It happened around 10:30 a.m. Wednesday in the concourse area beneath the Municipal Services Building.
Another employee spoke with the victim shortly after the incident.
"It was some crazy guy who was on the elevator and he was feeling her leg," said Gwen Frazier.
Sources tell Action News the victim ran from the elevator at the next stop and called police.
Police arrived a short time later and found the suspect. According to Frazier, the man was found in the women's bathroom.
"This same man was in the women's bathroom. At the same time there were two women in the stalls," she said. "So they waited for this crazy guy to come out of the bathroom and they arrested him," she said.
The alleged groper remains in police custody. The case has been handed over to the Special Victims Unit.