When it is complete next summer, the $1.9 billion Allegiant Stadium in Las Vegas will showcase some of the most high-impact, fan-centered amenities ever found in an NFL stadium. The soon-to-be home of Raiders football will sport a sleek black glass exterior, retractable natural turf field, premium lounges and four rolling doors framing a 90-foot-tall, 200-foot-wide view of the Las Vegas Strip. What won’t be so apparent is the design, planning and construction work that went on behind the scenes, a culmination of more than two years of work by two of the country’s largest contractors, two design firms and 70-plus subcontractors.  The numbers sum it up: work on the 65,000-seat, 1.75 million-square-foot venue has involved the removal of 895,000 cubic yards of dirt, 12 miles of concrete drilled shafts, miles of piping and 19 construction cranes. When finished, the structure will encompass 28,000 tons of structural steel and 105,000 cubic yards of concrete, held together in part by 482,000 structural bolts. With so many people, schedules, materials and moving parts on the $2 million-a-day project, the most impressive statistic is that construction is on schedule and on budget ...