The San Diego County Water Authority celebrated the final phase of a project to double the capacity of the San Vicente Dam Thursday in Lakeside.
A celebratory blast at the base of the dam kicked off the construction phase of the $570 million project.
The city of San Diego's 220-foot San Vicente Dam is being raised an additional 117 feet.
The San Diego County Water Authority says it is the tallest dam raise project ever in the country.
Water Authority General Manager Maureen Stapleton says when construction is complete, the reservoir's storage capacity will more than double.
"This project alone will result in 150,000 acre feet of storage within our region," Stapleton say. "That's enough water for 300,00 homes for a full year."
She says when filled to capacity the taller dam will provide an emergency supply and store water during wet seasons to carry over for use during dry seasons.
The entire project is expected to be completed in late 2012.