A series of bench-scale experiments was carried out to determine the rate and efficiency with which benzene and p-xylene, components of gasoline, could be removed from an unsaturated soil by air stripping. Glass columns, 30 cm in length, were packed with soil and wetted to volumetric moisture contents of 10 and 18 percent. Air saturated with one of the volatile organic compounds (VOCs) was used to load the column. Clean air was used to strip the contaminant from the soil. Benzene and p-xylene concentrations in the soil water and air were reduced four orders of magnitude after a few hours (2-8) of stripping. Benzene was removed faster than p-xylene. Air flow was the rate-limiting step early in the stripping, however slow desorption from the soil became rate-limiting as the stripping progressed. As moisture content increased the rate of removal of both contaminants decreased.

The Picacho earth fissure transects subsiding alluvial sediments near the eastern periphery of the Picacho basin in southcentral Arizona. The basin has undergone land subsidence of as much as 3.8 m since the 1930's due to compaction of the aquifer system in response to ground-water-level declines that have exceeded 100 m. The fissure extends generally north-south for 15 km and exhibits horizontal tensile failure as well as up to 0.6 m of normal dip-slip movement at the land surface, with the west side of the fissure downthrown. The fissure was observed as early as 1927, following an earthquake, and is the longest earth fissure in Arizona. Vertical and horizontal displacements have been monitored along a line normal to the fissure. The survey line extends from a bedrock outcrop in the Picacho Mountains on the east, past an observation well near the fissure, to a point 1422 in to the west. From May 1980 to May 1984, the western, downthrown side of the fissure subsided 167 ±1.8 mm and moved 18 ±1.5 mm westward into the basin. Concurrently, the eastern, relatively upthrown side subsided 147 ±1.8 mm and moved 14 ±1.5 mm westward. Dislocation modeling of deformation along the survey line near the fissure suggests that dip-slip movement has occurred along a vertical fault surface that extends from the land surface to a depth of about 300 m. Slip was 9 mm from May to December 1980 and 9 mm from March to November 1981. Continuous measurements were made of horizontal movement across the fissure using a buried invar-wire horizontal extensometer, while water-level fluctuations were continuously monitored in four piezometers nested in two observation wells. The range of horizontal movement was 4.620 mm, and the range of water-level fluctuation in the nearest piezometer in the deeper alluvium was 9.05 m. The maximum annual opening of the fissure during the study period was 3.740 mm from March to October 1981, while the water-level declined 7.59 m. The fissure closed 1.033 mm from October 1981 to March 1982 while the water level recovered 6.94 m. Opening and closing of the fissure were smooth and were correlated with water-level decline and recovery, respectively, in the nearby piezometers. Pearson correlation coefficients between the water-level fluctuations in the deeper piezometers and horizontal movement ranged from 0.913 to 0.925. The correlogram of water-level decline as ordinate, versus horizontal strain as abscissa, exhibits hysteresis loops for annual cycles of water-level fluctuation as well as near-vertical excursions for shorter cycles of pumping and recovery.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

A report produced through an agreement between the City of Coolidge and the University of Arizona.

Prepared by Richard A. Herbert with contributions from Coolidge Regional Park Interdisciplinary Team.

Energy developments in the Southwest have established a basis for the examination of complexities involved in environmental decision making. The coalfired generation facilities exhibit an impact potential on the social, physical, and economic surroundings of both local and distant communities. A recent seventeen-volume report directed by the U.S. Department of Interior, The Southwest Energy Study, is an indicator of the magnitude of the situation. The Four Corners Program is a team research project with emphasis placed upon technology transfer. Simulation models are used to estimate the physical, economic, and social effects of a range of decisions concerning alternate power schedules. The research results are communicated to interest groups in other than the usual report form. A workshop environment allows the participants to interact with the decisions, the models, the results, and one another. One of the simulation models is the groundwater model. The groundwater model is used to estimate head declines in the confined and unconfined portions of the Navajo Sandstone and the Mesaverde Formation on Black Mesa. The Mesaverde Formation is found to be isolated from the Navajo Sandstone by the Mancos Shale and other intervening layers. A simulation routine developed by the Illinois State Water Survey is modified and adapted to the problem. As a result of the small amount of published aquifer data, minimum or below minimum values of aquifer properties and a sensitivity analysis were incorporated into model considerations. Pumping rates and pumping durations of groundwater for slurry transfer of coal define the decision space. The mining pumpage will have a negligible effect upon the Indian wells located in recharge areas of the Navajo Sandstone. The effects of mining pumpage upon potentiometric surfaces in the artesian portion of the Navajo Sandstone will range from zero to twenty percent of the artesian head, depending upon location and aquifer properties. Theoretical effects of groundwater pumpage on four monitor locations are quantified in terms of ranges of variation. These results can help to evaluate development plans for decision makers and other interest groups. With the future acquisition of measured drawdowns, consideration of theoretical and actual results can provide additional precision to aquifer parameter estimates. The Four Corners Program has a two year duration. The goal of the first year effort was the completion of simulation modeling. Beyond technical or prejudicial hurdles, the workshop encounters will require a public relations and communications posture which is conducive to group participation. The effectiveness of simulation as a means of technology transfer to a variety of users is yet to be evaluated.

Arizona is presently in the midst of a general adjudication for the Gila River system -- the watershed which comprises the southern two- thirds of the state. The purpose of the adjudication is to prioritize all water claims in the river system: both state -established and federally reserved rights. Arizona adheres to a bifurcated (or divided) system of water law which only recognizes a component of ground water -- called subflow -- to be appropriable. Wells which pump non-appropriable water -- called tributary flow -- are not to be included in the adjudication. The problem is that federal laws do not recognize this artificial bifurcation. The challenge lies in identifying a subflow zone which satisfies the hydrologic fiction of existing state precedents and the hydrologic reality of federal statutes. At the core of the problem lies the fate of Arizona's perennial stream water and the fulfillment of federally reserved tribal water rights. Thus, larger questions loom: can Arizona law reconcile its glutinous past with a water -scarce future, will the adjudication ever reach a finality, and even if it does, will it be a finality that all sides can live with?