A Road Trip to Silverfall Valley
1In July, sixth grader Ezekiel Marchand and his mother drove to Silverfall Valley, a national park with granite cliffs and tall waterfalls. The park and its numbers are made up, but they are based on real parks. One road runs up the narrow valley floor. On summer days, about 5,000 cars a day drive it, and the parking lots fill by 9 a.m., so drivers circle the loop looking for spaces. At the visitor center, Ezekiel met Ranger Ingrid Solano, a scientist who studies the park's air and natural sounds.
2Ranger Solano explained that the park monitors two impacts of traffic. Sound stations record all day, and a computer counts the share of minutes from 8 a.m. to 6 p.m. when an engine can be heard. Small tubes clipped to posts soak up nitrogen dioxide (NO₂), a gas in car exhaust that can harm people's lungs and plants. Each tube hangs for the same two weeks in July, then goes to a lab, which reports the amount in parts per billion (ppb). One station stands at a backcountry camp 6 km from any road, where the engine noise heard comes mostly from airplanes passing high overhead.
3The park wants a plan for next summer. The plan must cut the cars on the valley road to 2,500 a day or fewer, leave room for at least 12,000 visitors a day to reach the trailheads, and cost no more than $3 million a year. It also must not add any new pavement, because pavement would cover the valley's meadows.
4After the park chose a plan, the rangers checked its first summer with the same stations. They also kept stations beside Pine Gap Road, a road in another part of the park where nothing changed.