Abstract: At 8:00 a.m. on June 9, 2008, five Titan employees began working in the lowest, or what the employees called the basement, level of the tower side of the Pennington Avenue drawbridge. Based on employee interviews, the following events led up to the accident on Monday morning. The employees had completed the work on the nontower side of the bridge the prior week. To complete the project, two electric pumps were rented and used to pump the water out of the basement level on that side of the bridge. However, when they moved to the tower side, the basement level was lower and contained more water than the previous side. When the electric pumps seemed inadequate to be able to pump the water up the additional distance (an estimated 30 feet versus 20 feet on the nontower side), the Titan foreman for the project decided on Friday to rent a gasoline powered pump to use on the tower side. The foreman reasoned that the pump could run Friday while they were completing work on the opposite side, and again on Saturday while no one was working. The foreman and another employee shared the task of refueling the pump every couple of hours on Saturday until the water had been pumped out. The foreman stated that he believed any buildup of carbon monoxide would have time to dissipate before the employees began working in the area on Monday morning. The employees began shoveling debris and putting it into drums for disposal. Around 9 a.m., Employee A began pressure washing the area using approximately 500 gallons of water mixed with 1 gallon of ZEP Pine Cleaner and a small amount of Clorox Industrial Bleach. Shortly thereafter, the employees began suffering symptoms of carbon monoxide poisoning and began exiting the work area. Employee A continued to work until he began feeling dizzy and nauseated and decided that he needed to exit the area. Employee A, who had asthma, had managed to exit the lower level but collapsed at the top of the stairway. Emergency services were called and all five employees were taken to the University of Maryland Medical Center for treatment. Based on the medical records of the employees, which were reviewed by a MOSH Medical Records Officer, when admitted to the hospital the employees had carboxyhemoglobin levels ranging from 10.1 to 17.3. All of the employees were diagnosed with carbon monoxide poisoning. Three of the five employees were treated in the hyperbaric chamber. All five employees were treated and released the same day.