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TECHNICAL WORKPLAN <br />ADDITIONAL MONITORING WELL WORKPLAN <br />GENERAL DYNAMICS OTS TRACY TEST FACILITY <br />32727 Corral Hollow Road <br />Tracy, California <br />This workplan (WP), prepared by Chow Engineering, Inc. (CE), for submittal to the <br />Department of Toxic Substances Control (DTSC) on behalf of General Dynamics OTS <br />(California), Inc. (GD-OTS), presents the scope of work for an additional monitoring well <br />at solid waste management unit number 21 (SWMU 21) at the former GD Tracy Test <br />Site (TTS) located at 32727 Corral Hollow Road, approximately 3.5-miles south of <br />Tracy, California (site). The location of the site is presented on Figure 1. A map of the <br />site is presented as Figure 2. <br />1.0 INTRODUCTION <br />To better understand the hydraulic conductivity and other characteristics of mineral oil in <br />the subsurface at the site, an additional monitoring wells and soil sampling are <br />proposed at SWMU 21. <br />MW-6 is 49.5 feet below ground surface (bgs) and is frequently dry as it is not screened <br />deep enough. The new well MW-6B will be screened approximately 60-70 feet bgs. <br />MW-6 will remain open for use in application of 2% hydrogen peroxide (H202). <br />This work plan proposes the installation of one (1) additional groundwater monitoring <br />well, to allow water sample collection to better assess the levels of TPH in the <br />groundwater. <br />2.0 SITE DESCRIPTION AND PREVIOUS INVESTIGATIONS <br />The site is located on approximately 500-acres of land at 32727 Corral Hollow Road, <br />approximately 3.2-miles south of the intersection of Interstate Highway 580 SW and <br />Corral Hollow Road, near Tracy, California. <br />The full history of the SWMU has been presented in earlier reports. <br />2.1 Site Lithology, Stratigraphy and Hydrogeology <br />The geological map (modified from Dibblee, 1980; and Dugan and Matelek, 1990) <br />shows the site surface to consist of Quaternary landslides underlain by the Neroly and <br />Clerbo formations. The map shows that the Callahan fault which trends NNW on and <br />CE Project No. 99R-4041 <br />Additional Monitoring Well Work Plan 1