The Bangalore Development Authority has said it would perform one-time cleaning of the Bellandur Lake in 2020 after all the sewage treatment plants have been installed.
One-time cleaning would mean draining the lake and removing the silt, a procedure the BDA has been following in cleaning up 100 lakes. Of the 210 lakes in the city, the BDA has control of 123.
The agency rejected suggestions for wet dredging made by expert committee members and researchers from the Indian Institute of Science (IISc). "Wet dredging will be a long and time-consuming process for such a large lake," an official said.
In fact, on September 8, 2017, the state government had asked the National Green Tribunal to reconsider its April 19, 2017 order of performing one-time cleaning of the lake.
However, the BDA submitted an action plan on February 28, assuring the court that it would perform one-time cleaning of the Bellandur Lake from December 2020 after the Bangalore Water Supply and Sewerage Board installs all the STPs around the waterbody.
An official said the BDA is working on a plan to pump out water from the lake and maintain its water level. The first step is to install sluice gates to regulate the flow. Water will then be pumped out in phases. Segment chambers will be created in the lake to help the process.
"Only part of the 951-acre lake will go dry at a given time. We'll remove silt from the dried up area and move to other segments," an official said.
The BDA will create three islands in the lake, which it says would help maintain biodiversity. The agency has estimated Rs 550 crore as the cost of desilting.
The BDA has decided to send the lake's water downstream in a phased manner during monsoon and when there is fresh inflow.
"In the 10-kilometre area around the lake, we'll create bunds and raise their heights to ensure that the lake's boundary is clearly demarcated. "We'll use this area to beautify the lake," he said.