Rainwater conservation Society

A community that is prepared for the rainy day

Jains Pebble Brook at Okkiyam Thoraipakkam on Chennai’s IT Corridor. Photo: Special Arrangement  

Names can turn out prophetic. Equally well, a name can be out of step with the bearer’s life. Jains Pebble Brook on Old Mahabalipuram Road (OMR) belongs to the former category, though the contrary held true for a long time. Onomatopoeic, the name of this 620-unit apartment complex in Okkiyam Thoraipakkam gurgles with the sound of gushing waters. It suggests water sufficiency. The odd fact is that the community was not born water-sufficient but had sufficiency thrust on it.

For years, water was its vexatious issue, sending maintenance costs through the roof. If that was any consolation, a legion of other communities on Old Mahabalipuram Road were similarly scourged. Without supply from Metrowater, many a community on the IT Corridor still depend heavily, if not entirely, on water tankers.

“On an average, we would purchase 11 tankers of water every day. With each water tanker delivering 30,000 litres, they met a daily requirement of 3.3 lakh litres,” says A Shanmugam, president, Jain’s Pebble Brook Flat Owners’ Association. “The cost per tanker being ₹3,000, the daily outlay on water alone was ₹33,000, which worked out to a whopping sum of nearly ₹10 lakh per month.”

Clearly, the community had to extricate itself from this situation. And it set about this effort by first covering the obvious ground. That meant getting the huge STP plant into overdrive and recycling the water for flushing purpose.

As with frugality in all areas, this measure yielded results. But walking the path of frugality without a broader horizon in view is like walking tortoise-like down a cul de sac. One will eventually hit the dead end — only that it would arrive slowly.

Save water, save money
  • When a gated community’s association plans a major initiative, it obviously had to ensure buy-in from residents — particularly so when the exercise entails substantial cost.
  • On how the executive committee of Jains Pebble Brook Flat Owners’ Association won residents over to its water conservation plan, Association president Shanmugam has this to say: “Initially, we told them we were planning to introduce rainwater harvesting, without explaining the nuances of what was being done. We just told them that we would need to collect ₹3,000 per flat as development expenses that would go towards creating rainwater harvesting systems, STP improvement work, pavement correction and waste management. It was a one-time collection, done around two years ago. We spent around Rs. 2,00,000 per block (altogether, four blocks) for rainwater harvesting,”
  • The Association president points out that the benefits are obvious. “Originally, each household was paying ₹800 every month as water charges per head (each member of the house) per month. If there are three persons in a household, they would have to pay ₹2,400 as monthly water charges. Now, it is down to ₹175 or ₹200 per head during the monsoon. Even during summer, they pay only ₹300 to ₹350 per head. Because the open wells are also giving us water regularly.”

The next move illustrated that recyling is more valuable when it accompanies resource generation, which in this case is water. So, around two years ago, the community chose to act on a geologist’s advice. That marked the beginning of the real turnaround.

“Around five years ago, we brought a geologist to offer us a solution. He pointed out that the soil type was clayey, and what made matters worse was that around 30 feet into the earth, there was solid rock to deal with, which automatically posed a challenge to both saving and extracting water. The geologist strongly advised against sinking borewells, and asked us to dig open wells. Remembering that consultation, we created five open wells, each around 30 feet deep,” explains Shanmugam. “As the soil was clayey, it would not retain much of the rainwater, which would run off to Okiyyam Maduvu.”

The western section of Okiyyam Maduvu, the canal linking Pallikaranai Marsh to the Buckingham Canal, snakes behind the gated community.

“The idea behind creating the five open wells is to harvest the water absorbed by the soil,” he elaborates.

With this move, the community was on the path to getting its water math right, but there was still an awful lot of ground to traipse across.

Valve and filter sumps at Jain's Pebble Brook in Okkiyam Thoraipakkam. Photo: Special Arrangement

Valve and filter sumps at Jain's Pebble Brook in Okkiyam Thoraipakkam. Photo: Special Arrangement  

“During summer, we managed to extract 2500 to 3000 litres of water every day from each well. During winter, whenever the skies were bountiful, on an average, anywhere from 10,000 to 15,000 litres of water every day from each well would be the gains.”

As is obvious, these numbers together did not add up to a solution. The next path emerged clearly. The focus had to be divided between terra firma and the terrace, with the latter receiving the lion’s share of it.

It was around the time, conversations in Federation of OMR Residents’ Associations (FOMRRA) were getting more intense and regular. Jain’s Pebble Brook was particularly inspired by how Sabari Terrace in Sholinganallur had moved from water poverty to sufficiency through its customised rainwater harvesting model.

“In the last two years, we studied various projects, one of them being Sabari Terrace’s. In its RWH system, the water from the terrace was being diverted to the sump via pipes that run beneath the top of the car parking area on stilt. Sabari Terrace being a compact community, they could manage that comfortably. Given its size, Jain’s Pebble Brook with its 13 blocks had to work out its own customised solution. Besides, we have more working space, and therefore decided to bring the pipes underground to the two sumps.”

Initially, the community wanted to test their RWH model in two blocks that boasted the biggest dimensions of terrace space.

“Initially, around one and a half years ago, two suitable blocks of the type measuring 339 feet by 53 feet (17,967 sq.ft) of terrace space were used. As we finally ended up using four blocks of same dimensions, the overall terrace area where rainwater is being harvested in this manner is 71,868 sq.ft.”

Each block in the community has around 13 to 14 rainwater outlets. In the four blocks, these outlets were all connected to the sumps via underground pipes six-inches in diameter. Before being connected to the sumps, these pipes go through a filter point marked by a traditional method of filtering.

“In the last six months, we connected two other blocks to the two sumps, which can hold up to 4.3 lakh litres of water. As we are discovering now, it takes only one hour of torrential rain to fill up both these sumps. We were therefore drawn into using two smaller sumps, originally built to collect Metrowater and obviously in disuse, to store the excess water, directed via pipes from the two main sumps. After bouts of heavy rains, we may run on filled sumps for a couple of days. The pattern would be repeated in the next cycle of rains that may happen a few days later.”

Here is the amazing bottom line that justifies the exercise.

“During the rainy season — on an average, for 10 to 15 days in a month, we depend on the rainwater that we have harvested.”

Jains Pebble Brook Flat Owners’ Association understands mind-boggling RWH numbers could be achieved if the remaining nine blocks are also brought into this system.

Shanmugam explains the Association’s position. “We are thinking about repeating the exercise for the other blocks, but what is holding us back is the prohibitive cost of constructing sumps as huge as our existing main sumps. These two sumps are really capacious, but not huge to hold all the rainwater that is being harvested during heavy rains. So, you can imagine the challenge.”

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Printable version | Sep 18, 2021 2:43:11 AM | https://www.thehindu.com/society/a-community-that-is-prepared-for-the-rainy-day/article35532117.ece

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