LAB DEVELOPS NOVEL METHOD TO CLEAN GASOLINE SPILLS

Researchers at Lawrence Livermore National Laboratory have developed a process to remove underground gasoline at leak or spill sites. The dynamic stripping process includes heating and steam cleaning soil and was discussed earlier this month at the American Geophysical Union meeting in San Francisco. Kent Udell of the University of California at Berkeley and university colleagues developed the dynamic underground stripping process by adding vacuum extraction to the steam injection method used

Dec. 20, 1993

3 min read

Researchers at Lawrence Livermore National Laboratory have developed a process to remove underground gasoline at leak or spill sites.

The dynamic stripping process includes heating and steam cleaning soil and was discussed earlier this month at the American Geophysical Union meeting in San Francisco.

DYNAMIC STRIPPING

Kent Udell of the University of California at Berkeley and university colleagues developed the dynamic underground stripping process by adding vacuum extraction to the steam injection method used by oil companies to extract heavy crude.

The laboratory tested the process by injecting higher pressure steam under an area where four tanks had leaked gasoline during the late 1970s. The trapped gasoline was forced to flow toward a central extraction or production well.

The process was enhanced by using huff and puff steam injection, then vacuuming liquid and vapor out of the hole. It also uses injected electricity, to heat impermeable clays and free fuel absorbed in those highly conductive areas. The team controlled the process by watching steam and heat move underground with electrical resistance tomography (ERT).

About one third of the fuel was condensed at the surface for recycling, while the rest ran two V-8 engines that provided a vacuum for extracting vapor. About 7,800 gal of gasoline have been removed from 80,000 cu yd of soil at depths of 60-140 ft.

"We have apparently succeeded in removing all free product from the site," said Roger Aines, a laboratory scientist working with the team.

FAST, EFFICIENT

The demonstration project took just a few months. A more traditional method of injecting and extracting cold water to remove gasoline in theory could take as long as 200 years in a comparable situation because much of the gasoline was trapped 20 ft below the water table, which rose after groundwater pumping in the vicinity was stopped.

Much of the distilled gasoline is clean enough to run a car engine, the laboratory said, and in large scale applications, such as removal of refined products from soil around refineries, the ability to recover usable product will be valuable.

"Dynamic stripping cuts the heart out of a spill," said Aines. "It removes the concentrated, free standing contaminants quickly so you don't have them continuously reaching into the soil and extending cleanup projects for years.

"Once stripping has removed the core of the contamination, traditional methods of soil and groundwater cleaning can be used to clear up the 'bathtub ring,' if you will."

Udell is beginning to explore removal of chlorinated solvents such as trichlorethylene and perchlorethane, common contaminants in Superfund sites. The team may apply the process to remove solvents at a military base slated for closure.