SANTA FE — The vast, stunning swath of northern New Mexico split by the Rio Grande Gorge had barely been named a national monument when a Colorado utility began reaching out to local leaders about building a power line through the area. Tri-State Generation and Transmission Association is eyeing the possibility of running a line from a substation north of Alamosa, Colo., to a site somewhere west of Taos. “We are in the very initial stages of studying this project,” and no route has been identified, said Tri-State spokeswoman Sarah Carlisle. But the company’s study area for the Valley Corridor...