Winstanley Enterprises said its WinBrook Office Park development in Rocky Hill should be open by September. The Concord, Mass.-based developer, which owns the nearby Inwood Business Park, held an official groundbreaking at the Brook Street site last Wednesday. Two of the three buildings at the 171,000-square-foot development have already been framed, and the foundation for a third has been poured. CBRE New England is handling leasing for the new site. A list of tenants has yet to be released.