The federal environmental regulatory agency in the U.S. defines green remediation as “the practice of considering all environmental effects of remedy implementation and incorporating options to maximize the net environmental benefit of cleanup actions” (USEPA Office of Solid Waste and Emergency Response, April 2008). With this definition in mind, the focus of this paper is to evaluate all environmental effects of changing from a conventional pump-and-treat (P&T) technology to a “green” technology. This case study examines the effects on energy, air pollutants, water, land and ecosystems, raw materials, and long-term stewardship during the treatment of a large tetrachloroethene (PCE) plume located in Los Angeles, California. Through ten years of P&T, approximately 4,200,000 gallons of impacted-groundwater have been pumped, treated, and discharged to the sewer system. It is estimated to take an additional 28 years for continued treatment. A “green” technology using in-situ chemical oxidation via sparging ozone gas to the groundwater was successfully pilot-tested in October 2007 and subsequently expanded to full-scale in April 2009. In-situ ozone sparging has shown significant progress to treat the plume while at the same time reducing power consumption by approximately 82%, site visits and traffic miles by 74%, fuel consumption by 74%, and vehicular emissions by approximately 81%, and also no net water consumption with zero discharge to the sewer system or storm drain, and eliminate the generation of secondary waste like spent granular activated carbon.