Tuesday, February 09, 2010

High-rises built on tank beds rest on shaky foundations

High-rises built on tank beds rest on shaky foundations


Bosky Khanna and Senthalir S. Bangalore

The Bellary building crash has sent alarm bells ringing among high-rises built on wetlands in the city. The under-construction building that collapsed in the North Karnataka city was built on a wetland, and ended up killing 28 persons.
Bellary's black cotton soil proved to be the nemesis of the five-storey building. City mayor Basavaraj pointed out that the soil was loose, and no proper soil testing was conducted before undertaking the construction.
In Bangalore, a large number of high-rise residential and commercial buildings have come up on encroached lake and tank beds. According to statistics available with Bruhat Bangalore Mahanagara Palike (BBMP), a total of 183 lakes have been identified in the city. "At least 233 acres have been encroached upon in the 69 lakes that have been taken up for encroachment clearance drive," said a senior BBMP official.
He added that most of the buildings that had come up on these encroached lands were residential buildings. Besides, there were also educational institutions, apartments and commercial complexes.
MU Ashwath, secretary, organising committee of Association of Consulting Civil Engineers (ACCE), said: "We cannot say anything on whether buildings that have come up on wetlands in Bangalore will collapse anytime. It all depends on the layout, position of columns, type of building and the load it takes."
Emphasising that the foundation determined the construction of a building, he said that black soil could shrink and expand. The soil quality would result in imbalances in the structure, leading to its collapse, he said.
According to Bangalore Development Authority (BDA) Master Plan 2015 rules, a 30-metre space should be maintained as buffer zone between the structure and the lake boundary. No construction should be allowed in that buffer zone, a BDA official said, and added that structures violating this rule would be considered as encroachments and would be cleared.
Corroborating this, Dr TV Ramachandra from Energy and Wetlands Research Group Centre for Ecological Sciences, IISc, said that a building constructed on a wet base would collapse in the eventuality of it being subjected to any pressure.
He said that rules were being flouted. One reason why a tall tower could not be constructed on the land where the Kempe Gowda bus stand stood now was because it was a wetland. Most lakes like Bellandur, Agara, Madiwala, Varthur, Ramasandra, Malathahalli, Puttenahalli, Vibhutipura lake on Old Airport Road, and even Ulsoor had been encroached upon. Surprisingly, all those structures had come up with sanctioned plans and permissions from civic agencies concerned, he observed.


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