A U.S. Court of Appeals for the District of Columbia Circuit denied a request by the American Trucking Associations and the Truckload Carriers Association to reconsider a waiver granted by the Environmental Protection Agency.

The EPA granted the waiver to the California Air Resources Board in January 2009, giving the agency the authority to enforce regulations related to Transport Refrigeration Units, or TRUs. The court decision was made Friday.

The rules, which were adopted in February 2004, requires that TRUs equipped with diesel engines seven years or older be replaced or retrofit with new engines. This applies only to TRUs operating in California. While the rules were scheduled to take effect in December 2004, CARB had to get the EPA waiver to enforce them. The rules were effective Dec. 31, 2009.

According to the court, the ATA argued that "EPA misinterpreted and unreasonably applied the statutory criteria when approving the California rule." Specifically, the ATA felt the rules did not "meet compelling and extraordinary conditions." But the EPA said this refers to the factors that tend to cause pollution - the "geographical and climatic conditions that, when combined with large numbers and high concentrations of automobiles, create serious air pollution problems."

While the ATA argued that California doesn't need the rule, the EPA said that California suffers from "some of the worst air quality in the nation."

ATA also took issue with the fact that the rule applies to all carriers that operate in California, calling it "a de facto national rule because many trucks pass through California and will be subject to the rule." The court responded by saying that ATA's argument was weak.

"The California rule does not require any other state to adopt California's approach," the court said. "If ATA's members operate trucks in California, they must comply while operating in California. If they do not operate in California, they need not comply."

ATA also said the EPA did not consider the cost of compliance to the rule, but the court argued that the EPA did adequately consider the costs, which are about $2,000 to $5,000 per unit. In addition, the court said the phased implementation of the rule would minimize costs.

With the denial of the associations' request, CARB is now free to enforce the regulation, which has already hit many carriers who failed to register equipment and meet the standards.