In recent decades, there has been increasing interest in the use of waste tires in the form of tire-derived aggregate (TDA) in civil engineering. TDA is a light-weight fill material that has desirable engineering properties. The media provides an alternative to typical fill material, such as rock aggregate obtained via gravel mining. The emergence of waste tires used in these applications has motivated numerous studies investigating the potential benefits and barriers associated with this method of reuse. For many of its intended civil engineering applications, TDA comes into contact with water and may leach organic and inorganic compounds, possibly degrading the quality of nearby ground and surface waters. The primary objective of this study is to investigate the potential for leaching of TDA constituents as a function of time. Contractor's Report Produced Under Contract By: Humboldt State University Brad A. Finney, Ph.D., Professor Richela K. Maeda Environmental Resources Engineering