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Melinda Chapman: I'm Melinda Chapman. I'm the groundwater specialist for the USGS here in North Carolina. I'm also the project chief of our baseline groundwater sampling effort that is related to potential shale gas expiration in North Carolina. We've had some test well drilling since the 1970s but have not allowed directional drilling for the industry to come into the state yet. It's very important that we get background groundwater quality data, and we have not worked in this area since the 1960s or 70s. A lot of folks are using groundwater as their primary drinking water source, so they depend on the resource.
So it's important for us to get that baseline information just in case there are changes related once drilling does occur or is allowed by the state.
Sharon Fitzgerald: My name is Sharon Fitzgerald. I'm with the USGS in North Carolina also in the same office as Melinda. I'm working with her on her project to establish a sampling plan and a quality assurance and quality control plan so that we generate data that is very defensible and we will stand behind. We're doing all kinds of-- huge lists of analytes to help determine whether there is environmental impact from the hydro-fracking operations.
Melinda Chapman: The principal objectives are to establish baseline geochemistry for the shallow groundwater system in the area.
So we're looking at for instance how much calcium is in the water, how are it is what's the pH, what are any trace organics, is there any naturally occurring methane that is shallow. Can we determine if it is a biogenic shallow resource or if it's tied to some discharge of deeper thermogenic gas that is natural with the-- of course-- the shale gas resource.
Sharon Fitzgerald: This is a reconnaissance effort so we're doing 50 wells. It's probably enough for reconnaissance. We're doing various analyses at the wells and hopefully that will be a good snapshot of the entire area.
Melinda Chapman: Right. The study area is about 77 square miles. It's about a quarter of Lee County in the southeastern extreme part of Chatham County along the Deep River. And we are in Triassic Basin of North Carolina. The early Mesozoic basin of the eastern U.S. deposits are sedimentary layers here part of a rift basin that formed when the super continent Pangaea split apart from North America and Africa. So these are freshwater sediments there-- shale, sandstones, and conglomerates-- those types of rock. And the concern here, there has been some explorations since the mid-70s. The gas is shallower here. It's in an organic rich black shale named the Cumnock formation.
It's a bit shallower here so the drinking water wells are a bit closer to the gas reservoir compared to other areas of the country.
Sharon Fitzgerald: One of the main things we're looking for is not just is there methane is there not methane, but also we can look at the isotopes of the carbon and the hydrogen on the methane to determine whether the source is very old petrogenic fracking stuff or if it's new biogenic gases which will be lighter--that happen just naturally in the environment.
Melinda Chapman: It's also a matter of the groundwater versus shallow groundwater too.
Sharon Fitzgerald: Right.
Melinda Chapman: And there was some historical coal mining in this area that did have some methane explosions associated with it, so we know there is some natural methane here just not sure how shallow that continues. We have a unique opportunity here. I don't think in any other state that we've heard of to come in before the industry is here to obtain these baseline samples.
Sharon Fitzgerald: We have partners. We have universities cooperating with us. We have State agencies cooperating with us.
Melinda Chapman: We're working with Duke University, with Dr. Rob Jackson, Dr. Avner Vengosh in the Nicholas School of the Environment, and his primary PhD student is Adrian Down. UNC Chapel Hill is also collecting strontium isotopes at the wells also. And our support for the project is from North Carolina Department of Environment and Natural Resources and the USGS through our water mission area.
So the primary issue here is even though there is some county water some surface water resources most folks still obtain their water supplies from wells, which is shallow groundwater. So we're talking in general an average of 300 feet in depth or so. The Shale gas resource in this area can be as shallow as 2000 feet. So those are the differences we're looking at.
Sharon Fitzgerald And I guess there's evidence out there that even though that sounds
like a big difference 2000 versus 300 that there's still a possibility that chemicals or gases could possibly come up and affect the water resources.
Melinda Chapman: Well the issue too is the flowback water that comes out of these wells is held in surface ponds, so they had deeper groundwater that has a higher salinity in general and you have it mixed with hydro-fracturing chemicals that are held in the holding ponds on the surface. They're generally aligned but if you get a large rainstorm that could runoff or it could potentially leak and affect shallow groundwater wells in the area.
I think the challenges are that there haven't been many of these baseline studies conducted, so we didn't have a set of analytes ready for us, so we had to do quite a bit of investigative work.
We tried to hit most everything that we thought was most indicative, most important to establish before to see if there's a change pre- and post development of the resource.
Melinda Chapman: So we looked at areas where there is ongoing exploration, production just to see what they're looking for what the state agencies and the federal agencies are looking for in the groundwater samples.
Sharon Fitzgerald: It really is a known unknown, so it's important to start looking at this whole topic rigorously on a national scale, and North Carolina is sort of ahead on this in that we have the opportunity to get in there any activity occurs so we can get a baseline. So we're just covering our bases trying to analyze everything before anything happens so we have an idea of what's there. And then if there are any changes we can try to see if we can relate them back or not.
Sharon Fitzgerald: The products will be an interactive Google map of the generalized well location. No homeowner’s names or addresses will be displayed, and it'll be a clickable map where you can click on the real location and the chemistry data will be associated with that point and will be available to the general public as well as state federal agencies and universities.
Melinda Chapman: So all the data will be available, to the homeowners, to the public. It's an open book.
[End of Audio]
Duration: 8 minutes
NC Shale Gas study
Melinda Chapman, Sharon Fitzgerald
Title: Shale Baseline Sampling of Groundwater in North Carolina
Melinda Chapman and Sharon Fitzgerald discuss the U.S. Geological Survey groundwater sampling program to characterize water-suppy well water quality in the area of North Carolina with potential for shale gas production. The sampling program is designed to provide a pre-devolpment baseline that can be compared with well-water quality after shale gas development has occurred to assess any impacts on water quality.
Location: Sanford, NC, USA
Date Taken: 4/15/2013
Video Producer: Douglas Harned , U.S. Geological Survey
Note: This video has been released into the public domain by the U.S. Geological Survey for use in its entirety. Some videos may contain pieces of copyrighted material. If you wish to use a portion of the video for any purpose, other than for resharing/reposting the video in its entirety, please contact the Video Producer/Videographer listed with this video. Please refer to the USGS Copyright section for how to credit this video.
Additional Video Credits:
Melinda Chapman- Project Chief
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