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Published on September 28th, 2009 | by Tina Casey

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Hi-Tech Steam Lays the Green Clean on Visalia Superfund Site

September 28th, 2009 by  


Dynamic Underground Stripping is a steam-based remediation technology that cleaned up a Superfund site in Visalia, California, 100 years ahead of schedule.With the help of a high tech underground steam cleaning technology developed at UCal-Berkeley and the Lawrence Livermore National Laboratory, a creosote-soaked Superfund site in Visalia, California has been cleaned up more than 100 years ahead of schedule, saving millions of dollars and pointing the way toward a more efficient and sustainable means of dealing with polluted sites.

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The site, which was just officially removed from the Superfund list, is known as Southern California Edison’s Pole Yard.  For 80 years utility poles were treated there with the wood preservatives creosote and pentacholorphenol.  By the 1970’s the site was saturated with contaminants up to 100 feet deep, and it won the dubious honor of making the original Superfund list when the program first started.  Almost miraculously, the Livermore cleanup has restored groundwater at the Pole Yard to drinking water quality.


Superfund Cleanup Then…

The conventional treatment for a site like the Pole Yard would be to pump out the groundwater and send it through a treatment process.  That is exactly what Southern California Edison was doing for 20 years, week after week.  At the rate of 10 pounds per week, the operation was expected to last well into the next century, all the while churning through fuel used to run the process.

Superfund Cleanup Now…

In the 1990’s, scientists at Livermore tested a steam-based process that was expected to work 50 times faster than conventional pump-and-treat.  The test site was a contaminated area on the grounds of the lab.  Conventional treatment was expected to take up to 60 years.  Sure enough, the high-tech cleanup took about one year.  The process, which Livermore calls dynamic underground stripping, uses steam to vaporize contaminants, which are removed through extraction wells.  It can be even more effective when combined with another Livermore innovation, a process that uses heat with oxidation to convert contaminants to harmless substances including water.

An Unexpected Development

Dynamic underground stripping involves bioremediation, in which naturally occurring microbes are used to break down petroleum products and other contaminants.  The Livermore team expected the microbes to work slowly at first, because they would need time to procreate and re-colonize after the soil was heated and cooled.   To the team’s delight, heat-loving microbes survived the treatment and continued to thrive without interruption, helped by the fact that the heat knocked their natural predators and their less hardy competitors out of the picture.

Cleanup at the Visalia Pole Yard

In 1997, cleanup using both of the Livermore processes began at the Visalia Site.  The operation was conducted by Steamtech Environmental Services of Bakersfield, which currently holds the only commercial license.  Compared to the 10 pounds per week of the conventional pump-and-treat process, the new operation achieved nearly 46,000 pounds per week over the first six weeks – a rate of over 5,000 times faster than previously.  The combination of the two process was key, as the oxidation operation eliminated the need to excavate or dispose of soil contaminated soil.  The result was not only cheaper and faster but also more effective: after remediation, the groundwater at the Pole Yard was determined to achieve drinking water standards.

Superfund in the Future…

The irony of conventional site cleanup is the high carbon footprint (and high cost) of shifting large quantities of soil and/or water around, sometimes over multiple decades – and even then, the result may not be complete.  The development of Livermore’s highly effective steam-based process, also known as Steam Enhanced Extraction, was based on research lead by Dr. Kent Udall under a Superfund grant program at UCal-Berkeley.  The Visalia success garnered a rare award from EPA for technical excellence, and that’s not all.  At a cost of $15 million, the process saved about $85 million.  It’s clearly part of a trend toward less energy intensive but far more effective in-place cleanup methods such as phytoremediation, some of which even use solar power and other sustainable power to run equipment.

Image: woodleywonderworks on flickr.com. 
 

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.



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