Dennis is a licensed landscape architect with 35 years of experience creating award-winning parks, plazas, and waterfronts. He spent most of his career at EDAW, where his work included Wharf District Park in Boston, Centennial Olympic Park in Atlanta, North Shore Park in Pittsburgh, and West Main Street in Louisville. In 2006, he served as president of the American Society of Landscape Architects (ASLA). In 2009, he served as president of the Landscape Architecture Foundation (LAF). He is currently a principal at Parker Rodriguez in Alexandria, Virginia.