Item 26 - Adoption of the City of Santa Ana Emergency Operations Plan

Home Browse Search

City of Santa Ana Emergency Operations Plan Part I Basic Plan 2.4.6 Dam/Reservoir Failure A dam is defined as an artificial barrier to impound water for storage or control. A reservoir is defined as a large, usually artificial structure for the storage of water, or also may be defined as the body of water stored within the structure. Dam or reservoir failures can result from a number of natural or human -caused threats including earthquakes, erosion of the structure or foundation, rapidly rising water levels, structural or design defects, construction flaws, or acts of terrorism or sabotage. Failures may result in sudden and rapid release of a large volume of water that inundates downstream or lower elevation areas. This surge of water can cause loss of life or serious injury through drowning or blunt force trauma; destruction of homes and buildings; large-scale evacuations and extended displacement of residents; destruction of roadways, railways and bridges; damage to flood control channels and drain systems; and damage to electricity, water, sewage, gas, phone and other utility equipment or distribution systems. Unlike damage from an earthquake, which may cause widespread damage but leave many properties undamaged or lightly damaged, a surge of water from a dam failure will likely destroy or badly damage every property and structure in the inundation area. Substantial governmental response and recovery may be required and may continue for an extended time beyond the initial emergency response and rescue stage. These efforts may include clearing debris from roadways and public properties, inspecting structures and demolishing unsafe structures, rebuilding roadways and bridges, re-establishing public services and utilities, and providing continuing care and shelter to displaced persons. Dam/Reservoir Failure Events - There have been a small number of failure events in southern California. St. Francis Dam - The most destructive dam failure occurred on the St. Francis Dam near Santa Clarita in Los Angeles County. Almost as soon as the dam reached its fill capacity after construction, workers began to notice seepages and leaks. Just before midnight on March 12, 1928, a sudden and catastrophic failure of the dam sent 12.4 billion gallons of water, along with large concrete sections of the dam, surging down the Santa Clara River in a 120-foot high wall flowing at 18 mph. The water swept through the towns of Valencia, Newhall, Fillmore, Barsdale and Santa Paula and flowed all the way to the Pacific Ocean near the City of Ventura, 54 miles away. Approximately 450 persons were killed, with many bodies never recovered, and nearly 1,000 homes were destroyed. It was later determined that the dam was built on a poorly designed and constructed foundation, which could not support the weight and pressure of the dam and water. Westminster Water Tank — On September 21, 1998, at 5:47am, a 5-million-gallon concrete aboveground water storage tank ruptured, sending a 6-foot high wave of water through a nearby fire station and the Hefley Square Townhomes in the City of Westminster. Six people were injured and 30 were left temporarily homeless after the wave gushed from the 22-foot high rupture in the tank. The fire station, 70 homes, 32 outbuildings, 2 businesses and 25 vehicles sustained damages or were destroyed. Gas, electric and telephone services were disrupted. 77