It wasn’t all that long ago the National Western Stock Show Association was talking about finding new ground on which to hold its annual extravaganza of agriculture and Western culture. Now the ground under its historic home in north Denver is about to be torn up as part of a $1 billion project designed, in part, to keep the show humming along in the city for another century. A flock of elected officials, dignitaries, project partners and neighborhood residents gathered on the National Western Center campus Wednesday to celebrate the beginning of “horizontal construction” on Phases 1 and 2 of the city’s campus overhaul project. “Horizontal Construction” at the property, as detailed by Brian Penner, operations manager for city contractor Hensel Phelps, entails preparing sites for forthcoming buildings, installing utility infrastructure, building two new roads and three new bridges and “an extreme makeover to the South Platte riverfront.” Creation of a new consolidated rail line through the property is also in the works, according to Gretchen Hollrah, executive director of the mayor’s office of the National Western Center. Hensel Phelps’ contract is the biggest the city will award for the initial phases of the project — $275 million.