As many geotechnical engineers like to say, soils are the foundation of everything. In a sense this is true, because the vast majority of engineering structures are built on land, which is generally composed of some sort of soil. Therefore, a strong understanding of soil is absolutely necessary in order to then design the structure, roadway, or artificial body of water that rests on the soil because regardless of what you are designing or construction, it will almost always eventually involve the ground. This understanding includes the plasticity and structure, the compaction and permeability characteristics, and the stresses and pressures that move through the soil. When considering sustainability application in geotechnical areas, there are two primary paths, either the replacement of materials or the modification of a design in order to improve the economic, environmental, and social impact of the project. This chapter will cover both of these paths using the following four specific applications: alternate granular fill materials, retaining wall design, mechanically stabilized earth walls, and geothermal energy foundations.