Mumbai has a unique problem (the two-month intense monsoon) so it has to evolve its own system. The civic body must ensure that the storm water drain project it is implementing now should serve as a base for future expansion and upgradation. They should not have to start from scratch at a later date - Ron Thomas, Project Director, MWH, a US-based consultancy firm that’s studying the city’s current drainage system to prepare a revised plan for the storm water drain project, Brimstowad.
( Check out the special on The Mumbai Project )
On a pleasant November afternoon, 15 labourers in safety suits gingerly lowered themselves into a manhole in the damp, dark, mucky bowels of the city. Their breath stirred by whirring exhaust fans that have been installed so that they don’t choke, their surroundings lit by halogen lamps, they checked the walls of the pipelines.
Thirty feet below the overburdened, potholed roads that are struggling to keep pace with the frenzied rapidity with which Mumbai is growing, a revolution is brewing. Here, underneath the city that best epitomises India’s astonishing — and astonishingly evolving — story of growth and change, 150-year-old storm water drains that are supposed to carry out fast-accumulating rainwater in Mumbai’s vicious monsoon are being revamped so that they can handle the flooding that brings the city to its knees every year.
There is at least one reason to be thankful for the deluge of July 26, 2005: Brihanmumbai Storm Water Drains (Brimstowad) — the project of revamping these drains — was born again in the wake of the devastation and the loss unleashed on that horrific day when Mumbai went six feet under.
The project includes redesigning the drains to accommodate the dispersal of 50 mm of rainfall per hour from the existing 25 mm; removing obstacles like encroachments; constructing pumping stations to drain out water during high tide; and deepening as well as widening the drains.
It’s been a long time coming. In 1988, three years after the floods of June 1985, Mumbai’s civic authorities had appointed Watson Hawksley International to study the city’s drains and prepare a plan for efficient disposal of rainwater. The result was the Brimstowad report, which asked the Brihanmumbai Municipal Corporation (BMC) to revamp the storm water drains network.
The report was submitted in 1993. It remained in cold storage till after the deluge of 2005. Why was that? “The BMC faced financial crises during the interim period hence the project could not take place,” said R.A. Rajeev, Additional Municipal Commissioner.
Now, with all the crises apparently washed away in the waters of a flood that killed more than 900 people in and around Mumbai, the project is back on the front burner. Worth Rs 1,800 crore (Rs 1,200 crore for the work and Rs 600 crore for rehabilitating 26,600 families who live above and around the drains), it is one of the most ambitious projects in Mumbai’s history — and one of the most critical if the city wants to reinvent itself as a truly global one. The Union government has allotted Rs 400 crore for it; more money from Delhi is on its way depending on how the project progresses.
The drainage system in any city depends on the topography. Mumbai is a cluster of seven islands and the current system was built before Independence. With rapid and spreading urbanisation, the plots that had once been meant to soak up excess water have become beds for concrete towerblocks.
“Initially the rainwater used to percolate to the soil, but now this soil is replaced by concrete pavements and roads so all the rainwater goes into the drains, increasing the volume to be handled,” said Ron Thomas, Project Director, MWH, the US-based consultancy firm that is now studying the city’s current drainage system.
The drains — already choked with plastic bags and other forms of refuse that are routinely thrown into them — cannot take the pressure. The result? Floods.
Tackling the drains and ensuring the dispersal of rainwater is terribly important — and doubly difficult — because of the sort of rainfall Mumbai receives. The pattern of rainfall has changed over the years. Mumbai now receives 3,200 mm of rainfall every monsoon compared to the 1,100 mm it used to get 20 years ago. And unlike cities like Singapore where it rains through the year, Mumbai’s intensely heavy rain is concentrated over two months.
It isn’t just the big underground drains. The city has 2,000 km of small drains which first receive the water, and then discharge it to the 440 km of big drains underground. The water then travels to 187 outfalls (points where the creek meets the sea) through 200 km of major nullahs and 87 km of smaller nullahs (open drains on the side of the roads).
The first phase of the project — involving the widening and deepening of drains — is underway. But that won’t be enough; the construction of the city’s first four pumping stations at Haji Ali, Cleveland Bunder (Worli), Love Grove and Irla nullah will be critical.
So will the reorganisation of the draining system stop floods in low-lying areas? Yes, because it will ensure that rainwater reaches the sea much faster than it currently does. For instance, directing rainwater from Hindmata in Dadar to Cleveland nullah (Worli) instead of Reay Road shortens the distance from 4.5 km to 1.5 km.
New Orleans, which is surrounded by water on all sides and which grappled with massive flooding in the aftermath of Hurricane Katrina in August 2005, has 130 pumping stations. The stations are capable of pumping out 10,000 cubic feet of water per second from the city streets to a series of canals and finally to Lake Pontchartrain.
During Katrina, most of the pumps stopped working and the water flowed from Lake Pontchartrain back to the canals and flooded the city.
Engineers over there have now proposed a permanent gated structure to prevent water from entering drains during high tide, and pumps at the mouth of two canals, which will push water back into the sea. In a crisis, operators will lower the gates and start the pumps. The stations are being revamped with storm-proofing equipment.
As New Orleans draws up and implements new plans, Mumbai’s civic body is struggling with a mammoth task — that of locating the cables, telephone wires, water pipelines and other public utilities snaking their way underground across the city.
None of this is mapped, and no one knows where one may run into these while revamping the drainage system. A storm water drain takes up a lot of space, and for them to be redone, many of the existing cables need to be shifted. “It’s time storm water drains figure in our town planning,” said Sharad Bhagwat, Director and Chief Engineer, MWH.
The civic body is now implementing the Geographical Information System (GIS), which will map all the utilities and provide accurate information about their positions. “The data will be put on the system within a year. This will make things easier,” said D.K. Pathak, Deputy Chief Engineer (storm water drains).
Any project as ambitious as this will have its critics. And Brimstowad’s detractors say the current plan focuses merely on bigger drains and neglects the smaller ones that they think are key to the dispersal of rainwater. “More importance should be given to the local drains because they are the key to preventing water-logging,” said S.D. Chawathe, Honorary Director (technical), Indian Water Works Association. But Rajeev says enough attention is being paid to the smaller drains.
Then there is the problem of citizens choking drains by throwing refuse into them. “Awareness is the key and we will tell citizens about the importance of cleanliness,” Rajeev said.
Ambitious projects are fine, but for Mumbai to be world-class, its citizens need to wake up to the civic sense that the developed world considers rudimentary.
Widening and deepening Mumbai’s 150-year-old storm water drains will help the drainage system accommodate and disperse greater volumes of rainwater during the monsoon. This means an end to flooding. Let’s hope the revamped system will be strong enough to be able to tackle even rare deluges like the one that crippled the city on July 26, 2005.
Is this enough?
Problem 1: No map of underground cables and pipes
Thousands of underground cables (telephone, water pipelines) will need to be mapped, and in some cases, shifted to accommodate the redone drains.
Problem 2: Slums on drains
As many as 26,600 people who live on top of and adjacent to the existing drains will have to be displaced and rehabilitated. It’s not an easy task as slumdwellers don’t want to move out of the localities they live in.
Problem 3: Lack of civic sense
People will have to stop clogging the drains by throwing debris and garbage into them.
Problem 4: Drains not cleaned
The BMC often does not complete cleaning the drains before the monsoon sets. Work is also not done properly; garbage is left on the sides of the road and when it rains, it goes back, choking the water passage.
In the pipeline
The city currently has no pumping stations; compare that to New Orleans, which has 130. These pump out water into the sea and are especially useful during high tides. The BMC has passed tenders to build 8 pumping stations in Mumbai. Work will begin early 2008. The deadline is 2011.
The Katrina catastrophe
Construction workers install large water pumps along the 17th Street Canal in New Orleans, Louisiana, in an effort to help prevent flooding in case of future storms. More than two years later the hurricane hit the New Orleans coast, in August 2005, residents are struggling to recover and rebuild their city.
The July 26 effect
The Rs 1,800 crore storm water drain project was revived after the city went under water on July 26, 2005. The Love Grove sewage treatment plant in Worli is one the locations where the civic body is planning a pumping station. The plant already has four sluice gates to release water into the sea.
What’s being done now?
** The civic body has started desilting and widening six big drains across the city.
** After this, they will clear all encroachments and build walls around the big, open drains.
** Proper access roads will also be constructed, that will lead to all the big drains.
** Plans are on to beautify the banks of the Mithi river at Kalina and Powai and create a tourist spot.
Why did it take 14 years to start revamping the city’s ancient drainage system?
In the 90s, the civic body was in financial crises so we could not implement it.
The 2005 deluge was enough to drown the city. Even this year we witnessed water-logging. Has the BMC failed?
The 2005 rains were unprecedented and no city in the world could have done anything about it. We assure people that once the Brimstowad project is over, we will be equipped to tackle any eventuality.
You mean something like the 2005 floods?
Even if it rains so much, we would be able to clear the water within four hours.
Experts say Brimstowad focuses on just large drains and ignores the smaller ones. Is that so?
We are focusing on large and small drains.
Is work being delayed because public utilities underground are not mapped?
Work is underway and we are taking all steps to clear the hurdles coming in the way.
2,000 km: The length covered by the city’s small drains, which first receive rainwater
440 km: The length covered by the city’s big, underground drains which receive the water discharged by the small drains
187: The number of points in Mumbai where the creek meets the sea
For more details: Check out the special on The Mumbai Project