So it took a lot longer than expected to complete the rain garden, the lack of rain along with super hot days did not help my desire to dig.
How to build a Rain Garden.

1. Pick a location and remove sod
2. Excavate and excavate some more.
3. Excavate to at least 40 cm (16 inches if there's already good drainage, twice that if bad drainage)
4. Redirect the downspout, to create an input for the garden and divert runoff.
5. Loosen the bottom, another 40cm, and add/mix in compost
6. Plant flood and drought-resistant plants. Preferably Pollinators.
7. Add 10 cm (4 inches) of mulch, make an inlet, and output pretty with river rocks

Why build a Rain Garden?
Rain gardens are designed to hold all the rainwater coming off the roof. Until it can be absorbed into the soil. Reducing the strain on the city's storm drain system.
And that's where our spare time has gone for the past three months.

My backyard is in shambles after all the dedication to the front yard.
Attached Images