PIC for representation purpose (October 2018)
BENGALURU:
Wednesday’s heavy rains which created havoc in Koramangala and adjoining areas, and the subsequent fast-track solution of a parallel drainage system, injection wells and desilting of Bellandur lake by the powers that be have created a sense of deja vous among Bengalureans, especially residents of those habitually rain-affected areas.
The following article by Muralidhar Rao was posted in ‘Praja’ on September 13, 2018. thebengalurulive is carrying it again to show how little things have changed on the ground since then.
‘Koramangala 4th Block flood mitigation plan’
A few weeks back, there was an announcement of the commencement of work on the subject plan, with a pooja, presided over by the BTM Layout (under which Assembly constituency the area falls) MLA, Ramalinga Reddy.
The announcement talked about laying of pipelines along the 80 Feet Road, in the vicinity of Sony-World junction and Maharaja junction, and, with the area already badly congested, there was anxiety among residents to understand what the whole proposal was, as also how it’s going to affect their overall mobility.
I requested Srinivas Reddy, EE, BBMP, if he could make a presentation to 4th Block (which includes S T Bed Layout) residents on the proposal, or at least provide the drawings. But he seemed to suggest he was busy. Subsequently, I spoke to Govardhan Reddy, the Block Congress convener, and it is based on my understanding of what he had stated that I have put together this report.
The thin blue line indicates the underground pipeline originating somewhere near the Sony-World junction and ending at the ‘wet-well’ somewhere near Wipro (Kamal Bakery) junction, into which flood water accumulating along the stretch will enter through gratings on the surface. From the wet-well, the water is supposed to be taken to Bellandur lake through 6,-foot diameter pipes (seen in picture below, and indicated in deep blue colour, in the picture above). (During the time Mr Muralidhar Rao had reported the story, the six feet diameter pipe was being laid from NGV to nagasandra — the sewage line — the work is still under progress).
The crossing of the storm water drain (SWD) near ‘Seva-in-Action’ is supposed to be through a ‘siphon’ arrangement as depicted in the picture below:
Now, there is already a sewage line below the SWD, which if you assume as 4 ft dia (b), ‘c’ is 6 ft, and if the bed of the SWD is 12 ft from the ground level, then the excavation has to be to a level of minimum 22 ft from the ground level.
From there, it flows through along points marked pic 3, pic 2, and then along the SWD from pic 4, and empties into Bellandur lake at pic 1 (beyond the SWD wall seen in the picture). The crimson arrows indicate the direction in which the pictures were taken.
The whole idea of publishing this report is to help the community understand what is in store, make their own assessments (many are engineers, some specialised in hydrology too), and engage with the powers that be to make correctives, if required. Well, even for an electrical engineer like me, the following questions arise:
1) Water (rather sewage) is flowing into Bellandur lake in the SWD. So, the natural gradient is available. But, is it good enough for high flood discharge? If not, is there a fear of water backing up, and causing bigger damage?
2) The siphon arrangement appears very dicey. There is every chance of muck collecting at the bends and blocking the flow. How is it proposed to be cleaned? And is it going to be gravity flow through it from the wet-well, or is it going to be pumped?
3) The flood-water channelisation through roadside gratings into the underground pipeline along the length of the 80 ft road also appears a tricky job.
The bigger question that arises is, when undertaking such massive jobs which have a huge impact on the life of the community, shouldn’t there have been wider citizen consultations before starting work on it? The entire area is cluttered with those massive pipes, which means huge sums have already been spent.
Well, all in all, the city governance certainly calls for total re-structuring.
The author, an electrical engineer by profession, is vice-president of Bangalore Apartment Federation and an active member of ‘Praja’.
The original article is fetched from here: (http://praja.in/en/blog/murali772/2018/09/13/koramangala-4th-block-flood-mitigation-plan)
About the Author
