From the Proceedings of the 1989 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 15, 1989, University of Nevada, Las Vegas, Nevada / The prehistoric Indian population in Las Vegas Valley found abundant water for their needs from springs flowing from the base of numerous fault scarps throughout the valley. The faults are generally considered to be compaction faults caused in part by subsidence resulting from dewatering aquifers as the climate became dry and warm during the interglacial periods of the Pleistocene. The valley's aquifers, for historical purposes, eventually reached steady state conditions which lasted through nearly the first half of this century. Urban growth then created a demand for water that was satisfied by overdrafting the ground-water system, which reactivated subsidence. Today, subsidence effects cover about 1,000-1,300 km² of the valley and the maximum vertical displacement is about 1.5 m. As the demand for water continued to increase with population, large imports from the Colorado River via Lake Mead provided abundant water, which helped create additional hazards: a rising shallow water table, resulting from over irrigating landscapes (secondary recharge), intersects land surface in places in the central and eastern part of the valley creating a hazard to structures and facilities; the potential increases in liquefaction; and, the potential for degradation of the deep aquifers from downward percolation of the poorer quality water from the shallow system.

From the Proceedings of the 1989 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 15, 1989, University of Nevada, Las Vegas, Nevada / Bottom sediments from several urban lakes located in the Phoenix metropolitan area were collected and analyzed for organic priority pollutants. The lakes selected for analysis were broadly representative of the diversity of lake characteristics found in the Phoenix area. That is, lakes were sampled that had different types of primary water sources and that were located in watersheds of differing degrees of urbanization. Preliminary results indicate that only nine of the 114 listed organic priority pollutants were found in measurable quantities in the sediments of the lakes surveyed. The pollutants detected were either phthalate esters or volatile or semi-volatile halogenated compounds. None of the pollutants were common to all the lakes sampled. Dibutyl phthalate was detected in three of the six lakes. A larger database is being developed and will be necessary to determine whether a statistical correlation exists between watershed characteristics and feedwater, and organic composition of lake sediments.

From the Proceedings of the 1989 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 15, 1989, University of Nevada, Las Vegas, Nevada

From the Proceedings of the 1989 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 15, 1989, University of Nevada, Las Vegas, Nevada

From the Proceedings of the 1989 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 15, 1989, University of Nevada, Las Vegas, Nevada

From the Proceedings of the 1989 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 15, 1989, University of Nevada, Las Vegas, Nevada / Arizona's Groundwater Management Act has changed the perspective that water providers must use when planning to meet growing water demands. The goal of safe-yield in the Active Management Areas and the requirements of both the Second Management Plan and the Assured Water Supply provisions will require all water providers to consider other options besides additional groundwater development when expanding their water supply plans. A simplified process will be presented that stresses the need for well thought-out, cost-effective water resource planning to meet management requirements for both public and private water providers. The process relies on an initial projection of water demand, an analysis of demand reduction potential, an examination of supply alternatives, and a discussion of the characteristics that must be considered when weighing the demand reduction and supply alternatives for implementation. Development of water supply plans that meet existing and future needs for growing service areas will be increasingly important to water providers in Arizona and throughout the and West.

Complete issue of the Proceedings of the 1989 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 15, 1989, University of Nevada, Las Vegas, Nevada

From the Proceedings of the 1990 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 21, 1990, Arizona State University, Tempe, Arizona

From the Proceedings of the 1990 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 21, 1990, Arizona State University, Tempe, Arizona / New regulations concerning the management of underground storage tanks (USTs) have resulted in increased awareness of environmental contamination resulting from leaking USTs. The objective of the typical underground storage tank investigation is to determine if any subsurface contamination has occurred as a result of tank or product line leakage, fuel spills or overfills. Soil contamination at underground storage tank sites is usually discovered during the removal and replacement of USTs. Techniques that can be used to detect the presence of soil contamination adjacent to existing USTs include soil vapor analysis, exploratory boring, and soil and ground water sampling. The lateral and vertical extent of contamination must be determined at any site which contains detectable quantities of contamination. Two common methods for determining the extent of contamination are over-excavation and borehole drilling and sampling. Boring design and location considerations include number of borings, borehole depth and spacing, and site sub -surface conditions. Differentiation between perched sub -surface water and aquifers is critical. Once an appropriate boring plan has been established, then a sampling and analysis plan must be adopted that meets the needs of the particular investigation. The determination of the extent of contamination at an underground storage tank site is the first step leading to site closure and remediation.

From the Proceedings of the 1990 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 21, 1990, Arizona State University, Tempe, Arizona / Remedial techniques for sub-surface soil and water contamination are dependent on the lateral and vertical extent of petroleum hydrocarbon contamination and the type of petroleum hydrocarbons which have been released into the sub-surface. Specific remedial technologies are required for diesel fuel and heavy oils compared to the more volatile gasoline compounds. Available remedial technologies for vadose zone contamination include excavation and treatment; soil vapor extraction and possible vapor burning; bioremediation; and chemical treatment. Remedial technologies for ground-water contamination include water recovery, contaminant volatilization, carbon adsorption, bioremediation and water reinjection. Specialized apparatuses are utilized when petroleum hydrocarbon product floating on the water table surface must be separated from the ground water. A number of hydrologic considerations must be evaluated prior to any remediation scenario. These considerations include geologic characterization of the sub-surface soil matrix, and aquifer.