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Open Drains Versus Point of Source Infiltration

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Open Drains
Point of Source Infiltration
Contamination of rivers creeks, wetland & oceans
Maintains Hydrological integrity og natural water systems
Causes urban flooding
Prevents urban flooding and preserves pure water to be recycled
Depletion of flora and fauna
Maintains healthy flora and fauna
Causes erosion and sediment migration
Promotes soil stability
Uncontrollable water runoff due to excessive flow
Regulates water movement compatible with nature
Soil contamination and degradation
Promotes healthy soil
Causes air pollution
Purifies air
Creates thermal pollution (depletion of ozone layer) and consequent global warming
Eliminates thermal pollution at ground level, regenerates ozone layer and regulates planet temperature
Causes disease infection
Promotes healthy atmosphere
Causes global water contamination
Achieves global water purification
Creates anaerobic conditions which cause oxygen depletion in water and proliferates harmful anaerobic microbial activity
Creates aerobic conditions that oxygenate water and induces aerobic microbial activity
Provides habitat for vermin, snakes, rats and mosquitoes
Eliminates habitat for vermin, snakes and mosquitoes
Creates conditions for human accident and loss of life, particularly of street urchins / children
No possibility of children falling into strong water currents flowing through drains
Tempts urban slum households to dump garbage and even sewage waste
Creates proper civic sense

 The above is an attempt to list out the pros and cons of open drains versus point of source infiltration being presently debated throughout Bangalore after the tragic death of two young children in the last few months.
 
Regards,
Chari

Comments

psaram42's picture

Excellent comparison of pros and cons

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  The points compared are very simple and important yet so difficult for the general public to understand. Many in powers to be refuse to see the obvious as the practice of open drains is there for such a long time almost 2500 years since the Roman Empire times. It is high time that our city of Bangalore takes a lead in abandoning this practice of open drains for the better.

 One point to add perhaps:-

  Point source infiltration widens the existing roads too as the present open drains area can be utilized as nice foot paths!

n's picture

Some disadvantages too

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On the infiltration side:

- Higher maintenance cost (though required on a much rarer basis), skilled labour required.

- Higher initial cost. Long-term costs are far more economical (cost to human lives, cleaner etc.)

- Greater learning curve for authorities, requires change in the age-old mindset. This is the most difficult step. Public couldn't care less what happens outside their house. They will welcome it once it becomes apparent that the annual flooding is reduced to a great extent (some flooding will still occur with wastewater drains overflowing with rainwater runoff esp. due to encroachments downstream).

- The screening process needs to be proven and robust (it is).

The above shortcomings are weak and can be easily overcome. There needs to exist strong support for the more modern infiltration system irrespective of who happens to promote it. Very good tabular comparison - all that is needed is graphical/dramatic photos and/or computer-generated graphics to sway the non-technical people as also the decision-makers.


thampan's picture

 RKchari Sir,  request you to

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 RKchari Sir, 

request you to kindly clarify a quick doubt 

what is the rate at which the infiltration will take place ? ( how many cubic centi meters of water per second in one infiltrator, dimensions of the infiltrator)

Wanted to calculate the time it would take to clear off a storm burst in bangalore by infiltration.

RKCHARI's picture

Responding to Comments

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Dear Psa, n & Thampan garus,

I would like to respond point-wise if I may:

1. Higher maintenance cost - not correct as it requires absolutely no maintenance. It is literally fit it and forget it kind of technology!

2. Higher initial cost - again not true as retention tanks are made of recycled, virgin polypropylene resins which costs much less than concrete or rough granite slabs being presently used in lining three sides of the open drain.

3. Annual flooding will be completely eliminated - not just reduced to a great extent. This technology has been tried and tested in 30 countries worldwide and has been proven for the last 40 years!

4. Unable to fathom what the "screening process" implies. Kindly clarify.

5. I have plenty of dramatic power point presentations and videos that I would love to publicise as much as possible. BBMP and BWSSB authorities have all been more or less shown / covered by us. We need an upsurge of public support in the wake of the authorities not being able to handle tragedies like Abhishek & Vijay.

6. Rate of infiltration - we design the retention tank and what covers it to suit the rainfall - quantity and velocity of actual rainfall basis. So infiltration from road surface to retention tank is alomost instant. Infiltration from retention tanks to ground water table can take as long as it likes since capacity to "hold" water temporarily is made to suit quantum of rainfall arrived at after studying (normally) 100 year's rainfall pattern. We install our infiltration systems absolutely in consonnance with scientific data and it is not a hit and miss system.

7. PSA garu, point about extended road width is definitely additional benefit. We have a matching flo-grid cover which is designed to be pevious and yet strong enough to withstand wear and tear for 50 year! So water gets infiltrated from the sidwalks as well as from road ends and in thhe case of a double road having a median, throughh the median area also.

I hope these clarifications help.

Regards,

Chari

RKC

tsubba's picture

chari sir

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i have been reading some of the materials you sent. two questions i had (both related):

#1. can you comment on the scalability of the solution?

#2. can you describe instances of city-wide or layout-wide implementions. how much volume, for how long, what are running costs(sustainability). say something happens and need to fix it. can it done locally - skills materials etc.

i am sorry if these have been answered already. kindly point me to that source.

 

RKCHARI's picture

Answering Mr. T. S. Bhatta

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Hi,

1. No issues on scalability. We have the capacity and required expertise to solve any and all water related problems irrespective of the magnitude. Presently Atlantis is installing a similar infiltration / drainage system for Australian Railways from Sydney to Perth across the Australian continent!

2. Not really clear what you mean by city-wide or layout-wide implementation. What we offer is to capture 100% of rain that falls on any catchment area, with 0% run-offs and 100% re-use. Similarly we ensure 0% runoff in instances where we install our SW drains with 100% infiltration to recharge ground water table.

Capacity-wise, our retention tanks are literally unlimited - being only limited by the total catchment area within which it has to be installed. We can install anywhere - under car parks, pathways and literally any place - horizontally or vertically going up to maximum depth of 2.74 metres.

The only difference between a retention tank for rainwater harvesting and an infiltration tank for storm water infiltration is in the fact that the RWH retention tanks are covered with impermeable liner while the Infiltration tanks are wrapped with geo-textile material only..

3. Once installed there is NO Running / Maintenance cost whatsoever (except use of minimal electricity when pumping water from RWH retention tanks to taps within the house).

4. We guarantee both RWH and SW Infiltration tanks to run without any hassel for 50 years. So we believe there really is no need for anything to be "fixed" in case of malfunction. If however outside agencies like BESCOM / Cable or Pipe laying bodies wantonly break or destroy any of our installation, we would have no problem in fixing it as everything we supply is in modular form - literally like a Lego set which can be clipped on and off as easily as the child's game. No skilled labour is required to install it - merely ITI graduates with basic mechanical skills that an average plumber has. It is truly a screw-driver technology which can be installed by any man with even average IQ.

I hope that answers your queries / doubts. Please feel free to ask me in case any more clarifications are required.

Regards,

Chari 

 

RKC

n's picture

More on responses

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At RKCHARI:

1) Maintenance from the complete system point of view. For example, soil on sides or base of the infiltration unit subsides - more work than at open drain to observe, access and repair. Did mention it is rare - no system can physically be zero maintainence (individual components can be longer lasting but they don't work in isolation)

2) Similar to above.

3) Wastewater drains are still open and can overflow (refer earlier comment in parenthesis)

4) Screening for debris, contaminants etc. Again, maintainence required to clear natural or man-dumped debris at inlets.

Not trying to pick but just trying to get a more technical view than typical sales brochure stuff; the previous post bottom line does show support for the system. Reiterate that the best people are probably decision-makers (read ministers). Cheers.


thampan's picture

infiltration

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 RK chari sir,

could you give numbers please ?

In bangalore, due to the slopes, there is  a lot of flow water also.  So it is not just the rain water in that area but the surface flow from other nearby areas which needs to be collected. 

Even with a flowing drain ( which is clogged and has a capacity problem), if there is a 3 cm rain fall, the bilekahalli junction on bannerghata road turns into a 3 feet deep lake with the full width of the road.

I just want to understand,

1) what the typical capacity of a settlement tank will be.

2) How many of such would be required for say bilekahalli on bannerghata road 

so that there is no flooding on the road.

RKCHARI's picture

Reiterating what we claim!

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Hello n,

We maintain there really is NO maintenance required once infiltration system is in place. The matrix tanks are fully wrapped in geo-textile, covered with eco-soil and river sand followed by drainagee cells or flo-grids. Once all this is installed properly, there would be no question of soil subsiding. The entire system is made to function at 100% efficiency throughout its life. There is no moving parts and no opportunity for people to interfere unless they do so wantonly.

If you mean capacity-wise our retention / infiltration tanks cannot be unlimited, I am afraid that again is incorrect. We design the underground infiltration system using proprietary software which ensures capacity to temporarily retain water is more than sufficiently calculated on the basis of 100 year's rainfll pattern.

Why are wastewater drains still open? If you mean sewage waste, it is most unfortunate and I would even go to th extent of saying it is a criminal offence on citizens being perpetrated by the municipal authorities. Every civilised society takes it sewage waste - both liquid and solid through underground concrete pipes all the way to municipal treatment plants. It hasnothing to do with storm water drains. One of th bane of our problem in Bangalore is that municipal engineers connect sewage outlets from any layout / home directly to open drains without any quams. That is why storm water becomes toxic and even poisonous.

Why would one require to "screen for debri and contaminants" when the whole system is installed underground? Once installed the top layer will be on level of present concrete shoulders / pavements / footpaths. There will be no openings except for concealed inspection ports and hence no opportunity for anyone to throw garbage or contaminate the storm water in any way.

Cheers,

Chari

RKC

RKCHARI's picture

Answering Mr. Thampan

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Hi Mr. Thampan,

By oversight, I missed your last comment above. My reply is as follows:

1. I do not understand what you mean by "could you give numbers please?" Kindly clarify and oblige.

2. Our SW infiltration units on either side of any and all roads are meant to take care of ALL water that flows in any catchment area, whether it relates to rainfall on that particular road or other neighbouring buildings / layouts etc. It is to avoid flooding of roads as described by you that closed underground SW infiltration systems are being suggested. Once SW drains cease to be open, there would be no flooding whatsoever! Have you ever seen road flooding anywhere abroad (except in case of flash floods, tsunami like situations?). So it is not a pipe dream. It is possible to have water free streets even after heavy rains.

3. Our single module tank has a capacity to hold 120 litres. However since they are modular they can be extended vertically upto five layers and horizontally from one end of any road to the other end (irrespective of length of road). We determine whether we require to install a single layer, double, triple, quadruple or penta layers based on pattern of rainfall and after studying entire topography and soil conditions.

4. Difficult to say exact number required from bilekhalli to bannerghata off hand. We would need much more inputs as mentioned above.

Regards,

Chari

 

RKC

thampan's picture

1) Numbers         a) Rate at

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1) Numbers 
       a) Rate at which the water infiltrates into the infiltration unit per unit surface area
       b) Surface area of a typical unit
 
2) The rains in bangalore are very different from those in australia or usa, in the intensity of rains and pattern of rain fall. Hence the request for numbers.
 
taking a look at the current water logging on bannerghata road.
 
  1. Assume road width = 60 feet
  2. water depth = 2 feet
  3. length of flood area = 400 feet
  4. total cubic foot of water = 48000 = 1359209 liters
  5. Number of units required to hold this water = 11326

Please note that the flow of water through the open drain is not considered in this calculation.

 

tsubba's picture

same qs

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same qs as t.

one of the systems i saw was a filter that would take out coarse particles from stream. very ingenious idea. basically an inlet, a tub and an outlet. heavy particles should in principle just settle in the tub and water flow out. but the question is how often do you have to clean the tub? i guess this is inescapble in any system, but we must think aboutcapacity and easy of emptying. who ever designed it chari sir, if you have access to him/her please congratulate.

from a city or layout perspective, what type of volumes are we talking about. in nmbers please. i will try to look up discharge rates into bellandur and hebbal for example. vrushabhavati is highly distributed so might skew estimates.

 

RKCHARI's picture

I know it wont be a satisfactory response... but

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Hi Mr. Thampan & Mr. Bhatta,

Atlantis promotes itself as a solution provider, not a seller of some plastic containers. They do not believe in a "one size fits all" concept.

Typically, their intellectual property rights lie in the tailor-made solution they are able to provide. Even I am not privy to the "tricks of the trade" in arriving at optimal numbers for any given situation.

It is therefore very difficult to give answers to your queries in terms of numbers. What Atlantis requires is a whole lot of actual data before they are able to provide realistic quotes with the ultimate aim of solving the problem.

I hope you will not consider this response as being 'upetish' ! I will nevertheless try and get some feedback based on your assumptions as a test case basis from the horses mouth. Kindly bear with me till then.

Regards,

Chari

RKC

tsubba's picture

PDGO

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please dont get offended tappu tiLi beDi, i  just mentioned  somethng that caught my eye.

i will mostly lurk on this thread.

 

thanks.

psaram42's picture

Understanding the concept is important

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 I can understand the feelings of Mr. Chari. By the way he does not have knowledge of Kannada. He badly needs a teacher to learn talking in Kannada. Hope he gets a tutor soon.

@ Thampan 

  1. The Bellandur Lake is 300 + acres and still is not sufficient to hold the rain water of even a part of the Bangalore city.
  2. The Australian idea is to facilitate infiltration locally of whatever the local rain fall is in situ.
  3. Obviously if the maximum rain fall in a day could be only 1 to 2 inches the tank height required would only be 2 inches.
  4. The company has beautiful solutions for transporting the water too in closed ducts.
  5. One needs to study the enormous material nicely presented at Atlantis official web site.
  6. Bangalore may be different from those cities in Australia.
  7. You need to look at the locations throughout the world where the Atlantis RWH systems are in place. There are locations at equator region too looks like if I am correct.
  8. Let us get expert views from IISc on the merits and de merits of the Atlantis system
  9. The Atlantis system has a world wide patent.

 

thampan's picture

Atlantis

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Chari Sir,

Agree that Atlantis may have a solution for bangalore's water logging issues. And it may perhaps be quite different from/similar to what they have done else where. 

The first questions that will appear in the minds  are what is the capacity of the proposed system ? Can it sustain the storms in bangalore ? how long will this work , given the the environment in bangalore ( including mud flow, waste flow, plastic flow etc) ?

 

I checked the atlantis website ( http://www.atlantis-america.com/ )but felt that the site did not have enough data/evidence to prove the efficacy of the system for bangalore.

 

 

 

tsubba's picture

drains

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Sir,

I am only trying to understand. Frankly the leading post is not an analysis of the pros and cons of the various options available to us, but merely a list of pros of one against the cons of the other. and the example chosen to con against is a very low hurdle. we all know existing system is insufficient. in anycase, as long as it starts a discussion that is ok. i have no problems.

but in order to understand this, we also need to knowthe capacity and limitations of the proposed solution. i can understand that chari sir might not be able to asses the limitations of his proposed solution. but atleast he should be able to inform us about its capacity? i think am not asking any unreasonable/uncomfortable questions. if in your opinion i am, please let me know, and i will moderate myself.

thanks.

ps: where did kannada come into play here?

RKCHARI's picture

What's Different?

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Dear Thampan Garu,

What is so different about rainfall and storm water management in Bangalore that it has to be proven on the ground here?

In any case I have already offered to install our units on a BOOT basis to the CM - which means there is no monetary risk / up front payment etc. Pay us only if it is proved to be successful on the ground here in Bangalore! How much more should we bend backwards to satisfy doubting Thomases?

Yes the Atlantis web site is limited in its efforts to promote their systems. Atlantis is owned by people who are of Chilean origin. Even after 40 years in Australia and becoming Australian nationals, they still think in Spanish. So their communication efforts in English is far from following the Queen's English. That may be one reason for ineffective web site development.

Cheers,

Chari

 

RKC

tsubba's picture

chari gaaru

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chari gaaru,

deenTlo doubting thomas issue ledu sir. vishyam teluskoDam maaku mukhyam.

Sir, BOOT is an issue that is relevant to the executive. We are just citizens, we are primarily interested in the properties of the solution, not the financial transaction. Our problem is we dont trust the executive to correctly assess our needs and evaluate solutions. if you see a good majority of our discussions are about whether the powers that be truely understand our needs. the other half is are they following it up on it correctly.

ordinary tarring of roads we did not have reasonable evaluations till recently, when high court came down on the corporation heavily. is it fair for you to  blame us for coming across as doubting thomases?

even if we do no apologies, that is the dharma of a citizen. to doubt.

RKCHARI's picture

Capacity of SW Infiltration system

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Dear Mr. Subbabhatta,

It is not so much my inability to mention capacity of infiltration as the fact that I have already mentioned several times that SW Infiltration systems promoted by Atlantis actually has unlimited capacity.

As explained elsewhere, the retention tanks are modular and like Lego sets, can be easily clipped on to form as long a horizontal holding tank / space as one wants and as deep as one wants (maximum recommended depth being not more than 5 layers totalling to 2.74 metres).

So how to specify any fixed capacity? We install units to cater to quantum of rainfall, its velocity and taking into consideration soil conditions. What more can one explain by way of capacity?

Ideally I would like to give a formal presentation-cum-demonstration to all interested Prajagalus. Shall fix a programme after Dussehara holidaysand let you all know.  Am also planning to invite the Technical Director of Atlantis sometime in October when I can hold a seminar-cum-presentation session for everyone.

BTW, PSA's reference to my lack of Kannidiga Language knowledge is I think in response to your earlier mention of "Tappu tiLe biDi"!!

Regards,

Chari

RKC

thampan's picture

@psaram sir & Chari sir

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@Psaram Sir

1. agree

3. It is not the water falling on the roads alone that needs to be stored. It is the water flowing from nearby areas (concrete roof tops for example) also. Hence I doubt it when you say, only 1-2 inches of storage space is required. 

7. Is there an installation by atlantis for any city in the world for entire storm water management ?

9. No one is questioning Atlantis's patents.

What i was trying to understand is this.

  1. It will take some time before the rain water gets infiltrated into the soil.
  2. The water has to be held in some storage tank for this to happen.
  3. Excess water from this tank has to be led away
  4. This will have a capacity constraint
  5. Based on observed rainfall patterns and water logging on the roads, the excess flow is expected to be very high
  6. If the flow capacity in the new proposed system is not adequate, there will still be water logging on the surface.

@Chari Sir,

Monetary payment is not the only factor to be considered in any public project.

  1. You propose to install the system on BOOT model.
  2. Assume that the CM gives you permission to install it on say bannerghata road
  3. After you have done your work, if there is still flooding it will be a loss for you, for the CM & people of bangalore

Please do not be offended by the questions. I am sure that you will face much more of these when you proceed in the discussions with authorities. 

The cost of the installation will have to be borne by the people in some way or the other ( even if it is a BOOT). Hence the questions from my side as a Praja.

On another note, it is high time that bangalore made rain water harvesting mandatory for all buildings and covered spaces. If the city moves towards rain water harvesting ( using Atlantis solution or any other), the problem of storm water will reduce to a great extent.

 

psaram42's picture

Elaboration of the Atlantis RWH concept as understood by me

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Thampan Sir,

Let me try to explain further to your comment above. First let us go to the basic concept of RWH (Infiltration to ground water). 

  1. Imagine that it is raining on a foot ball field lined up with impervious concrete wall all along the edge, so that water is contained on the field it self.
  2. If the rain is x inches in a day the water in the tank will be only x inches high. It cannot exceed this value.
  3. This water will eventually dry up in y number of days as the water is allowed to infiltrate, unless the field is on solid rock.
  4. If all the rain due in the most rainy year in Bangalore some how happens in a day, the maximum height will be xhigh inches.
  5. It will eventually infiltrate hopefully in to the field in a years time
  6. If not that much extra water can be allowed to run off, by limiting the tank height to xhigh-xr inches where xr is the shortfall. 

This is the basic concept of RWH (Point or in situ Infiltration to ground water). 

Now let us come to the Atlantis patent. The tank size has to be xhigh for each square foot covering the whole Foot Ball Field. The bottom of each box is left open for infiltration. Of course this will involve digging the whole foot Ball field, at an extra cost. The field is dug up, the modular boxes arranged properly and the foot ball field brought back to original by filling up the mud on top of the stacked boxes. 

Next let us come to the valid objection no 2. Viz what happens if there is concrete sitting area for the spectators of some z sq ft. The Atlantis Company will now design the RWH tank below the foot ball field to allow for the known volume of extra water when it rains xhigh inches. Of course this extra water need not be infiltrated as a slow process but directly discharged in to the underground plastic tanks directly through plastic pipes as usual. 

I hope the concept for entire Bangalore can now be worked out. You need not worry any way as Atlantis engineers are responsible for design as well as execution as a turn key project.

Kindly see the minutes of the meeting held on at my place. I wish more Praja had attended, than only 3 of us. 

If GW Infiltration is not required you need not allow the infiltration by covering the bottom by an impervious patented Atlantis Plastic sheet. This gives you 99.** % pure drinking water absolutely free!

The excess run off in the earlier example also is pure drinking water absolutely free.

Thanks.

RKCHARI's picture

Responding to Mr. Thampan

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Thanpan Sir,

Let me respond point-wise in reply to your comment addressed to PSA Garu & self:

Point 3: The SW Infiltration system does take into account ALL rain that falls inside any catchment area. Which means it takes care of rainfall from buildings on either side of the road and the road surface itself.

Point 7: Yes several cities including several in Australia, America, Spain, Chile, Equador, China, Japan etc. Total estimated Kilometres of SW infiltration system is around 200,000 Kms worldwide.

Point 9: PSA's remark is I think meant to be a confirmation of the fact that the Atlantis system, by getting worldwide patent coverage has been accepted as a valid technology.

Sub Point 1: Correct

Sub Point 2: Correct again

Sub Point 3: Firstly, tank capacity is very precisely calculated. Even so, if there is an over flow (excess water) why does it have to be led away? The idea of the infiltration tank is in a way a system to ensure gradual 'leakage' of water that is temporarily stored, to make ground soil absorb rainwater.

So if some excess water directly gets absorbed by-passing the temporary retention tank, what is the problem? In any case the natural package consistng of eco-soil and sand all around the tank including just below the pervious concrete or bitumen, is meant to absorb water and it will ensure nothing remains on top of the road.

Sub Point 4: Therefore, as mentioned in sub point 3 above, there is no capacity constraint.

Sub Point 5: Not true as the infiltration is amazingly fast. We take the velocity of rainfall into account while designing the system.

Sub Point 6: Question does not arise. Flow capacity will never be inadequate. It also comes from sheer experience from installing such units for 40 long years!

Sub Point 3 of Comment to me: Our level of confidence in our system allows us to take this monetary risk. We are 200% convinced the system promoted by us will not fail. It will be foolproof and citizens of Bangalore will never regret it. Might sound as if we are bragging, but believe me Sir, we are promoting what we consider to be truly pathbreaking technology as far as India is concerned.

No, there is no question of my taking offence at your efforts to seek clarification. More than anything else, as a fellow citizen of Bangalore it is my bounden duty to ensure I am not promoting any dud stuff to earn quick money and disappear! To do things in such a way that it would truly satisfy everyone is our Company's vision and mission and as a senior citizen, I do not propose to "kick the bucket" having hood-winked everyone!!

Warm regards,

Chari

RKC

RKCHARI's picture

Responding to PSA Saar's analysis of Atlantis Technology

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PSA Saar,

It looks as if you have understood Atlantis technology so perfectly that you will probably do a better job explaining it to BBMP authorities than the Atlantis guys themselves!!

Hurray for the first true convert to this technology!

Regards,

Chari

RKC

thampan's picture

name of one city

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RKC Sir, 

1) Name of one city with entire storm water management covered by Atlantis ? 

 

Psaram sir,

I have understood the concept. The doubts raised are not about the absolute technical feasibility about the solution for say a football ground but about the scale required for bangalore and matching up with the ground realities ( when 95% of the land is impervious)

On bannerghata road, today , there is 2 feet of flooding with half an hour of intense rains which takes an additional 2 hours to clear. 

what is the maximum infiltration rate of the system that this entire water is going into the tanks below and then to the subsoil within minutes of rainfall.?

I have not got a number as answer to this question except that it is all taken care of. if it is taken care of, there should be a number available some where. Please provide this number.

From the Atlantis website ( not exact words)

1) Water flowing into the subterrenian tanks should be filtered using atlantis filtration system.

2) excess water is led away.

So it is atlantis who say that excess water has to be led away and not me.

I guess i have repeated the question several times. Will wait for numbers now.

tsubba's picture

distributed vs centralized

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the way i think about it, all earth is basically a storm water management system. some of it is drains and some sinks.

bellandur is a natural sink for drains around it. but since belandur could not handle all the water it would receive, some of it would drain into varthur, and since varthur could not take in all it would empty into lakes further down stream and so on until water reached important rivers. ofcourse a good chunk of it went to refurbish the water table.

so what is point here? point here is that even a huge natural lake (which could resize itself freely) like belandur was not sufficient to disperse the water it collected, through either: 1) infiltration or 2) evaporation. eventually some of it actually had to actually overflow.

so atleast to me it does not appear that it is as trivial as: x amount will infiltrate in y days,  i can understand that one could perhaps through careful engineering divert some fraction of this, but i would imagine that, that engineering would be against desired holding capacity, or available area or something like that. When I read traditional references on RWH (including Zenrainman's work), that is how it appears to me. No system claims 100% absorbption or efficiency or infinite capacity.

a good chunk of water will still have to flow into belandur. and the real question is how much of it can infiltration system(tm) force in to the water table using: (1) storage and (2) materials. the rest will have to flow through channels in to the lake. and the question for us then is, whatever is overflowing into the streets, what percentage of it can infiltration system divert underground.

that is, the reason to implement infiltration system(tm) is to augment the water table of blr(which is very much desirable). but by itself it cannot guarantee anything about flooding of our streets. for that we still need to work on improving the efficieny of our drain systems.

am i right?

 

 

tsubba's picture

BIAAPA

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chari gaaru.

unsolicited reco.

have you contacted BIAL? that is an important area. as you might know, there is a serious shortfall water table in the area and they have banned drilling there. there is a lake too just behind bial.

also namma metro could perhaps be interested. bmtc ttmcs etc...

n's picture

Infilteration for heavy rainfall

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If I understand the contention between the "skeptics" and the "promoters" it is this - skeptics want to know how the infiltration can occur fast enough for a heavy downpour (like the one in Mumbai a few years ago when they had 900+ mm of rain in a few hours). "Supporters" are saying that infiltration tanks are built with extra capacity. Infiltration systems are designed for various rainfall patterns (10-year, 50-year, 100-year and so on). What if there is a 1000-year rainfall? The right question probably is this - what is the alternate in case the infiltration doesn't happen as fast or faster than the inflow? Is there an exfiltration to let the excess water flow to a detention "lake"? Have there been rare cases (especially in the experience of the company) where the designed infiltration units have not been adequate? What has been the consequence? Worse than the flooding that occurs now with overflowing open drains? Most probably not. In my opinion, the concept of infiltration systems (constructed by any company or by govt. pwd) is by far much better and widely followed in developed countries than runoff system.

BTW, astounded that BOOT on a pilot basis has not been accepted. The system can be deconstructed if it doesn't work on a test area. What else do they need? 


RKCHARI's picture

Skeptic Vs Promoters

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To answer your question about Atlantis' experience of their infiltration system having failed anywhere, you will be glad to know that even when New Orleans / South Carolina in the U.S. was hit by Katrina typhoon, our infiltration system managed to take care of the bulk of the residual water on roads literally overnight. Sure there was major flooding when the typhoon did hit the city, but tsunami & typhoon-like situations apart, the important thing to realise is that roads were not damaged and bulk of residual water on roads were infiltrated the next day.

As you rightly pointed out, SW infiltration in any case is a saner option to opt for than open drains.

Regarding TSB's comment of Atlantis itself saying "excess water is led away", I believe they are referring to some instances where Raj Kalve like open Nallahs are existing for 100s of years and the local Municipal authorities do not want to close them for whatever reason they deem necessary. In such cases, treated SW is 'led away'. Atlantis have experience of such installations in Malaysia.

Also it refers to the rare cases when rainfall happens to be in excess of the designed infiltration tank capacity. In such cases the spill over (which in any case happens underground) is automatically led away to other underground areas where they get absorbed.

No I have not approached BIAL although we are actively involved with a Private township development project around the BIAL area.

Re BOOT project, the proposal was made only last week and I believe is being sympathetically considered. The Dussehara holidays have delayed a formal response from the authorities.

 

RKC

tsubba's picture

geometry

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n & rkc saars.

there are multile reasons why blr floods. #1. blocking of inlets to lakes, #2. blocking of outlets of lakes, #3. blocking of drains and finallly, and by any means in no small measure due to geometry(both horizontal and vertical) of roads. in order to really adress the issue of flooding all these must be addressed. it would be unfair to expect IS(tm) to surrogate the fundamental problems we have. It can help, but cannot solve the issues we have. i am not talking about extreme situations.

n saar. existing systems are very low hurdle. not a good measure. also, it is very important to retain our natural lake systems in a healthy condition.

n's picture

Infiltration vs lakes

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At t.subbabhatta - inlets, outlets and drains to lakes are eliminated in an infiltration system. Similarly, geometry is irrelevant to a large extent. Here is a source of explanation (though not very good or comprehensive). Again, the infilration occurs from all surfaces (limited only by how much investment is done to build the system under roads, near homes, road sides, parking lots and so on). The company's website has some good information on various systems including photos and videos. Good source of knowledge if you have the time to look and digest. Lakes won't dry up - all they will get is rainfall directly (good and pure) and maybe from the surrounding catctment area. Better than getting runoff water with the pollutants, debris etc. or not getting it (like now) with encroachments. In fact, in some developed countries it is mandated that area around wetlands be lined with geotextiles to prevent "run-in".

Bottomline? Properly designed infiltration systems are the best bet as of today. Have exhausted my quota of words. Phew :-)


tsubba's picture

lakes

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hmm...

that is not my understanding. lakes dont work that way. but i will get back later in detail.

again, i am not doubting the technology. i am only trying to understand its viability at the scale that it is required here and given our problems. 

saying BOOT doesnot satisfy me. thampan's question still remains.

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