Abstract: Employee #1, a wastewater treatment operator trainee, was conducting a routine water test at a secondary gallery distribution box (basin) at a sewer treatment plant. The 60 ft by 40 ft by 18 ft deep box was a below-ground chamber enclosed by a concrete slab and filled with approximately 12 ft of water. Employee #1 was stepping onto a 49 by 24 in. section of grate (one section of a grid) covering the box when the section moved from its outer support channel and fell into the basin. He remained conscious and held onto a cable inside the box for approximately 2 hours, when he was pulled out by fellow operators. Employee #1 was wearing a hardhat and rubber gloves and was using a handheld dissolved oxygen meter. He threw his hardhat onto the ground above the box, where it was discovered by rescuers. Employee #1 was hospitalized with strains, abrasions, numbness of his right shoulder and forearm, and an infected lung. A hepatitis vaccine was also administered.