Assessing the Feasibility of Using a Sealed Landfill for Agricultural Graze Land

Abstract

The average American produces approximately 4 pounds of trash per day, approximately 55% of which is buried in municipal solid waste landfills. Once full, these landfills are closed, sealed, and maintained according to the United States Environmental Protection Agency’s standards and regulations, and then monitored or remediated as necessary. There is great interest in putting closed landfills to some sort of productive use—particularly via agricultural activities. This project was commissioned by the City of Tucson Environmental Services Department as a part of an effort to explore ways to reuse one or more of the 16 landfills it manages in the Tucson metropolitan area. The objective of this project was to assess the feasibility of using a closed and sealed landfill to support safe goat browsing. A site investigation was conducted at the Harrison Landfill in Tucson, Arizona to assess the site’s history and to characterize the soil quality and uptake of deleterious metals by the following plants commonly observed at the landfill: buffel grass (Pennisetum ciliare), desert broom (Baccharis sarothroides), Russian thistle (Salsola kali L.), creosote (Larrea tridentata), salt cedar (Tamarix ramosissima), and four-wing salt brush (Atriplex canescens). Site characterization data were combined with goat browsing and plant consumption patterns to determine exposure risks. It was observed that soil concentrations of metals (Al, Ag, As, Be, Ba, Fe, Co, Cu, Cr, Cd, Fe, Mn, Ni, V, Se, Mo, Sn, Sb, Pb) did not exceed Arizona Department of Environmental Quality’s soil remediation standards. Furthermore, salt cedar, willow baccharis, buffel grass, Russian thistle, desert broom, creosote, and four-wing saltbush contained metal concentrations that fell well within maximum tolerable levels (MTLs). This project determined that, after soil and plant assessment, urban, arid landfills in general may be safely used for economic development through agricultural grazing ventures.