This document summarizes the challenges faced and lessons learned from implementing a rooftop rainwater harvesting (RWH) system at BM Cassia in Bangalore. The key challenges included lack of understanding of the RWH objective among residents and vendors, limited space for water tanks and recharge pits, and lack of rains for testing. These were addressed through community engagement, creative design solutions, and negotiating with vendors. Operational challenges like flooding during heavy rains were resolved by adding bypass valves and stormwater outlets. Regular maintenance and educating staff helped optimize the system.

1. BM Cassia RWH
Challenges & Learnings
Rajesh Agrawal
Water workshop
Organized jointly by BAF, ADDA, Citizen Matters & Biome
23 Mar 2019
at TERI Auditorium, Domlur
Presented for ADDA Water Workshop III

2. RWH – Challenges & Learnings
Challenges Solutions
Requirements
• Confusion regarding RWH Objective
Dialogue with Residents & Vendors
Balance – Storage vs Ground-Water Recharge
Design & Implementation
• Space for Tanks
• Space for Recharge-Pits
• Type of Filter
Dialogue with Multiple Vendors
Tanks under a Ramp
Recharge-Pits in garden near Storm-water outlet
Bottoms-Up conventional Sand/Charcoal filter
Testing & Acceptance
• Lack of Rains for 2 years
• Basement Flooding
Negotiation with Chosen vendor
Basic functional testing was done with piped water
RWH Bypass designed and implemented
Operational
• Rooftop Gardening/ Wet Waste Processing
• Pipes bursting & flooding during heavy rains
• Inability to leverage more than 30 min of heavy rain
Leverage Operational Staff to Diagnose & Fix
Education and regular maintenance
Additional Storm-water outlets created
Added more pipes to pump RWH water to sumps

3. Backup Slides

4. To Recharge Pit & Storm Water Drain
Rain water from Rooftop
Multiple RWH Bypass Valves
Pressure Guage
Filter bypass/
Cleaning Valve
Basement
Water Tanks
30KL
2KL
RWH
Valve
Pump
Ground level Water Tank
Gardening/ Car-Wash
Water to Sump
Sump Valve
Filter
Lake
BM Cassia RWH Schematic

5. BM Cassia RWH Pictures
Recharge Pit
At Construction
At Completion
Filters, Gauge and Storage Tanks in Basement

6. RWH Project Information
• Initial Project Vendor – Refurb India
• Rooftop Surface Area – 1700 Sq. M
• Total Cost – Rs 5.75 Lakhs
• Pipes & Valves
• Tapping into rooftop water & diverting to filters that take it to Tanks
• Tanks to Sumps
• Storage Tanks
• Pumps
• 2 Recharge Pits
• Project Dates Nov 2011 to Jan 2012
• Upgrades Done
• Additional Stormwater Outlets – For use during excessive rains
• Additional connection from Tank to Sumps – To utilize more RainWater
• RWH Water-Meters – For Accounting