earth berming. what is this?

Answer 1

A berm is a barrier. An earthen berm is a barrier made out of dirt.

You can make a hill out of dirt (say 3 feet high) and surround a container of oil. Depending on the size of the container, and the area contained in the earthen berm, if the container were to rupture and empty, it would be held within the confines of the earthen berm.

Answer 2

I found a few acceptable definitions :
In the natural building movement, berming refers to piling earth against an exterior wall to create thermal mass or reduce the visible footprint of an earth-sheltered home.
Berms are also used to control erosion and sedimentation by reducing the rate of Surface runoff. The berms either reduce the velocity of the water, or direct water to areas that are not susceptible to erosion, thereby reducing the adverse effects of running water on exposed top soil.