Daniel Samuelsen said he fell into the tunnel, near the mouth of Parleys Canyon, and broke his leg during a hike on Wednesday morning.
When his cell phone died, he found a rock and banged it against the tunnel walls in hopes of attracting someone's attention. But no one ever came although numerous hikers passed by above the tunnel.
"I thought I was going to die," Samuelsen told ABC affiliate KTVX in Salt Lake City.
By Saturday afternoon, after four days without any food or water since the fall, it became clear that he needed to take action. Samuelsen decided to crawl out of the corrugated tunnel. He was able to find a piece of wood and make a split of sorts for his severely fractured leg. He eventually crawled to a nearby highway, where he was discovered by a motorist.
"I was near tears when someone finally stopped. I clasped my hands together and was like 'thank you, thank you,'" Samuelsen said. "I was so happy to see somebody who cared enough about me to stop and realize I needed help."
According to doctors at St. Mark's Hospital, Samuelsen's right leg is broken in numerous places, and may need to be amputated, because the wound was open for four days.
Kate Moss Achilli, director of marketing communications for St. Mark's Hospital, said Samuelsen was admitted to the hospital with a compound fracture in his lower right leg and was severely dehydrated. He was treated with surgery and IV fluid.
"He has had surgery for his wounds and is doing okay at this point," Moss Achilli said.
Doctors are determining whether he is safe to discharge, but amputation is still an option at this point.
"I am about to be moved into physical therapy right now and thought of that frightens me, because my leg was broken for four days," Samuelsen said. "Anytime I move it into a standing position I get an intense rush of pain."