This environmental assessment quantifies the water-quality-related benefits associated with achievement of the proposed BAT (Best Available Technology) and PSES (Pregtreatment Standards for Existing Sources) controls for hazardous and nonhazardous landfills. Based on site-specific analyses of current conditions and changes in discharges associated with the proposal, the U.S. Environmental Protection Agency (EPA) estimated in-stream pollutant concentrations for 65 priority and nonconventional pollutants from direct and indirect discharges using stream dilution modeling. EPA assessed the potential impacts and benefits to aquatic life by comparing the modeled in-stream pollutant concentrations to published EPA aquatic life criteria guidance or to toxic effect levels. EPA projected potential adverse human health effects and benefits by: (1) comparing estimated in-stream concentrations to health-based water quality toxic effect levels or criteria; and (2) estimating the potential reduction of carcinogenic risk and noncarcinogenic hazard (systemic) from consuming contaminated fish or drinking water. Estimates of upper-bound individual cancer risks, population risks, and systemic hazards result from modeled in-stream pollutant concentrations and standard EPA assumptions. The assessment evaluates modeled pollutant concentrations in fish and drinking water to estimate cancer risk and systemic hazards among the general population, sport anglers and their families, and subsistence anglers and their families.