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I PROBLEM ASSESSMENT REPORT 14800 West Frontage Road Manteca California 5.2.2 2 In-Situ Bioremediation This groundwater remediation alternative involves the infection of nutrients, an appropriate bio-culture, and air (or some combination of these) into the vadose zone, capillary fringe, and affected areas of the groundwater table An appropriate monitoring program must be implemented concurrently with the treatment process to evaluate its effectiveness, the rate of biodegradation, and ensure the maintenance of optimum conditions for the bio- mass Prior to implementing an in-situ bioremediation alternative, key subsurface conditions and characteristics must be ascertained to ensure the adequacy of this Itreatment alternative Some of these key elements include 1) The lateral and vertical heterogeneity and/or homogeneity of the subsurface material and/or soil types as defined by the Unified Soil Classification System 2) The horizontal and vertical permeabilities of subsurface soil 3) The types, concentrations, and distribution of hydrocarbons in the vadose Iand groundwater zone 4) The biological and chemical oxygen demand of the water-bearing zone and any potential bio-culture 5) The pH of the affected soil mass and groundwater zone I 6 The identification of an natural) occurring micro-organisms present in the ) Y Y 9 9 subsurface which may potentially consume the contaminants in question Once these subsurface characteristics and conditions have been adequately evaluated, a determination must be made as to whether in-situ bioremediation is technically feasible For example, if permeability of sod represent a potential problem in ensuring the effective introduction of nutrients, bio-culture, and/or air into the affected areas of the subsurface, I then the feasibility of enhancing local permeabilities must be evaluated In some cases, these difficulties may-be overcome by a series of appropriately located trenches If a preliminary assessment of the subsurface conditions indicates the lack of appropriate micro-organisms, then an appropriate artificial bio-culture must be specified If the pH of soil and/or groundwater is untenable for the proposed bio-culture, then a plan to alter the pH to appropriate levels must be developed IAfter technical problems have been identified and resolved, a preliminary design of a potential treatment system can be accomplished The preliminary costs of a potential treatment system can be compared to other groundwater treatment alternatives Finally, nontechnical considerations, such as the length of remediation, can be considered concurrent with technical feasibility and potential project costs 1 90-097A PAR 13