Author: Nagesh Battula

For us at Organo eco-habitats, our projects have been our biggest teachers from the beginning of our journey. The lessons we learnt at Organo Naandi were applied to Organo Antharam. And what we learnt from Antharam will help us in our other projects. 

The recent flooding during heavy rains taught us a valuable lesson. The relentless rains over the last couple of months resulted in a lot of upstream water coming into the site. 

Eco-STP at Antharam:

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As shown in the scale model above, the eco-stp consists of three stages of purification after which the water is treated and can be reused. For more information on how the STP functions, please see this Eco-STP white paper: https://tinyurl.com/mrhwascz‍

The entire STP, which is a concrete structure is below the ground and is covered with parking above. 

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Due to incessant rains and flooding during this year’s rainy season, there was a lot of water run-off from the dug well and other areas towards the low-lying area where the STP is situated. 

Since the water management strategy is not in place completely around the farm areas and clusters, there was flooding and the water flowed towards the STP from the Nala and the dug well.

As the STP was also under construction and backfilling has not been done, water seeped around and underneath the STP. The structure acted like a boat and due to lot of volume and less surface area, the buoyant force lifted the STP up from underneath. If all the columns and parking slabs had been in place on the top, this would not have been an issue. With no counter-weight equalizing the pressure from the top, around 800 tons of steel and concrete was lifted up due to the water pressure.

Our Studio went back to the drawing table and, after multiple discussions with structural engineers and water management experts, has come up with a design and working methodology to ensure this doesn’t happen again.

Weep holes as shown in the diagram above, are created at the center and all around to ensure water seeps in and the pressure equalized inside and outside the structure. Such holes are placed even around the walls of the STP as well.

A methodology to ensure the holes are packed has also been established along with when the backfilling has to be done. 

METHODOLOGY

1. Concrete shall be mixed with integrated water proofing compound of FOSROC make as per manufacturer's specifications
2. Lay the PCC with holes as shown in the base slab
3. Keep the rebars of base slab as shown in the drawing
4. Concrete the base slab leaving the holes as shown in the grade slab
5. Do not back fill the soil all-round the STP
6. For construction purpose above grid 3 and from grid C to D can be backfilled
7. Complete the construction of column, roof slab and parking structure
8. Re-concrete the holes in walls and bae slab after applying Nito bond of FOSROC make.
9. Grout the periphery of all holes and make it watertight.
10. Complete the water proofing for walls inside and outside, base slab top
11. Make sure 2.0M water column is maintained in the STP all the time to avoid uplifting of it
12. Do the remaining sides backfilling of STP

Issues like this typically happen in water rich areas where the water table is high. The situation doesn’t present itself in areas with low water tables like Antharam. But on the off chance that flooding happens, we recommend that some holes be left in the raft until the complete loading of the structure is done.

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