Halliburton has reached a $1.1 billion settlement over its role in the 2010 spill in the Gulf of Mexico, the worst in U.S. history.

The U.S. District Court for the Eastern District of Louisiana must still approve the settlement, Halliburton said. The amount will be paid in three installments over the next two years and will be kept in a trust until all appeals are resolved, the company said.

In April 2010 a blowout and explosion and occurred at BP’s Macondo well, killing 11 workers and spilling millions of barrels of oil for months after the disaster. The full economic and environmental impact of the spill remains unknown.

Under the settlement, Halliburton is protected from further punitive damages if the court rules in the future that the company was negligent in its role in the blowout, said Mark McCollum, the company's chief financial officer. Plaintiffs could choose to hold out for a larger settlement, but in that case, Halliburton would most likely appeal the decision, which would further delay payments.

Halliburton provided cementing services for BP’s well and placed the centralizers responsible for stabilizing the drilled hole during cementing. The company said the spill was BP’s fault because it decided to use only six centralizers, which Halliburton said was an effort by BP to save time and money.

The companies sued each other over which was responsible in 2011. In October 2013 a former Halliburton manager, Anthony Badalamenti, pleaded guilty to accusations that he destroyed evidence related to the spill. Badalamenti, who was given one year of probation, said it was discovered after the spill that the use of fewer centralizers on the well made little difference and he ordered the program manager to destroy the results of the simulation.

BP has so far paid about $28 billion for its part in the blowout.

April marked the spill’s fourth anniversary, and the National Wildlife Federation (NWF) released a report cataloging persistent health and environmental effects due to the incident.

More than 8,000 birds, sea turtles and marine mammals were injured or killed in the months following the disaster, according to the NWF report.

The report called special attention to the effects of controversial dispersants used to clean up the spill. Two million gallons of chemical dispersants were used after the blowout, according to the NWF, which merely break up large volumes of oil into smaller amounts and scatter it.

That’s why oil continues to wash up on wetlands and beaches and contaminate the food chain in the Gulf region, the NWF said.

With wire services