More About Recreational Water Monitoring:

The Delaware Department of Natural Resources and Environmental Control monitors recreational waters to ensure their quality for swimming. Point sources of pollution, and rainfall-driven runoff from the land (nonpoint source pollution), may introduce disease-causing organisms into swimming waters. Fortunately, in Delaware, as a result of ongoing efforts to improve the treatment of wastewater and eliminate some discharges, Delaware's guarded beaches are no longer impacted by point sources of pollution. Efforts are also underway to control nonpoint source pollution by installing central wastewater collection and treatment systems to eliminate septic systems and by better managing our agricultural, commercial and residential lands.

Recreational water samples are analyzed to determine the levels of Enterococci bacteria. Enterococcus is one of several indicator organisms that signal the presence of potentially harmful bacteria and viruses. Currently, Delaware uses the following Enterococcus standards (colonies per 100 milliliters):

Delaware Enterococcus Standards

Water Type Geometric Mean Instantaneous Value Resample Value
Fresh 100 185  
Salt 35 104 104

The geometric mean is used to determine the long-term safety of a recreational beach for swimming. The instantaneous value allows the Department to assess current water quality conditions. Results are available 24 hours after the sample is delivered to the laboratory. If these standards are exceeded, the Department will use these results, in addition to other factors, to make a decision as to the safety of the waterbody for swimming. A "no swimming" advisory may be issued.

Bacteriological water quality can be affected by a number of factors, including human-induced contamination and a number of natural factors. For example, windy conditions create water turbulence. Naturally occurring bacteria that live on the bottom can be churned up into the water column by wind-induced waves. This will result in elevated levels of Enterococcus bacteria. If elevated levels are the result of natural conditions, and are presenting no threat to the public's health, an advisory will not be issued.

As a result of the passage of the Beaches Environmental Assessment and Coastal Health (BEACH) Act of 2000, the US Environmental Protection Agency is in the process of developing new recreational water quality standards. The State of Delaware will amend its standards in order to meet the requirements of the new federal regulation. 

Want Beach Monitoring Advisories hot off the press? Join the Beach Monitoring list from DNREC Online Email Lists.

For more information, please contact Debbie Rouse at 302-739-9939.