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Great Lakes Monitoring

Beach Indicators
The Swimmability Index


To assess fecal contaminant` levels in nearshore recreational waters by using a surrogate indicator for pathogen types causing potential harm to human health through body contact with nearshore recreational waters.


Waters should be safe for recreational use. Waters used for recreational activities involving body contact should be substantially free from pathogens, including bacteria, parasites, and viruses, that may harm human health. This indicator supports Annexes 1, 2 and 13 of the Great Lakes Water Quality Agreement.


Currently, there are two methods recommended for beach water quality monitoring: counts of either E. coli and/or enterococci in recreational waters measured as number of organisms per volume of water (e.g., EC/100 ml). When the bacteria standards are exceeded, local authorities may ban swimming at a beach or issue an advisory that water is unhealthful for swimming.  In the rest of the text, we'll use the term "posting" to describe either of these two actions.  A small number of postings may be due to weather conditions (lightning, high water).

Frequency of swimming advisories or closings at specific locations are reported annually and become the basis of a "Swimmability Index" (the percent of swim season individual beaches have not been posted due to bacterial contamination and/or other environmental condition, including pre-emptive postings based on past experience).

The BEACH Act aims to protect beach-goers from disease-causing pathogens by establishing a national baseline for beach water quality and by providing grants to states to develop and implement water quality monitoring and public notification programs. A health risk assessment based on the number of days a beach is posted is suggested. A beach that is not posted during the swimming season has low risk. A beach that is posted 10% or more days during the swimming season has high risk. Beaches posted for one day or more but fewer than ten days (swimming season in the Great Lakes is defined as June to August) are characterized as medium risk. 


Most beaches are reported safe for swimming. Increased monitoring which began in 2002 and has continued results in increased advisories/closings. Thus far, it has been observed in the Great Lakes Basin that unless new contaminant sources are removed or introduced, beaches tend to respond with similar bacteria levels after events with similar precipitation and meteorological conditions. The latest source reporting for beaches closed more than 9% of the swimming cites "unknown causes" for postings at more than 75% of the beaches and storms as the cause at more than 16% of the beaches.

Analyses of beach closings data in both the U.S. and Canada show that as the frequency in monitoring and reporting increases, more advisories and closings are also observed, especially after 1999. In fact, both countries experienced a doubling of beaches that had advisories or closings for more than 10% of the season in 2000. Further analysis of the data may show seasonal and local trends in recreational water. If episodes of poor recreational water quality can be associated with specific events, then forecasting for episodes of poor water quality may become more accurate.

There may be new indicators and new detection methods available in the near future through current research efforts occurring bi-nationally in both public and private sectors, and academia. Although currently a concern in recreational waters, viruses and parasites are difficult to isolate and quantify, and feasible measurement techniques have yet to be developed. Comparisons of the frequency of beach closings and advisories are typically limited due to use of different water quality criteria in different localities. All coastal states have adopted recommended indicators for fresh water as a condition of receiving BEACH Act funding.

Next Steps

Wet weather sources of pollution have the potential to carry pathogenic organisms to waters used for recreation and contaminate them beyond the point of safe use. USEPA is providing administrative, technical and financial support to state and local agencies to assist in the identification and remediation of pollution sources at high use beaches that are affected by CSOs, SSOs, and stormwater. Also, many municipalities are in the process of developing long-term control plans to address wet weather impacts.

The Great Lakes Strategy 2002 envisions that all Great Lakes beaches will be swimmable and sets a Goal that by 2010, 90% of monitored, high priority Great Lakes beaches will meet bacteria standards more than 95% of the swimming season. To help meet this Goal, USEPA will build local capacity in monitoring, assessment and information dissemination to help beach managers and public health officials comply with USEPA's National Beach Guidance (U.S. EPA July, 2002) at 95% of high priority coastal beaches.

Creating wetlands around rivers or areas of wet weather sources of pollution may help lower the levels of bacteria that cause beaches to be closed or advisories issued. The wetland area may reduce high bacterial levels that are typical after storm events by detaining and treating water in surface areas rather than releasing the bacteria rich waters into the local lakes and recreational areas. Studies by the Lake Michigan Ecological Research Station show that wetlands could lower bacterial levels at State Park beaches, but more work is needed (Mitchell, 2002).

Needed Research

Variability in the data from year to year may result from changing seasonal weather conditions, the process of monitoring and variations in reporting, and may not be solely attributable to actual increases or decreases in levels of microbial contaminants. At this time, not all beaches are monitored in the Great Lakes basin, but most public coastal beaches in the U.S. will be monitored as a condition of the BEACH Act grants. Another BEACH Act grant condition is that recipients submit complete beach monitoring and advisory/closure data to the USEPA. The USEPA is looking at electronic reporting and testing using the Internet for recording and reporting results.

Due to the nature of the lab analysis, each set of beach water samples requires an average of 1 to 2 days before the results are communicated to the health unit beach manager. To ensure accurate posting of Great Lakes beaches, methods must be developed to deliver quicker results that focus on fecal contamination sources. This issue may be addressed in the near future, as the BEACH Act requires USEPA to study issues associated with pathogens and human health and to publish new or revised Clean Water Act Section 304(a) criteria. USEPA's National Exposure Research Laboratory in Cincinnati, Ohio, is evaluating methods for rapidly detecting recreational water quality and is carrying out epidemiological studies that relate swimming-associated illnesses to water quality. The information developed will be used by USEPA's Office of Water to develop monitoring guidance. USEPA's National Exposure Research Laboratory has conducted epidemiological surveys at four freshwater beaches in the Great Lakes. Until new indicators are available, predictive models and/or the experience of knowledgeable environmental or public health officials (who regularly collect the samples) can be used. Each method takes a variety of factors into account, such as amount of rainfall, cloud coverage, wind, current, point and non-point source inputs, presence of wildlife, to predict whether it is likely that indicator bacteria levels will be exceeded.


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