Abstract: Employee #1, who worked for a contractor at the work site, was in the basket of a self-propelled, two-wheel drive, JLG lift, model BONX, serial # 030878063., patching rough areas of new concrete. The lift was on a 20 ft by 40 ft barge made up of 10 ft by 20 ft flexifloats with flat tops. The barge was floating in a slough to access the underside of a highway overpass at a seismic retrofit construction site. The outgoing tide caused the barge to become stuck in the mud and list to one side. Employee #1 could not stop the lift from rolling off the corner of the barge and into the muddy slough. He and the boom basket were thrown upward, striking the bottom of the overpass before falling to the deck of the barge. Employee #1 sustained a fractured jaw, for which he was hospitalized. No form of blocking or chocking had been used on the lift's wheels.