Location: Mumbai Public School, Chembur, Mumbai
Duration: June 2021 – Ongoing
Typology of the solution: Blue-Grey Hybrid Groundwater recharge
Scale of the project : Neighborhood
About the project:
The siphonic surface drainage system (SSD) was implemented by Drainstar India as part of the TheCityFix Labs Nature-based Solutions (NbS) anchored by WRI India, at a municipal school in Mumbai. The school experienced waterlogging in the approach road of the school during the monsoons making it difficult for students and teachers to access the building. Hence, the main idea of the pilot project was a drainage solution that would reduce the waterlogging simultaneously recharge the groundwater/aquifer with the collected rainwater. The SSD comprises of a series of at-surface chambers that collect and filter rainwater. These are then channeled through small diameter pipes
designed and aligned to provide quick suction of water that falls in the target surface catchment area. The filtered rainwater is channeled through these pipes to an injection well deep into the ground to recharge the aquifer.The solution is undergoing monitoring through the monsoon period of 2023 (June-Sept’2023) in Mumbai to observe the reduction in waterlogging at site and the net potential recharge of aquifer. Awareness-building sessions were also conducted for students and teachers about the solution and the significance behind it. The security guard at the school campus was also trained to maintain the filter chambers.
The main objective of the project was to reduce waterlogging taking place in the approach road to the school during monsoon and use the rainwater to recharge the aquifer after thorough filtration.
Project Implementation and activities:
- The waterlogging area was identified within the school, and the cause for the waterlogging was also identified.
- The rainfall surface run-off volume was calculated based on the ground surface material (in this case concrete).
- Based on the volume, the planning and designing of the filter chambers and number and dia of the pipes was computed using a specialised software.
- Parallelly, a hydrogeological test was conducted at the site to ascertain the soil profile and the aquifer level. Accordingly, the spot for boring an injection well was identified and the depth of the drilling required was also identified. The required length of the siphonic pipes also became clear at this stage.
- Once the injection well was drilled, procurement, excavation, placing and alignment of the filter chambers, filter bags, pipes, overflow systems were executed at the site.
- Post implementation, an awareness session was conducted for students and teachers about the need for conserving rainwater and putting it to sustainable use. The concept of rainwater harvesting and groundwater recharge in the context of climate change was also covered in the session.
- The security personnel were trained regarding the maintenance of the filter chamber to ensure there is no debris or clogging of the chambers which may prevent the filtration of rainwater and entry into the pipe system.
- Drainstar India – Provided the technology and design and implemented the project
- Brihanmumbai Municipal Corporation – Provided the land parcel and necessary permissions to execute the pilot project
- Municipal School Security Staff – Responsible for the maintenance of the solution
- WRI India – Facilitated the project through the TheCityFix Labs NbS Accelerator
Source of Finance:
Drainstar India was allocated a service contract through the TheCityFix Labs Nature-based Solutions Accelerator, anchored by WRI India. The accelerator is funded by Caterpillar Foundation, Department of Environment, Food & Rural Affairs (DEFRA), Norway’s International Climate and Forest Initiative.
Capex: INR 7,63,402 (includes design, hydrogeological survey, 3 filter chambers, pipework, injection well, training of stakeholders and monitoring & evaluation)
Opex: INR 10,000 (annual – includes filter bag changes and regular thorough cleaning of filter)
Since the project was being implemented in a school site, safety precautions needed to be ensured throughout the design and implementation. The type of filter screens, the spacing between the screens, the placement of the filter chambers had to be thought through accordingly, and the implementation had to be carried within the small window of festival holidays that came in between.
The other challenge that was faced is the clogging of these filter chambers because students were throwing solid wastes into these chambers, hence, the students were made aware during the awareness sessions about avoiding throwing of any waste within the chamber. The security was also trained to clean the filter chamber at a regular interval.
- Tracking of waterlogging/flood level during monsoons in the approach road to the school.
- Estimated amount of groundwater recharge
- Students/teachers/others made aware of harvesting rainwater, mitigating floods and groundwater recharge in the context of climate change.
- Design and planning of the solution is very important, and this has to be done with the involvement of relevant stakeholders. Example – Identification of the target catchment area/waterlogging hotspot, placement and typology of filter chambers, need for rainwater harvesting or an injection well system amongst others.
- Showcasing the solution visually through animation or an infograph helps the stakeholders on site easily envision the solution and understand how the system functions.
Scalability and replicability potential and conditions for success:
The SSD can be used in waterlogging/flood hotspots in the city to channel the rainwater in these low-lying areas to a rainwater harvesting tank to reuse the water for landscaping/other domestic purposes or an injection well for groundwater recharge.
Aishwarya Raman, Sole Proprietor, Drainstar India