Dec. 23 (Bloomberg) -- Exxon Mobil Corp. agreed to pay $6.1 million to resolve a federal criminal charge that the company spilled 15,000 gallons of diesel fuel into a river that flows into Boston Harbor, the Justice Department said.

A court-appointed observer also will monitor ExxonMobil Pipeline Co.’s Everett, Massachusetts, marine terminal for three years, the Justice Department said today in a statement. The spill into the Mystic River from a leaking valve at the terminal occurred in January 2006.

“We very much regret” the spill, ExxonMobil Pipeline spokeswoman Patricia Errico said in an e-mailed statement that confirmed terms of the agreement.

The settlement, which is subject to court approval, includes a fine of $359,018, cleanup costs of $179,634 and a $5.64 million “community services payment” to the North American Wetlands Conservation Act fund to restore wetlands in Massachusetts, the Justice Department said.

Irving, Texas-based Exxon Mobil, the world’s biggest oil company, earned $14.8 billion in the third quarter, an increase of 58 percent from a year earlier.

Exxon Mobil rose 19 cents to $75.10 in New York Stock Exchange composite trading.

To contact the reporter on this story: Greg Stohr in Washington at gstohr@bloomberg.net; Jim Polson in New York at jpolson@bloomberg.net.

Last Updated: December 23, 2008 16:37 EST