Safe to Swim in Jordan Lake?
We often get asked about the safety of water for body contact sports at presentations of our work to various groups and at our Facebook page. The greatest concerns expressed are contamination by disease-causing organisms and algal toxins.
We’ve introduced this new page to provide factual information about how water quality is tested in Jordan Lake and provide links for further reading.
EPA Guidelines for Recreational Water Quality
EPA’s 2012 Recreational Water Quality Criteria are intended as guidance to states in developing water quality standards to protect swimmers from exposure to water that contains organisms that indicate the presence of fecal contamination. The criteria specify:
- indicator organisms to test
- frequency of testing
- estimated illness rate per 1,000 swimmers corresponding to the recommended
- standard maximum value for indicator organisms
Indicator organisms are NOT harmful to human health. They only indicate the presence of fecal contamination. Fecal matter of warm blooded animals, defined as mammals (humans included) and birds, may contain pathogens. The organisms are bacteria, viruses and parasitic protozoa (e.g., that cause Giardia). However, direct measurements of pathogens are extremely expensive and time consuming because there are so many agents and their identification is not always simple.
Setting a standard for acceptable fecal contamination is not a guarantee that human illness will be entirely prevented. EPA conducted observational studies at seven beaches to support the 2012 Recreational Water Quality publication. The results were used establish a relationship between the measured counts of selected indicator organisms and incidence rate of gastrointestinal illness. From this, EPA published the following:
GM is the geometric mean of the number count of indicator organism measured as colony forming units (cfu) per 100 mL of water. The GM is calculated from weekly samplings. It should not exceed the stated values shown in the table in any 30-day period. The STV is the statistical threshold value for the bacteria samples. It approximates the 90th percentile of the water quality distribution and should not be exceeded by more than 10 percent of the samples taken.
Weekly Sampling Needed
EPA recommends weekly sampling of indicator organisms to capture the time variability in water quality. Rainy weather can greatly increase the number count of indicator organims. It flushes animal fecal matter off the land into rivers to produce a spike in indicator organisms. Suspended soil particles not only give rivers a muddy appearance after rains but they also allow attachment by bacteria, prolonging their survival time.
Rain also causes water to seep into sewer lines through poorly sealed joints. If the carrying capacity of the sewer line is exceeded, raw sewage mixed with rain water will be bypassed into streams. Failure of sewage pumping stations and too much sewage arriving at the wastewater treatment plant can also cause bypassing. These events have occurred in the Jordan Lake watershed though usually limited to heavy rainfalls.
But even weekly sampling is not enough to give 100% assurance to swimmers that the level of indicator organisms is under the EPA published threshold. Hourly or daily sampling still does not solve the problem. This is because of the time delay in processing samples. At least 24-48 hours are needed to culture (grow) the sample in the laboratory before counting. A non-culture method, based on modern molecular biology principles, was put forth by EPA in 2013. It reduces the assay time to a couple of hours but has not yet been widely implemented by states.
The geometric mean calculation of indicator organism numbers helps to capture time variability. Its value changes with each new measurement added to the data pool. [The geometric mean is a running average calculated by taking the nth root of the product of n values.]
Freshwater Pathogen Monitoring NOT REQUIRED in North Carolina
The North Carolina Recreational Water Quality Monitoring Program falls under the Shellfish Sanitation and Recreational Water Quality Section in the Department of Environmental Quality (DEQ). A two page brochure explains the state’s monitoring program in the form of Frequently Asked Questions and Answers and is recommended reading.
Directly relevant to Jordan Lake is the following quote from the brochure :
QUESTION: Can I get sick from swimming in freshwater lakes and rivers?
ANSWER: Yes. Freshwater is affected by runoff and point source discharges just like coastal waters. Unfortunately, the state does not currently have a monitoring program for inland recreational waters. The public should avoid freshwater swimming after heavy rain, especially near storm drains.
A representative of DEQ explained to CJL that monitoring freshwater recreational areas falls to County health departments. However, monitoring is not mandatory. Wake County Environmental Services samples weekly for E. coli and enterococci at beaches in the Falls Lake State Recreation Area along with several other beaches in the county during the summer months. The data are published at the Wake County website.
Fecal Coliform Results at Jordan Lake
The Jordan Lake State Recreation Area (JLSRA), like Falls Lake State Recreation Area, is managed by NC Parks and Recreation Division under the NC Department of Natural and Cultural Resources. Its seven beaches are all within Chatham County.
Prior to 2014, the County’s Department of Public Health shared responsibilities with JLSRA for biweekly fecal coliform sampling, the indicator organism recommended in EPA’s 1976 Water Criteria. Fecal coliform is no longer the recommended indicator organism. EPA’s 1986 Recreational Water Quality Criteria shifted to enterococci (for marine and freshwaters) and E. coli (for freshwaters) as shown in the table above.
Because North Carolina does not have a freshwater monitoring program, neither JLSRA nor Chatham County is required to make measurements of indicator organisms. However, after Chatham County stopped their participation in monitoring, Jordan Lake Superintendent Shederick Mole decided to continue with monthly measurements through the services of a private contractor. Superintendent Mole shares these data when citizens call with questions about water quality.
We have obtained permission from JLSRA to report the fecal coliform results. Here are data for all 7 beach areas so far this bathing season.
The graph shows that the fecal coliform levels range widely, both with month and beach location.
With exception of Poplar Point for the August sampling, the fecal coliform level does not exceed the recommended value for safe bathing. However, the levels are highest in August at several beaches.
Heavy rainfall can be a major contributor to high coliform levels. Both the May and August sampling dates were preceded by heavy rainfall over a week-long period. By contrast, the sampling dates in June and July were preceded by a week or more with little rain. We cannot speak of trends when only one sample is taken each month. However, the coliform levels are generally higher for May and August than for June and July.
Taking weekly samples, as recommended by EPA, would better capture the trend and provide greater assurance to bathers.
Recognizing the shortfalls of bacteria counts , swimmers should take the following precautions:
- Don’t swim after a heavy rainfall
- Don’t swallow the water
- Rinse off after swimming
Other Water Quality Issues
The local news media have carried many articles about the suspension of the Jordan Lake Rules which would have required taking measures throughout the watershed to limit phosphorus and nitrogen inputs so as to reduce the growth of algae. Under strictly natural conditions, algae are important members of a healthy food chain. However, with excess nutrients, their levels become greatly elevated. They become nuisance organisms causing taste and odors and depleting the water of oxygen during night hours, leading to fish kills.
The blue green algae, more properly known as cyanobacteria, can also be a human health concern. This organism secretes cyanotoxins. In 2016, EPA issued guidelines and recommendations to protect recreational users from illnesses caused by cyanotoxins. The common illnesses are rashes, diarrhea, vomiting and breathing difficulty. In some cases, exposure to cyanotoxins can lead to liver, kidney and nervous system problems. A companion EPA report details the gaps in knowledge, most notably limited health effects data and poorly understood exposure routes ( ingestion, inhalation and dermal).
DEQ has not analyzed for cyanotoxins in Jordan Lake. The analysis of cyanotoxins is very expensive and thus only triggered when cyanobacteria are at levels high enough to produce measureable amounts of cyanotoxins . Routine identification of the species of algae over many years at Jordan Lake has so far indicated that cyanobacteria are below the threshold of concern for production of cyanotoxins. However, we must remain vigilant because the mix of algal species in a lake depends on many changing natural factors as well as nutrient input.
leaking chemicals from trash
Trash on the shoreline can also cause chemical pollution of the lake when the level rises after rainfall and inundates leaking containers of all types of residual fluids. For instance, our volunteers routinely find containers holding lubricants, hydraulic fluids, industrial adhesives, and gasoline along with an assortment of aerosol sprays, fire extinguishers as and pesticide spray applicators.
Any amount of chemical leakage can be considered as pollution. However, the lake holds hundreds of billions of gallons of water. Dilution of leaking containers by this huge amount of water probably makes it impossible to detect chemicals leaking out of containers amidst the shoreline trash with even the most sensitive of instruments. Nevertheless, citizens should be concerned about any amount and type of pollution in a reservoir that supplies drinking water to 300,000. Of course, we should add visual pollution to the list because it influences citizens’ perception of water quality, rightly or wrongly.