DALLAS - Swarms of earthquakes in shale-gas producing regions have raised concerns about possible damage to aging infrastructure in the Southwest.
In Oklahoma, state Department of Transportation Director Mike Patterson told the state Transportation Commission on April 7 that he was consulting experts from California to assess the impact on bridges.
"We don't know what it's doing to our roadways and, specifically, we don't know what it's doing to our bridges," Patterson told the commission. "In the last week, Oklahoma -- not the United States, but Oklahoma -- has experienced 11% of all earthquakes in the world."
The Oklahoma Geological Survey has identified 1,356 Oklahoma earthquakes so far this year, including 142 in the first week of April.
"If this is the new norm, then we need to get on board with how to design bridges that can possibly withstand the earthquake, whenever that might come," Patterson said.
Patterson's presentation to the commission came as Oklahoma legislators considered diverting funds from the transportation budget to public schools in the wake of past and proposed tax cuts. On April 2, the state Senate Appropriations Committee approved a plan to reduce by half the $59.7 million increase approved in 2006 to maintain roads and bridges.
Over the past eight years, ODOT's Rebuilding Oklahoma Access and Driver Safety fund financed replacement or rehabilitation of hundreds of bridges and rehabilitated hundreds of miles of roadway.
"What they voted on in there would annihilate the governor's bridge program," Bobby Stem, executive director of the Oklahoma Association of General Contractors, said in a prepared statement after the vote.
A recent analysis of bridges in the National Bridge Inventory showed Oklahoma had 414 bridges that were both structurally deficient and "fracture critical."
ODOT spokeswoman Terri Angier said inspectors only found earthquake damage to a bridge one time, after a magnitude 5.6 temblor in 2011 with an epicenter near the town of Prague. That quake was the largest in the state's history. Most of the recent quakes have been relatively small, measuring magnitude 3 or less.
In addition to damaging the bridge in 2011, the Prague quake destroyed 14 homes, damaged other buildings, injured two people and buckled pavement, according to a state report.
Another bridge between the towns of Lexington and Purcell, Okla., has been closed since cracks were found in the 76-year-old structure, but the damage has not been attributed to earthquakes.
Gov. Mary Fallin is seeking federal assistance for businesses in the two towns Lexington affected by the bridge closure.
Several businesses in Lexington are reporting a 30% to 50% decline in sales as a result of the bridge closure, Fallin wrote in a letter to the Small Business Administration.
"The major decline in revenue has led to businesses moving or closing their doors permanently in order to avoid further indebtedness," Fallin wrote. "Many of these businesses are considering permanent closure as they can no longer afford to maintain their businesses due to the bridge closure," Fallin wrote.
Patterson said Oklahoma has 1,500 bridges that are over 80 years old that were designed to last 50 years.
In Texas, the state Railroad Commission, which regulates the oil and gas industry, announced the hiring of a seismologist on March 28 after protests from residents of North Texas over a series of earthquakes in the Barnett Shale play.
The seismologist is David Craig Pearson, a former team leader for a Los Alamos National Laboratory seismic experimental field team, who also holds a doctorate in geophysics from Southern Methodist University.
"My objective is to develop a broad understanding of the impact of oil and gas extraction activities on the day-to-day lives of Texas residents," said Pearson, who began work April 1. "I believe the Railroad Commission must be able to quickly and factually determine the accurate location of all earthquakes in the state and be able to determine the cause of earthquakes, be they natural or man-made."
After a series of earthquakes in North Texas last year, civil engineers inspected several dams but no signs of damage were reported.
The Eagle Mountain Reservoir manager made daily inspections, according to Chad Lorance, spokesman for the Tarrant Regional Water District. Engineers made crest surveys of the dams to look for changes.
Nearby Dallas-Fort Worth International Airport halted the use of injection wells for hydraulic fracturing waste on airport property after last year's earthquakes.
One of the most recent earthquakes centered near Enid, Okla., measured 4.5 on the Richter scale and was felt in Wichita, Kan., and the Kansas City area. In two days, March 29-30, USGS recorded 11 Oklahoma earthquakes ranging in magnitude from 2.7 to 4.5.
In Arkansas, the state Oil and Gas Commission halted injection wells from coming on line in 2011 after a series of earthquakes, the largest of which was 4.7 on the Richter scale. The Arkansas quakes were particularly worrisome because they were near the New Madrid seismic zone, which triggered some of the strongest earthquakes in U.S. history in 1811 and 1812.
Fourteen families in central Arkansas have filed a lawsuit against oil and gas companies that operated the injection wells.
In Arkansas, the state Highway Transportation Department covered 40% of the cost of a $255 million seismic retrofit of the Hernando de Soto Bridge that carries Interstate 40 across the Mississippi River to Memphis.
The Tennessee Department of Transportation has provided the bulk of the bond finance for the project, which began in 2000. The crossing is located less than 100 miles from the New Madrid Fault.
On April 11, Ohio announced new restrictions on injection wells after several earthquakes, including a 2011 temblor near Youngstown that measured 4.0 on the Richter scale. The new rules require companies to install seismic monitors if hydraulic fracturing occurs within three miles of a known fault or an area which has recently experienced quakes.
In March, drilling was suspended at the site of two earthquakes in Poland Township in northeast Ohio, 70 miles southeast of Cleveland.
In response to media coverage of the earthquakes, the Interstate Oil and Gas Compact Commission in Oklahoma City last month announced a multi-state agreement to share information about findings by geologists in Kansas, Ohio, Oklahoma and Texas. The commission is an oil and gas industry group that promotes the rights of states to regulate energy exploration and production.
Regarding the earthquakes, Gerry Baker, associate executive director of the commission, said, "the states have demonstrated that they're willing to take a closer look at the issue itself."
However, Baker said that the interstate program on earthquakes will not have any formal structure and will serve as a "central clearinghouse" of information.
"We had heard from a number of states that had projects underway," Baker said. "And people would say 'I wonder what Oklahoma's doing?' or 'I wonder what Ohio's doing?' It was just sort of a common understanding that we should be talking to each other on this particular issue."
Scientists have long known about the relationship between injection wells and earthquakes, said Scott Tinker, director of the University of Texas Bureau of Economic Geology.
"It's like saying that cars cause car wrecks," Tinker said.
The injection wells pump the fluid used to fracture a horizontal gas or oil well back into the ground. If the fluid is pumped into a fault, it can act as a lubricant, causing a seismic slip, according to Cliff Frohlich, a seismologist at UT who studied the earthquakes.
Each well uses about 4.5 million gallons of water mixed with chemicals and sand to fracture shale rock formations, allowing gas or oil to flow into the well.
"One way to look at this is that Texas is a huge laboratory," Frohlich said. "Since we're producing petroleum in places that we haven't been before, this is a phenomenon that we need to understand, but it's not appropriate to say it's vastly dangerous."
