SITE INFORMATION AND CORRESPONDENCE FILE 1

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' f r J 595 Eleventh, Tracy Page 2 In the June 15, 2001, report, Wright Environmental selected Option #1 (soil excavation) for approval. This option was previously considered by Wright Environmental and in correspondence dated October 6, 1999, they stated, 'After r some discussion, WSI (West Side Irrigation District) voted to deny encroachment. Rational for denial was due to aged condition of(the) 4'diameter cbncrete line. Soil excavation in the Tracy area has proven to be a viable, cost effective corrective action. At this site, because of the proximity of the fragile irrigation line and previous denial of encroachment by WS], the feasibility of { excavation is in question. If WSI will grant access for soil excavation near their pipeline, then the effectiveness and cost of this option should be evaluated. In order to evaluate the other two options (horizontal well and insitu-enhanced bioremediation) discussed in lbe June 15, 2001, report, feasibility tests must be conducted. If the options are determined to be viable, then the costs of performing them must be determined. Investigating the feasibility of dual phase extraction (Option #2) should be based on the ability of the extraction system to effectively draw a sufficient vapor pressure in the area of contamination and provide effective groundwater extraction that increases the amount of vadose zone targeted for soil vapor extraction. Aquifer tests and soil vapor extraction tests are required before this option can be evaluated. A work plan to install wells necessary for conducting the field tests and detailing the performance of the field tests to evaluate this option should be submitted to PHS/EHD. Wells and details for performing field tests necessary to investigate the feasibility of in-situ, enhanced bioremediation (Option #3) should be included in the work plan also. The State Water Resources Control Board Clean Up Fund has closely scrutinized the costs and effectiveness of oxygen releasing substances added to the groundwater. Justification of the cost when comparing the effectiveness of this option will be difficult. Additionally, the CVRWQCB has indicated that waste discharge requirements will be applied to the use of oxygen release compounds so their approval will be required prior to its use. Introduction of bacteria into the T groundwater will also require CVRWQCB approval and conditions. The June 15, 2001 report submitted by Wright Environmental is very detailed. With the addition of field-testing data (feasibility), detailed cost breakdowns for each option and selection of the most cost effective option, a Corrective Action Plan can be prepared for this site. In future quarterly monitoring reports, please provide a table that includes the historical groundwater contaminant levels for each well so that review of the previous impact to each well can be accomplished without reviewing all of the previous reports. Additionally, CVRWQCB staff requests a "time-vs- concentration" graph for MW 2, 3, and 9. /f