In a far-reaching initiative to strengthen Westchester County as a major innovation hub, County Executive Robert P. Astorino announced a $1.2 billion private investment today to build a bioscience and technology complex on a vacant site owned by the county in Valhalla adjacent to the Westchester Medical Center and New York Medical College. Called the Westchester BioScience & Technology Center, the nearly 3 million-square-foot, mixed-use complex on 80 acres would be developed by Fareri Associates, a premier developer in Westchester and Fairfield counties with more than 40 years of experience.