By Anna Driver

HOUSTON (Reuters) - Exxon Mobil Corp is
suing the United States to recover more than $45 million in
clean-up costs at its refining and petrochemical plants in
Baytown, Texas, saying the government controlled the facilities
during World War Two.

Exxon argues it should be reimbursed for what it spent to
clean up toxic substances around the complex because the
government assumed ownership and or "substantial operational
control" of the plants throughout the war in the 1940s and up
to the Korean War in the early 1950s, according to a lawsuit
filed in federal court in March.

"The wartime-related operations at these plants resulted in
the generation and disposal of a significant amount of waste at
the Baytown site," the lawsuit said.

In a separate filing, the government denied it had assumed
operational control over the facility during wartime.

The Baytown plant, owned by Exxon predecessor Humble Oil,
began as a small refinery around 1920. During the 1940s, Exxon
says, the government reconfigured and expanded the plant to
make war-related materials including aviation fuel, rubber and
toluene, the lawsuit said.

The refineries and five other production plants at Baytown
generated "substantial hazardous waste" that was disposed of at
the site, while treated wastewater was discharged into nearby
bodies of water, including the Houston Ship Channel, the oil
company's complaint said.

Under the Comprehensive Environmental Response,
Compensation and Liability Act of 1980, the owner or operator
of a facility is responsible for response costs for the release
of hazardous materials, Exxon's lawsuit said.

"Since 2004, ExxonMobil has been working in good faith with
the government to resolve these claims," Exxon spokeswoman
Kristen Hellmer said in a statement. "In light of the looming
statutory deadline to file our contract action, ExxonMobil has
determined it necessary to proceed with filing our contract
claim."

Exxon said that it still hopes for an amicable resolution.

"Exxon is liable as the current owner and operator of the
Baytown complex, and as the owner and operator of the Baytown
refinery when the disposal of hazardous substances occurred,"
the U.S. government said in its response to Exxon's complaint.

A spokesman for the U.S. Department of Justice declined
additional comment.

"For Exxon, this is chicken feed, it's barely a rounding
error on their annual budget," said Tom "Smitty" Smith, state
director of consumer environmental group Public Citizen.

Exxon reported a net profit of $7.56 billion in the second
quarter.

Exxon and the government had engaged in confidential
settlement discussions, which have so far been unsuccessful,
the two sides said.

Exxon's Baytown complex, located about 25 miles east of
Houston, is home to the largest refinery in the United States.
The facility also has a chemical plant, an olefins plant and a
plastics plant.

A hearing on the case is set for Sept. 24 in U.S. District
court in Houston, where the case was transferred from the
Eastern District of Virginia.

The case is Exxon Mobil Corporation v United States of
America, U.S. District Court for the Southern District of
Texas, No. 10-02386.
(Additional reporting by Jeremy Pelofsky in Washington;
Editing by Gary Hill)