As part of the Superfund Innovative Technology Evaluation (SITE) Program, the U.S. Environmental Protection Agency (EPA) evaluated passive water treatment (PWT) technologies for metals removal from acid mine drainage (AMD) at the Summitville Mine Superfund Site in Southern Colorado. PWT technologies have been demonstrated to be effective in removing high concentrations of metals (aluminum, copper, iron, manganese, and zinc) from AMD. These systems supply alkalinity to the mine drainage along with aeration to precipitate metals such as aluminum and iron as oxides and hydroxides (oxyhydroxides). The technology is waste-stream specific, requiring characterization of all organic and inorganic constituents. Two technologies were evaluated for this project: the Successive Alkalinity Producing System (SAPS), a PWT technology, and the Aquafix treatment system, which is a semi-passive treatment technology. In consideration of the severity of the AMD quality at the Summitville site, an iron settling pond pretreatment system was constructed upstream from the SAPS pond. This pond provided a means to aerate the AMD, allowing oxidation and precipitation of ferric ion prior to SAPS treatment. From the Reynolds Adit collection sump, AMD was delivered as influent to the SAPS at a rate of 5 gallons per minute (gpm). This influent was aerated by passage through a spray nozzle to atomize the AMD as it settled into the pond. The iron, and potential co-precipitated metals, settled to the bottom of this pond prior to delivery into the SAPS.