(CNN) -- How do you rescue a man stuck in grain to just above his waist?
Very carefully -- and slowly -- said Corpus Christi, Texas, firefighters who built a special wooden box that enclosed the trapped man. They were then able to lower the grain level around the worker enough to pull him him to safety Wednesday night, hours after he became stuck in a grain elevator.
Thirty firefighters, rotating in teams, spent about five hours in the delicate rescue effort at the Corpus Christi Grain Co., said Assistant Fire Chief Randy Paige.
The 50-year-old unidentified man was alone inside the grain elevator Wednesday afternoon when he became stuck, said Paige, who did not know what the employee was doing inside or what variety of grain was in the structure.
The man was discovered more than an hour later by co-workers, and the rescue began, with a successful conclusion around 8:30 p.m.
The man was taken Wednesday night to a local hospital for observation and was in stable condition, Paige told CNN. The man did not complain of injuries.
Firefighters who arrived on the scene opened a hatch on the side of the round elevator, which is about 100 feet in diameter and about 75 feet tall, officials said.
They could see the employee who was a few feet above ground level in the tank. He also was standing above valves that release grain to an area below ground, Paige said.
As they got to work, they also saw that the grain rose in a "V" shape along the tank's walls to about 50 feet above the worker, who was in the middle of the elevator, Paige said.
"This stuff is real fine and granular and he was unable to move," the chief said.
Crews used plywood to build wood shoring that was about the shape of a small closet. They put it in position around the employee.
When they opened the valve, the grain dropped and they were able to pluck the employee to safety.
"We had to be very careful and slow at this," said Paige. "We were worried about an avalanche effect."
The fire official was proud of his team, which had three members inside the tank at all times. They had to deal with warm temperatures and were able to get fluids, by water and intravenously, to the trapped man.
"Luckily, the dust was not too bad."
It all came down to training and resourcefulness, Paige said.
What were the other options?
Plan B called for using a hoisting device at the top of the elevator, but crews were worried about the stress on the employee's body if they tried to pull him up. Plan C involved a vacuum truck that would have removed the grain.
"Luckily, Plan A worked on this one," said Paige.
A person who answered the phone at the business Wednesday night said no one was available for comment.