Last year, there were 640 oil spills in the US that affected groundwater or surface water in some way. As The Rural Blog notes, many of these crude oil spills go unnoticed and unreported.
In the last seven years there have been 2,500 reported spills. And that number is probably low due to underreporting. Some oil and gas agencies don't even track spills at the state level.
Desirée Plata, a professor at Yale University who studies oil spills, says the lack of information hurts both environmentalist and industry efforts. “If the information were available,” she said, “operators could show that they spill a small amount relative to the volume they produce and transport.” Plata explained that water spills can create more problems than land spills because the contaminants spread faster.