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' TECHNICAL WORKPLAN <br /> 1 <br /> ADDITIONAL INVESTIGATION WORKPLAN <br /> ' GENERAL DYNAMICS OST 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 of the State of California Department of Health <br /> Services (DTSC), on behalf of General Dynamics OTS (California), Inc. (GD), presents <br /> ' the scope of work for additional assessment of soil impacted by Total Petroleum <br /> Hydrocarbons at solid waste management unit number 21 (SWMU 21) at the former GD <br /> ordnance testing facility located at 32727 Corral Hollow Road, approximately 3.5-miles <br /> ' south of Tracy, California (site). The scope of work also includes an assessment for <br /> possible TPHd and O&G impact to groundwater, if any, at SWMU 21. The location of <br /> the site is presented on Figure 1. A map of the site is presented as Figure 2. <br /> 1.0 INTRODUCTION <br /> The additional investigation of TPHd and O&G impact to soil, and possibly groundwater, <br /> has been requested by the DTSC based on the analytical results for soil samples <br /> collected during the implementation of the Corrective Measures Study (CMS) workplan <br /> at SWMU 21 in March and April of 2002. The analytical results confirmed that both <br /> TPH-d and Oil & Grease had impacted the soil above 1000 mg/kg in one 8" boring and <br /> three (3) 1.5" geoprobe locations southeast and down slope of SWMU # 21. See <br /> Figure 3. <br /> This work plan proposes the installation of four additional 8" diameter borings, to allow <br /> soil and water sample collection in order to better define the vertical extent of petroleum <br /> hydrocarbons in the soil, and to verify that groundwater has not been impacted by <br /> previously released petroleum hydrocarbons from SWMU 21. <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 /> CE Project No.99R-4041 <br /> Additional Investigation Work Plan 1 <br />