Saturday, January 12, 2013

Ogallala Acquifer

You may recall, environuts in Newbraska were concerned the proposed Keystone XL pipeline would put the massive Ogallala Acquifer at risk of contamination. Here's a really good article that blows that meme to smittereens:

Local View: A science-based approach to the Ogallala Aquifer "
Over the past 40 years, it has been my good fortune to focus my research on Nebraska's Sandhills and the Ogallala Aquifer. Thanks to the University of Nebraska's Conservation and Survey Division and to the U.S. Geological Survey, I have been able to drill more than 1,000 test holes into the Ogallala formation."
[---]
"The Ogallala Formation is layered rock, not a lake or a sandpit. Some people say "the lake beneath my feet" when referring to the aquifer. Others think of it as loose sand identical in all directions. These are misconceptions. Our portion of the Ogallala/High Plains Aquifer is made of widely varied sediments eroded off the Rocky Mountains and then deposited in what is now Nebraska by streams and rivers similar to the Platte over a span of 5 million to 30 million years ago. Eventually, those sediments became layers of different types of rocks.

In the western reaches of the state, the Ogallala formation is exposed at the surface. Going eastward, the Ogallala and related rock units dip; the top of the aquifer can be as deep as 300 feet or so below the land surface.

Detailed test-drilling shows that those many layers of sediment that became rock vary tremendously in all directions. Some are heavily cemented siltstones and sandstones that impede the flow of water; others are highly porous sandstones and conglomerates, with the ability to contain vast amounts of moving water between the grains. No matter which direction you drill -- up, down, or sideways -- you'll go only a few hundred yards or so before hitting a different rock type.

In contrast, UNL environmental engineer John Stansbury's report (on worst-case consequences of a spill, released in July) makes the incorrect assumption that the Ogallala Aquifer is uniform sand in all directions and right below the surface. The calculations of a projected 15-mile plume (of leaked oil) did not take into consideration the geology of the aquifer."
[---]
"Yet another consideration is the depth to the water of the aquifer. Through most of its alignment, the pipeline is some 10 to 50 to 100 feet above the top of the Ogallala formation. It's questionable whether the leaked oil could work its way down through the overlying sediments; they contain interspersed seams of silt and clay.

Even so, no leak, large or small, is something to take lightly. For me, the area of greatest concern is Holt County, where the water table is at or near the surface. Any leaks there could go directly into the waters of the shallow aquifers, although not easily into the deeper Ogallala Aquifer. In this area, it is my understanding that TransCanada will build a protective, sealed cement conduit that will surround the pipeline."
[---]
"These geology and hydrology realities, gleaned from over 75 years of research into Nebraska's subsurface, should put people's minds at ease about the fact that the overwhelming majority of the Ogallala/High Plains Aquifer is not at risk from a pipeline spill"
My only question is why did this dude wait until now to produce this article. I'm sure the environuts will also ask that question and accuse him of being in the pay of "Big Oil".

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