Anadarko Petroleum Thursday agreed to pay $5.15 billion to resolve decades-old environmental claims in a settlement the US said would discourage companies from engaging in corporate makeovers to avoid pollution liability.

The record environmental settlement covers dozens of claims against Kerr-McGee, an oil company Anadarko acquired in 2006. Prior to the takeover, Kerr-McGee restructurings shifted its environmental liabilities into a separate chemical unit called Tronox.

The US government and Tronox trustees launched the suit against Anadarko in 2009.

Last December, US bankruptcy judge Allan Gropper ruled the Tronox reorganization was "fraudulent" and that Anadarko owed Tronox trustees as much as $14.5 billion. Tronox fell into bankruptcy in 2009 before emerging in 2011.

The settlement is "the largest environmental enforcement recovery ever by the Department of Justice," the department said in a statement.

"If you are responsible for 85 years of poisoning the Earth, then you are responsible for cleaning it up," said US Attorney Preet Bharara. "That's why this case was brought. And that's why the defendants are paying a record $5.15 billion -- to fund that colossal cleanup and to make things right."

Bharara said Kerr-McGee had played a "corporate shell game" to avoid responsiblity.

Anadarko's $18 billion purchase of Kerr-McGee expanded the Texas company's oil and gas holdings, including in the Gulf of Mexico, where Kerr-McGee had long operated. But in earlier decades, Kerr-McGee also had major chemicals and nuclear operations.

Those non-oil assets, as well as the environmental liabilities, were spun off in Tronox before Anadarko acquired Kerr-McGee.

"There can be no dispute that Kerr-McGee acted to free substantially all its assets -- certainly its most valuable assets -- from 85 years of environmental and tort liabilities," Gropper had concluded in December.

As a result, the "cleansed" Kerr McGee became "more attractive as a target of an acquisition," the judge wrote.

John Hueston, an attorney with Iris & Manella who represents Tronox claimants, said the settlement will address a number of "environmental disaster sites" across the country.

The payments will include $1.1 billion to clean up contamination at an industrial park near Lake Mead in Nevada and $1 billion for the Navajo Nation to remediate radioactive contamination from Kerr-McGee's Cold War-era uranium mining.

Other payments will go to clean up thorium contamination at a superfund site in New Jersey, with additional funds going to clean sites in Texas, Mississippi, Georgia and other sites.

Hueston called the agreement "historic" and said the sum would be sufficient to remediate all sites. Holding out for a larger payment from Anadarko risked delaying the cleanup, he added.

"It's an important precedent to deter companies from taking action like this in the future and at the same time provide a means of remedy in case they do," Hueston said.

Anadarko said the agreement removed doubts that have depressed the value of its stock.

The settlement "eliminates the uncertainty this dispute has created, and the proceeds will fund the remediation and cleanup of the legacy environmental liabilities and tort claims," said Anadarko chief executive Al Walker.

"Investor focus can now return to the tremendous value embedded in Anadarko's asset base."

Anadarko was a partner of BP's in the 2010 Deepwater Horizon accident in the Gulf of Mexico. It paid BP $4 billion in 2011 to resolve claims related to the accident.

Anadarko said the settlement will be paid following US District Court approval, expected by the end of the third quarter. The company will cover the payment from cash on hand and a $5 billion credit facility.

Anadarko estimates a net tax benefit of $550 million in the upcoming quarter due to the settlement.

Anadarko shares jumped 14.4 percent to $98.96.