Developer Lowe Enterprises has completed construction of the second phase of the $500 million County Operations Center and annex project in Kearny Mesa, among the largest ongoing construction projects in San Diego County.

The newest phase includes two 150,000-square-foot, four-story steel-frame office buildings, according to a statement from Los Angeles-based Lowe Enterprises. There is also a 15,000-square-foot conference center.

The 47-acre project is being built in multiple phases on Overland Avenue, and will eventually house several county of San Diego departments in six buildings. Approximately 2,400 county employees from numerous departments have now relocated to the new buildings.

“We are proceeding ahead of schedule and under budget to deliver to the county expanded facilities that will allow it to further consolidate county operations from outdated facilities to this new campus,” said Mike McNerney, senior vice president of Lowe Enterprises Real Estate Group.

Lowe completed the first phase of the project, consisting of two 150,000-square-foot office buildings and a seven-level, 1,800-space parking structure, in October 2010. That phase has since achieved LEED Gold certification for energy efficiency, the company said.

The third phase is planned to include a new 150,000-square-foot building for the Registrar of Voters, with construction expected to begin in the fall and set for completion in December 2013. Two additional four-story office buildings, similar to the buildings in prior phases, and another parking structure will be built in future phases, the statement said.