The Stone Arch Bridge may close this summer if state funding isn't allocated by the end of the waning legislative session to repair its deteriorating foundation, leaders of the Minneapolis Park Board and the Minnesota Department of Transportation warned Friday.

They're asking lawmakers to include $13 million for bridge repairs in the bonding bill that is still working through the Legislature.

"We still have 60 hours and counting down until Sunday night for them to pass a bill," Park Board Commissioner Chris Meyer said at a Friday news conference held on the bridge. "If we don't get funding for the bonding bill now, the risk of needing to close the bridge for safety reasons will increase."

MnDOT owns the popular 135-year-old pedestrian bridge over the Mississippi River in downtown Minneapolis, but the Park Board handles the maintenance of the trail. According to a 2017 MnDOT inspection, the bridge is overdue for major work and needs all new mortar and some new stone.

If funding doesn't come by the session's end, MnDOT says it will not have enough money to continue annual inspections and maintain the structure.

Gov. Mark Dayton had included the $13 million for inspection, design and construction of the bridge in his 2018 capital budget proposal released in January, but no money has been allocated in either the House or Senate bills, Meyer said.

To the millions of runners, cyclists and walkers that pass through the human highway yearly, the bridge's poor condition is not noticeable. It's the foundation of the structure that is in question, said MnDOT state bridge planning engineer Amber Blanchard.

The bridge was built in the late 1800s using stone and mortar. Blanchard said workers need to do what's called mortar repointing, which requires chipping away 4 to 5 inches of crumbling mortar and replacing it with new material.

The process is easier to do in dry conditions, so workers will likely have to set up barriers around the bridge's bases to block the river's flow.

"Pieces of mortar are falling off and really it's disintegrating and disappearing from the stone," Blanchard said. "If we don't do anything the deterioration will continue. We may have to close it sometime this summer."

Meyer said that there is no other way to get the much-needed funding.

For at least four years, MnDOT leaders have asked legislators for funds to repair the foundation without ­success.

In 2016, they asked for $2.5 million for repairs. Costs have increased dramatically in two years, park board officials say.

"Stone replacement costs alone have doubled since previous inspections," according to a Park Board news release.

The last time the bridge's foundation was repaired was in 1965. Had the bridge been part of the state's trunk highway system, it would have already been repaired, Blanchard said.

She added that the agency could make do with $1 million for continued inspections and to prepare for rehabbing the bridge.

However, the $1 million "doesn't address the underlying issue of the deterioration of the mortar above and below the water level," said Commissioner Charlie Zelle. "The longer we wait, we risk continued deterioration and significantly more expensive repairs. The time to act is now."