Open Drains Versus Point of Source Infiltration

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.

 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.

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.

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

i will mostly lurk on this thread.

thanks.

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.

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.

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?

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? 

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.

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.