TransCanada’s cleanup of its oil spill on the Keystone pipeline in Marshall County resumes in earnest today. After a nice ten-day break during the bitter year-end cold (because, hey, no rush, it’s just contaminated soil out in the middle of South Dakota farmland), TransCanada’s crews returned to the 5,000-barrel spill site yesterday, with “major site activities” scheduled to resume today.
According to a December 27, 2017, e-mail from the Department of Environment and Natural Resources, TransCanada has hauled away 839 truckloads of contaminated dirt. At approximately 20 cubic yard per load, that’s not quite 17,000 cubic yards of poisoned earth. If that were all topsoil, that dirt pre-spill could have filled over 14,000 4’x8′ raised-bed gardens one foot deep.
The DENR also issued a new water permit to TransCanada yesterday, allowing the company to remove and dispose of groundwater from its digging at a maximum rate of 80 gallons per minute. The permit says any such water will be “sampled and collected for transport and disposal at a properly licensed disposal.” The permit expires February 28… which perhaps we can take as a hopeful sign that TransCanada anticipates cleaning up all of its oily mess before the spring thaw.
TransCanada has been keeping its Facebook page clean, making no social-media mention of its pipeline spill since November 27. Nothing but happy, happy holidays, and lots of things made with oil.
Do we know what they used for backfill?
Where are these truckloads being dumped?
The contaminated soil is being taken to a Clean Harbors Landfill in Sawyer, North Dakota.
Nick, that I don’t know. I’ll need to review the DENR open case file and the PHMSA corrective action order to see if those docs specify.
But first, lunch! See if someone can beat me to it…. ;-)
Per TransCanada’s corrective action plan, submitted 12/7/2017:
—”Impacted soil in this Plan includes both native soil in the traditional sense and engineered fill such as gravel and rock that may be present in the pipeline trench or used for equipment access.”
—”Unless specified otherwise in the Project-Specific Work Plan, fill and abandon the sample hole as required by backfilling with granular bentonite to approximately 2 feet from ground surface. For the interval above the groundwater table, hydrate the bentonite every foot using potable water. The top 2 feet of the borehole will be backfilled to match the surrounding environment.”
—”The Project-Specific Work Plan will provide procedures to fill and abandon the excavation. Typically the top two feet of the excavation will be backfilled to match the surrounding environment.”
A quick search of the documents doesn’t say where specifically they’ll obtain this fill, but I wouldn’t imagine they’d drive far for it.
17,000 cubic yards is about 13,000 cubic meters. Soil can have about 2.8 grams of Uranium per cubic meter (1 gram weighs as much as a paper clip), and can have a total mass of about 1250 kilograms per cubic meter (dry).
So they have hauled away approximately 36 kilograms of uranium….mixed in with not quite 16 million kilograms of soil, assuming a typical average soil with no enhancement from man-made sources like phosphate-based fertilizers. Typical NORM concentrations.
One kilogram of natural uranium (after processing, etc.) can generate about 45,000 kiloWatt-hours of electricity. So that 36 kilograms would generate 1.62 million kiloWatt-hours of electricity.
An average on-shore 2.5-3 MW wind turbine will generate 6 million kiloWatt-hours every year, so what they have dumped would be the equivalent of 98.6 days of wind energy for one turbine.
That only assumes the U-235 is being consumed, and no U-238 or Th-232 is converted into a nuclear fuel, and does not include the losses incurred from separations and processing (which likely make this approach too expensive to do!).
Fascinating math, Rob! Given average annual U.S. household electricity consumption of 10.8 megawatt-hours in 2016, those 36 kg of uranium could power 150 homes for a year, right?
Can we feasibly extract uranium from soil?
Unfortunately, no. It would be easier to extract uranium from seawater than from soil, but we cannot even do that profitably yet. In essence all the in situ mining methods do is change the chemistry so that the uranium is soluble for extraction, but those are done where the uranium is at much higher concentrations. But instead of soil, I would rather tackle the extraction of uranium from legacy mining tails first, if it were ever possible.
Thorium probably stands a better chance of extraction from soil one day. It is 5-6 times as prevalent as uranium in nature. All of the thorium is Th-232, so no enrichment is necessary as it is for U-235.
While I spoke of uranium, you can do a similar exercise with many of the other critical elements that you need for solar, wind, and energy storage. But they all need some form of chemical and/or physical extraction, which means comparing costs of extraction with the benefit of having that extra source.
You mention seawater and in situ mining, à la Powertech/Azarga: do all of the soil extraction methods require dissolving the dirt first and then extracting the target mineral?
I speculate that extraction by the right plants is a better bet as an initial pre-concentrator for other methods, once the levels get high enough. It would take a while, but at least the sun is providing the energy for the process.