The Justice Department has dropped a criminal case against four people accused of vandalizing the Lincoln Memorial Reflecting Pool after newly disclosed government records pointed instead to a rushed and flawed installation of the pool’s new protective coating. Polyurea is the thick, rubber-like protective coating sprayed across the bottom of the Reflecting Pool. The experts said the coating itself was appropriate for the project, but identified potential installation problems involving seams, tie-ins and expansion joints. Expansion joints are intentional gaps that allow the concrete slabs beneath the pool to expand and contract as temperatures change. The U.S. Attorney’s Office then requested all Interior Department records related to the coating and its installation.