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TECHNICAL WORKPLAN <br /> ADDITIONAL INVESTIGATION WORKPLAN <br /> GENERAL DYNAMICS OTS TRACY TEST FACILITY <br /> 32727 Corral Hollow Road <br /> Tracy, California <br /> This amended workplan (WP), prepared by Chow Engineering, Inc. (CE), for submittal <br /> to the Department of Toxic Substances Control (DTSC) on behalf of General Dynamics <br /> OTS (California), Inc. (GD-OTS), presents the scope of work for additional assessment <br /> of total petroleum hydrocarbons (TPH) in soil and groundwater at solid waste <br /> management unit number 21 (SWMU 21) at the former GD Tracy Test Site (TTS) <br /> located at 32727 Corral Hollow Road, approximately 3.5-miles south of Tracy, California <br /> (site). The location of the site is presented on Figure 1. A map of the site is presented <br /> 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, additional monitoring wells and soil sampling are proposed at <br /> SWMU 21. With additional monitoring wells to provide data, hydraulic testing (e.g., a <br /> "slug test") is then proposed for the confined wells. Also, soil sampling at the potential <br /> seepage face on the hillside on the south side of SWMU 21 is proposed. <br /> This work plan proposes the installation of two additional groundwater monitoring wells, <br /> to allow water sample collection to better define the extent of TPH in the groundwater, <br /> and to better determine the direction and rate of groundwater flow. Collection of three <br /> (3) soil samples is also proposed southeast of MW-8 on the hillside. These soil <br /> samples will be collected to determine if groundwater is seeping out of the hillside from <br /> the aquifer. <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. The majority of the surface area of the site <br /> is located in a water gap (Elk Ravine) transecting the northeast slope of a southeast- <br /> northwest trending anticlinal ridge of the Altamont Hills. A northeast trending <br /> intermittent stream, Corral Hollow Creek, is located approximately 150-ft northeast of <br /> Corral Hollow Road in the bottom of the water gap. Outcrops of very coarse-grained <br /> (conglomerates) to fine-grained (sandy siltstones) sedimentary strata, obscured by <br /> undifferentiated coarse to fine-grained detrital deposits at the foot of the ridge, are <br /> CE Project No.99R-4041 <br /> Additional Investigation Work Plan 1 <br />