As auto-touring increased, the newly-formed National Park Service recognized that roads needed improvement. Road-building in this region was not easy. Granite rock was blasted away to form roadbeds. Powderhouses were used to store blasting powder. In 1933, access to Yosemite Valley from Wawona was improved with the completion of the Wawona Tunnel. The tunnel's power lines, its carbon monoxide sensors, and its high-speed fans made it an engineering feat. Workers used 275 tons of blasting powder and spent nearly two years drilling the tunnel at a rate of roughly 20 feet per day.