At Organ Pipe Cactus National Monument, a remote desert area in southwestern Arizona bordered by Mexico to the south and a Native American reservation to the east, red-lettered signs warning ofâ BLASTINGâ began appearing over the past week. Crews have been blasting the hillside while excavators and backhoes are clearing a path for the Trump administrationâs towering border wall sections, a pace that environmental groups are concerned that sacred burial sites and ancestral lands are at risk of being irreversibly damaged.