Overview
A planted basin that receives runoff from roofs or paving, filled with engineered soil and an overflow to a drain.
Medium€€≈500–1500 LBest in permeable soils
Materials
- Marking paint, string line
- Shovel/spade, wheelbarrow
- Washed sand + compost mix (engineered soil)
- Mulch (e.g., shredded bark)
- Native wet-tolerant plants (edge: sedges/iris; centre: rushes)
- Underdrain (perforated pipe + geotextile) to overflow
Tools
- Spade, mattock
- Level and straightedge
- Utility knife, pruners
- Garden hose for testing inflow
Safety & Risks
- Call utility locate service before digging.
- Keep basin rim below surrounding grade to prevent overflow onto paths.
- Avoid liners that trap water against building foundations.
Maintenance
- Weed monthly in first year; top up mulch annually.
- Prune dead growth in spring; replace failed plants.
- Flush underdrain if ponding exceeds 48 hours.
Permits / Notes
- Front-yard changes may require approval in heritage zones.
- Street curb-cuts require municipal permits.
Steps
- Stake the outline at least 3 m from foundations.
- Excavate 20–30 cm; keep the topsoil aside for reuse elsewhere.
- Install underdrain if needed; protect with geotextile.
- Backfill with engineered soil; shape a level inflow shelf and a slightly lower outlet notch.
- Plant in zones (centre: wet; slopes: tolerant; rim: drought).
- Mulch and water in; test with a hose and confirm safe overflow path.