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GEOMAMTRIX <br /> groundwater The apparent groundwater speed is calculated as high as 200 feet per year, but <br />' variable groundwater flow direction and a low groundwater gradient has helped keep PHCs <br /> limited to a small volume The potential for additional migration of PHCs in groundwater is <br /> low and the potential for impact to groundwater production wells located more than 2,000 feet <br /> from the site is negligible <br /> 5.0 REMEDIATION EVALUATION <br /> Indicator parameters for biological activities were measured in the groundwater samples <br /> collected from the three new monitoring wells and two existing wells to evaluate intrinsic <br /> bioremediation of petroleum hydrocarbons in groundwater at the site These parameters <br /> included pH, DO, ORP, dissolved iron (Fe), dissolved manganese (Mn), nitrate, and sulfate <br /> The results of these parameters are summarized in Table 6 and included in Appendix B <br /> 1 <br /> DO in groundwater is typically depleted during aerobic biological respiration Negative ORP <br />' measurements typically indicate reducing conditions in an anaerobic environment. Lower pH <br /> in groundwater may be a result of the carbon dioxide generated during aerobic biological <br /> respiration Nitrate and/or sulfate can be used as alternative terminal electron acceptors in <br /> anaerobic biodegradation of organic matter, resulting in reduced nitrate and/or sulfate <br /> concentrations in groundwater Fe and Mn can be converted to their more soluble forms in <br /> reducing conditions, resulting in increased dissolved Fe and/or Mn concentrations in <br /> groundwater The results of these indicator parameters are compared to the concentrations of <br /> TPHg and BTEX in the groundwater samples <br />' The results of these parameters indicate naturally reducing conditions in the saturated zone <br /> beneath the site As a result of the reducing conditions, using Oxygen Release Compound <br /> (ORC) to enhance in situ aerobic biodegradation of the petroleum hydrocarbons in the <br /> tsaturated zone beneath the site would be costly A preliminary cost estimate provided by <br /> Regenesis (ORC vendor) and the Port for enhanced in situ bioremediation at the site would be <br />' more than $100,000 <br /> Excavation of affected soil would be cost prohibitive due to the lateral and vertical extent, <br /> (i e , expensive engineering systems would be required to protect existing structures and <br />' ongoing operations at the site) <br /> 1 <br /> 1 XPROJECTY"s16437 00016437-08 doc 14 <br /> 1 <br />