Rainwater harvesting is the activity of collecting rainwater and storing it for later use or recharge to the groundwater. The goal is to utilize the rainfall runoff going to sewer /drain /rivers. This ancient technique is increasingly recognized as a sensible way of providing potable water. For centuries the planet has relied upon rainwater harvesting to provide water for the family, landscape, and agriculture. Rainwater harvesting promotes self-sufficiency and water appreciation.
Rainwater harvesting advantages:
- To raise the groundwater table
- Storing water to future demands
- Improve yield of an aquifer
- Improve existing groundwater quality through dilution
- Prevents saline water ingress in coast areas
- Rain diversion into collection tanks prevents flooding and erosion.
- Conserves energy by bypassing the energy input required to operate a centralized water system.
Three chief components of a rainwater harvesting
- Collecting the rainwater
- Filtering collected water
- Recharging the filtered water through pits and bore wells
Purpose of this Method Statement
This method statement describes the procedure and resources required to do the work. Use any other resources and methods not referred to in this method statement to suit the project requirement. Always execute the work safely complying with the required standard.
This method statement summarizes suggested method of executing works safely within any constraints. This method statement offers advice and guidance to the personnel involved in this activity to:
a) Carry works in a manner that’s safe at all times;
b) Know the hazards involved in the activity;
c) Ensure controls to steer clear of hazard exposure are in place.
The sequence of activities is a repetitive process and many aspects are common to distinct sites. Include with detail, any crucial aspects specific to the project. Always follow the approved checklists prior to the start of the activity.
What this Method Statement covers
The scope of this document covers:
- Safe work method for constructing rainwater harvesting system
- Work procedure
- Materials, equipment and tools needed to carry the work
- Applicable standards throughout the execution of the project
- IS : 15797 Indian Standard for Rooftop rainwater harvesting – Guidelines
- Rainwater harvesting and conservation manual by CPWD, New Delhi
- Boulders and gravel
- Coarse Mesh
- PVC pipes
Equipment & Tools
- Borehole drilling equipment
- Equipment and tools to earthwork
- Tools for brickwork and P.C.C.
Health, Safety and Environment
Execute all activities with due regard to Health, Safety & Environment of all the workers and third parties.
- Barricade the work area.
- Restrict access to children from entering the borehole and recharge pit areas
Personal Protective Equipment (PPE)
Refer to the PPE Standard Operating Procedure for more details
- Ensure that the components and materials provided are as per the necessary criteria
- Refill materials for recharge bore and pit should be free from clay and lumps
Fix gutters and drain pipes to collect roof water and transport it to recharge pit
- Drill 300 mm dia bore of 30 m deep with borewell drilling machine.
- Fill the bore with 3 to 6 mm dia pea gravel.
- Put a PVC casing pipe of 2.5 meter length with 3 mm perforations up to gravel layer of recharge pit. Keep 1.8 meters above ground level into the recharge pit.
- Excavate 4 m x 4 m x 2 m deep pit to construct the brickwork chamber. Keep borehole as the centre of recharge pit.
- Construct a chamber of internal size 3 m x 3 m x 2.25 m height with 230 mm thick brick masonry. Apply waterproof plaster on the brick walls.
- Refill bottom 750 mm thick layer with 50 to 200 mm stones. Middle 750 mm thick layer with 5 – 10 mm gravels. Top 750 mm thick layer with 1.5 to 2 mm coarse sand.
- Fix PVC pipes above ground level to get inlet drain and overflow discharge.
- Cover the pit with 100 mm thick R.C.C. cover slab.
- Clean the catchment area before the arrival of monsoon.
- Cover the rooftop outlet with a coarse mesh to avoid leaves and other obstructions
Keywords: rainwater harvesting, RWH, rainwater harvesting system, rainwater collection, collect rainwater, Safe work method statement, method statement.