River flooding threatens to close I-75 as evacuees make their way home

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A flooding river in North-Central Florida that threatens to close a 36-mile stretch of Interstate 75 continued to rise gradually overnight into Thursday. But, as of 8 a.m., it was still too soon to say when — or if — state transportation officials might close the road.

Thousands among the estimated millions of Floridians who evacuated for Hurricane Irma are continuing to return home this week. A decision to close I-75 — one of the primary north-south routes in the peninsula — would divert them all onto detours 200 or 300 miles off their original path, when heavy traffic and limited availability of gas have already been ongoing frustrations.

The area of concern is the little-known Sante Fe River north of Alachua — which rose drastically Monday and Tuesday into Wednesday as a consequence of Irma’s heavy rains that sparked historic-level flooding in Jacksonville on Monday.

The river runs under a bridge on I-75, and if it rises to a level that Florida Department of Transportation officials say is unsafe, they’ll shut down the interstate from I-10 in Lake City south to U.S. 441 in Alachua.

The Florida Department of Transportation alerted residents Wednesday morning of the prospect that the interstate could close. Officials with FDOT and the U.S. Geological Survey were on site to monitor the river and the bridge above it round the clock, as the Sante Fe rose throughout the day.

While Gov. Rick Scott’s office wouldn’t say how high the river would have to climb before FDOT would close the bridge, an official from the USGS told the Herald/Times they were informed by 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 57.07 feet as of 7:15 a.m. Thursday, within a foot of FDOT’s reported cut-off.

RELATED: “Irma leaves behind new threat: Rising flood water”

Meanwhile, drivers on Thursday should continue to expect to traffic jams and long delays in parts of Florida as they make their way home after the hurricane last weekend.

Tuesday appeared to be the worst of the returning traffic so far, with Wednesday seeming to show less intense congestion on the roads. But FDOT officials say “travelers should be prepared for significant delays” through Saturday.

Traffic jams have most frequently appeared on stretches of southbound I-75, I-95 and Florida’s Turnpike, westbound I-4 and eastbound I-10 — the main roadway arteries back through Florida.

As of 8 a.m., traffic congestion was reported on southbound I-95 and I-295 through and around Jacksonville. There were also delays reported on westbound I-4 near Sanford and on southbound I-75 near Tampa.

It looked like typical rush-hour traffic was hitting pockets of Tampa, Orlando and South Florida as Floridians begin returning to work and school in areas of the state, but there appeared to be no major backlogs yet that were visibly associated with the evacuating traffic returning.

It’s still early, though. On both Tuesday and Wednesday, the roads were clearest in the morning hours and became more crowded — with more logjams — by the afternoon hours.

Two typical bottlenecks where drivers can usually expect a delay are the I-10/I-75 interchange in Lake City, about 45 miles south of the Georgia line, and the interchange in Wildwood where I-75 meets Florida’s Turnpike in Central Florida.

As for the Sante Fe River and the threat to I-75, officials at the state Emergency Operations Center had estimated Wednesday evening the river was “nearing crest.” While it still crept higher overnight, how fast its rising has slowed compared to the rapid rise the river had on Monday and Tuesday, USGS data shows.

The Sante Fe rose in other areas nearby enough by Wednesday evening, though, that portions of two main highways in the region were forced to close.

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.

Because of the potential need to close I-75, FDOT had advised residents to consider alternative routes and 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.

The state plans to recommend those routes as detours in the event the vulnerable stretch of I-75 needs to be closed.

Earlier Wednesday, FDOT did warn closures and “extensive rerouting of traffic” could also hit U.S. 27, U.S. 41, U.S. 441, State Road 47 and possibly U.S. 121 in the area — which would affect their use as possible detours.

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.

Clark reported from the Herald/Times Tallahassee bureau.