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.
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| 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.
