This dissertation examines the contestations over the politics of knowledge, risk, and environmental justice in three fenceline sites. Mobilizing the fenceline standpoint to study risk strengthens our objective understanding of the social situatedness of risk. To illustrate how a fenceline standpoint contributes to stronger objectivity of risk contestations, I survey public discourse of coal slurry extraction in Black Mesa, Arizona using an environmental justice framework. Discursive justifications for the construction of the slurry pipeline reveal how environmental injustice in the fenceline community emerged through urban controversies over water and power generation that excluded a fenceline standpoint. Insights from Black Mesa frame the next two cases: open burning hazardous waste at Radford Army Ammunition Plant, and M6 Disposal at Camp Minden, Louisiana. At Radford, scholar-activist research examines the contestations of risk at one of the most hazardous waste facilities in the nation. I analyze the construction of risk from open burning of hazardous waste from a fenceline standpoint. I discursively situate the controversy over fenceline community risk from open burning, by showing the inadequacies of official risk assessments. Critical discourse analysis of risk shows the extant contestations over the practice of open burning. In juxtaposition to Radford, the Camp Minden open burn controversy demonstrates how a fenceline movement successfully constructed alternatives to open burning. Fenceline success in Minden is forcing scrutiny over the risks produced by the practice of open burning explosives across the United States. The activation of fenceline knowledge and expertise, through grassroots organizing, is propelling inquiry from scientific and technical experts of the American Chemical Society who are questioning why the Department of Defense and the Environmental Protection Agency have approved the use of open burning at other sites despite safer alternative technology. Synthetically, each case illustrates the importance of fenceline knowledge as a crucial site of expertise. I present an argument for how a fenceline standpoint can challenge regulatory and producer constructions of fenceline risk. The creation of a program of research: Critical Risk Analysis, offers a model for scholar-activist intervention on the fenceline. The Camp Minden Dialogue demonstrates a successful example of how fenceline expert-activists can influence the construction of risk. Normatively, I build the argument that environmental justice research within Science and Technology Studies ought to situate the fenceline standpoint as equal to the competing epistemological claims of production and regulatory experts in order to strengthen the objectivity of our research in contested fenceline sites. / Ph. D.