Investigations of Sources of Contaminants of Concern in the San Juan River

Metals attached to suspended sediments or dissolved in river water pose a potential health risk to communities that depend on that water for agricultural and domestic uses. Exceedances of Navajo Nation surface water quality standards for metals (especially lead and arsenic) indicate that communities on the Navajo Nation along the San Juan River are exposed to this potential risk. Sources for these metals within the basin include mining legacy, natural deposits, agriculture practices, oil and gas production, illegal dumping, urban sources, and other environmental sources. Understanding the contribution from each source can help the Navajo Nation take action, where possible, to improve San Juan River water quality and reduce the potential health risk to these communities. The objective of this work is to identify the sources of metals and trace elements including arsenic, lead, uranium, and other inorganic contaminants released to the San Juan River in the reach flowing through the Navajo Nation, and to quantify the contribution from each natural and anthropogenic source.