Retrospective STPs can trigger building collapse, says study

'Getting old apartments to install sewage plants won't serve any purpose'

Retrospective installation of Sewage Treatment Plants (STPs) in older apartment complexes of Bengaluru can impact the structural safety of buildings. This can potentially trigger a collapse, says a recent study.

Facilitated by the Bangalore Apartments’ Federation (BAF), the study was undertaken in response to notices issued by the Bangalore Water Supply and Sewerage Board (BWSSB) and the Karnataka State Pollution Control Board (KSPCB) to older apartment complexes.

These two agencies had made it mandatory for the complexes to put up STPs on a retrospective basis. Failure to do so would invite criminal action and disconnection of power and water supplies.

The study covered three different apartment complexes in the city with 65 to 160 units, and was conducted by structural engineering experts — B N Nagaraja, retired chief engineer, Central Public Works Department, and Ashok Rao, the founder of consulting firm Structures.

So, how does an STP exactly endanger an old apartment-dweller? In his report, Nagaraja notes: “Construction of an STP in the available space below the ground would endanger the structural safety of column foundations.”

Older apartments, Rao opines, were built based on the norms that prevailed at that time. “They were not designed to accommodate the complex systems required for an STP and implementing such a system after many years of construction of the apartment could endanger the entire structure.”

The BAF’s Srikanth Narasimhan maintains that the “retrospective STP implementation does not serve any purpose whatsoever, since older apartments are already connected to the underground sewage network (UGD) provided by the BWSSB, and are not polluting in any manner.”

In an affidavit to the National Green Tribunal (NGT), the state government had informed that the quantum of sewage let out by apartments into the UGD is less than 3% of the overall sewage. Smaller buildings and individual houses account for the rest 97%.

The BWSSB, says BAF joint secretary Vidya Goggi, had failed in its basic duty to put up STPs at the endpoints of the UGD. This, she says, is the root cause of lake pollution.

“Having failed miserably in doing its job and trying to
cover up for its own incompetence, absurd rules are passed which make no sense whatsoever.”

DH News Service

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