THERMONIC EXPLORATION FOR OPTIMUM WELL SITES ON THE SAHUARITA BOMBING RANGE SOUTH OF TUCSON, ARIZONA, U.S.A.  

William M. Turner, Ph.D.

INTRODUCTION  

The City of Tucson, to accommodate water supply for growth in the southern part of Tucson, embarked on a ground-water exploration program on the Sahuarita Bombing Range.  The area of exploration had been used during the W.W.II as a training area for bomber pilots.  The area of the Sahuarita Bombing Range is shown in Figure 1.

HYDROGEOLOGIC SETTING  

The area of exploration is comprised of Quaternary alluvium deposited above an old erosional surface on well-indurated, poorly sorted Pantano Formation of Tertiary age.  The erosional surface is known as the "Rillito" surface in the Tucson Basin.  The best well sites are found in buried channels filled with well-sorted alluvium.

PROCEDURE 

AGW scientists directed the construction of 27 Thermonic observation holes each 10 feet 3 m) deep and about 1,320 feet (400 m) apart along a north-south line.  The total length of the north-south line was about 6.75 miles (10.9 km).  We measured temperatures in the 27 observation holes.  The processed data relates to the geothermal heat flowing to the land surface at each location.  Processing of the data relied on proprietary methods developed by AGW to filter effects of downward propagating solar heat, diurnal temperature variations at depth, and the varying thermal conductivity of the soils.  The thermal conductivity of the soils is strongly dependent on moisture content that can vary greatly from point to point in the subsurface.  We processed the data further using our proprietary "valley mapping function." 

We projected the favorable zones for a short distance from each of the Thermonic observation holes based on the direction of ground-water flow.  We determined the direction of ground-water flow from the ground-water-level-elevation contour map of the area.

RESULTS

At time of the Thermonic well-site location program, the City of Tucson Water Department was drilling two exploratory wells to a depth of 1,000 feet (304 m) each.  Neither well was sited at a Thermonic target and both were subsequently abandoned. 

Until the Thermonic survey was conducted, The City of Tucson Water Department had used electrical resistivity methods and data from more than 500 gravity stations in their ground-water exploration program with poor results. 

Further Thermonic exploration in other areas of the Tucson Basin for the Tucson Water Department were stalled because the City Water Board observed that it was easier to get money from the City Council for test holes than for Thermonic geophysical ground-water-exploration programs.  Their mindset cost Tucson ratepayers a great deal of money.  A look at the financial importance of Thermonic ground-water exploration shows why. 

Our discovery of very high production wells near Vail, Arizona, 20 miles east of Tucson, caused the City of Tucson to trade wastewater services for the wells. 

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