CARLSBAD, CA—Presidio Residential Capital and Cornerstone Communities have broken ground on The Reserve, a 635-unit community on 156 acres—more than half of them designated as open space—that is being built on a former rock quarry in northeast Carlsbad. The retail value of the project, which will offer 293 single-family detached luxury townhomes and 342 luxury apartments when it opens in 2016, will exceed $200 million.