The new Lone Tree library will welcome patrons for the first time Saturday after more than a year of construction, but visitors shouldn’t be surprised if they see some heavy machinery and workers in hard hats in the area anyway. The shimmering 25,000-square-foot center, on a new street at 10055 Library Way, is just one piece of Lone Tree’s rapidly developing RidgeGate area. The Douglas County Libraries at Lone Tree is the second of three new branch buildings the Douglas County Library District has opened or will open this year.