The dam can be created on its base have all type. Whether it be a stone. Gravel, sand or soil. There are many other soil dam cheap, because the use of construction materials that exist in the area and the nearby dam is the most. So there's no need to transporting construction material from other.
The dam can be built on the foundations of all types of footwear. The base will be a stone, gravel, sand or earth dam is mostly because it is cheaper to use building materials that are in the vicinity of the dam and nearby are the majority. So no need to transport construction materials from the others.
The dam can be built on the base of all types of shoes, whether the base will be the rocks, pebbles, sand or soil, Seung dam is usually cheap because building materials available in the dam and the nearby.