Corps worries that fracking gas wells might hurt dams
By RANDY LEE LOFTIS
Environmental Writer
Published 31 July 2011 10:50 PM
In most of Texas and several other states, the corps has declared a 3,000-foot buffer around its dams and water-control structures within which it will not allow new wells, drilling pads or pipelines.
The corps also has a national team studying potential risks to dam safety from minerals extraction.
Hydraulic fracturing, or fracking, in which drillers inject millions of gallons of water at extreme pressures to fracture rock and release gas, tops the corps’ list of worries.
The corps wants to know whether increased geological pressures from fracking could cause differential movement, or shifts along natural faults, weakening dam foundations.
“That could precipitate a fairly quick failure if it was not detected in time,” Branch said.
Two less worrisome possibilities are also under review. One is whether extracting large volumes of gas beneath or near a dam might make rock and soil subside.
Another is whether huge amounts of liquid waste from drilling, pumped into disposal wells, can trigger earthquakes.
Questions about dam safety could add another potential complication to shale gas, which has become a major source of natural gas nationwide.
The combination of fracturing and horizontal drilling – running pipe a mile or more from the wellhead to reach the gas – has made possible tens of thousands of new wells, including in North Texas’ Barnett Shale<
http://topics.dallasnews.com/topic/Barnett_Shale> region.
At least in the case of dam safety, the corps’ questions suggest there might be little or no research supporting blanket assurances that the practice poses no public risk.
It also shows that the government has been slow to study the potential threat.
New wells have been drilled or permitted within the 3,000-foot zone around Joe Pool Lake’s dam, for example, but only recently has the corps responded to complaints that wells might harm dams.
Federal jurisdiction is limited by the corps’ incomplete ownership of surface title and mineral rights beneath its own reservoirs – decisions made decades ago to save money.
For that reason and others, including the nearly complete lack of scientific research to prove or disprove a risk, any national policy on wells near dams seems far off.
Caution advised
Spokeswoman Ramona Nye said in an email the agency was not aware of cases in which oil or gas wells harmed dams.
Texas has no general rule keeping wells a certain distance from dams but would consider a scientifically and factually valid request to do so from the corps, Nye said.
In 2009, the Railroad Commission set a no-drilling buffer zone around an underground gas-storage depot in Jack County, she said.
The organization says on its website that “a comprehensive set of federal, state<
http://topics.dallasnews.com/topic/Arkansas_State_University>, and local laws addresses every aspect of exploration and production operations. These include well design, location, spacing, operation, water and waste management and disposal, air emissions, wildlife protection, surface impacts and health and safety.”
A check of institute publications on fracking did not turn up discussions of dam safety.
Two dam safety experts said they believe the corps is asking valid questions.
“Until the science involving any short- and long-term relationship between hydraulic fracturing and foundation destabilization, dam safety and reservoir stability is better understood,” he said in an email, “it is my general opinion as a hydraulic engineer that we should approach hydrofracturing in the vicinity of these structures very cautiously.
“This wisdom is especially important for hydrofracturing around high-hazard classes of dams.” A high-hazard dam is one with great potential for loss of life and property in case of a failure. It does not mean that a dam failure is likely.
“It seems reasonable that the corps is researching this issue,” Wright said, adding that the search for answers could be long and complex.
“I am pleased that the corps takes the position of placing public safety of paramount importance. I hope everyone would be as conscientious.”
Marc McCord of Dallas, an opponent of fracking, also welcomed the corps’ interest in possible threats to its dams.
However, after talking with corps officials for months about natural-gas wells near Joe Pool Lake’s dam, he said he’s seen little movement toward action by either federal or Texas agencies.
“We have multiple agencies failing to enforce the law and each blaming it on another so that nothing is done to protect the general public from commercial enterprises that seek to profit at citizen expense,” McCord said.
Most of the public dispute over the expansion of natural-gas drilling has been over fracking’s possible water-quality impacts.
The Texas Railroad Commission and the gas industry say there is no documented case of fracking polluting drinking water. Environmentalists dispute that.
Increased pressures
The corps’ concern with gas wells isn’t over water quality.
“Ours is specifically associated with the safety and integrity of our projects,” said the corps’ Branch. “It’s a different way of looking at it than most folks have done in the past.”
Fracking usually takes place thousands of feet underground, so deep that many experts say it can have little or no effect near the surface.
But corps experts have envisioned a scenario in which naturally occurring faults might transfer the high-pressure force of fracking upward toward a dam’s foundation.
“They’re basically changing the stress state of the existing geology,” Branch said. “You’ve got the geology as it exists today, and they’re going in and changing that by increasing the pressures that are in that.
“And those increased pressures are associated with those high pressures used as part of the hydrofracturing process.”
The weight of a reservoir’s water also applies great pressure to the earth, but in a uniform load rather than the concentrated force of fracking, Branch said.
“The fracture pressures they’re using are in the neighborhood of 8,000 pounds per square inch, and that’s a much more significant load than you get from the weight of the pool,” she said.
Potential damage to a dam from differential movement of the earth shifting along a fault would probably be gradual, allowing repairs as it happens, Branch said. But it could be quick, posing immediate risks, she added.
“We know that based on experiences elsewhere, these are concerns that have been noted,” Branch said. “That’s why we want to make sure that we fully understand the mechanisms that are developed so we can develop appropriate policy to address those.”Finding those answers will be complicated because every dam has different local geology. The variations may be great enough to prevent the adoption of a national buffer zone to cover all federal dams.
The 3,000-foot buffer that Brig. Gen. Thomas Kula, commander of the corps’ Southwestern Division, ordered March 17 is not impermeable. It does not prevent wells on land where the corps did not obtain ownership or mineral rights when it built a dam and reservoir.
No current law or rule lets the corps ban all drilling on land it does not control through ownership or mineral rights, Kula noted in his order.
Kula ordered corps offices in his division to examine oil and gas projects within 3,000 feet of a corps dam or water-control structure. Regardless of ownership, if the agency determines that a well would endanger dam safety, it can take legal action.
McCord, the Dallas environmentalist who has pressed the corps to take a tougher stance on wells near its dams, said corps officials told him some companies had complied voluntarily with the 3,000-foot buffer zone, but others had not.
“This leads me to wonder why no governmental agency is doing its job in regulating the oil and gas industry by forcing compliance with legal restrictions on their operations,” he said.
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