How to Excavate a Berm

Consult a topographic map or sketch your landscape on graph paper. Mark the contours of the land and the drainage areas. A berm will change the way that water flows around an area. Place berms in the path of water to redirect it or to create a rain garden. Do not place a berm in an area where water already pools. This area is one of poor drainage. Plants planted on a berm in this area may become waterlogged.

Sketch your berm into the landscape on paper. Lay out the berm in the landscape corresponding with your map using rope. A berm should be no more than 2 feet high and five times as long as it is high. The ends of the berm should taper off into the ground. Most berms are given a slight curve, or a crescent shape.

Remove grass from the area beneath the berm to prevent the grass from sprouting into the berm. Dig into the protected, uphill side of the berm to remove soil for use as the berm's fill. For berms around trees, dig into the location where a tree will be planted to create a planting pocket. Use the backfill that the root ball displaces to construct the berm.

Tamp the dirt in the berm tightly using a tamping tool. Water the soil using a garden hose to release air pockets that could develop in the berm. Continue to tamp and layer on the soil until it is the desired height.

Fill in the soil on the inner side of the berm for a water garden with a mixture of 1 part sand and 1 part compost. This mixture drains well.