Ground Water Pollution Assessment of Landfills in the Rio Nuevo Area, Tucson, Arizona.

Abstract

A protocol for evaluating the leachate generating potential and subsequent ground water pollution of landfills located in the desert southwest, along ephemeral streams, was tested at four landfills in the Rio Nuevo Project area, Tucson, Arizona. The landfills involved were the "A" Mountain, Rio Nuevo South, Nearmont, and Rio Nuevo North landfills. Six regional ground water monitor wells were installed as part of this study. Existing shallow monitor wells were also sampled. Concentrations of chloride, total dissolved solids (TDS), nitrate-nitrogen, and organics, and values of specific conductance (EC) were the indicators used for contaminated ground water. Using these indicators, it was determined that the Rio Nuevo North Landfill is a source of ground water contamination. Leachate is also being generated in the perched ground water under the Rio Nuevo South and Nearmont landfills, but the regional ground water quality there is so far unaffected. Low levels of organic contaminants were noted across the study area. The source of water for leachate generation at the Rio Nuevo North Landfill was not determined, but a likely source at the Rio Nuevo South Landfill was determined to be major runoff events in the Santa Cruz River. The protocol presented in this thesis was found to be sufficient for determining that leachate was present. However, it was not sufficient for determining the source of water infiltrating the landfills.