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SECTION 1.4 INTRODUCTION <br /> majority of the site is overlain with concrete and asphalt Vehicle maintenance bays and equipment <br /> storage buildings are located east of the fueling station (Figure I-1) <br /> 1.2 OBJECTIVES <br /> The overall project objective is to complete the delineation of petroleum hydrocarbons in the <br /> subsurface beneath the Stockton Yard and use the additional data to (1) conduct a human health <br /> and groundwater risk assessment and (2) assess potential remedial alternatives to mitigate <br /> residual petroleum concentrations, if necessary, based on the risk assessment results, <br /> CVRWQCB Basin Plan objectives and Caltrans objectives The objectives that will be <br /> accomplished by the tasks described in this report include the following <br /> • Evaluate the stratigraphy beneath the site <br />' • Assess the extent and magnitude of petroleum hydrocarbons in soil and in groundwater <br /> through the evaluation of previous subsurface investigation data and horizontal and vertical <br />' groundwater sampling <br /> • Evaluate the hydraulic characteristics of the saturated zone(s) <br /> 0 Monitor the dissolved-phase petroleum hydrocarbons in groundwater <br /> The results of this investigation will be used to conduct a human heath risk assessment and <br /> groundwater impact analysis The completed Human Health Risk Assessment and Groundwater <br />' Impact Analysis Report will present the current risks for complete exposure pathways, and <br /> discuss CVRWQCB Basin Plan water quality objectives and site-specific corrective action goals <br /> to achieve site closure In addition, in accordance with Caltrans objectives and Task Order <br />' agreements a separate report that includes an evaluation of potential remediation alternatives and <br /> the respective magnitude of costs will be prepared <br /> 1.3 APPROACH <br /> URSGWC prepared a scope of work that outlined six tasks to achieve the above objectives <br /> (Woodward-Clyde, 1998) The scope of work was partially completed under the previous <br /> contract (Number 43X929), that expired on April 30, 1999 A new scope of work (URSGWC, <br /> 1999) was submitted and approved by Caltrans in June 1999, concurrently with the approval of <br /> the new contract (Number 43A0019) The tasks are outlined in the scope of work described <br /> below <br /> S 4PROJ14I040100041SYYARl14MAINTYARCSADOC URS Greiner Woodward Clyde <br />