We calculated the drainage area that the rain garden will receive, conducted two percolation tests, and sized the basin accordingly. We next dug out the basin and created a flat bottom, approximately 6" below the invert of the overflow drain pipe. We've since mulched the area and are now selecting plan species for the bottom, sides, and perimeter of the garden.
The cage at lower right is for our house cat. The dead grasses at left are a first attempt from last year at a roof terrace screen. Trial #2 will be implemented yet this summer.