This chapter is an application case study of a methodology to select optimal onshore environmentally friendly drilling (EFD) systems at Green Lake near McFaddin, Texas. The chapter describes sensitivity analysis procedures, which will help decision makers examine the robustness of the optimal solution to changes in input parameters in system selection decisions, where the system is made up of components (drilling technologies) that can be combined in many different ways. Two different sensitivity analysis techniques are presented. One is a sensitivity analysis for weighting factors of each attribute and the other is a sensitivity analysis for uncertainty of the overall attribute inputs.