Abstract: At approximately 7:32 a.m. on September 21, 2003, Employee #1, a bulk cement pneumatic tanker truck driver, was transferring dry cement from bulk cement pneumatic tanker trailers to a fixed storage silo. During the transfer of the cement, the fixed storage silo became full and Employee #1 was instructed to put the rest of the dry cement into a set of semi-permanent tanker trailers that were being pulled by a Peterbuilt tractor, License Number 9B21685, Vehicle Identification Number 1XP-GAO7X3YD534885. While Employee #1 was loading the trailers, four coworkers heard a loud noise. One of the coworkers went to investigate the noise, but did not notice anything unusual. A second coworker went outside to further investigate, but due to the lack of outside lights, and the dark and foggy conditions, he did not see anything different from the first coworker. Approximately 30 minutes later, a third coworker went looking for Employee #1 and found him lying between the trailers in a large pool of blood. Additionally, the Peterbuilt tractor was idling and the product discharge valve was closed on one of the trailers. Emergency services were contacted and Employee #1 was pronounced dead. A fourth coworker arrived about 15 minutes after the third coworker and reported that the pressure gauge on the trailer with the closed discharge valve was at 12 psi. He relieved the pressure by opening the outside vent and venting it back through the hose coming from the other trailer. A detailed investigation determined that the exhaust pressure from the tractor was being sent into the trailer with the closed discharge valve, but no product was being transferred due to the shut valve. However, the exhaust pressure was passing through this trailer's transfer system and through a hose into the top of the second trailer, causing additional pressure and difficulty transferring product into the second trailer as well. In response to this issue, Employee #1 was thought to have climbed to the top of the second trailer to loosen the cam locks that hold the hatch shut, releasing the pressure. The sudden release of pressure caused the hatch to spring open, striking Employee #1 in the face and causing him to fall approximately 11 feet to the ground.