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Gwinnett studying effect of septic tanks on Lake Lanier water
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Wastewater is treated in large filtration pools at F Wayne Hill Water Resources in Gwinnett County on April 8, 2015, before being released back into Lake Lanier. Gwinnett County is sponsoring a $2.4 million, three-year study of water quality along Gwinnett lakefront on Lake Lanier. - photo by Scott Rogers

Gwinnett County has hired Georgia Tech Research Corp. to study the effects of septic systems on Lake Lanier.

The $2.4 million contract lasts for three years and will involve sampling of groundwater, lake water and lake sediment. Sampling will only be done in Gwinnett County, said county spokeswoman Karen Shields.

Gwinnett relies on Lake Lanier and the Chattahoochee River for its drinking water needs, and more than half of the water supply for all of metro Atlanta passes through the lake.

Gwinnett is launching the research after the Georgia Environmental Protection Division announced this summer that it was moving forward with a plan for tighter regulations for water and sewer utilities in the Lake Lanier watershed.

The new regulations are coming through a total maximum daily load for nutrients like nitrogen and phosphorus flowing into the lake. The TMDL represents the total amount of nutrients that can flow into the lake while meeting federal water quality standards.

To meet federal standards, nutrients in the lake will have to come down over time. The most obvious targets for new restrictions are sewer utilities and municipalities, but they’ve been subjected to Clean Water Act regulations for years.

One unsolved problem around Lake Lanier and its connected river systems are “nonpoint sources” — the streets, farms, subdivisions and other pieces of human development that over time cause sediment and other runoff, including those nutrients, into local waterways.

The nutrients are a problem because they promote algae growth in the watershed, which can choke streams, kill fish and degrade overall water quality.

Septic tanks are one of those potential sources of the nutrients that regulators are trying to control in Lake Lanier, and Shields said there are 640 tanks in the lake watershed in Gwinnett.

Many septic tanks rely on a leach field to drain treated wastewater back into the sediment once the water has passed through the septic tank itself.

“Lake Lanier provides drinking water for Gwinnett County and much of metro Atlanta, either directly or downstream from the Chattahoochee River,” said JC Lan, deputy director of engineering for Gwinnett County Water Resources. “This research will provide data to help us better understand water quality in the lake and what can be done to continue to improve it.”

Gwinnett hopes its research will help determine ways to reduce nutrient runoff into Lake Lanier, and if successful provide a model for Georgia EPD to help protect lake water quality.

Gwinnett is just one of the counties involved in the Lake Lanier Stakeholders, a group of organizations, governments and utilities around the lake that have a role in water quality. The group also includes the Chattahoochee Riverkeeper, a local environmental conservation group that applauded Gwinnett’s decision to study the lake.

“Monitoring data shows that nutrient levels in the lake are too high and research can certainly help guide communities, agencies and other stakeholders in planning for reductions,” said Dale Caldwell, the group’s Gainesville-based watershed protection specialist.

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