Two lanes of I-4 remain closed

A creeping army of sinkholes continues to invade the area, threatening to swallow homes, closing a two-mile stretch of U.S. 27 near Lake Wales and potentially being the cause of a large depression on Interstate 4 that shut down three lanes near Plant City and turned the highway into a parking lot.

Parts of at least 10 roads were shut down or partially blocked today, with little relief in sight. Department of Transportation workers were using ground-penetrating radar on I-4 and taking soil samples late into the night to find out what caused the "roadway irregularity'' on the eastbound lanes near the Branch Forbes Road exit.

The DOT shut down two lanes of I-4's four eastbound lanes in the mid-afternoon, backing up traffic for miles. By mid-evening, the agency had shut down a third lane. The lanes will be shut down at least through Wednesday morning's commute.

Thousands of motorists were caught in the jam, including Chris Drummond, who was trying to get home to Lakeland. Talking at a quick pit stop at a gas station in Plant City, Drummond was obviously frustrated at what had already been a 2 and a half hour commute.

"Oh, outstanding,'' he said when asked how his trip had been. "My fun meter is pegged."

Work crews were expected to labor overnight and into the morning.

A preliminary study showed a 1 1/2- to 2-inch dip in the roadway, covering part of the center and left lanes, said Marian Scorza, a FDOT spokeswoman.

DOT officials were not calling it a sinkhole.

"Right now it's a depression in the roadway," Scorza said at about 6 p.m. "There is no hole."

At 9:30 p.m., she said, "They haven't found anything they can assess right now. They can't assess that it's a sinkhole. They don't know what it is."

With an estimated 47,000 vehicles a day using eastbound I-4, transportation officials are asking motorists to be patient. The agency did not immediately create an official detour, saying motorists tend to head en masse to alternate routes and clog them as well.

Workers will be taking core samples from underneath the roadway to try to determine what caused the depression and what needs to be done to fix it, Scorza said.

"If you hit a dip at 70 mph, it's not a good thing. So we need to know what's going on underneath the roadway."

The I-4 disruption could cause havoc and delays for area businesses that depend on that artery to ship and receive goods.

Andy Fobes, a spokesman with the Tampa Port Authority, said on average 10,000 to 11,000 commercial trucks come in and out of the Port of Tampa each day, delivering or receiving containers, cement, building products, fuel and a variety of cargo.

"It would be a sticky situation and one that would have to be remedied fairly quickly," Fobes said.

He said commercial truckers will have to use alternate routes if I-4 eastbound lanes remains closed for a long period.

"The trucks would have to find another route and try to mitigate any loss of time in reaching their destination," Fobes said.

While the exact cause of the problem on the interstate is still uncertain, sinkholes in the last two days have shut down several other stretches of road in the Plant City area, not far from the I-4 dip in the road.

Sinkholes have forced the closure of at least part of nine roads in northeastern Hillsborough, mostly in the Plant City area.

And two sinkholes discovered early today near Lake Wales closed a two-mile stretch of U.S. 27 between State Road 60 and Country Road 640. The larger sinkhole is about 65 feet wide and 20 feet deep, DOT spokeswoman Cindy Clemmons-Adente said.

Officials do not know how long U.S. 27 will be shut down. Clemmons-Adente said crews could start filling the cavity and repairing the road within 24 to 48 hours.

The sinkholes have mostly been appearing since Monday in Hillsborough and Polk counties, where groundwater levels plummeted as farmers pumped millions of gallons of water to protect oranges and strawberries from freezing temperatures.

The aquifer level in some places fell 60 feet since the string of freezing nights started, said Robyn Felix, spokeswoman for the Southwest Florida Water Management District.

She could not say whether the pumping caused the sinkholes but said a rapidly falling aquifer can be a trigger for sinkholes.

"Sixty feet is a fairly large drop," she said. "To be pumping night after night is unusual."

Sinkholes form when water dissolves soft limestone and creates an underground cavity. Pressure from groundwater in the cavity supports the layer of earth between the cavity and surface, said Tony Gilboy, geologist with the water management district.

When the groundwater is removed, the top of the cavity collapses, creating the sinkhole.

"The cavities that exist in the limestone are already there. They are part of Florida," Gilboy said. "The catalyst is lowering of the water level that holds things up."

Unless farmers and grove owners resume heavy pumping, new sinkhole formation should slow or stop, Gilboy said.

Berry farmers aren't the only ones using water during the freeze, the head of the Florida Strawberry Growers Association said.

Ted Campbell, executive director and spokesman, said the freezing temperatures prompted farmers, nursery owners and homeowners to run irrigation systems, drip hoses and run water to keep crops, plants and outside water lines from freezing.

"The strawberry grower uses the majority of the water during freezing temperatures, no question," he said. "But we all are part of the mix."