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petroleum hydrocarbons, and potential exposure pathways under current and potential future uses. Schematic of the CSM is provided as Figure 16. 4.1 Physical Model Early investigations in the vicinity identified a series of four hydrogeologic zones defined as the A-, B-, C-, and D-zones (SECOR, 2003). In the southern leasehold, the A- and B-zones appear to be contiguous and are comprised of laterally discontinuous sand and clay layers of various thicknesses. The C-zone is the most continuous sand layer under the Facility and is separated from the other zones by 2 to 10 feet of silty clay. The D-zone consists of thin, laterally discontinuous sand layers interbedded with silt and clay. Groundwater typically flows towards the east and southeast with some local and seasonal variability. Hydraulic gradients are typically low, generally ranging between 0.002 to 0.005. 4.2 Exposure Pathway Analysis Current and reasonably likely future land uses were used to develop a model describing potentially complete exposure pathways for human and ecologic receptors at and near the Facility. The potential exposure pathways are illustrated on Figure 16. Current and Reasonably-Likely Future Land Use. The Facility and surrounding area are currently zoned by the City of Stockton (City) as Port-owned land. The Facility is currently used to store and distribute refined petroleum products including gasoline, diesel, ethanol, and aviation gasoline. The surrounding area is also used for industrial purposes. The property management coordinator for the Port of Stockton (Ms. Debbie Callie) was contacted regarding reasonably likely future use at the Facility and surrounding Port-owned area. Ms. Callie indicated that the Port had no future plans to use the area for anything other than industrial purposes. Summary of Water Use. The Facility is supplied with water from the City municipal supply. Based on the City of Stockton's Master Water Plan (West Yost Associates, 2008) and a review of Department of Water Resources (DWR) well records, groundwater in the area surrounding the Facility is not used for drinking water. The nearest surface water body is an un-named stormwater canal located approximately 1/4 mile to the southwest which is connected to the Stockton Deep Water Channel (Channel), located approximately 3/4 mile to the north. The Channel feeds the San Joaquin River which eventually empties to San Pablo Bay. An irrigation water well (No. 01 N06E08R002M) was identified in DWR's North Central Region's Water Data Library (WDL). The well was previously identified by SECOR (2002) and determined to be located approximately 1.5 miles southeast of the Facility. Additionally, an undefined well (No. 01 N06E17A001 M) was identified in the WDL; however, the database indicates that the well was destroyed in 1997. The WDL indicates that a well (No. 01 N06E16H001 M) previously identified by SECOR (2002) to be an industrial Revised Cleanup Plan Page 14 NuStar Stockton Terminal-Stockton,California November 7,2012 1014-12