Pennsylvania environmental officials are attempting to track the source of explosive levels of methane in two private water wells in a shale gas field in Dimock, Pennsylvania.
That in itself is not especially newsworthy. The small town in northern Susquehanna County has been the focus of state and national investigations since 2009, when gas linked to nearby drilling by Cabot Oil & Gas seeped into the aquifer and caused a water well to explode. It’s significant, however, that the recent problems emerged in the middle of a 9-square mile area where the DEP banned drilling four years ago due to chronic methane migration problems. It’s also significant that the agency allowed fracking to resume at two nearby gas wells.
| EPA technician collects samples at a Dimock home last year|
Photo James Pitarresi
Last August, Cabot Oil & Gas reached an undisclosed settlement with 32 of 36 Dimock families suing for damages related to pollution of their water wells. Other lawsuits are pending. Due to widely publicized concerns, the federal Environmental Protection Agency began its own investigation last year. After six months of testing, the EPA found elevated levels of arsenic, barium, manganese, or methane, in five of 64 water wells – roughly 8 percent. It concluded that the concentrations could pose health risks, but those risks were mitigated by treatment systems drilling companies had installed or planned for the homes. The federal Agency for Toxic Substances and Disease Registry is now following up with an evaluation of it’s own.
In recent weeks, investigators, responding to complaints, have found two new cases where methane concentrations in private water wells pose an explosion hazard, said Colleen Connolly, a spokeswoman for the DEP. The contaminated water supplies are near the Costello and Gesford gas wells. Those wells, drilled into the Marcellus Shale, were fracked last fall, Connolly said.
And this makes the story more than another gas-migration case. The industry has disputed claims that fracking – the use of pressurized chemical solution to break rock and release gas in deep formations – poses a threat to water tables above them. In fact, it has denied that it has ever happened. That denial is at the root of a national controversy that has raised the stakes on the outcome of ongoing investigations by the DEP and the EPA in Dimock and elsewhere.
It is known that methane migration can happen naturally in gas rich zones. It is also known that drilling (apart from fracking) can cause or intensify problems by opening pathways through the aquifer into pressurized zones below. The problem is managed by casing the well bore with cement to seal off the aquifer, a method that is effective but not foolproof.
Not do be confused with drilling, fracking is done to stimulate the flow of gas after the well bore has been cemented. It’s functionally and technically a separate process from drilling. The industry’s insistence that fracking cannot create pathways for pollution to reach the aquifer has drawn scrutiny in several controversial cases.
An EPA investigation in 2011 found water wells near fracking operations on the Wind River Indian Reservation in Pavillion, Wyoming were polluted with synthetic chemicals, glycols, alcohols, methane, and petroleum hydrocarbons “consistent with gas production and hydraulic fracturing fluids.” The drilling company implicated in the study, EnCana, has denied responsibility, and the industry is challenging the EPA conclusions.
In a lesser-known case, the Ohio Division of Mineral Resources Management concluded that fracking caused an explosion in Bainbridge in 2007. One house was destroyed and 19 other homes were evacuated due to high methane levels. According to the agency’s investigation, the problem arose when Ohio Valley Energy Systems Corp fracked the well without properly cementing the production casing.
The most recent problem in Dimock surfaced after a water well near a gas well turned turbid in early February, according to the DEP's Connolly. She declined to disclose the location, but residents report that crews have been working at two affected homes near the intersection of Carter Road and State Route 3023, which are also near gas wells that have been fracked.
Cabot Spokesman George Stark was unavailable for comment today. The company has blamed the problem on a frozen pipe used to vent methane gases, Connolly said.
The water wells have been taken off line, and methane concentrations have fluctuated since the problem began, Connolly said. Regulators have not reached conclusions about the cause of the problem, and they are continuing to monitor the work of Cabot, Connolly said. Cabot contracts Crews were at the site last week with a drilling rig used to service and inspect gas wells.
While there is relatively little documentation associating high volume hydraulic fracking to water pollution -- apart from spills and accidents related to handling fracking chemicals and waste above the surface before and after they are injected into the ground -- risks of methane migration from drilling are relatively well known. In September, 2009, the DEP issued a draft report that found methane migration from gas drilling, had “caused or contributed to” at least six explosions that killed four people and injured three others in Pennsylvania alone over the course of the decade preceding full-scale Marcellus development. The threat of explosions had forced 20 families from their homes. At least 25 other families have had to deal with the shut-off of utility service or the installation of venting systems in their homes. At least 60 water wells (including three municipal supplies) had been contaminated.