But quantity of silt removed may not exceed 10 per cent of annual average
The BMC begins its pre-monsoon de-silting work in April. File pic
The Brihanmumbai Municipal Corporation (BMC) has started floating tenders to clean nullahs, aiming to remove 10 per cent more silt this year at a cost of Rs 300 crore. Chief Minister Eknath Shinde had instructed the civic body last year to clean nullahs to their bed level, following which 11.7 lakh tonnes of silt or 20 per cent more than the average quantity was removed. This year the BMC has asked contractors to clean nullahs till the tide level.
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With the Storm Water Drains (SWD) Department of the BMC has started its annual process to clean nullahs before the monsoon, the corporation has been floating tenders to clean major, minor, roadside nullahs and the Mithi river, in a step-by-step manner. The civic body removes on average 10 lakh tonnes of silt by May 31 every year.
According to a former engineer working with the SWD department, the corporation determines the quantity of silt to be removed based on past experiences, assuming that removing around 10 lakh tonnes of silt—approximately 20 cm-30 cm in height) yields satisfactory results to cope with the monsoon. However, no comprehensive study has been conducted.
CM Shinde had visited the nullahs in the last week of May 2023 and instructed the civic body to clean the nullahs till rock bottom. The SWD department claimed to have removed 11.70 lakh tonnes of silt from nullahs and rivers across the city last year till June 12, which is 20 per cent more than the targeted quantity. But this year the estimated silt quantity removed may not exceed 10 per cent of the average quantity of 10 lakh tonnes.
Field experiences indicate that the actual silt volume reaches rock bottom, which is approximately three times the current target. “The bottom of nullahs and rivers should not be lower than the tide level of the sea otherwise the seawater will push back into drains. So we will ask contractors to remove silt up to tide level and according to our estimation, the quantity may not exceed more than 10 per cent of the yearly average,” said an official from the BMC.
There are 309 major drains and four rivers with an approximate total length of 290 km. The city has 508 small nullahs that are 605 km long. There are also 475 km of 100-year-old underground stormwater arch drains. Apart from these, there are around 2,004 km of roadside gutters. While 75 per cent of nullah-cleaning is done before monsoon, 10 per cent happens during the monsoon and 15 per cent after monsoon. Pre-monsoon desilting of gutters, nullahs and rivers begins in April.
Till now, the BMC has floated tenders with an estimated cost of Rs 80 crore for Eastern Suburbs and Rs 145 crore for major and minor nullahs in the Western Suburbs. The estimated cost for desilting tenders of city nullah and the Mithi River hasn’t yet been disclosed, but it is likely that the total cost of desilting would go up to Rs 300 crore with the inclusion of gutters and the remaining nullahs.
Year-round cleaning in slum areas
The BMC has also decided to clean nullahs around slum areas around the year. A separate contractor will be appointed for cleaning of slum pockets and nullahs in their vicinity. “This will help reduce choking of nullahs and ensure they are clean throughout the year,” an SWM department official told mid-day, adding that the civic officials noticed that a large amount of waste is dumped in nullahs and drains that flow around slum areas.
“We need to keep the nullahs 100 per cent clean around the year. The nullahs get choked due to floating material, mainly plastics. If we start proper solid waste management in slums, the amount of floating material coming into nullahs will automatically reduce.
These contractors will clean minor nullahs around the year. If we keep minor nullahs clean, it will help us maintain the flow of major nullahs the minor ones drain out into these,” the official said.
11.7 Lakh
Amount of silt removed last year (in tonnes)
2023 May
Month CM Shinde told BMC to dredge till bed
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