D.C. Mayor Adrian Fenty is set to announce Friday that a Yes! Organic Market will become the retail anchor for a new mixed-use development at 2323 Pennsylvania Ave. SE, marking the first all-organic grocer to open east of the Anacostia River. News of the deal first emerged earlier this month in the Washington Post, part of a partnership between developer Tim Chapman and Yes! owner Gary Cha. Thanks to a $900,000 grant from the District,…