Earth fissures and related subsidence features adjacent to the Tucson Aqueduct, Central Arizona Project, Pinal and Pima Counties, Arizona

Earth fissures are a geologic hazard that could interrupt delivery of water to users of the Central Arizona Project (CAP) Tucson Aqueduct. Since the first earth fissure reported in Arizona was discovered near Eloy in 1927 (Leonard, 1929), dozens more have formed in Picacho basin and Avra Valley. The planned location of the Tucson Aqueduct in Picacho basin was changed to minimize the likelihood of damage by fissures and land subsidence, but the hazard is so widespread that the potentially harmful areas could not be avoided entirely. In 1988, the "Sandario Road" fissure formed near Marana High School in Avra Valley. The area had been identified in a previous study as a zone of potential hazard. The fissure cracked the aqueduct but did not drain it, probably because the aqueduct was specially reinforced there due to the recognized potential for damage. Good planning minimized repair costs and, if the aqueduct had been in operation then, would have prevented an interruption in service. Periodic monitoring of the Tucson Aqueduct is required because early detection of a problem is the best way to achieve a timely, less expensive solution. The u.S. Bureau of Reclamation (USBR) conducts bimonthly inspections of all known fissures located close to the CAP. The object of this investigation is to identify any additional existing features near the Tucson Aqueduct that should be included in the bimonthly inspections. (18 pages)Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu