Side cast and wasting traditionally has been the most common construction method. It also has been responsible for the highest erosion rates and making large areas unproductive. In this method, most if not the full road width is placed in undisturbed soil (Figure 110). Excavated material is side cast and wasted, rather than incorporated into the road prism. The advantage is uniform subgrade and soil strength. It is unlikely that the travelled road width will be involved in fill failures. An obvious disadvantage is the potential for erosion of loose, unconsolidated side cast material.
Proper compaction techniques result in significant cost reduction and reductions in erosion. Erosion potential is directly proportional to the excavation volume especially if it is side cast in unconsolidated and loose fills. Conventional side cast techniques where most of the road surface is excavated into a stable hill side results in approximately 25 to 35 percent more excavated material when compared to "balanced" road design and construction where the excavation is incorporated into the road prism. In the former case, most if not all of the excavated Material is wasted as loose side cast material readily available for erosion. In the latter case, it has been incorporated into the fill, properly compacted, and presumably unavailable for erosion.
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