In a significant move to combat the recurring problem of urban flooding and enhance groundwater levels, the Greater Chennai Corporation (GCC) has embarked on an innovative project. The civic body is installing large underground stormwater retention and infiltration tanks beneath the playgrounds of several city schools.
The 'Sponge City' Strategy for Chennai
This initiative is based on the 'sponge city' concept, a sustainable approach where rainwater is captured and absorbed locally rather than being rapidly drained away. The project utilizes German EcoBloc technology to create a decentralized network of underground water buffers in areas of the city that are particularly prone to flooding.
"We do not want to put more concrete in the grounds," explained V Sivakrishnamurthy, Deputy Commissioner (Works) for GCC. "The tanks are installed beneath playgrounds, walkways, and open spaces, ensuring that no usable land is lost once construction is completed. It is a flexible technology that does not disturb underground infrastructure. It helps with groundwater recharge in the school and the locality."
Project Locations and Current Status
The installations are targeted at nine GCC school playgrounds located in Zones 8, 9, and 10 of the city. The specific locations include:
- Palavayal Market Street
- Pulla Avenue, Shenoy Nagar
- Aminjikarai
- Royapettah Begum Street
- Nungambakkam
- MGR Nagar
- CIT Nagar
- Puliyur
- Nesapakkam
A GCC official provided an update on the progress: "Nearly 90% of the work was completed at Corporation Middle School, Aminjikarai, and CGHSS, Pulla Avenue, in Shenoy Nagar. Work is yet to start in MGR Nagar, CIT Nagar, and Nesapakkam. Work is underway at the other schools."
How the EcoBloc Technology Works
Each site will house an underground detention tank with a substantial storage capacity of 250 cubic metres, equivalent to 2.5 lakh litres of water. The system is engineered to capture rainwater during heavy downpours, store it temporarily, and then allow it to percolate slowly into the soil.
R R Sivaraam from Stone Hands Project and Consultancy Private Limited detailed the technology: "The EcoBloc system uses recycled polypropylene modules wrapped in geo-textile filters and supported by geogrids and aggregates. Four deep infiltration bores at each site aid faster percolation."
The design offers multiple benefits. The modular structure is robust enough to withstand loads of up to 60 tonnes, allowing playgrounds to function normally above it. Remarkably, the system can infiltrate nearly 75% of the captured rainwater at the same location, promising a significant improvement in local groundwater levels over time. Furthermore, as the tanks operate entirely by gravity, they require no electricity and minimal maintenance.
By reducing surface run-off and temporary inundation in surrounding neighbourhoods, this project represents a critical step towards building a more resilient Chennai. It tackles the dual challenge of urban flooding and water scarcity through a single, smart infrastructure solution.
