Photos: Newly active Texas sinkhole unearths forgotten fears

Daisetta: When the massive sinkhole first appeared in Daisetta in May 2008 (above), some residents had feared it might engulf their small Southeast Texas town. But after growing close to 600 feet (183 m) across and 75 feet (23 m) deep, it stabilized, swallowing up some oil tanks and several vehicles but sparing nearby homes. Some residents used humor to calm their fears, making “Sinkhole de Mayo” T-shirts, a reference to Cinco de Mayo. For others, the sinkhole, which eventually filled with water , became a new fishing spot.

But earlier this month, city officials announced the sinkhole had expanded after a long hibernation, renewing fears from some residents. Officials say there hasn’t been any significant expansion since the new growth was detected April 2, but they’re monitoring the sinkhole and keeping the public informed. In a preliminary report released Thursday, state researchers said the expansion was actually a new and smaller sinkhole that formed adjacent to the one from 2008.

“I don’t think (residents) should panic or anything. But it’s something that they should watch,” said Richard Howe, a private geologist with Houston-based Terra Cognita who's helping Daisetta officials monitor the sinkhole. Daisetta sits on a salt dome, a natural formation created below the ground over millions of years where oil brine and natural gas accumulate. Salt domes create good conditions where oil can migrate and accumulate, Howe said. This was the reason Daisetta became a booming oil town in the early 1900s.

But Howe said a cause for the 2008 sinkhole was never determined. A more comprehensive study could be done, but it would be costly and “a small town like this is not flush with cash,” he said. Howe, who also helped Daisetta in 2008, is working for the city on a volunteer basis. Howe suggested the underground cavern in the salt dome that first collapsed and formed the 2008 sinkhole likely expanded, creating a new sinkhole that seems to have merged with the original one.

In the preliminary report , the Bureau of Economic Geology, a research unit at the University of Texas, said the new sinkhole has a diameter of about 230 feet (70 m) and is about 30 feet (9 m) deep. The report said there was no indication the new sinkhole had impacted Farm-to-Market Road 770, the main roadway through the town.

The new sinkhole may or may not expand much, but more study is recommended “to better understand the cause ... to minimize risk associated with similar possible future events," according to the report by the bureau, which functions as the State Geological Survey.

Sinkholes tend to be common in regions where soluble rocks, including salt domes and limestone, can be dissolved by groundwater, according to the U.S. Geological Survey. Florida, for example, sits above limestone and is highly susceptible to sinkholes.

Howe said officials have placed steel posts 50 feet (15 m) apart in a pasture area near the sinkhole to monitor any changes in their elevation and to act “as an early warning if this thing continues to move south toward homes and buildings.” “This thing could be like this for another 15 years ... or it could be 100 years, or it could change tomorrow. It’s just no way to predict it,” said Howe, adding nothing can be done to stop the sinkhole if it continues expanding.

Daisetta City Secretary Joan Caruthers said officials are working to set up a website that will provide updates and are planning to hold a public meeting in the future. Caruthers said they want “a little more information” before scheduling the public meeting.

After the sinkhole appeared in 2008 (above), county commissioners asked the state to set up monitoring devices that could be an early warning system. Caruthers said she’s not aware if any such monitoring system from the state was ever set up. The sinkhole was monitored for several years after 2008, but there was no recent active monitoring by the city, she said.