LAWRENCEVILLE - Lake Lanier could be added to a federal list of polluted waterways because it has too much chlorophyll a.
The microscopic plant matter, which signals the presence of algae, is caused by fertilizer and other nutrients washing into the lake when it rains, although discharged sewage can also contribute to its growth, environmental officials said.
High chlorophyll levels pose no danger to human health but can drive up water treatment costs and even kill fish by sucking oxygen out of the water, the officials said.
No decision has been made yet on whether the lake, a major source of drinking water and recreation for metro Atlanta, should be placed on the federal list, said state Environmental Protection Division spokesman Kevin Chambers.
EPD is reviewing water samples from the impoundment at Gwinnett County's northern tip and will eventually decide whether it should recommend its inclusion on the list, Chambers said.
The federal Environmental Protection Division would have the final say on whether Lake Lanier makes the list, Chambers said.
Gwinnett County has already been told by state officials that the popular lake will be put on what is known as the "303d list," said county Public Utilities Director Frank Stephens.
It's inclusion should have no effect on a sewage discharge permit the county is getting from EPD so it can expand the F. Wayne Hill Water Resources Center near Buford, Stephens said.
Gwinnett needs the permit to accommodate its future population growth and economic development.
Chambers said excessive chlorophyll levels were found at three Lake Lanier testing sites: Brown's Creek, Lanier Bridge and Flowery Branch. Those spots are not near Gwinnett County.
Chlorophyll levels also exceeded state pollution limits at Lake Allatoona, Carter's Lake and Lake Walter F. George (Eufaula), Chambers said. Those three are also being reviewed for possible inclusion on the federal list, he said.
"There were certain monitoring stations that showed the problem and others that did not in all the lakes," Chambers said.
He said it appears that most of the problem is caused by fertilizer and other nutrients washing into the lakes, "and that is causing algae growth."
The federal Clean Water Act requires states to set limits on various pollutants. If any pollutants are found to exceed those limits, the body of water is placed on a federal list of impaired waterways.
A spokeswoman for federal EPA was unable Tuesday to provide information about the federal list or the procedure for being placed on it.