The occurrence of subsidence in south-central Arizona is a major concern because it is a core area of the state, with major agricultural and urban centers. The Phoenix and Tucson metropolitan areas are located within this area, as well as agricultural production areas within Pinal and Maricopa counties. Figure 3-4 Subsidence near Eloy. Dates on the pole mark more than 15 feet of subsidence from groundwater pimping between 1952 and 1985. U.S. Geological Survey Urban areas are especially vulnerable to the damaging effects of subsidence.
Cities are dense areas of population, with large numbers of buildings and facilities.
Railroads, earthen dams, wastewater treatment facilities and canals also are prone to damages from subsidence. Sewer lines, laid at precise gradients, can have their slopes reduced or even reversed, with serious consequences. Any structure built across the path of a fissure likely will suffer serious damage. Careful and expensive construction procedures were worked out to protect the CAP canal from subsidence damage in certain areas. Despite these precautions, the canal was damaged by an earth fissure in Pima County in 1988.