TALLAHASSEE — A rapidly rising river — caused by the historic flooding that Jacksonville saw Monday — threatens to force 36 miles of Interstate 75 to completely shut down in north-central Florida, from Interstate 10 in Lake City south to U.S. 441 in Alachua.
The swelling Santa Fe River, which closed two nearby highways late Wednesday, was the latest headache for motorists traveling back south after evacuating because of Hurricane Irma.
Stretches of U.S. 41 and U.S. 27 north of High Springs — on the border of Alachua and Columbia counties — were blocked off because of rising water under bridges that spanned the Sante Fe, state officials said. Drivers were re-routed on local detours.
Officials said late Wednesday that I-75 would remain open, but it could still be closed if the Santa Fe continued its rise. An estimate of when it would close was not available.
Closing this stretch of I-75 would force drivers onto long detours that could add as much as 200 or 300 miles to an already-grueling trip home.
The I-75 bridge over the Sante Fe River near mile marker 408 "remains safe and passable," state transportation officials said earlier Wednesday.
"The river is expected to crest at historic and unprecedented levels, presenting a potential threat to the safety of travel on this bridge," the Florida Department of Transportation said in a statement. About that time, the river under I-75 had "rapidly risen 15 feet within the past 36 hours due to the heavy rainfall over North Florida from Hurricane Irma."
McKinley Lewis, a spokesman for Gov. Rick Scott, said FDOT bridge inspectors and the U.S. Geological Survey were monitoring river levels at the bridge around the clock.
An official from the USGS told the Times/Herald it was informed by the FDOT the interstate would have to be closed at a river level of 58 feet.
According to the USGS, the Sante Fe River at O'Leno State Park — less than a mile to the west of I-75 — measured at 56.61 feet as of 4:15 p.m. Wednesday.
The flood threat at the bridge was an additional reason state officials urged residents not to drive home yet Wednesday.
But thousands still did, and the state advised them to plan accordingly for long waits and traffic jams.
"Travelers should be prepared for significant delays" through Saturday, the FDOT advised.
Heavy traffic was reported on southbound I-75 as early as 5:30 a.m. Wednesday — with conditions by early evening showing continued pockets of moderate to severe congestion from south of Lake City through Gainesville and Ocala into Wildwood.
Gainesville traffic officials advised drivers Tuesday to "expect delays (and) consider alternate routes."
The FDOT advised residents to consider back-road highways — such as U.S. 19, U.S. 98 and U.S. 27 (where it was still open) along the Big Bend from south of Tallahassee to Ocala or Tampa Bay, or I-10 east to Jacksonville and south on I-95 and I-4 from there.
U.S. 301 — which crosses the state on a path southwest from Jacksonville to Tampa — was not recommended as a detour route, because it's used as a supply road to ferry fuel and other necessities into the state, Lewis said.
Farther south, the interchange in Wildwood where I-75 meets Florida's Turnpike is a headache on a normal day, but the bottleneck has been especially hellish to navigate as evacuees fled and now return through Central Florida's north-south routes.
It was backed up again for several hours on Wednesday.
Another trouble spot — the I-10/I-75 interchange in Lake City, about 45 miles south of the Georgia line — also had another day of congestion as evacuees made their return from Georgia and Alabama. I-10 eastbound also had heavy traffic, particularly through Tallahassee.
Occasional gridlock hit westbound I-4 out of Orlando and southbound I-75 into the Tampa Bay area near Spring Lake and farther south near Temple Terrace and Brandon. By early evening, the heavy traffic had filtered down to the Bradenton area, too.
Meanwhile, the southbound turnpike had some congestion through Orlando, near Port St. Lucie and — during morning and evening rush hour — through Palm Beach County and southward, but the roadway was largely free-flowing most of the day.
Southbound I-95 along Florida's Atlantic Coast had heavy traffic reported on the I-295 bypass around Jacksonville and north and south of the city. There was also some evening rush-hour traffic through Fort Pierce and Broward County.
In Georgia, southbound I-75 lanes were log-jammed on Tuesday from the Floridians seeking to return, and that returned by midday Wednesday but not as heavy. Congestion was reported between Atlanta and Macon. The stretch from Macon south to the Florida line appeared to have no delays.
Tolls remain suspended all throughout Florida and on Georgia's I-75 express lanes in Atlanta.
Contact Kristen M. Clark at email@example.com. Follow @ByKristenMClark