Cleaning up a toxic groundwater plume using heat

Hoses carry vapors to large pipe that leads to filter system. Vapors are created using high-temp electrodes that extend 30 feet into the ground. Seaplane Lagoon and San Francisco are in background.

There are various methods to clean up groundwater contaminated with solvents and petroleum products. Beneficial chemicals can be injected to neutralize the toxic chemicals.  Sometimes bacteria, either those naturally present or some that have been added, can do the job.  In some cases at Alameda Point the Navy inserts steel beams called electrodes into the ground that are hooked up to their own power line.  They dial up the power to 1,100 amps (a household electric stove is around 40 amps), and let the heat turn the chemicals into vapor.  This is the method the Navy is using in a limited application just east of the Seaplane Lagoon.

Power pole with filter tanks for water and toxic vapors.

The cleanup operation has been underway since May.  It will end in mid October to review results. 

The operation is called a pilot study, but pilot studies like this one will do more than just provide information.  It will most likely accomplish cleanup of part of the plume.  A similar setup was successful near Building 5.

So, why label this a pilot study when this high-temp heating method of cleanup has already been proven effective in cleaning up groundwater?  This cleanup area, called Operable Unit – 2B, is complicated.  The full work plan is not yet ready.  It appears that this work was begun under the label of a “pilot study” as a practical way of getting cleanup underway prior to approval of the full work plan.   At least one other pilot study at Alameda Point accomplished cleanup goals well ahead of final work plan approval.

Electric power system for six-phase heating system for groundwater cleanup.

Once the heat from the electrodes turns the toxic chemicals into vapor, the vapors are sucked up through a series of holes, into hoses, and then to a filter system.  The water is filtered out, then the chemical vapors and chemical liquid are separated and trapped in a carbon filter for disposal.

The heat treatment system is called six-phase heating.  It gets the name because it employs six evenly spaced electrodes wired together with a neutral electrode in the middle.  The steel electrodes are hammered to a depth of 30 feet.

This cleanup area is currently not part of the first land conveyance from the Navy in June of 2012.   

Author: richard94501

My blog is Alameda Point Environmental Report covering environmental issues from wildlife to cleanup at the former Navy base in Alameda now called Alameda Point. Articles on my blog are frequently printed in the Alameda Sun newspaper. I also host a Twitter site and a Flickr photo site. I hope you find my stories and photos of interest. Richard Bangert Alameda, California

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