[header] How to build a dry well [title] Dig a 12-inch (30. 5 cm) deep trench from the area of standing water to the location of the dry well holding tank. [step] The trench should begin at ground level and gradually angle down to a 10 percent grade at the holding tank. [title] Enlarge the soil drainage test pit to fit the holding container. 
[step] The lip of the container should be 8 inches (20. 3 cm) below the surface after 2 inches (5 cm) of gravel is added to the bottom of the pit.