EPA links Hydraulic Fracturing to Drinking Water Contamination

The drilling industry and policymakers may no longer be able to claim that "there has never been a single proven case of ground water pollution associated with hydraulic fracturing."

The EPA has released a preliminary report documenting aquaifer contamination and points a finger towards gas production practices. Here's the EPA press release, links to the report and related coverage.

EPA Releases Draft Findings of Pavillion, Wyoming Ground Water Investigation for Public Comment and Independent Scientific Review
 Release Date: 12/08/2011 Contact Information: EPA HQ: Larry Jackson, 202-564-0236, jackson.larry@epa.gov; EPA Region 8: Richard Mylott, 303-312-6654, mylott.richard@epa.gov

(Denver, Colo.–December 8, 2011) The U.S. Environmental Protection Agency (EPA) today released a draft analysis of data from its Pavillion, Wyoming ground water investigation. At the request of Pavillion residents, EPA began investigating water quality concerns in private drinking water wells three years ago. Since that time, in conjunction with the state of Wyoming, the local community, and the owner of the gas field, Encana, EPA has been working to assess ground water quality and identify potential sources of contamination.

EPA constructed two deep monitoring wells to sample water in the aquifer. The draft report indicates that ground water in the aquifer contains compounds likely associated with gas production practices, including hydraulic fracturing. EPA also re-tested private and public drinking water wells in the community. The samples were consistent with chemicals identified in earlier EPA results released in 2010 and are generally below established health and safety standards. To ensure a transparent and rigorous analysis, EPA is releasing these findings for public comment and will submit them to an independent scientific review panel. The draft findings announced today are specific to Pavillion, where the fracturing is taking place in and below the drinking water aquifer and in close proximity to drinking water wells – production conditions different from those in many other areas of the country.

Natural gas plays a key role in our nation’s clean energy future and the Obama Administration is committed to ensuring that the development of this vital resource occurs safely and responsibly. At the direction of Congress, and separate from this ground water investigation, EPA has begun a national study on the potential impacts of hydraulic fracturing on drinking water resources.

“EPA’s highest priority remains ensuring that Pavillion residents have access to safe drinking water,” said Jim Martin, EPA’s regional administrator in Denver. “We will continue to work cooperatively with the State, Tribes, Encana and the community to secure long-term drinking water solutions. We look forward to having these findings in the draft report informed by a transparent and public review process. In consultation with the Tribes, EPA will also work with the State on additional investigation of the Pavillion field.”

Findings in the Two Deep Water Monitoring Wells:
EPA’s analysis of samples taken from the Agency’s deep monitoring wells in the aquifer indicates detection of synthetic chemicals, like glycols and alcohols consistent with gas production and hydraulic fracturing fluids, benzene concentrations well above Safe Drinking Water Act standards and high methane levels. Given the area’s complex geology and the proximity of drinking water wells to ground water contamination, EPA is concerned about the movement of contaminants within the aquifer and the safety of drinking water wells over time.

Findings in the Private and Public Drinking Water Wells:
EPA also updated its sampling of Pavillion area drinking water wells. Chemicals detected in the most recent samples are consistent with those identified in earlier EPA samples and include methane, other petroleum hydrocarbons and other chemical compounds. The presence of these compounds is consistent with migration from areas of gas production. Detections in drinking water wells are generally below established health and safety standards. In the fall of 2010, the U.S. Department of Health and Human Services’ Agency for Toxic Substances and Disease Registry reviewed EPA’s data and recommended that affected well owners take several precautionary steps, including using alternate sources of water for drinking and cooking, and ventilation when showering. Those recommendations remain in place and Encana has been funding the provision of alternate water supplies.

Before issuing the draft report, EPA shared preliminary data with, and obtained feedback from, Wyoming state officials, Encana, Tribes and Pavillion residents. The draft report is available for a 45 day public comment period and a 30 day peer-review process led by a panel of independent scientists.

For more information on EPA's Pavillion groundwater investigation, visit: http://www.epa.gov/region8/superfund/wy/pavillion/index.html

Related News Coverage
Feds Link Water Contamination to Fracking for the First Time
(ProPublica 12/8/11)
E.P.A. Links Tainted Water in Wyoming to Hydraulic Fracturing for Natural Gas
(NYTimes 12/8/11)
EPA investigators connect fracking to groundwater pollution
(PghTribReview 12/9/11)

TEAM 2012 Pipeline Approved

Texas Eastern Appalachia to Market Expansion (TEAM)

Project Status: Regulatory Review

TEAM 2012 Project

  • Location: Greene, Fayette, Franklin Adams Counties, Pennsylvania
  • Capacity: 200 million cubic feet per day
  • Ownership: 100% Spectra Energy
  • Project Completion Date: November 2012
  • FERC Docket #CP11-67-000

Agreements in place

Spectra Energy, along with Range Resources and Chesapeake Utilities, have executed agreements to deliver up to 190 million cubic feet per day of Marcellus natural supply along our Texas Eastern Transmission, LP (Texas Eastern) system to the Northeast United States by November of 2012. We are happy to be working with these 2 companies and appreciate they recognize that our Texas Eastern system is in place and ready to be efficiently expanded to bring new supply to market.

Proposed Detailed Scope of Work

  • Addition of approximately 1.8 miles of 36-inch diameter natural gas pipeline generally within or adjacent to the existing Texas Eastern pipeline easement in Greene County, PA west of the Monongahela River.
  • Addition of approximately 3.2 miles of 36-inch diameter natural pipeline generally within or adjacent to the existing Texas Eastern pipeline easement in Fayette County, PA east of the Monongahela River.
  • Replacement of an abandoned 24-inch diameter pipeline with a new 36-inch diameter natural gas pipeline for approximately 7.3 miles eastward toward the Heidlersburg Compressor Station in Franklin County, PA. This replacement will generally be within or adjacent to the existing Texas Eastern pipeline easement.
  • Replacement of an abandoned 24-inch diameter pipeline with a new 36-inch diameter natural gas pipeline for approximately 4.00 miles eastward toward the Marietta Compressor Station in Adams County, PA. This replacement will generally be within or adjacent to the existing Texas Eastern pipeline easemen.
  • Replacement of a 24-inch diameter pipeline with a new 36-inch diameter natural gas pipeline for approximately 1 mile in Futton and Franklin Counties. This replacement will generally be within or adjacent to the existing Texas Eastern Pipeline easement.
  • Addition of approximately 26,000 horsepower (HP) at the existing Bedford Compressor Station and associated work in Bedford County, PA. In addition, 2 existing compressor units will be increased in horsepower by 3,300 HP each. 9 reciprocating will be abandoned in place, retiring 11,880 HP.
  • On Jan 25, 2011, we filed an application for a Certificate of Public Convenience and Necessity and Order Approving Abandonment authorizing the installation, construction, ownership, operation and maintenance of its TEAM 2012 Project in FERC Docket No. CP11-67-000. For further information, please see FERC’s pamphlet entitled “An Interstate Natural Gas Pipeline on My Land? What Do I Need to Know?” or visit FERC’s website (www.ferc.gov). You may also review hard copies of our application at the following locations.

http://www.prnewswire.com/news-releases/spectra-energy-corp-receives-ferc-app...

Visit the U.S. Energy Information Admistration for more maps and information about natural gas pipelines.

Another 'safe spill' into our drinking water -- Inadvertant Returns?

Another spill into our region's drinking water sources. And more lame coverage and fact-checking of science-based claims. 

"Bentonite is a form of impure clay that easily absorbs water and is used to facilitate gas and oil well drilling."  Absorb water, is that all the drilling industry uses it for? 

Here's the article.

Gas-drilling gel spills into northwestern Pa. creek
Thursday, November 17, 2011
The Associated Press

JOHNSONBURG, Pa. -- A company has halted Marcellus drilling in one northwestern Pennsylvania town after a kind of clay used to expedite the process spilled into a local reservoir.

Hunt Marcellus Operating Co. tells the Bradford Era that it stopped drilling in Johnsonburg after some bentonite gel was released into Silver Creek and made its way into a drinking water reservoir controlled by the Johnsonburg Municipal Authority. Bentonite is a form of impure clay that easily absorbs water and is used to facilitate gas and oil well drilling.

It wasn't immediately clear how much of the substance got into the reservoir. But water authority chairman Eric Poague says the substance is not expected to affect the safety of the water -- though it could make it cloudy -- because bentonite is a "non-toxic substance that comes from the earth."

********

Sure Bentonite clay  is "a non-toxic substance that comes from the earth" -- it is also known as "Haliburton Gel." But how is bentonite being used by the gas drilling industry? 

Bentonite clay is a super absorbant powder/clay substance used in multiple ways -- in drilling mud slurries, to soak up chemical/hydrocarbon spills.  Some say that highly concentrated flowback water and drill cuttings are being treated with bentonite clays which turn this drilling waste into a semi-solid slurry 'frackwater goo'  that can then processed as part of the solid waste stream and sent to landfills. 

According to the Oil and Gas Accountability Project, “drilling fluids or muds are made up of a base fluid (water, diesel or mineral oil, or a synthetic compound); weighting agents (most frequently barite is used); bentonite clay to help remove cuttings from the well and to form a filter cake on the walls of the hole; chrome lignosulfonates and lignites to keep the mud in a fluid state; and various additives that serve specific functions, such as biocides, diesel lubricants and chromate corrosion inhibitors….Drilling muds that circulate through the well and return to the surface may contain dissolved and suspended contaminants including cadmium, arsenic, and metals such as mercury, copper and lead; hydrocarbons; hydrogen sulfide and natural gas, as well as drilling mud additives, many of which contain potentially harmful chemicals (e.g., chromate, barite).” (http://www.earthworksaction.org/pubs/OGAPMarcellusShaleReport-6-12-08.pdf)

  * * *

A little more digging into the incident (see comment below) brings up the industry phrase "Inadvertent Returns" that occur during the HDD drilling of natural gas pipelines which go under streams, wetlands and other kinds of enviromentally sensitive areas where the "cut and cover" trench option is not doable. Seems like they were drilling to place a pipeline under Silver Creek, and these kind of blowout incidents of bentonite clay based slurries are not uncommon.  The acticle for the really curious.

Inadvertent Slurry Returns during Horizontal Directional Drilling: Understanding the Frequency and Causes.

I feel a pricking in my thumbs...shale gas this way comes

Coming from Pittsburgh to Bristol, I thought I'd have a respite from shale talk...

Turns out Britain looks to be sitting on 2x the cubic feet of recoverable gas that the Marcellus contains.  The Bowland and Lias plays are poised to become to household names.  

Residents in the historic spa town of Bath are concerned because of an exploratory permit to frack near the source of the ancient Roman spring,  a UN World Heritage site.  Drilling companies supply Parliament with long reports and testimony abut the safety and excellent regulatory structures Britain already has in place to safely develop this low carbon emitting energy resource. There has never been a case of groundwater contamination in the US they claim. Economically depressed, former coal-mining regions in Wales are delighted at the prospect of jobs and economic revival. Investors scurry for insider buys and leasing control -- who will supply the sand, pipe and labour? Environmentalists fear well water and aquifer contamination.  The discussion has not yet turned to phase 2 impacts -- the pipeline and compressor infrastructure and its impacts on air quality, ecosystem fragmentation, and the loss of bucolic QOL and tourism issues.  It sounds o' so familiar.  

Here's a skim of some recent news:

Vast reserves of shale gas revealed in UK  (Guardian 9/21/11) 
Huge natural gas field in north-west England revealed, but environmentalists alarmed at controversial fracking method  

The potential for shale gas is worth exploration (Guardian 9/21/11)
The industry is governed by one of the most robust and stringent regulatory frameworks in the world 

'Fracking threat' to Bath's hot springs, says council  (BBC 9/28/11) 

Fracking plans may pose threat to Bath's ancient springs  (Independent 9/29/11)

Protestors ramp up pressure over shale gas 'fracking' fears (Wales Online 9/30/11)

 

And for some background an official gov't report.

I just want to say one word to you. Plastics

Mr. McGuire: I just want to say one word to you. Just one word.
Benjamin: Yes, sir.
Mr. McGuire: Are you listening?
Benjamin: Yes, I am.
Mr. McGuire: Plastics.
Benjamin: Exactly how do you mean?

    —The Graduate (1967)

Night shot of the new Ethylene Cracker Complex in Singapore
Source: Shell Eastern Petrochemicals Complex (SEPC)

A brief petrochemical lesson: Methane is typically what people think of as “natural gas.” Methane is the stuff that burns cleaner than other carbon-based sources of fuel, like oil and coal. But when “natural gas” is mined from the earth, the second largest component by volume is a chemical called ethane. Somewhere between one and six percent of natural gas coming from the ground is ethane. Why is that important? Ethane can be converted to the hydrocarbon ethylene. Ethylene is the “feedstock” (or raw material) used to make most plastics, including polyethylene and PVC.

Polyethylene is the most widely used plastic in the world. Almost all plastic packaging, including shopping bags at grocery stores, the plastic wrap around a loaf of bread, even the plastic bag your frozen peas come in, is made from polyethylene. PVC (polyvinyl chloride) is another widely used plastic—particularly in construction of homes and businesses. It’s used in everything from pipes and flooring to insulation, roofing, and even upholstery and clothing. Source: Marcellus Drilling News.

So what does that mean -- is petrochemical industry coming to our region?

"As more wet gas is delivered to market, we anticipate that the [Marcellus] region could become a major hub for America's chemical industry." (ICB, 8/26/11)

Pa., W.Va., Ohio vie for huge new Shell gas plant (AP, 9/3/11)

Shell plans world-scale chemical plant in USA (Shell Press Release, 6/6/11)

Prior to opening their state of the art Ethane Cracker Complex (ECC) in Singapore, Shell commissioned an Enviromental, Social and Health Assessment (ESHA) study. This industry sponsored report summarizes the expected key emissions, discharges and waste to the environment from the ethane cracker (fractionation) plant:

  • Emissions to air (CO2 ~ 2.4 million tonnes/yr, CO ~ 650 tonnes/yr, NOX ~ 2000 tonnes/yr, SO2 ~ 2 250 tonnes/yr, PM10 ~ 200 tonnes/yr) from cracking furnaces, steam boilers, flare, heaters, and the Vapour Destruction Package (VDP). Also trace emissions of benzene from the VDP;
  • Emissions to water from stormwater run-off, treated effluent (proces water, contaminated water & sanitary wastewater) and ~ 300-400 m3/hr of cooling water tower blowdown water;
  • Non hazardous wastes (
  • Hazardous wastes (~ 590 tonnes/yr) including coke, tar, activated sludge, polymer, waste lube oils and waste catalysts;
  • Noise emissions (total predicted sound power level of ~127 dBA) largely generated by cooling water tower, flare, heaters, boilers and furnaces, steam turbines, generators, compressors, motors, coolers and pumps.

This is all coming at a time when President Obama has just overruled EPA science and blocked crucial new protections against smog pollution that have been years in the making, and our legislators are focused reducing and easing air quality standards to support industry.  Any connections?

Obama pulls back proposed smog standards, in victory for business (Washington Post, 9/2/11)

A Debate Arises on Job Creation and Environment  (New York Times, 9/4/11)

Who is Henwil? -- Our region deserves better reporting.

10,000 gallons of an industrial detergent overflowed into the Mon river. The cleanup is mishandled and the toxic pollutant dumped again, this time into the Allegheny.  

Both our local papers cover the story half-wittedly, leaving readers to piece together what happened and track down the who's and why's.

Industrial detergent spilled in Mon, Allegheny rivers
Saturday, September 03, 2011
The Associated Press / carried by Pgh Post-Gazette

State environmental officials say the same kind of industrial detergent that spilled into the Monongahela River in Fayette County a few days ago has now gone into the Allegheny River from a Harmar treatment plant.

The spill of ethoxylated alcohol from the Allegheny Valley Joint Sewage Authority treatment plant in Harmar occurred Thursday, said plant manager Rich Chiavetta. The state Department of Environmental Protection says it was reported Friday. Mr. Chiavetta said about 10,000 gallons was released. The Pittsburgh Water and Sewer Authority said the drinking water supply was not affected.

On Wednesday, the same chemical leaked from a containment pit in Newell into the Monongahela River. A number of fish were killed due to the spill.

The chemical is found in some household detergents and can be harmful in concentrated form, but officials say it is toxic to aquatic organisms.

First published on September 3, 2011 at 2:08 pm

http://www.post-gazette.com/pg/11246/1172067-100.stm?cmpid=latest.xml

The trib-review does a bit better if you read it three times and try to put the puzzle together...

Industrial detergent, toxic to fish, spills into Allegheny River

By Michael Hasch and Mary Ann Thomas, PITTSBURGH TRIBUNE-REVIEW
Saturday, September 3, 2011
Last updated: 11:03 am

The same industrial detergent that spilled into the Monongahela River this week in Fayette County flowed into the Allegheny River from the Allegheny Valley Joint Sewage Authority treatment plant in Harmar Friday, the state Department of Environmental Protection said.

The product -- ethoxylated alcohol, also known as Trideceth-3 -- is also found in some household detergents and can cause skin and eye irritation in humans. But it is toxic to aquatic organisms, according to a hazardous materials data sheet. Allegheny County emergency dispatchers said the spill was reported Friday afternoon near the Hulton Bridge and that the Pittsburgh Water and Sewer Authority immediately closed its intake valve in Aspinwall to prevent the contaminant from entering the water system.

However, Rich Chiavetta, plant manager of the Allegheny Valley Joint Sewage Authority, said the contaminant actually was released into the Allegheny River on Thursday.

The concentrated detergent spilled into the Monongahela River on Wednesday afternoon from the Henwil Corp. in Newell, a company that blends chemicals for water treatment plants*.  A company spokesman said 2,620 gallons of ethoxylate detergent spilled and filled a containment pit, but some leaked through a crack in the wall of the pit. Several dozen fish were killed by the spill.

DEP spokeswoman Katy Gresh said McCutcheon Enterprises Inc., a waste management company in Allegheny Township, Westmoreland County, cleaned the spill. Gresh said she understands McCutcheon took the detergent that it cleared from the Mon, transported it to Harmar, and deposited it at the treatment plant for disposal. Chiavetta, who believes about 10,000 gallons of the contaminant was released into the Allegheny, said proper procedures were followed. He said that the plant accepted the same industrial detergent several weeks ago, analyzed it and treated it without incident. Chiavetta suspects the detergent this time was more "highly concentrated ... and it upset the plant."

Gresh said the DEP is investigating.

The Pennsylvania Fish and Boat Commission said preliminary indications are that fewer than 100 fish have been killed but there could be more.

The Pittsburgh Water and Sewer Authority said it was notified at 1:30 p.m. Friday about the fouled water and took immediate steps to make sure the drinking supply remained safe. "None of this substance passed into Pittsburgh's drinking water supply," a company statement said.

Source:  http://www.pittsburghlive.com/x/pittsburghtrib/news/pittsburgh/s_754930.html

So my read ...

It seems the waste managment company, McCutcheon Enterprises, responsible for cleaning up the spill that leaked into the Mon from Henwil's containment pit, took the "spilled Trideceth-3, an ethoxylated alcohol" to a wastewater treatment facility on the Allegheny (who had accepted and treated this chemical before), but this load was more concentrated and "upset the plant." leading to a second release of the industrial detergent into the Allegheny river.  Hmnn a little more info here -- what are the water treatment procedures for this chemical prior to releasing it into waterways? Is it dilution or some other treatment process? What does "upset" mean?  What caused the alarm bells to ring and alert the PSWA to shut down the drinking water intake?

*Also they mischaracterize the company behind the source of the spill -- to call Henwil Corp a company that blends chemicals for water treatment plants is a partial description at best. These folks provide and blend water treament chemicals for industrial uses -- including slickwater hydraulic fracturing and treating of produced waters from natural gas drilling. 

Note, Henwil on their website claims ...

"We are located about 50 miles south of Pittsburgh, Pennsylvania on the Monongahela River. Our manufacturing facility offers interstate, rail, and barge access. The plant boasts tankage from 500 gallons to 3.5 million gallons. Blending tanks range from 50 gallons to 10,000 gallons. Reactor sizes are 50 to 4,000 gallons.

At Henwil, our goal is to help you manage your water treatment needs. Whether it is water produced during oil and gas well drilling, mineral slurry drying, or incoming water clarification at a paper mill, we have the experience and knowledge to benefit your process."

NB: ethoxylated alcohol is an additive, or friction reducer used in slickwater hydraulic fracturing, in other words natural gas drilling. 

See: SPE 119900 Critical Evaluations of Additives Used in Shale Slickwater Fracs

Let's hope the DEP's investigation brings some clarity to the situation, as well as processes to avoid this ineptitude in the future.

 

Aerial view of the Henwil chemical mixing and storage facilities on the Monongehela in Newall, PA.
Source: Henwil

An industrial detergent spilled a second time and flowed into the Allegheny River from the Allegheny Valley Sewage Treatment plant according to the state DEP.
Source: WPXI

Coal Worse than Shale Gas | Shale Gas Worse than Coal

So in terms of contributing to greenhouse gas emissions which is worse -- coal or natural gas?

Two studies, two different answers. 

A Carnegie Mellon study just published in Environmental Research Letters (8/5/11) did a lifecycle comparison of greenhouse gas emissions from coal and natural gas for electrical generation purposes and finds shale gas extracted from the Marcellus is better than coal in terms of overall greenhouse gas emissions.

Cornell published a study earlier this year in a letter to the journal Climate Change that found in terms of overall greenhouse gas emissions -- shale gas is not much better than coal. 

Intrigued by these discrepant findings...read on. 

The CMU Findings...

Life cycle greenhouse gas emissions of Marcellus shale gas

Mohan Jiang1, W Michael Griffin2,3, Chris Hendrickson1, Paulina Jaramillo3, Jeanne VanBriesen1 and Aranya Venkatesh1

Abstract. This study estimates the life cycle greenhouse gas (GHG) emissions from the production of Marcellus shale natural gas and compares its emissions with national average US natural gas emissions produced in the year 2008, prior to any significant Marcellus shale development. We estimate that the development and completion of a typical Marcellus shale well results in roughly 5500 t of carbon dioxide equivalent emissions or about 1.8  g CO2e/MJ of gas produced, assuming conservative estimates of the production lifetime of a typical well. This represents an 11% increase in GHG emissions relative to average domestic gas (excluding combustion) and a 3% increase relative to the life cycle emissions when combustion is included. The life cycle GHG emissions of Marcellus shale natural gas are estimated to be 63–75  g CO2e/MJ of gas produced with an average of 68 g CO2e/MJ of gas produced. Marcellus shale natural gas GHG emissions are comparable to those of imported liquefied natural gas. Natural gas from the Marcellus shale has generally lower life cycle GHG emissions than coal for production of electricity in the absence of any effective carbon capture and storage processes, by 20–50% depending upon plant efficiencies and natural gas emissions variability. There is significant uncertainty in our Marcellus shale GHG emission estimates due to eventual production volumes and variability in flaring, construction and transportation.

Source: Environmental Research Letters (8/5/11)

These findings run counter to a Cornell study published earlier this year which claimed natural gas releases almost as much greenhouse gas emissions as coal when you take into account the full lifecycle. 

The Cornell study used different assumptions for drilling and power plant combustion efficiencies. It selected a shorter, 20-year timeframe to calculate the global warming potential of methane emissions. CMU study numbers were based on a 100-year window, spreading out the impact. The Cornell study used data that showed the natural gas drilling, flaring, processsing and infrastructure aging process to be much "leakier" than the CMU study, which relied on more conservative figures. 

NB: LCA's or lifecycle analysis studies are based on "averaged" national data. The well production rates, and methane leak rates are not yet out for Marcellus-related developement and production.  Well production data, how much methane is leaked versus how much is produced for cleaner burning energy generation, will clearly affect how coal compares to natural gas. These horizonatal wells will have to produce a lot of methane to compensate for the early ineffecienices and losses...  

The Cornell Findings ...

Methane and the greenhouse-gas footprint of natural gas from shale formations
by Robert W. Howarth, Renee Santoro and Anthony Ingraffea

We evaluate the greenhouse gas footprint of natural gas obtained by high-volume hydraulic fracturing from shale formations, focusing on methane emissions. Natural gas is composed largely of methane, and 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the life-time of a well. These methane emissions are at least 30% more than and perhaps more than twice as great as those from conventional gas. The higher emissions from shale gas occur at the time wells are hydraulically fractured—as methane escapes from flow-back return fluids—and during drill out following the fracturing. Methane is a powerful greenhouse gas, with a global warming potential that is far greater than that of carbon dioxide, particularly over the time horizon of the first few decades following emission. Methane contributes substantially to the greenhouse gas footprint of shale gas on shorter time scales, dominating it on a 20-year time horizon. The footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly so over 20 years. Compared to coal, the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.

Source: Climate Change Letters (4/12/2011)

Don Hopey of the Pittsburgh Post Gazette provides a short comparative review of the two studies study in Gas less polluting than coal in the long run, CMU study says

As does Scientific American Climate Footprint of Marcellus Shale Gas Could Be Less Than That of Coal

Also see this earlier post on Marcellus Media and a new NRDC  report on the "leakiness" association with current natural gas development practices.

And a year later, a story by Reid Fraziers on for Allegheny Front "Scientists Square Off Over Fracking's Impact on Climate" (Essential Public Radio 6/22/12)