An earthquake would probably cause the most damage to the dam, said Brown. Earthquake risk in this area is relatively low, but still a factor. The dam suffered no problems from earthquakes centered near Klamath Falls in 1993. Harza Engineering of Concord, Calif., ran computer models to determine the impact of a dam breakdown. Its inundation maps will be included in the city's revised Emergency Action Plan Simulations were run for both fair weather and wet weather dam breaks.
Water levels are higher under the fair-weather scenario.
The study showed a maximum water level increase of 5.4 feet in Phoenix in fair weather. The water would arrive there 2.8 hours after a break. In wet weather, an increase of 1.9 feet would arrive in 1.8 hours. About 200 homes and businesses would be affected. Most are within one half block of Ashland Creek.