ANTIOCH, CA-Buena Vista Equities of Irvine, CA is spending $50 million to develop 450,000 sf of retail, light industrial, R&D, and commercial service space here in two separate developments: the Delta Business Park and the Deer Valley Retail Center and Office Park. Combined, the projects’ 60 buildings represent the largest speculative development in Contra Costa County.The 25-acre Delta Business Park is under way near Somersville Road and the Pittsburg-Antioch Highway. The 30-acre Deer Valley Retail Center and Office Park is under way near Deer Valley Road and Lone Tree Way. Both projects will have a significant commercial condominium component.Bill Hillis of Colliers International, one of the listing brokers, tells GlobeSt.com that the impetus for the development is demand. Contra Costa County has one of the region’s lowest industrial vacancy rate, and Antioch’s vacancy rate is less than 1%. The first phase of the 221,000-sf Delta Business Park will contain 170,850 sf in 16 buildings ranging in size from 4,000 sf to 60,000 sf. Two of the buildings will be broken up into commercial condominiums starting at 1,500 sf. The second phase is currently planned as one 50,000-sf building. About 65,000 sf in eight buildings has been put under contract, Hillis says.Deer Valley will have 24 buildings developed in two 125,000-sf phases. The retail component will consist of 80,000 sf in 10 free-standing buildings. The office component will consist of 14 one- and two-story buildings ranging in size from 1,800 sf to 30,000 sf. Including Silicon Valley College, which is taking 30,000 sf, Hillis says nine of the buildings (75,000 sf) have non-refundable commitments, including lease deals, sale agreements and lease options.M.S. Walker & Associates Inc. is the construction management and general contracting company for each of the projects. Buena Vista managing director Carl Willgeroth could not be reached for comment. Buena Vista Equities is an equity investment and real estate development firm. The company is a subsidiary of the McKinley Reserve, a private, Wisconsin-based company with interests in a number of diverse business activities.