Paul Carter, horticulture expert at the Norfolk Division of the US Army Corps of Engineers, measures the circumference of a tree in the Millennium Project site at Arlington National Cemtery in Arlington County, Virginia, in the United States on February 6, 2013. The Millennium Project will clear 27 acres of property on the cemtery grounds, and add an additional 30,000 burial and inurnment sites. Horticultural experts estimated the age of all trees in the Millennium Project site based on height, trunk circumference, and other factors. Many of the oldest, non-invasive trees will be retained. Experts use the data collected from the first few trees cut down as part of the project to confirm these estimates of age.