New Jersey agreed last month to settle the litigation for $225 million, prompting broad criticism that the Christie administration had taken pennies on the dollar to end the hard-fought case. Not only was the sum less than what the state offered to accept in 2012, but it also came at an odd moment: A ruling on damages was believed to be imminent, after an eight-month trial last year at which the state sought to prove its damages claim.

Environmental advocates and some lawmakers have accused Mr. Christie, a Republican, of sacrificing the environment to help the state address more immediate shortfalls in its budget, allegations the Christie administration has vigorously rejected. On Thursday, the Assembly Judiciary Committee held a hearing on the proposed settlement, which still requires a judge’s approval.

Records of the settlement proposals are not public; the state official and others interviewed for this article who had knowledge of the talks spoke on the condition of anonymity because the talks were also not public. Whatever the political and legal analysis that led to the $225 million deal, the seeds of an agreement were planted years earlier.

Familiar to drivers on the New Jersey Turnpike, the Linden refinery, known as Bayway, has reinforced the image of the state as almost irretrievably toxic. There, marshland adjacent to a creek was “now mostly covered with a tar of petroleum products or filled with other hazardous constituents and debris,” according to a state environmental official quoted in a 2006 affidavit. He also cited 45 acres of “sludge lagoons,” former tidal marshes that had been used as hazardous-waste disposal facilities.

Exxon agreed in 1991 to clean up both the Bayway and Bayonne sites, subject to state approval, with “no cap” on what it would pay, as Mr. Christie recently pointed out. The company says that to date, it has spent about $260 million on those efforts.