Note: Please read article as originally posted at EPA Region 10 Building on Brownfields Newsletter.

What’s ozone sparging?
New technology put to work at former dry cleaners

A redevelopment project in Twin Falls, Idaho, is using ozone sparging technology to clean up groundwater contamination at a former dry-cleaning business.

While TerraGraphics Environmental Engineering, Inc. is no newcomer to the brownfields arena, this is the first time the veteran company is using ozone sparging on a cleanup project, says Jon Munkers, the company’s Boise office manager and an environmental scientist.

The remediation technology transforms the contaminant perchloroethylene (perc), a dry-cleaning chemical found on the site, into less toxic chemicals, Munkers explains. While clean up began in March, monitoring wells already are showing good results from the ozone sparging.

Formerly known as Mr. A’s Dry Cleaners, the Twin Falls property was a dry-cleaning business from the mid-1980s until December 2006, when it was vacated to prepare for brownfields assessment and the future sale of the property to a Pocatello developer.

A Phase I assessment initially revealed significant environmental concerns, so a Phase II assessment followed. The Phase II consisted of collecting soil samples from nine boreholes, installing two up-gradient and one down-gradient monitoring wells, collecting down-gradient and up-gradient groundwater and soil samples, and installing nine sub-slab vapor points. The final report, completed last year, showed dry-cleaning solvent contamination in the soil and groundwater, as well as dry-cleaning solvent vapor intrusion into the building.

Remediation this year has consisted of ozone sparging as well as the installation of a vapor extraction system under the building’s concrete slab. With the groundwater concerns, first understanding the direction the water was flowing was difficult because of the fractured basalt surrounding the groundwater, Munkers says.

Pulsed ozone sparging has become viewed as a highly effective remedial technology for treating contaminated soil and groundwater in-situ. The process involves injecting high-concentration ozone gas into saturated soils and groundwater to chemically oxidize volatile organic compounds, semi-volatile organic compounds, chlorinated solvents, petroleum hydrocarbons and other organic compounds.

With ozone sparging, concentrated ozone gas is directed to the subsurface through a stainless steel manifold using either stainless steel piping or ozone-resistant tubing. Sparge wells are installed throughout the target zone to deliver the ozone gas to the contaminated soil or groundwater.

The company chose to use ozone sparging because it was looking for quick results, Munkers says. He expects to see the property’s groundwater issues resolved in a year and the vapor issue resolved in a couple of years.

Meanwhile, the redeveloped property is preparing for its grand-opening activities in July. The new business will sell nontoxic cleaning supplies, bringing this brownfield full circle.

This entry was posted on Sunday, August 31st, 2008 at 4:34 pm and is filed under ●Environmental Engineering, ●Environmental Service/Product Providers.

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