Contrary to popular belief, Lake Lanier is usually pretty darn clean, water officials say. 

“100% false,” Amy McGuire, executive director of the Lake Lanier Association, said of the idea that Lake Lanier is dirty. “We have the most incredible water standards.” 

Her assessment is seconded by Becca Risser, the headwaters watershed specialist for the Chattahoochee Riverkeeper, who met with The Times last week at River Forks Park and waded into the water to collect samples for E. Coli testing. 

“I've certainly heard people say that, but one of the things that I always try to remind people (of) — and it's really satisfying about my work — is that most of the time Lake Lanier is really, really clean,” Risser said. 

With Memorial Day weekend coming up, lake goers will also be happy to know that recent water quality tests are encouraging. 

“Our reports are fantastic,” McGuire said. 

The Lake Lanier Association conducts year-round tests at 27 sites, including beaches, docks and shorelines. McGuire said they test for E. Coli, turbidity and toxic blue-green algae, also known as cyanobacteria. 

Toxic algae tends to thrive when it’s warm and sunny. Luckily, it’s easy to spot because it looks like spilled paint floating on the surface of the water. 

E. Coli is the ‘No. 1 human health risk’ 

E. coli, however, is the main cause of concern. It is the best indicator of fecal contamination and water safety, according to the U.S. Environmental Protection Agency. 

“While there's a lot of different things that could become water quality problems, E. coli bacteria is the No. 1 human health risk,” Risser said. “That's the thing that's most likely to make a person sick if they're encountering it in the water.” 

When testing for E. Coli, more than 235 MPN per 100 mL is considered high. MPN refers to the most probable number technique, a statistical method of estimating the concentration of bacteria in water. 

“(At that level) if you had 1,000 people that had full contact with the lake, completely submerged — ears, nose, mouth — 36 of those 1,000 people would contract some kind of illness,” Jason Ulseth, head of the Chattahoochee Riverkeeper, told The Times last year. 

To check the water quality in your area, visit the Chattahoochee Riverkeeper’s Neighborhood Water Watch website. 

Risser said her testing on May 17 at River Forks Park and Lake Lanier Olympic Park showed E. Coli levels below detection, less than 50 MPN. 

Her testing at Don Carter State Park, on the other hand, returned a result of 260 MPN, well above the safety threshold. 

But Steven Emery, the park manager, said their own tests a couple days before showed levels below 10 MPN. 

What explains the difference in results?

Lake Lanier’s water quality can change quickly 

The likely answer, officials said, is that tests are a snapshot in time and that water quality can change drastically in just a couple of days, which is why it’s important to test regularly. 

“The lake’s a very dynamic environment, so by Wednesday it could have gone up or down,” Emery said. “You’re testing one specific location at one point in time. … What we really look for are trends. If it’s high every week, we may need to do some further research as to why that may be.” 

The EPA says a monthly average level of 126 MPN per 100 mL is high and warrants close monitoring. 

If E. Coli levels remain elevated, a park will issue an advisory warning people to swim at their own risk. 

Don Carter State Park closed for several days in 2017 due to high E. Coli levels.

Mike Axton of the U.S. Army Corps of Engineers  noted that Don Carter State Park is closer to Lake Lanier’s two tributaries, the Chattahoochee River and Chestatee River, which can result in higher levels of pollution. 

The Corps oversees 18 beaches around Lake Lanier, including Buford Dam Park, Old Federal Day Use Park, Burton Mill Park and Duckett Mill Campground, all of which tend to be remarkably clean, Axton said. 

“In recent history, there’s only been one time that we had to go back out and re-sample,” he said of E. Coli testing. 

He said the Corps conducts tests from March through September — seven times before the following federal holidays: Memorial Day, Juneteenth, July Fourth and Labor Day. 

Don’t swim after a heavy rain — and don’t feed the geese!

Officials say the largest source of pollution is stormwater runoff. They advise staying out of the lake for up to three days after a heavy rain, especially people who are immunocompromised or those who have open wounds or sores. 

“When it rains, whatever’s on the ground gets picked up and carried into Lake Lanier, so that is the time of most concern, the 72 hours after a rain event,” said Linda MacGregor, Gainesville’s director of water resources.

The droppings of nearby wildlife, especially geese, also tend to be a major source of E. Coli in the lake. 

Canadian geese were introduced to Lake Lanier with the expectation that they would migrate, but they decided to stick around, making them an ever-present source of fecal contamination around the lake.

“With water quality, the biggest thing is … educating people on not feeding geese where they’re swimming,” McGuire said. “The E. Coli level can really increase in that area.” 

Officials say E. Coli in Lake Lanier rarely comes from wastewater treatment plants. 

“We treat to very high standards,” MacGregor said of Gainesville’s plant. “Our permits are among the most stringent in the state of Georgia. … All across the state where water utilities discharge into various other streams and lakes, they have different requirements and many of them are not as stringent as Lake Lanier’s requirements.” 

For example, take biochemical oxygen demand, which the Environmental Protections Division uses as a measure of how clean the water is. 

“A lot of plants in Georgia have a limit of 30,” MacGregor said. “Our monthly BOD limit is 2.5.” 

McGuire, of the Lake Lanier Association, said she toured wastewater treatment plants last week in Gwinnett and Forsyth and was “very pleased” with their water quality. She will tour Hall County’s water treatment plant next week. 

“Hall county so far has really shown a great deal of concern over the quality of the water in the lake,” she said. “Hall County has really stepped up to help us with our trash.”