The federal government plans to start excavation over the next two weeks on a massive triumphal arch across the Potomac River from Washington, D.C., Secretary of the Interior Doug Burgum said Thursday, launching a controversial project championed by President Trump. Construction at the site is expected to take two to three years, with an intense 20-hour-a-day, year-round work schedule, the National Park Service has said, meaning the project could wrap up toward the end of Mr. Trump's second term. The 250-foot-tall arch — which will be clad in granite and topped by three golden statues plus an observation deck —...