How to Build a Rain Garden

Fill all but the top 6 to 12 inches of the excavated area with rain-garden soil. Slope the sides gently. If the soil you excavated is relatively free of clay, you can use a mixture of 65 percent native soil to 35 percent compost, or 2 scoops of soil for each scoop of compost. If you dug out clay soil, refill with a mixture of 60 percent screened sand and 40 percent compost. If you are creating a dry well, fill that with washed round stones 1½ to 2 inches in diameter. Also pack stones around the overflow area to prevent erosion.