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Additional Groundwater Investigation and Remeron Feasibility Evaluation Work Plan Stockton Center Site Authority-University Park January 25,2005 Page 10 6.0 REMEDIATION FEASIBILITY EVALUATION The proposed scope of this investigation includes a detailed examination of subsurface conditions through detailed lithologic logging of soils, discrete-depth soil sample collection for analyses of chemical and physical properties, monitoring of chemical and physical parameters, and bench scale testing of site soil and groundwater. The bench scale testing is intended to evaluate the effectiveness of ozone injection, bioremediation, and/or other remediation technologies at the site. Detailed geologic logging and analyses of physical properties of the soils is expected to yield important information about the complex site hydrogeology. It may potentially aid in recognition of preferred flow pathways (contaminant migration conduits) and in identification of potential means of remediation. Analyses of soil characteristics will include laboratory hydraulic conductivity tests (flexible wall, or tri- axial lab permeameter tests), bulk density/moisture content (to assist in effective porosity evaluation), total organic content(to evaluate oxygen demand of the soil)and particle size distribution and hydrometer tests(to classify soils). Site management has requested the feasibility evaluation of less obtrusive, less aggressive, more cost effective remediation alternatives. Chemical oxidation of the hydrocarbons into carbon dioxide and water by ozone injection is a potentially viable option for the site since it is anticipated to be effective on the site's most recalcitrant contaminant, 1,2-DCA. Residual oxygen from the reactions also encourages bioremediation in the outer reaches of the chemically oxidized zone (halo). Ozone injection is potentially attractive for the site because it may reduce contaminant concentrations in the vadose zone as well as in the saturated zone. Subsurface hydrogeologic conditions beneath the site, however, may not be amenable to contaminant remediation by ozone injection, and/or engineering may be necessary to increase the effectiveness of ozone injection. New ozone treatment techniques combining peroxide with the ozone, to increase the effective radius of the application, are showing promise for vadose zone treatment. Ozone injection has also been documented to create nuisance conditions such as metals mobility in certain environments,however. Enhanced natural attenuation through oxygen infusion (bioremediation) is also a potential low-cost, relatively unobtrusive, longer-term remediation option in which high levels of dissolved oxygen in groundwater are achieved through mass transfer from a high surface-area interface (installed in monitoring wells). Insufficient subsurface data currently exists to effectively evaluate the progress of natural attenuation at the site, the potential for enhancement of the natural attenuation process through oxygen infusion, and/or the viability of active remediation alternatives such as ozone injection. Investigation and monitoring of chemical and physical conditions and bench scale testing of site soil and groundwater are proposed to address these issues. Field parameters such as dissolved oxygen (DO), oxidation/reduction potential (ORP), pH, temperature, conductivity; and chemical parameters such as nitrogen, phosphate, total iron, ferrous iron, sulfate, alkalinity, biological oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon, total inorganic carbon, and total dissolved solids (TDS) are some of the indirect indicators of natural attenuation and the feasibility of ozone injection, oxygen infusion, etc. Bench scale testing is proposed to evaluate ozone injection and bioremediation (oxygen infusion, etc.) as feasible remediation methods of site soil and groundwater, to address potential concerns such as increasing the mobility of lead, arsenic, chromium and other metals in the site groundwater, and the potential consumption of ozone/oxygen by naturally occurring organic matter (thereby reducing the effectiveness of the treatment). Generally, the bench scale testing will provide insight into the subsurface conditions which will impact the remediation processes.