**ADVANCE FOR WEEKEND AUG. 11-12 ** Workers burn oil off the tundra from a leak in an oil transit line at the Prudhoe Bay oil field on Alaska's North Slope Saturday, Aug. 19, 2006. A series of leaks caused BP to shut down the oil fields in 2006. An upcoming state study shows that all kinds of spills, from crude to gasoline to tainted water, have occurred with regularity over the last decade. (AP Photo/Al Grillo)