SEATTLE -- Engineers investigated the area where a man was trapped for more than an hour Thursday morning after the sidewalk collapsed beneath him on the Seattle waterfront.

Victor Sosa was on the waterfront near the Washington Street Public Boat Landing when he heard the sidewalk above the seawall collapse at about 7:45 a.m.

RAW VIDEO: Trapped Man Lifted From Hole
SLIDESHOW: Man Swallowed By Seattle Sidewalk

"All of a sudden the steel structure shook, really like an earthquake. I looked around, stood up and saw the sinkhole and someone who was walking by at the time heard the man scream," said Sosa.

The man in his 70s fell down a 10-foot deep hole and was trapped.

Firefighters brought in a ladder truck with heavy rescue equipment to shore up the area and then two firefighters entered the hole and attached a rescue harness to the victim, who was conscious.

The man was brought out of the hole and transported to Harborview Medical Center for an examination.

KIRO 7 Eyewitness News reporter Michell Millman shot this video of the man being loaded into a medic unit.

Department of Transportation engineers surmise that the seawall ate away the underneath of the sidewalk, causing it to crumble.

Ron Paananen with the DOT said he didn't believe the collapse posed a threat to Alaskan Way or the Alaskan Way Viaduct.

"We're going to do some more investigating. The seawall that caused this failure is not part of the main seawall that holds back Alaskan Way," said Paananen.

The DOT will continue to examine the area, which was purchased by the agency a year ago to use as a staging area for the viaduct replacement project.