Monitoring the Effects of Ground-water Withdrawals from the N Aquifer in the Black Mesa Area, Northeastern Arizona

In 1968, Peabody Coal Company began strip-mining operations on land leased from the Navajo and Hopi Tribes on Black Mesa (fig. 1). Of the 11 to 13 million tons of coal that are extracted each year, an average of about 5 million tons are transported as slurry by a 273-mile-long pipeline from the coal-lease area west to the Mohave Generating Station near Laughlin, Nevada. Transporting the coal in slurry form consumes, on average, about 3,800 acre-ft of water annually. The slurry water is provided through a network of 8 wells that tap the confined parts of the D and N aquifers underlying Black Mesa. Most of the slurry water is pumped from the confined part of the N aquifer which also is the primary source of water for municipal users within the 5,400-square-mile Black Mesa area. The Navajo Nation and Hopi Tribe became concerned about the long term effects of industrial withdrawals from the N aquifer on the availability and quality of water supplies for domestic and municipal purposes. These concerns led to an ongoing investigation of the water resources of the Black Mesa area begun in 1971 by the U.S. Geological Survey (USGS) in cooperation with the Arizona Department of Water Resources (ADWR) and the Bureau of Indian Affairs (BIA)