We have seen in Chapter 3 (Technical Aspects of Statutes, Standards, and Regulations) and in Chapter 5 (How to Write Environmental Documents) that the NEPA process implementation often leads to a specific requirement for mitigating environmental impacts. Frequently, such mitigation is best built into the design of the proposed project using control technologies that either eliminate the emission of pollutant(s) to the environment or reduce them. Some of the methods of achieving this visible benefit of the NEPA process are described in this chapter. The approach to emission control methods (most preferred to not preferred) is shown in Figure 1.