Estimated E. coli colony counts per 100mL of water:
Low risk: E. coli ≤ 235
High risk: E. coli > 235
Estimated risk level based on EPA Beach Action Value information.
The public is advised to check the National Park Service Chattahoochee River National Recreation Area (CRNRA) website and other Regulatory agencies for potential river advisories before accessing the river.
A Background on Water Quality Indicators
E. coli:
E. coli is a type of bacteria found in the gut and feces of many warm-blooded animals. For this reason, it is a useful indicator of fecal contamination in water. Fecal contamination may occur via broken sewage pipes, urban runoff, agricultural runoff, and more. While E. coli is not the only harmful bacteria or pathogen that can be found in surface water, it is an important indicator of the potential fecal matter and pathogens that may be present. When E. coli is present, there may also be other contaminants. E. coli is an affordable and efficient way to calculate the contamination levels in surface water so that the public can know when to exercise caution.
Total Coliform:
Total coliform is the number of coliform bacteria in the water. Total coliform is comprised of many different bacteria that are not limited to fecal types. Not all total coliform is harmful. Total coliform can be used to monitor contamination; however, it is not ideal for monitoring fecal contamination.
Expression of Data:
Both E. coli and Total coliform are expressed using “most probable numbers,” or “MPNs”. A MPN represents colony-forming units (cfu)/100 mL. Simply, this is how many units of bacteria are most likely present in 100 milliliters of water.
Turbidity:
Turbidity is the clarity of water, calculating how clear or cloudy it is based on the amount of suspended particles present. It is an indicator of erosion and runoff. Highly turbid waters may harm organisms by blocking sunlight, harming filter feeders, clog fish gills, and more. Turbidity may also indicate an increase in E. coli following runoff and erosion events.
Conductivity:
Conductivity refers to the ability for water to conduct an electrical current. Many chemicals and substances conduct electricity, such as salts and metals. Some, however, do not conduct electricity, such as oil. Conductivity varies between water sources. When testing for conductivity, a baseline for each sampling location can be established. Going forward, any significant changes may indicate the presence of pollutants.
Risk Level:
Green: E. coli does not exceed 235 cfu/100mL, indicating low risk. Recreational activities are mostly safe.
Red: E. coli exceeds 235 cfu/100mL, indicating high risk. Avoid recreational use at this time, as possibility for illness has increased. This applies to both humans and pets.
Based on BacteriALERT Realtime Monitoring standards
Sources:
https://www.usgs.gov/special-topics/water-science-school/science/bacteria-and-e-coli-water
https://www.epa.gov/region8-waterops/addressing-total-coliform-positive-or-e-coli-positive-sample-results-epa-region-8
https://archive.epa.gov/water/archive/web/html/vms55.html
https://www.epa.gov/national-aquatic-resource-surveys/indicators-conductivity