The source of elevated constituents is speculative, but... - Part 8

Okay, so the yellow dots they used in the graphic really got me thinking that this paper, "An evaluation of water quality in private drinking water wells near natural gas extraction sites in the Barnett Shale Formation" they talked about on the UT Arlington webpage might be a bit slanted against natural gas extraction.

I read their paper with a somewhat open mind to see the "powerful evidence" they had that further study was required because, as the website points out:

Researchers believe the increased presence of metals could be due to a variety of factors including: industrial accidents such as faulty gas well casings; mechanical vibrations from natural gas drilling activity disturbing particles in neglected water well equipment; or the lowering of water tables through drought or the removal of water used for the hydraulic fracturing process.  Any of these scenarios could release dangerous compounds into shallow groundwater.

You will notice that with the exception of drought (which we in Texas have been experiencing) all of the factors they list as the possible culprit for this increase in metals (arsenic) involve natural gas extraction.

They make their case two ways.  First, they sampled groundwater in the Barnett Shale area and ran it for chemicals one would expect to see coming for this type of activity.  Second, they compared the results to what we knew the levels of those contaminants to be prior to gas extraction activities commencing in the area.

The idea here is to show that the groundwater post 1999 is more contaminated then pre-natural gas extraction groundwater samples.

They were able to do this for only arsenic and TDS (although they make a case for the other metals being elevated as well).  Based on this comparison of the ground water now, with the groundwater pre-2000, they present "plausible scenarios" to explain why the metals are elevated, concluding:

At a minimum, these data suggest that private wells located near natural gas wells may be at higher risk for elevated levels of constituents than those located further from natural gas wells.

This before and after is based on:

This comparison shows a significant increase in the mean concentration, maximum detected concentration, and MCL exceedances for As, Se, and Sr in our study area when compared to historical data and previous characterizations of these aquifers.

Like I pointed out in my last post, it is this comparison that forms their conclusion.  So skeptical me asked what the comparison would be if you looked at the pre-2000 historical data and compared it with the post-1999 historical data. So I did.

Running a query on the same dataset they used in the report, I looked at the post-1999 results for arsenic in the groundwater wells in the four counties the Railroad Commission calls "Core Counties."  Wise, Johnson, Denton, and Tarrant are in the heart of all the natural gas wells in the Barnett Shale area.  If there is going to be arsenic contamination due to any of the factors listed in the UTA website, it will show up here.

My query of the dataset showed 170 water samples were analyzed for arsenic after 1999.  Of 170 analytical samples for arsenic, as recently as 2011, only two show any arsenic above >2 ppb.  5.93 ppb and 2.93 ppb.

These 170 analytical reports for arsenic from 48 unique wells within these four core counties.  None of them show the concentration of arsenic reported in the paper.  All of them are in the same geographic area where active natural gas wells are located.

What about the counties of Palo Pinto and Jack where there is only red and yellow dots shown on the graphic?  Not a lot of data for these two counties.  Pre and post is all under 10 ppb.

Not enough data to show a comparison.

So where does this leave me?  My take away is that there is no connection between gas extraction and metals in the groundwater.  Here is why:

1. The absence of BTEX in all the wells UTA sampled rules out "industrial accidents" and "faulty gas well casings" as the cause for an increase in arsenic.
2. The absence of arsenic in the historical wells post 1999 rules out "the lowering of water tables through drought or the removal of water used for the hydraulic fracturing process."

Still, I am faced with the fact that they did find arsenic above the 10 ppb MCL in about a third of the wells they tested.  Why?  This leaves only one possible factor in play:

Mechanical vibrations from natural gas drilling activity disturbing particles in neglected water well equipment

There are a number of issues in play here before I can accept that "plausible factor":

1. Does a neglected well release arsenic due to mechanical vibrations in the area?
2. Why is there arsenic in some wells in the same aquifer and not in others from the same aquifer in the same geographic area?
3. Did the sampling, preservation, and analytical method UTA used bias the results to show a positive result for arsenic?

Here is what I would want to see done first:

1. Re-sample the wells that were positive for arsenic above the MCL utilizing the same protocol used to collect the water samples for the historical data.
2. Analyze those water samples using EPA method 200.8
3. Have the analysis performed by a NELAC accredited laboratory

Doing this would rule out any errors produced by UTA and would allow us to apples with apples compare the arsenic data from the private wells with the arsenic data from the historic wells.  This, in my opinion, would help show a true value of arsenic that we can relate to an MCL and support looking at mechanical vibrations as the culprit if there are a number of wells that actually exceed the MCL

If you got this far, thanks for reading.

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