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View Diary: Revised Keystone XL still crosses vital Ogallala Aquifer, Republicans pressuring Obama to give OK (56 comments)

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  •  Are you thinking a pipeline leak in Nebraska (5+ / 0-)
    Recommended by:
    Magnifico, Mindful Nature, semiot, FG, MGross

    Would contaminate the entire aquifer?  Even a significant part of it?

    If so, that's not how oil contamination in groundwater behaves. Petroleum released to porous media tends to cause relatively small areas of contamination (compared, to, say, chlorinated solvents or nitrate, which can contaminate several miles of aquifer). Moreover, petroleum hydrocarbons in groundwater do not migrate long distances because of their propensity to biodegrade in the subsurface.

    I'm not suggesting that approving this pipeline constitutes wise energy policy, but suggestions such as you've implied, or that the diarist made explicitly:

    An oil spill from the Keystone XL pipeline could contaminate the Ogallala Aquifer, potentially putting at risk the water supply of eight states and 30 percent of the groundwater used for irrigation nationwide.
    ...are not supported by science.
    •  More studies are needed (17+ / 0-)

      The extent of contamination isn't known. Reuters said there was just one study that looked at crude oil in aquifers. Unless, you know of more recent studies this is what Reuters was reporting in June 2011, Nebraska Water Scientists Warn of Oil Pipeline's Risk, Call for More Study.

      A single study by the U.S. Geological Survey in Minnesota is the sole source for what scientists know about crude oil behavior in aquifers...

      Great Plains states are risking an unknown level of environmental and economic hurt if the U.S. State Department persists in routing a controversial tar sands pipeline atop the Ogallala Aquifer without further study.

      That is the scientific warning coming from a pair of University of Nebraska professors with expertise in groundwater flow and contamination...

      “Uncertainty about crude oil plume behavior in waters of the Nebraska sandhills region has practical implications,” wrote John Gates, an assistant professor in the Department of Earth and Atmospheric Sciences, and Wayne Woldt, an associate professor in Biological Systems Engineering and the School of Natural Resources. “We feel that it is highly desirable to study contaminant risks in the sandhills in a more thorough and systematic way.”


      Unique conditions that make the region susceptible to oil contamination include very permeable sandy soils, groundwater hovering near the surface and a network of abundant groundwater-fed lakes and marshes.

      “Hydrologic studies in the sandhills have already shown that all of the conditions are right for producing very short lag times between a pipeline crude oil release and water contamination,” Gates and Woldt wrote in their letter. “Because lakes and streams in the sandhills are fed almost exclusively by groundwater, risks are not limited to the aquifer, but extend to surface water as well.”

      According to the State Department, 64% of the groundwater wells in Nebraska are within a mile of the Keystone XL original route. Nebraska's part of the aquifer certainly is at risk.
      •  There's little question a leak of any significance (9+ / 0-)

        would contaminate the aquifer in the immediate vicinity of the release. The geology of the Sand Hills area, as I understand it, is conducive to vertical migration of contaminants through the unsaturated zone.

        My point is that such a release likely would not migrate very far laterally because of a number of factors that inhibit lateral migration (specifically, adsorption, volatilization, and biodegradation). That is what is observed at pretty much every hydrocarbon release site.

        And -- the Reuters article you've cited is incorrect.  The Bemedji site is not the "sole source for what scientists know about crude oil behavior in aquifers." There are many, many crude oil release sites and even more refined product sites, both of which help inform our understanding of how hydrocarbons in the subsurface behave. The USGS fact sheet for the Bemidji site notes, for example, that in the period 1994 to 1996, there were 83 crude oil spills per year from pipelines. Pretty much any spill is going to be characterized and studied as part of its cleanup.

        But I agree with the USGS: the Bemidji site is one of the better-studied sites in the world because the USGS and others decided to capitalize on the spill and turn it into a research center for understanding hydrocarbon behavior in the subsurface, much like other sites (such as the Borden site in Ontario) have been made into research sites.

        From the USGS fact sheet for Bemidji (link above):

        Long-term monitoring of the plume since 1984 has shown that, near the water table, the concentration of total dissolved organic carbon (TDOC) and dissolved oxygen (DO) downgradient from the oil body has remained relatively stable suggesting
        that degradation of the plume has reached equilibrium. In the anoxic zone (Zone 3), concentrations of reduced chemical species Mn2+, Fe 2+ , and CH4  have increased with time, indicating a sequence of Mn reduction, Fe reduction, and methanogenesis.

        * * *

        Although these geochemical processes have changed over  time, the plume has not migrated as far as predicted considering  the ground-water flow velocities and sorption constants for these  compounds (Baedecker and others, 1993). As of 1996, the leading edge of the plume of ground water containing a total BTEX
        concentration greater than 10 micrograms per liter had moved only about 200 m downgradient, whereas advective flow of ground water since the spill has been about 500 m. The primary  reason is that have biodegraded under oxic and
        anoxic conditions.

        The rate of removal of organic contaminants by natural attenuation and the factors that affect rates of biodegradation are  important considerations in making decisions concerning cleanup of contaminated ground water. Biodegradation of petroleum-derived hydrocarbons in oxic and sub-oxic environments is
        generally considered a more efficient attenuation mechanism than is biodegradation in anoxic environments. However, research at this site has demonstrated that biodegradation in anoxic environments can remove substantial amounts of hydrocarbons from ground water (Lovley and others, 1989; Baedecker and others, 1993; Eganhouse and others, 1993; Cozzarelli and others, 1994).

        So from 1979 to 1993 the dissolved phase plume had moved 200 meters (about 656 feet) and, though I don't have data readily available, I suspect it long ago reached a stable or receding state due to hydrocarbon biodegradation rates equaling or exceeding the mass flux of dissolved hydrocarbons from the area where liquid hydrocarbons are still present in the subsurface at and below the point of the leak.

        •  Interesting (11+ / 0-)

          Thanks for the explanation! With that many pipeline spills (83) in just a 2 year period, it seems that the concern is justified for what a spill would mean for the Sandhills.

          What Woldt and Gates are concerned about in the Reuters article is that the Sandhills are different from the other areas and that the Bemidji study has different "geography" (I think the article probably meant geology). What I took away was the sandy soils in the Sandhills may mean the spill spreads laterally and so such a hypothesis should be tested before a pipeline is built.

      •  And -- please don't misunderstand me (4+ / 0-)
        Recommended by:
        Magnifico, bnasley, libnewsie, semiot

        The Univ. of Nebraska professors are correct that site-specific conditions at the point of release, if and when one would occur, are going to play a role in the transport potential and fate of the hydrocarbons that may be released. And they're correct that the conditions at Bemidji would be different than in Nebraska.

        But just because the findings and observations at Bemidji would not translate directly, the overall weight of evidence of hundreds if not thousands of hydrocarbon release sites that have been studied over recent decades tells us the general behavior very likely would be similar.

        Again -- I'm not saying the pipeline is a good idea. And I'm not saying the potential for groundwater contamination needn't be considered in the evaluation of whether to grant a permit for construction. It should be.  

        But the main point I'm trying to make is that we shouldn't exaggerate the significance of that potential; especially with respect to the volume of the aquifer prism likely to be contaminated by either phase-separated hydrocarbons or dissolved-phase hydrocarbons from reasonably conceivable leaks.

      •  Source for the last paragraph? (3+ / 0-)
        Recommended by:
        Magnifico, Creosote, cotterperson

        "According to the State Department, 64% of the groundwater wells in Nebraska are within a mile of the Keystone XL original route. Nebraska's part of the aquifer certainly is at risk."

        Is that stated correctly?  It does not make sense to me.  Almost 2/3 of the water wells in NE are located in a 2 mile wide strip along the pipeline route?

        Where are we, now that we need us most?

        by Frank Knarf on Fri Apr 20, 2012 at 08:17:04 PM PDT

        [ Parent ]

        •  Reuters/InsideClimate (3+ / 0-)
          Recommended by:
          Just Bob, Frank Knarf, cotterperson

          My paraphrase from the Reuters/InsideClimate article:

          The two scientists complimented the State Department for making it clear that in Nebraska, 64 percent of the groundwater wells are within one mile of the Keystone XL route.
          However, going back to the scientist's original letter (pdf):
          According to data in the SDEIS, approximately 64% of groundwater wells within 1 mile of the proposed pipeline route are located in Nebraska, with about 10% in each of the other states.
          It's clear I misunderstood what the article was saying and so, what I wrote is incorrect.
    •  It the case of the Keystone pipeline the solvent (4+ / 0-)

      is naphtha used to dilute the crude oil. The naphtha is returned via a second pipeline for reuse.

      Others have simply gotten old. I prefer to think I've been tempered by time.

      by Just Bob on Fri Apr 20, 2012 at 10:06:47 PM PDT

      [ Parent ]

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