ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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amec— Other important O&M assumptions include: o Each recirculation well pair is assumed to operate for 6 hours per week. Recirculation will occur in one direction for three hours and then in the opposite direction for the remaining three hours. o Annual system operating time is assumed to be 8,400 hours per year for 30 years. o The performance monitoring system will comprise 90 multi-level wells spaced at 100-feet centers along two transects, with 45 wells in the upgradient monitoring well transect, and 45 wells in the downgradient monitoring well transect. The total cost of in situ treatment with a bio-curtain greatly outweighs the costs for wellhead treatment and water replacement (the current strategy). Furthermore, as discussed in Section 3.2, the bio-curtain system may not be effective at completely treating and containing VOC- affected groundwater in the vicinity of the WWTP. Therefore, bioaugmentation is not considered to be an effective alternative for treating groundwater beneath the WWTP area. 3.5 ENERGY REQUIREMENTS The amount of power required to pump water for recirculation and control the metering pumps is estimated to be 846 mega-watt hours (MWh) per year of operation (Table B.2-1). This is much lower than the energy requirements of the biosparging system described in Technical Attachment#1 and is not a major consideration for implementing a bioaugmentation biocurtain. 4.0 CONCLUSIONS Based on analysis of effectiveness, implementability and cost of biosparging (presented below) it is concluded that bioaugmentation is not feasible for treating COC-affected groundwater near the City of Ripon WWTP Lagoons. The effectiveness analysis concluded that: • In theory, bioaugmentation could be effective at destroying VOC mass in situ; however; in practice, adequate distribution of the microbes across the bio-curtain alignment is highly uncertain, therefore the effectiveness of bioaugmentation is highly unlikely. The implementability analysis concluded that: • The final as-built system would be an almost mile long fenced compound adjacent to the Stanislaus River. There are significant implementation challenges associated with public acceptance of an almost mile long fenced remediation compound adjacent to the Stanislaus River. AMEC Geomatrix, Inc. \\oad-fs1\doc_safe\9000s\9837.006\4000 REGULATORYTFS Assessment_Apx B_01 2711\Attachment B.2\Attach B-2.doc 132-11