Sand Valley Concrete, a major stationary source in a non-attainment area, has been operating its existing facility with 2 mixers for 15 years in compliance with air pollution standards. The company was recently awarded a contract to rebuild a stretch of highway. In order to provide the quantity of concrete needed for the project timetable, Sand Valley must increase its production capacity by 50%. The company decided to modify the plant by adding two additional mixers to its existing ones. Although this modification may be deemed a "reconstruction", triggering NSPS standards, because the new mixers meet a more stringent standard of emissions than the old ones, Sand Valley argues it does not need to go through the permit process. Is Sand Valley correct? Explain.