The 2010 Gulf of Mexico oil spill has come back to haunt British Petroleum (BP) once again: a U.S. judge has ruled that BP’s recklessness caused the 2010 massive oil spill. BP already agreed to pay billions of dollars in criminal fines and compensation to people and businesses affected by the disaster, but now the company may face up to $18 billion in civil penalties under the Clean Water Act.

The spill four years ago from Deepwater Horizon oilrig killed 11 workers and sent millions of barrels of oil into the Gulf of Mexico. BP pleaded guilty from the beginning and helped with damage claims. However, BP has also always maintained that the company’s contractors for the ship, Halliburton and Transocean, hold the same amount of blame as they do in the disaster. But with this new decision, BP has been pegged as the number one culprit.

“BP’s decision was primarily driven by a desire to save time and money, rather than ensuring that the well was secure,” U.S. District Judge Carl Barbier wrote in regards to BP’s decision to forgo a crucial test, instead opting to complete its drilling and move the rig to another site as quickly as possible.

The $18 billion decision may end up being much more than the $3.5 billion BP had set aside for civil penalties under the U.S. Clean Water Act. BP set that money aside under the expectation that the court would rule the company liable for simple negligence. However, the ruling of gross negligence means BP could face a penalty of up to $4,300 for each barrel of oil spilled.