A large gasoline spill Thursday morning prompted some evacuations and caused a huge traffic mess on Harbor Island Thursday morning. The spill was reported after a pump failed just before 5 a.m. at the Shell Harbor Island Petroleum Terminal, fire officials said. Firefighters shut down the area and established a 1,000-foot safety perimeter until Shell employees could reach the scene to clean up the spill. Meanwhile, the closure of the terminal left dozens of trucks stuck waiting to deliver loads, creating a huge cluster of traffic in the area, especially with the main West Seattle Bridge closure. Officials estimate 6,800 gallons of fuel spilled from the 160,000 gallon tank, but none of it appears to have reached the nearby Duwamish River. The scene was secure enough to turn the cleanup efforts over to Shell and the Department of Ecology around 9:30 a.m. and Seattle firefighters left the scene. No one was injured.