In situ chemical oxidation has been used successfully to remediate soil and groundwater contamination at numerous industrial facilities contaminated by chlorinated solvents and polycyclic aromatic hydrocarbons (PAHs). The Sempra Energy Utilities former MGP site in Los Angeles, California was the site of a number of industrial activities following the termination of MGP operations. The site contains soils impacted MGP residuals, predominantly polynuclear aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs) and dicyclopentadiene (DCPD). A treatability study determined that ozone (O3) was an effective in situ treatment option for the Site. The pilot test area for the DCPD and MGP residuals is a sand and gravel alluvial formation. Groundwater is encountered at a depth of 30 feet below grade. Initial concentrations within the alluvium were as high as 1900 ppm in soil. Ozone, generated on site was pulsed into twelve, multi-level O3 injection points. Vapor monitoring verified that ozone sparging and injection has distributed ozone uniformly throughout the subsurface. Significant reductions in concentrations were observed in the soil and groundwater after the completion of the three-month pilot test.
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