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Workplan for Vertical Groundwater Investigation And Bench Test for In-Situ Oxidation 7835 Thornton Road, Stockton, CA Page 6 of 8 extraction would have limited effect on the sorbed contaminant mass, whereas in-situ oxidation has a tendency to aid in desorption of contaminants bound to the soil substrate. This occurs because the hydroxyl radicals created by the oxidation process are non-selective, and in addition to attacking the target contaminant compounds, they also attack the soil-based organic matter that binds the contaminants to the soil. We propose to evaluate in-situ oxidation using a modified Fenton's Reagent as the oxidizing solution. Fenton's Reagent has long been used in the wastewater treatment industry. In government-sponsored studies, the in-situ injection of Fenton's Reagent has been shown to be effective in oxidizing organic contaminants such as fuel hydrocarbons and chlorinated solvents. Fenton's Reagent is one of strongest oxidizers known due to the formation of hydroxyl radicals by the catalysis of hydrogen peroxide. Classic Fenton's Reagent consists of a solution of H2O2 catalyzed by iron, typically in the form of FeSO4. The oxidizing strength of the solution is maximized when the treated water is at a pH of approximately 3-5. This is typically accomplished by the addition of sulfuric acid (which is a common adulterant of commercial- grade FeSO4). Temperature will rise with the reaction. The optimal temperature is between 70- 100° F. To control temperature and pH, it may be necessary to stage the introduction of peroxide. Working in conjunction with In-situ Oxidative Technologies, Inc. (ISOTEC), we propose to use a modified Fenton-based process that has been designed to function at natural subsurface conditions, with pH — 7.0 and temperature within 10° C of normal. ISOTEC uses patented reagents designed for neutral subsurface conditions and efficient hydroxyl radical and superoxide generation. ISOTEC's oxidation and reduction method utilizes a site-specific delivery system designed to treat organic contaminants within an area of concern. ISOTEC oxidants and catalysts react with the organic contaminants within the subsurface producing innocuous by-products such as carbon dioxide and water. ISOTEC's process utilizes patented chelating agents as the catalyst for the reaction rather than FeSO4, which tends to limit the leaching of naturally occurring metals that occurs in the acidified environment of classic Fenton's chemistry. ISOTEC's reagents have also been designed to increase the mobility of the oxidants by preventing precipitation or fixation of iron to native soil, thereby promoting its availability for hydroxyl radical generation from peroxide. Bench Test The oxidizing strength of the reagent has the potential to alter the valence of metallic ions and halogens. The Regional Water Quality Control Board, Central Valley Region (RWQCB) has expressed particular concern about the possibility of oxidizing trivalent chromium to the more toxic and mobile hexavalent species and/or oxidizing bromide to the +5 valence state creating the toxic bromate ion. Consequently, bench testing is required before RWQCB will consider permitting the injection of oxidizers into contaminated aquifers. Depending upon the results of the bench testing, injection may be permitted with or without Waste Discharge Requirements, or may be forbidden altogether. G:\GROUNDZE\KNOWLES.HAM\REPORTS\WKPLAN_deepwell—bench2.doc