Authorities said a Clear Channel employee was driving the truck through the site at Artesia Boulevard and Normandie Avenue when it became stuck just before noon. It was trying to hoist up a sign.
The worker was able to get out of the truck and notify police.
The site is known as the Gardena Sumps, which the state says contains chemical contaminants. The truck was stuck on a black, synthetic, protective cap that covers about three acres of the site.
After several hours, a massive crane was able to hoist the truck out without puncturing that cap.
No one was hurt.