HOUSTON --As the city looks to close its budget gap, they're trying to find some of the nearly one billion dollars the city is owed. This week, we've been digging for extra money owed to the city of Houston. That includes unpaid ambulance bills totaling $319 million. You can find all sorts of stuff buried in the folds of your couch. Maybe your remote, your lost wallet, a few extra dollars. And it's there for the picking. But when it comes to hundreds of millions owed in city ambulance bills, it's going to be a little tougher to fine. There's something behind that ambulance you might not see. It's the bill for $1,000, and it's attached to every Houston ambulance ride to the hospital. The problem is the city only collects about half those bills, and when we looked under Houston's couch cushions to see the kind of bills that Houstonians have racked up in unpaid ambulance bills, the number is staggering. In the dark, dirty, dusty corners of the city's couch are $319 million worth of unpaid ambulance bills. Almost all of them are more than three years old, and there isn't much money under there that the city ever hopes to collect. "Ninety percent of your $319 million debt is uncollectable?" we asked Houston EMS Billing Supervisor Frank Carmody. "Right," he replied. Carmody has a tough job. Only half the people who call 9-1-1 for an ambulance in our city have insurance that will pay for the trip. But we found out the city wasn't even asking the uninsured to pay the bills. "We're looking now for the private carriers and if there is no private carrier, we're making demand on the individual," Houston City Attorney Dave Feldman said. "Had that not been done?" we asked him. "No, it had not been done." "Why?" "The vendor wasn't doing it." The city contracts with ATS, a billing company, to send and collect ambulance bills. "Is this contractor doing a good job?" we asked Carmody. "I think they're doing a good job," he said. Really? The city attorney said the company wasn't sending bills to the uninsured. Their rates were higher than the national average and when the city threatened to fire the contractor last summer, the company all of a sudden collected a little more of those unpaid bills. "It's increased," Carmody said. "By how much?" we asked. "By about four to five percent," he said. "Which means how much money?" "Right now, it's about $2 million." Surprise! They worked a little harder and found $2 million in savings under this cushion, and it collected $2 million more in other unpaid bills. "They were working at it, but they weren't working at it to our satisfaction," Carmody said. Just $319 million more to go. To put the size of the unpaid ambulance bills in perspective, if the fire department had just 4 percent of those ambulance bills, the department wouldn't have had to make a single cut from next year's budget.