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• "� feasibility Study—Enhancement of Existing Remediation Activities 8200 N. Highway 99, Stockton, CA Page 7 of 10 X Criterion 4—Regulatory and Community Acceptance: This alternative should meet with public and regulatory acceptance if the bench scale and pilot tests indicate the system will be effective in reducing constituents of concern and not mobilize metals at the site. 3.0 COMPARISON OF ALTERNATIVES Both groundwater extraction and chemical oxidation are technically feasible. Additional groundwater extraction is less expensive and can be implemented quickly upon approval of the proposed scope of work in the feasibility study. Both groundwater extraction and ISCO are expected to be effective within limits_ Groundwater extraction alone has a reasonable likelihood of achieving a measure of control over the groundwater plume in the area around MW 12. However, without eliminating the contaminant mass in the source area, the system would need to be operated for an open-ended period of time and the source area remediation activities may need to be enhanced. The goal of this feasibility study was to review the best option to enhance the remediation of the plume at and around MW 12. If confirmation soil borings indicate the remediation activities near the source area need to be enhanced as well, ISCO treatment can be reasonably expected to have a pronounced effect in reducing source-area contaminant mass. 4.4 PROPOSED ALTERNATIVE FOR REMEDIATION GZA proposes to control the downgradient plume of contamination near MW 12 by installing an extraction well upgradient of MW12, enhancing the existing groundwater extraction and treatment system. The installation of an additional extraction well will be cost effective and can be implemented with great speed. Upon approval of the following scope of work, a well installation permit application will be submitted to EHD. The site will be cleared by Underground Services Alert at least 48 hours prior to any drilling or trenching activities. EHD and RWQCB will be notified at least 48 hours prior to any scheduled site activities. 4.1 Extraction Well Installation and Sampling A C-57 licensed drilling company will advance a soil boring at the approximate location shown on Figure 3 using a drill rig equipped with hollow stem augers. Soil samples will be collected at five-foot intervals to total depth of each boring for lithologic identification and field screening for contamination. Soil samples will be collected with a split spoon sampler containing clean brass or stainless steel liners. Samples selected for laboratory analysis will be capped, labeled for identification, and immediately placed in an ice-chest chilled to 4°C. G:\GROUNDZEITULEBURG\Reports10709 FS rem enhancement.doc