An agency that operates three toll roads in Orange County, California, may default on $2.4 billion of bonds unless a planned restructuring takes place, according to a report from state Treasurer Bill Lockyer.

The Foothill/Eastern Transportation Corridor Agency is set to refinance some of its debt the week of July 8 as part of the plan to cut borrowing costs and extend repayment by 13 years.

Orange County’s 51 miles (82 kilometers) of toll highways, the most extensive system in the state, the world’s ninth-biggest economy, have missed revenue forecasts since opening in the 1990s. The agency approved the restructuring last month.

Without the restructuring, “the agency is not likely to meet its bond covenants going forward and without significant revenue increases, toll revenues would soon fall below the level needed to meet debt service obligations,” according to Lockyer’s report.

“It makes sense because interest rates are low and we will be able to lower annual debt service growth,” Lisa Telles, an agency spokeswoman, said by telephone. “It makes good business sense.”