SHALLOW GROUNDWATER IN CHINLE, ARIZONA (NAVAJO NATION): FACTORS AFFECTING GROUNDWATER METAL CONCENTRATIONS IN THE PUBLIC WATER SYSTEM

The Chinle area is in northeastern Arizona on the central portion of the Navajo Nation. Water sources include springs and wells (tanks). The principal hydrostratigraphic units for the region are the Chinle and Supai formations. The lithologies include sandy and gravely clay, conglomerate and sandstone. Although problems with uranium contamination are widespread in the region, other metals pose water quality problems. In particular, the Chinle area currently suffers from serious discoloration problems, which is crucial for the health and well-being of people and of major concern in rural communities of the Navajo Nation. We report major and minor element chemistry from springs and wells in the area.

In January 2010, four wells (ranging from 60-397 m-deep) all produced high levels of concentration Fe and Mn (0.9 mg/L and 0.48 mg/L, respectively). These values exceed USEPA standards. We observe the rates of high concentration systematically increasing towards the NE, towards the mouth of Canyon De Chelly. Based on the mineralization and the presence of metals in the public water system, there can be a possibility of other contaminants.

Ongoing testing will take place at the UNM Analytical Laboratory. Analytical procedures include titration for alkalinity, analysis of cations via inductively-coupled plasma-optical emission spectroscopy and anion analysis with ion chromatography.