Step 4: Install topsoil
Materials required: topsoil, shovel, tamper, landscape rake, string, level, 8ft 2x4 (optional)
- Fill rain garden with topsoil to depth of 200mm (8in).
- Tamp down the soil by walking on it or dropping tamper on the soil surface from a height of 150-300mm (6-12in). Before each lift of soil is installed, soil should be compacted enough that deep footprints are not created.
- Install another 50mm to 200mm of soil (depending on depth of garden) and tamp down.
- Install final lift of 50mm if garden is 450mm deep, and tamp down.
- Rake topsoil to create an even surface with a 2% slope. Check that the surface does not have low areas by using a level and string, or run a 2x4 level across the surface.
Sections of the garden that are lower than the surrounding area, due to compacting soil over time, will tend to pond water during large rain events and can be remedied by filling the area to level with soil, beneath the mulch.