City of Austin to treat harmful algae growth on Lady Bird Lake

AUSTIN (KXAN) -- The City of Austin said it would soon apply a treatment on Lady Bird Lake to try to mitigate the growth of harmful algae.

The treatment program is part of the city's third year undergoing a pilot program that aims to reduce the algae on parts of the lake.

Lanthanum-modified clay will be applied near Red Bud Isle and along the north shore of the lake between I-35 and the lagoon near the Festival Boat Ramp. The clay material may help prevent or slow the growth of harmful algae in areas where it's applied, according to a release from the city.

The clay binds to phosphorus, which is a key source of nutrients for algae. Once it binds to a mineral form, the phosphorus becomes unavailable to the algae and "essentially robs the algae of one of its primary food sources," the release said.

The first applications are expected to happen at Red Bud Isle on Monday, June 5, and east of I-35 on Tuesday, June 6, weather permitting. The city said if additional time is needed, the work will extend into Wednesday, June 7.

Additional applications are planned for July and August. 

The substance is safe for humans, the environment and wildlife, according to the city. It will be applied from a barge and will look like gray slurry being sprayed into the lake. It will temporarily cloud the water but will settle to the bottom within a few hours, the release said.

The city asks boaters to keep plenty of distance from the barge during the application process.

Last year, the City of Austin applied a total of 60,000 pounds in each area across three applications. In 2021, the city applied 120,000 pounds at Red Bud Isle. 

Potentially toxic algae on Lady Bird Lake

The city said Tuesday that staff has found blue-green algae in Lady Bird Lake and Lake Austin. These algae are presumed to be toxic.

The Watershed Protection Department said blue-green algae was found at every monitoring site on Lady Bird Lake and Lake Austin except at the Walsh Boat Landing.

The city has documented toxic algae yearly since 2019 in Lady Bird Lake. Toxic algae have been found every year since 2020, when sampling began, in Lake Austin.

The city recommends that people and pets avoid contact with algae, do not drink water directly from the lake, and rinse off after contact with the water. Do not allow dogs to lick their fur prior to rinsing. Swimming is prohibited in Lady Bird Lake.