 miles of coastline and several inland ponds checking bacteria levels, monitoring rainfall, and assessing other factors known to have an impact on water quality. Testing is done throughout the swimming season. By using a predictive model, they are able to make assumptions about the potential risk to swimmers following rainfall and other events, and can reliably predict where and when exposure to bathers is significant. Use of the model allowed the State to reduce the number of sampling sites and staff time, while expanding coverage of their public health protection program.

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