Beach Monitoring FAQ

How do agencies determine recreational water quality at beaches?
Why is E. coli used to assess recreational water quality?
Is there a “pathogen problem” at Ohio beaches? Are people getting sick?
What are the sources of pathogens at Ohio beaches?
How would use of the predictive models differ from the current way of assessing swimming safety?
How did you collect the data needed for developing the models?
How well do the models work?
Why was the USGS involved in this research?
Is anyone else doing the same kind of research?  Are other predictive tools being investigated?
Will this research continue?
Does USEPA allow the use of models for posting beach advisories?
How can we identify sources of contamination at beaches?
Whom can I contact if I’m concerned about swimming at a particular Ohio beach?

How do agencies determine recreational water quality at beaches? Typically, local or state agencies collect a water sample at the beach, four or five weekdays each week, throughout the recreational season (Memorial Day through Labor Day). Sometimes, more than one bottle is collected to best represent the water quality at a particular beach.   The samples are brought to the laboratory and analyzed within 6 hours of collection.  Membrane filtration or enzyme-substrate most-probable number methods are the most commonly used analytical methods.  Using these methods, it takes 18-24 to obtain results.

Membrane filtration – link to modified mTEC

Enzyme-substrate most-probable number – link to Colilert

Why is E. coli used to assess recreational water quality?
The E. coli bacterium, which is present in the feces of warm-blooded animals, is commonly associated with and is an indicator of several different disease-causing organisms, called pathogens. Viral pathogens are believed to be the major cause of swimming-associated diseases (Natural Resources Defense Council, 2006). There are more than 100 types of human pathogenic viruses that may be present in fecal-contaminated waters. Bacteria are true living cells and are larger than viruses.  Waterborne bacterial pathogens in the United States include species in the genera Salmonella, Shigella, Vibrio, Campylobacter, and rare strains of E. coli. Protozoa are one-celled animals.  The principal protozoan pathogens that are waterborne are Giardia lamblia and Cryptosporidium parvum.

Because of its association with pathogens and because it is comparatively easy to grow in the laboratory, E. coli is the basis for Ohio recreational water-quality standards. E. coli is the basis for freshwater recreational standards in other states; enterococci, another type of bacterial indicator, is used in standards for marine waters. 

There are several varieties of pathogenic E. coli and hundreds of varieties of harmless E. coli. One variety of E. coli that is pathogenic and relatively rare has been associated with undercooked ground beef—E. coli 0157:H7.

Is there a “pathogen problem” at Ohio beaches? Are people getting sick?
There is no true measure of the magnitude of disease associated with recreational water exposures (USEPA, 1999), in Ohio or elsewhere. That is because when people get sick after a weekend at the beach, the cause of illness is unknown. In addition, the illness is not reported unless there was an outbreak among a specific population, like a group of athletes participating in a triathlon. 

Swimming in polluted water can make you sick (Natural Resources Defense Council, 2006). Epidemiological studies in the United States have consistently found an association between gastrointestinal illness and exposure to contaminated recreational waters; however, the potential for other types of infections is not completely understood (USEPA, 1999). 

What are the sources of pathogens at Ohio beaches?
Polluted runoff and stormwater; sewage spills and overflows (including combined sewer overflows, sanitary sewer overflows, and sewage from private sewage-treatment systems); and fecal pollution from birds, dogs, swimmers, or boats.

How would use of the predictive models differ from the current way of assessing swimming safety?
Current methods to assess recreational water quality rely on collecting a sample of water from the beach area, transporting it to a laboratory, and determining numbers of indicator organisms, such as E. coli. It takes as least 18 hours to grow E. coli in the laboratory. Therefore, by the time E. coli results are compiled, beach water-quality conditions may have already changed. By contrast, it takes less than an hour to provide an estimate of recreational water quality using the model.

In USGS studies, we found that models yield more correct responses and better predict exceedance of the recreational water-quality standard than using the previous day’s E. coli concentration.

How did you collect the data needed for developing the models?
Lake-water samples are collected by local agencies each morning from two or three locations at each beach. After wading to knee-deep water, a sterile polypropylene bottle is opened about 18 in. below the water surface and filled. 

How well do the models work?
The models we developed are beach specific because the factors that affect recreational water quality are different at each beach. It usually takes several years of data collection to develop accurate predictive models. 

Although there is some uncertainty with using the models, the amount of uncertainty is quantified so that beach managers and the public can make informed decisions. We use the concept of a threshold. Probabilities equal to or above the threshold would indicate to the beach manager that E. coli concentrations are most likely above the bathing-water standard.  Probabilities below the threshold would indicate that E. coli concentrations are most likely below the standard. In other words, our models can work like a weather forecast. If there was a 70 percent chance of rain, would you go to a picnic? A 20 percent chance of rain?  Similarly, if there was a 70 percent chance that the standard will be exceeded, would you swim in the water? And again, because models provide an assessment of recreational water quality within an hour, they are better than the old methods that take 18-24 hours to complete. 

At Huntington, we tested the model developed from six years of data (2000-05) using data collected during the recreational season of 2006.  The model correctly predicted recreational water quality 80 percent of the time and worked better than the current method (using the previous day’s E. coli).  

Why was the USGS involved in this research?
Water quality and quantity are critical topics in which the USGS has developed expertise over many years. The relatively recent addition of biological science to our core programs gives us opportunities to apply science in a variety of new ways.

The USGS did not do this research alone. Agencies that cooperated with us were the Ohio Water Development Authority, Northeast Ohio Regional Sewer District, Cuyahoga County Board of Health, Cuyahoga County Sanitary Engineers, the Ohio Lake Erie Office, Ohio Department of Health, Ashtabula Township Park Commission, University of Toledo, Cities of Toledo and Oregon, and Toledo Metropolitan Area Council of Governments.

Is anyone else doing the same kind of research?  Are other predictive tools being investigated?
Yes, Lake County, Illinois and Project SAFE in northwest Indiana are examples of operational predictive models.  Operation models are models that are used to issue daily swim or recreational advisories.  A river-based operational model system, BacteriALERT, that uses turbidity to predict E. coli concentrations is used in the Chattahoochee River in Atlanta, Georgia. 

Will this research continue?
Because we believe this is a promising method, we will continue to improve the nowcast and refine predictive models for other beaches.  Usually, models improve as more data are collected.  Each year the model is tested, new data can be added and model variables can be recalculated to determine whether the predictive ability improves with an added year of data.   If a model at another beach is able to predict recreational water quality as well as or better than use of the previous day’s E. coli for several years in a row, beach managers may consider using the models to aid or direct decisions on posting beach advisories.

Does USEPA allow the use of models for posting beach advisories?  USEPA states that a monitoring program is essential to any beach-management program and recommends that the current E. coli laboratory method be used for assessing ambient waters and for making decisions concerning the protection of human health (USEPA 2002, p. 4-17).  However, USEPA also states that modeling tools may be used to supplement, not replace, monitoring.  Modeling tools can provide conservative estimates when there is a lag time between sampling the water quality and obtaining results.  If models are properly developed and applied, they can be used in making beach advisory or closing decisions (USEPA 2002, p. 4-22).

How can we identify sources of contamination at beaches?
Because many sources are nonpoint sources (not from a pipe or measurable source) and because many different factors affect pathogen survival in the complicated coastal environment, it is best to use several source tracking tools to identify sources.  Many of these tools provide anecdotal evidence when used alone, but provide a more convincing argument when used with other tools.

Identifying the spatial distribution of bacterial indicator concentrations, such as E. coli, helps to identify fecal contaminant “hot spots.”  Sampling along the shoreline to the beach can show if E. coli is coming from a point along the shoreline further away from the beach or from the beach itself.  Determining weather patterns that cause elevated E. coli concentrations can also help identify sources; for example, winds from a certain direction can be traced back to potential source areas.  Sampling shallow ground water in the beach area can also help to understand if beach sands serve as a reservoir of E. coli and pathogens.  More sophisticated and expensive microbial source tracking (MST) techniques can then be applied to specific areas.

Whom can I contact if I’m concerned about swimming at a particular Ohio beach?
You can find out who to contact about your beach by visiting the USEPA Beach Watch web site.

Information on Ohio Department of Health’s bathing beach monitoring program can be found at http://www.odh.state.oh.us/odhPrograms/eh/bbeach/beachmon.aspx

REFERENCES

Natural Resources Defense Council, 2006, Testing the Waters VIII: New York, 349 p., available at http://www.nrdc.org/water/oceans/ttw/titinx.asp

U.S. Environmental Protection Agency, 2002, National beach guidance and required performance criteria for grants: Washington, D.C., EPA-823-B-02-004.

 U.S. Environmental Protection Agency, 1999, EPA action plan for beaches and recreational waters: Washington, D.C., Office of Water, EPA-600-R-98-079.