NASHVILLE, Tenn. - An audit report from the U.S. Environmental Protection Agency's Office of Inspector General has recommended requiring the state of Tennessee to pay back most of a $2 million federal grant.

According to The Tennessean, the report charges that the state overestimated the benefits of the electrification project at truck stops and didn't comply with a requirement to use only materials made in the United States.

The funding was used to put electric heating and cooling units in at four truck stops to dissuade truckers from leaving their engines idling and generating pollution.

State officials said in a written response that the Department of Transportation was "surprised and deeply disappointed at the arbitrary and capricious nature of the OIG recommendations." The letter called the proposed penalty "harsh and unjust."