Definition - What does Berm mean?
A berm is a stationary barrier constructed of earth materials such as soil or rocks found on-site. It is constructed as a level space or mound that separates two areas. In trenchless technology, it is usually created as a way to prevent erosion and sedimentation. A berm can also be used to provide for a safe working environment during excavation by controlling surface runoff.
Trenchlesspedia explains Berm
Projects that require a substantially sized berm will sometimes be layered. This saves on cost and can also aid in the aesthetic quality of the berm. If this is the case, the lower layer will consist of fill material, either gravel, rubble or asphalt, which will make up a large portion of the berm. Above the fill, a layer of clay will be laid down to aid in retention of the top soil. However, some municipal ordinances require that a berm be made predominantly of clay. The top layer of the berm should consist of high-quality topsoil. Generally, the most effective berms are asymmetrical.