This seminar examines the state of knowledge in environmental law, and how regulators, litigants, and social movements bridge and fill knowledge gaps that were identified at the dawn of modern environmental law in statutes such as the National Environmental Policy Act, Clean Air Act, Clean Water Act, and Resource Conservation and Recovery Act. Environmental law begins with a plea: that agencies and other parties consider, limit, and mitigate the impacts of their actions. However, those impacts feature system effects, nonlinear interactions, feedback loops, discontinuous and threshold dynamics, and uncertain boundaries. The administrative state has at times crude or partial means to address these impacts. It relies on artificial constructs to respond to environmental impacts, such as worst-case scenarios, reasonable foreseeability, "best available" science in regulatory practice, notions of validity and reliability in federal rules of evidence, scales of spatial and temporal analysis that are inappropriately narrow or large and vague, and tools such as standards and allowances that rely on proxies or other approximations of the experience of pollution and its effects on human beings and landscapes. We will explore available tools and proposed reforms through topics such as environmental impact assessment, risk assessment, health impact assessment, scientific evidence, cumulative impact, socio-economic impact, environmental monitoring, disparate impact, community-scale impact, and ecological impact. Course requirements include a final paper, a class presentation based on the paper, in-class exercises, and class participation. PREREQUISITE: NONE. GRADING NOTICE: This class will not offer the CR/NC/H option. **A student who fails to attend the initial meeting of a seminar, or to obtain permission to be absent from either the instructor or the Registrar, may be administratively dropped from the seminar. Students who are on a wait list for a seminar are required to attend the first seminar meeting to be considered for enrollment.