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COMPLETED PROJECT

Project Report:

Scientific Investigations Report 2005-5187
Lithology and Thickness of the Carmel Formation as Related to Leakage Between the D and N Aquifers, Black Mesa, Arizona
by Margot Truini and J.P. Macy

Geohydrologic Characterization of the Carmel Formation—the confining unit between the N and D aquifers, Black Mesa, northern Arizona

Project Number: 9DX00
Project Chief: Margot Truini
Cooperating Agencies: Bureau of Indian Affairs
Period of Project: COMPLETED

Carmel Formation

PROBLEM

A study of the Carmel Formation as a confining unit is needed to better understand if leakage is occurring naturally and (or) if pumping from the N aquifer is inducing leakage from the overlying D aquifer in areas on the Hopi and Navajo Indian Reservations, Black Mesa Province, Arizona. The N aquifer is used heavily as the source of drinking water for both tribes; therefore, preserving the water quality is important. Concerns exist that pumping from the N aquifer for municipal and industrial uses may induce leakage of poor quality water from the overlying D aquifer. Previous studies have indicated that the Carmel Formation is a confining unit separating the D and N aquifers. A recent characterization of the D aquifer (Truini and Longsworth, 2003) has shown leakage does occur through the Carmel Formation from the D aquifer to the N aquifer in some areas of Black Mesa.

OBJECTIVES

The objective of the study is to develop a better understanding of the regional extent and lithology of the Carmel Formation in the confined portion of the N aquifer. Information about the extent and physical character of the Carmel Formation will provide a better understanding of how and where leakage of ground water can occur between the D and N aquifers.

APPROACH

The approach will be to apply available geophysical techniques that include aeromagnetic and gravity data, compile and interpret lithologic data from geophysical logs and drillers' logs; and collect information from springs that discharge from the base of the D aquifer, from the Carmel Formation, and from the N aquifer.

Lithologic information from geophysical and drillers logs will provide subsurface data on the regional extent and regional lithology of the Carmel Formation. The information from logs will be entered into the software Rock Works, which will allow the data to be viewed as cross sections.

RELEVANCE AND BENEFITS

This study meets several USGS project goals and relevance as outlined in USGS Water-Resources Division (WRD) Memorandum 95.44, including, 1) advancing knowledge of the regional system, 4) providing data or results useful to multiple parties in potentially contentious interjurisdictional conflicts over water resources, 6) providing water-resources information that will be used by multiple parties for planning and operational purposes, 7) furnishing hydrologic data or information that contribute to protection of life and property, and 8) contributing data to national databases that will be used to advance the understanding of regional and temporal variations in hydrologic conditions.

BIBLIOGRAPHY

Geo Trans, Inc., 1993, Investigation of the N- and D- aquifer geochemistry and flow characteristics using major ion and isotopic chemistry, petrography, rock stress analysis, and dendrochronology in the Black Mesa area, Arizona: Prepared for - Peabody Coal Company, Western Division, 1300 South Yale, Flagstaff 86001.

Lopes and Hoffmann, 1997, Geochemical analysis of ground-water ages, recharge rates, and hydraulic conductivity of the N aquifer, Black mesa area, Arizona: U.S. Geological Survey Water-Resources Investigations Report 96-4190, 42 p

Truini, Margot, project proposal [unpublished], Chemical characterization of the N-aquifer in the Black Mesa area, Arizona: approved by Western Region, October, 1992, updated July, 2002, 13 p.

Truini, Margot, 2002, Movement and ages of ground water and isotopic evidence of leakage from the D to the N aquifer, Black Mesa area, northeastern Arizona [abs.], in Science at the Highest Level, Geological Society of America, 2002 Annual Meeting, Abstracts with Programs, Denver, Colorado, October 27-30, 2002, p. 497.

Truini, Margot, and Longsworth, S. A., 2003, Hydrogeology of the D aquifer and movement and ages of ground water determined from geochemical and isotopic analyses, Black Mesa area, northeastern Arizona: U.S. Geological Survey Water-Resources Investigations Report 03-4189, 38 p.