Pollution Engineering - April 2009 - (Page 24) Remediation GOES FOR Needing a cleanup win and up against the buzzer, a three-part plan using in-situ chemical oxidation was able to score a game-clinching groundwater cleanup. By DAN BRYANT, Geo-Cleanse Intl. Inc., and ED KELLAR, MACTEC Engineering and Consulting Inc. I n 2007, the NBA’s Orlando Magic and their host city unveiled the design for the Orlando Events Center as the professional basketball team’s new downtown venue. Due diligence by the city identified a groundwater tetrachloroethene (PCE) plume with a source area located beneath the proposed arena footprint (see Figure 1). The maximum PCE concentration found in the source area groundwater was 14,600 mg/L, which exceeded the Florida groundwater Cleanup Target Level (CTL) of 3 mg/L. Trichloroethene (TCE; maximum concentration of 57 mg/L) and cis-1,2-dichloroethene (DCE; maximum concentration of 98 mg/L) were also detected at concentrations exceeding their CTLs of 3 mg/L and 70 mg/L, respectively. Shallow soil (2 to 4 feet below grade) was also impacted in two discrete areas. The maximum soil PCE concentration was approximately 0.49 mg/kg, which exceeded the Florida soil CTL for leachability of 0.03 mg/kg. The aquifer was primarily sand, with some finer-grained (silty sand) zones to a depth of approximately 40 feet below grade, underlain by a dense clay aquitard in the treatment area. Drawing up the play The city issued a request for proposal for a source area remedy with a fast-tracked, performance-based contract on Aug. 30, 2007. Construction was scheduled to begin in the late summer 2008, thus a very rapid and aggressive response was required to prevent any construction delay. Geo-Cleanse International Inc., Matawan, N.J., and Mactec Engineering and Consulting Inc., Newberry, Fla., agreed to partner for the project and developed a three-phase remediation plan. The first phase consisted of in-situ chemical oxidation (ISCO) with catalyzed hydrogen peroxide (CHP) to target the concentrated source area. The second phase consisted of additional ISCO using sodium permanganate to target residual contaminants potentially remaining after the catalyzed peroxide application. The third phase consisted of removal with offsite disposal of impacted shallow soil. Figure1: The above drawing shows the location of the injection points, monitoring wells and other points of interest on the site. 24 Pollution Engineering APRIL2009
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