In oral arguments Tuesday, the U.S. Forest Service said it was nearing completion of an environmental impact study that will transfer land east of Phoenix to two of the world’s largest mining companies for the purpose of building one of the largest copper mines on the planet. The massive project will hinge on the destruction of Chi’chil Bi?dagoteel, a mountain otherwise known as Oak Flat, that is sacred to many Native American tribes, particularly the San Carlos Apache, who consider the area among their most holy of sites.