Army Corps Expands Drilling Exclusion Zone Despite Its Own Study

The U.S. Army Corps of Engineers (USACE) recently announced it wants to expand a so-called drilling exclusion area around Joe Pool Lake Dam near Grand Prairie, Tex., from 3,000 feet to 4,000 feet. USACE presumably based its decision on a study that assessed various risks of oil and natural gas development.

USACE’s proposal to expand the no-drilling zone is curious, to say the least, since USACE’s own study actually indicates the current 3,000-foot restriction area is the recommended buffer. From the report:

“As mentioned already, an exclusion zone of 3,000 ft is recommended with regard to blowouts (p. 10)… A 3,000 ft exclusion zone seems reasonable for protecting the dam from surface events such as spills and explosions, although if surface spills are considered, surface locations for wells should have a considerable stand-off from the lakeshore as well to protect the water.” (p. 11)

But in USACE’s press release, the Corps appeared to reject what its own study had concluded:

“USACE has concluded the 3,000-foot exclusion zone at Joe Pool Dam does not sufficiently meet our minimal tolerable risk guidelines and therefore, poses a risk to the dam, the lake, and the public.”

Indeed, the USACE even acknowledges that its recommendations “are more conservative than the subject study recommends.”

Unfortunately, much of the early press coverage of the Corps’ decision simply repeated what USACE claimed. There was no explanation of how the study itself did not recommend expanding the buffer an additional 1,000 feet. Even the group that prompted the study, Westchester-Grand Prairie Community Alliance, was a bit confounded by the decision, as member Susan Read told

“I’m surprised they extended it beyond the 3,000. We just wanted them to enforce, maybe, what they had in place already.”

No Problems from Existing Wells

Interestingly, there are already existing wells within the USACE’s established buffer, which have not compromised the safety or integrity of dam. As the report notes:

“Joe Pool Dam and Lake are currently outside of the area of heavy development, but there are wells to within 3,000 ft (or a few closer) currently.” (p. 48)

Notably, the report found that there is no threat of water contamination from the fracking process itself:

“There is no geomechanically plausible mechanism for aquifer contamination directly from the Barnett shale via hydraulic fracturing…” (p. 5)

The report bases this conclusion on observations and geological realities:

“Theoretical and empirical data indicate that the hydraulic fracture treatments in the Barnett shale are largely contained within the formation. There are instances of some height growth, but there is no documented case of a fracture treatment propagating from Barnett depth toward the surface to contaminate an aquifer.  For a deep reservoir like the Barnett, there is as much as 6,000 feet of rock between the gas producing zone and closest surface aquifer. It is considered unlikely that the hydraulic fracture treatment could connect directly between the Barnett Shale and overlying, naturally fractured rocks that reach to the surface.” (emphasis added)

Arbitrarily Expands Injection Buffer

The Fort Worth USACE also indicated it would be “working to protect the project from the effects of induced seismicity by limiting injection wells within five miles of Joe Pool Dam.” Notably, this decision has nothing to do with the actual process of hydraulic fracturing, and fracking itself poses no credible threat to cause induced seismicity, according to the report:

“Geomechanically, the anticipated stress perturbations coming from drilling, hydraulic fracturing, gas extraction and related activities are not anticipated to be significant enough to reactivate any of these faults.” (p. 2)

“There is no documented case of induced seismicity beyond microseismic events to have occurred in the Barnett shale due to hydraulic fracturing.” (p. 9)

In fact, the report emphasizes only a slight risk of induced seismicity would come from injection wells near the dam.  But “although unlikely,” for precautionary reasons, that slight risk was taken into account in its decision:

“There are numerous injection wells in the Fort Worth Basin and only a few of them have been suspected of causing problems, but the fact that the earthquakes do occur suggests that more care should be taken in choosing injection well sites (avoid proximity to major pre-existing faults).” (p. 10)

“Given that an injection well can raise the pore pressure over a broad area (a reasonable radius of influence would be 1 km), the epicenter of an induced quake wouldn’t necessarily be centered at the well surface location. Combining all these factors and their uncertainty, a conservative exclusion zone for injection wells around Joe Pool Dam should be at least a 16,400 ft (5 km) radius.” (p. 72-73)

Although the study notes that a “conservative exclusion zone for injection wells” would be five kilometers (or just over three miles), the USACE decided to expand that buffer by an additional two miles anyway.

According to the Fort Worth Star-Telegram, the closest current injection well is nine miles from the dam. Grand Prairie’s city manager Tom Hart told the Dallas Morning News there is only one existing well site that would be affected by the expanded zone.

It’s also interesting that a 2012 USACE risk informed screening — which considered dam behavior, how well the dam meets current design criteria, as well as the potential consequences of dam failure — classified the dam as having “Moderate to High Risk characteristics” due to “potential embankment slope stability and erosion issues along with downstream consequences.”

Essentially, the issues identified have nothing at all to do with oil and gas development and instead are issues that fall exclusively on USACE’s shoulders. Yet, four years later, USACE arbitrarily expands its drilling exclusion area 1,000 feet despite a study that recommended such a move was unnecessary.

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