After nearly three years of construction, the San Diego County Water Authority is nearing completion of the Olivenhain dam near Escondido in northern San Diego County, the first step in an $800-million project aimed at creating a six-month emergency water supply for the county.
The 300-foot-high dam spans a 2,400-foot-wide canyon and will be filled with water from the Colorado River aqueduct to create a 200-acre reservoir.
The authority plans to begin filling the reservoir Aug. 6 by opening a 6 1/2-foot-wide pipe. The agency expects that it will be eight to 10 months before the reservoir is full.
The dam is the first part of a 10-year project. The authority also has plans to create a reservoir nearby in the dry Hodges Lake bed and to increase the capacity of the San Vicente reservoir.
Eleven miles of tunnel will connect the three reservoirs, and pumps will allow water to be moved in any direction in an emergency.
John Liarakos, a spokesman for the water authority, said the reservoirs will be used only if the county's system of aqueducts is damaged by an earthquake or other disaster.
Liarakos pointed out that the aqueducts run across several major fault lines, adding that the Olivenhain dam is designed to withstand a major quake.
The county currently has no emergency water supply, according to Liarakos.
When complete, the project will provide the entire county with enough emergency water to last as long as six months.