A method used at our range is less than perfect, but it did save on imported fill material.
They excavated a slope in front of the 100 yd line and used that material to build a berm at the 200 yd line. You shoot over the 100 yd targets to hit the 200 yd targets.
As the material was loam with gravel, there wasn't a drainage problem. (In other words, don't try this in soils with a high percentage of clay...
)
I believe the berm is around 15 ft high.
The range hasn't erected I-beams above the benches yet, but there is a required safety course where they emphasize the problem of shooting over the top of the berm.