[Beyond the potential harm to global climate systems, the Tar Sands project poses additional risks to vital fresh water aquifers along the route through US states. This post is part of FDL's continuing coverage of Tar Sands development and associated XL pipeline through the US. ed.]
First, the disclaimer. I’m an ecosystem researcher and I’ve been working in the Nebraska SandHills for 10 or so years. The SandHills are the major recharge zone for the Ogallala (or High Plains) aquifer. That’s where water goes into the system to (hopefully) replace what we take out via wells.
The SandHills are also the largest “grass stabilized” dune field in the world, and without the grasses, they would be the largest sand dune field in the Western Hemisphere. The soils are very very sandy and porous, allowing quick and efficient infiltration of any fluids that happen to impinge upon them. My colleague and I have just made the first measurements of the recharge rate (although only at a single point) in the region, and I have a pretty good idea of how easily things can work their way down to the water table (i.e. the aquifer).
Probably the thing about the XL pipeline that scares me the most is he potential for one or more “small” leaks. A small leak in the buried pipeline (several barrels per day) would probably go unnoticed for a long time. The monitoring equipment at the pumping stations are designed to read and control flows of thousands and thousands of barrels per day, and a leak of just a few or maybe even ten just wouldn’t register. In that case, oil/tar would leak, and leak, and leak, mostly unnoticed. It probably wouldn’t be discovered until the plume worked its way 12 or so feet up to the surface, and then only if someone happens upon the site. Most places in the SandHills see very little human traffic. This scenario could dump hundreds or thousands of barrels of oil before it’s ever noticed.
Once in the soil, the sands will act somewhat like a refinery. The lighter fractions (benzene, toluene, heptane, etc) will very quickly infiltrate downward to the water table, then it’s not just a soil clean up. It’ll require the pumping and treatment of millions of gallons of water.
How far down does the oil have to go to get to the water? Well, that depends. The SandHills consist of three major ecosystems. By far, the most common are “dunal uplands”. These are the large, sculpted dunal ridges that can rise up to 300 feet above the inter-dunal valley floors. If the pipeline is buried 12 or so feed below the surface, there could be 100 or more feet to the actual water table. The other common ecosystems are “dry valley floors” where the water table is between 3 and 30 feet below the surface, and “subirrigated meadows” where the water table intersects the land surface at least for part of the year. In either of these ecosystems, the leak would be directly (or almost directly) into the aquifer.
Is there a real threat of a leak? I certainly think so. TransCanada grossly underestimated the potential for leaks on their existing pipeline. They estimated that there would be one leak every 7 years. Since the line has opened (2 or 3 years ago) there have been 12 or so.
So what would the solution be? The country wants oil. The world needs the clean water of the aquifer. The pipeline will leak. Simply move the route to a less ecologically sensitive area! I’ll bet that the cost to move the route will be much less than TransCanada will spend cleaning up the mess they are sure to make!
I just wanted to add a bit more because of a couple of the comments. The greatest value of the Ogallala aquifer is as a provider of irrigation water. 30% of all the irrigation water used in the U.S. is “mined” from the Ogallala. Now in fairness, a massive spill in the SandHills probably won’t show up in water pumped in Kansas or Texas (at least for a thousand years or so). Many of the “connections” between parts of the aquifer are rather tenuous and it takes a long time for a particular “drop” of water to move from one place to another. On the other hand, it will affect very large parts of Nebraska, and we do use most of the water and produce most of the food that can be attributed to this resource.