Since the 1940s, federal agencies such as the Soil Conservation Service ([SCS], now Natural Resources Conservation Service [NRCS]) and the United States Army Corps of Engineers (COE) have constructed flood control dams in the Southwestern United States. For the most part, these dams were designed and built to protect downstream agricultural lands. Some of the more recently-constructed dams however, were multipurpose, serving as flood protection structures for agricultural lands as well as urban centers and military installations.
Over the past two to three decades, and since the construction of these flood control dams, urban centers downstream from these dams have grown significantly. This urban growth has significantly increased the downstream consequences related to potential failures of these flood control dams. The increased risk for major potential loss of life associated with potential dam failure scenarios has forced owners, operators, and regulatory agencies to pay closer attention to the safety of flood control dams in Arizona and other areas of the Southwest. The risk is further compounded by the deterioration of the dams themselves. Deterioration of the dams has been caused by:
- Transverse cracking due to desiccation and foundation settlement
- Loss of freeboard due to ground subsidence related to excessive groundwater extraction
- Earth fissures associated with differential ground subsidence
This paper focuses on the potential adverse impacts of earth fissures on the safety and long-term performance of single-purpose flood control embankment dams and the creative approaches taken by the dam owner, owner’s engineer and the dam safety regulator to achieve safe dam rehabilitation alternatives.