Focusing on a controversial gold mining project in Chile, this article examines how engineers and other mining professionals perceive and help shape Corporate Social Responsibility initiatives. Compensation agreements, environmental management, and community relations programs rest on what I call a logic of equivalence that makes the environmental consequences of mining activity commensurate with the mining companies’ mitigation plans. For example, legal codes enable engineers to measure, compare, and reconcile the costs and benefits of a project. However, the law is neither fixed nor uncontestable, and companies must respond to increased public scrutiny and the growing demands of communities, governments, and international actors. In Chile, campaigns against mining focused on the presence of glaciers at the mine site and the project’s possible effects on water availability. By introducing new moral dimensions to debates over corporate responsibility, these campaigns challenged established strategies of commensuration and existing ethical guideposts.