Hydrological and mechanical characteristics of soil in the area of salt deposits, northwest Phoenix, Arizona.

Abstract

The construction of a salt plant northwest of Phoenix, Arizona, after the discovery of a salt dome has caused concern about possible pollution of the agricultural land and groundwater, especially in the presence of subsidence cracks resultant from groundwater withdrawal. Therefore it becomes necessary to study geological and hydrological conditions and hydrological and mechanical characteristics of soil in and around the salt plant. Geologic sections north and south of the ponds show a lithologic sequence from ground surface to 50 feet depth composed of brown silty clay, caliche, brown silty clay with 15 to 20 percent of sand, grey or green silty clay, and sandy, gravelly and silty clay. However, the impression gained from the results of the investigations is that subsidence is the only probable source of pollution from the seepage along the cracks that might cut the ponds. Therefore, an instrumentation program should be set up to monitor any future subsidence due to groundwater withdrawal or future salt mining.