On a worksite managed by Whiting-Turner Contracting Company, an employee of Concrete Coring Company of St. Louis, was drilling a hole in bedrock using a core drill. Employees of Gold Mechanical, a plumbing contractor on the worksite, were conducting a live test of piping using pneumatic air. The injured employee was working adjacent to a pipe included in the live test. A cap from the pipe was propelled at a high velocity by the pneumatic air and struck the injured employee in the face and fracturing his jaw. The employee was hospitalized for treatment.