One of Dan Gilbert's and Tom Gores' biggest hurdles to building a Major League Soccer stadium and three new high-rises at the foot of downtown might not be Wayne County itself.

Instead, it could be Internal Revenue Service rules that ultimately seal the future of Detroit's skyline as the county awaits an answer on whether it can repurpose leftover bond money from 2010 and use it to build a new jail a few miles north.

Richard Kaufman, deputy for county Executive Warren Evans, said the county could face more than $175 million in exposure if it diverts the bond money to help pay part of the $300 million price tag offered by Gilbert for a new $420 million criminal justice complex at a different site. Gilbert's Rock Ventures LLC has also asked for what have generally been referred to as "operational savings credits."

That exposure would be triggered by repurposing $51 million in leftover bond financing from the Gratiot jail project to pay for construction of the criminal justice complex at any other site —including the one Gilbert is proposing at East Forest Avenue and I-75, Kaufman said.

At issue are the 45-percent federal tax credits Wayne County received on 10-percent interest it paid on $200 million in Recovery Zone bonds to pay for the half-built Wayne County Consolidated Jail. Because of IRS rules, the county would have to return $51.27 million in tax credits it already received and forfeit an additional $126.07 million, creating a potentially $177.34 million problem.

"There is no way the county of Wayne could make a decision to go to an alternative site with that potential exposure," Kaufman said. "The issue would have to be resolved in some way."

Evans has said his main concerns are whether Rock can build the jail complex in a timely fashion, whether the complex meets the county's needs and whether the county can't afford it.

One way to address that is what's known as a voluntary closing agreement program, or VCAP. Essentially, that allows the county to admit that it understands it is not using the bonds in the originally intended way, and that it accepts an as-of-yet unknown financial penalty, Kaufman said. The process typically takes up to five months, but the county is hoping for a resolution soon.

"The best metaphor is a plea bargain," Kaufman said. "We go in and admit that using this money at an alternative site would violate one of the rules, but we want to know what would be the penalty the IRS would issue if we did it, and then we know the extra cost for moving to an alternative site. "