Environmental group Greenpeace announced Monday it would send one of its ships on a three-month expedition to determine the extent of the ecological damage to the Gulf of Mexico from the BP oil spill. 'We all need to know the true extent and nature of this oil catastrophe, as well as the real reasons why this happened, so we can make sure it never happens again,' Greenpeace USA executive director Philip Radford said in a statement. The group announced that a Greenpeace ship, the Arctic Sunrise, would set off next month from Tampa, Florida to conduct a wide-ranging survey of the Gulf, examining everything from the plankton on the surface to subsurface plumes. Far from being encouraged by this weekend's news that the ruptured BP oil well had been capped, Greenpeace said in its statement that 'tens of millions of gallons of oil have spilled into the Gulf of Mexico, compromising the wildlife and ecosystems, destroying the region's fisheries, and affecting the ocean for decades to come.' The group said BP 'has made countless mistakes, devoted inadequate resources, and withheld information from and denied access to journalists and the American public.' Residents of the Gulf of Mexico have seen crude foul shorelines and cripple local economies since a rig leased by BP exploded and killed 11 workers in April, causing hundreds of millions of gallons of crude to pour into the sea over the past three months. 