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2 <br /> April 18,2012 <br /> Cardno ERI 2789C.Q121 Former Mobil Service Station 99CAS,Stockton,California <br /> WORK IN PROGRESS <br /> During the first quarter 2012, Cardno ERI installed an AS/SVE system at the site. Startup of the AS/SVE <br /> system will be submitted under separate cover. <br /> CONCLUSIONS <br /> Maximum concentrations were reported from wells MW4, EX1, and EX2 near the former USTs with TPHg <br /> concentrations up to 170,000 pg/L (EX2) and benzene up to 6,600 pg/L (EX1). Concentrations in the deep <br /> wells (DWI through DW4)are at least an order of magnitude less with a maximum TPHg concentration of 3,600 <br /> pg/L(DWI)and a maximum benzene concentration of 540 pg/L(DWI). Petroleum hydrocarbons were detected <br /> in off-site wells including TPHg concentrations up to 53 pg/L (DW4) and benzene concentrations up to 6.4 pg/L <br /> (DW4). <br /> The groundwater flow direction in the shallow zone is towards the east-northeast under a hydraulic gradient of <br /> 0.002. Groundwater flow in the deep zone is towards the northeast under a hydraulic gradient of 0.002. <br /> LIMITATIONS <br /> For any documents cited that were not generated by Cardno ERI, the data taken from those documents is used <br /> "as is" and is assumed to be accurate. Cardno ERI does not guarantee the accuracy of this data and makes no <br /> warranties for the referenced work performed nor the inferences or conclusions stated in these documents. <br /> This document was prepared in accordance with generally accepted standards of environmental, geological, <br /> and engineering practices in California at the time of investigation. No soil engineering or geotechnical <br /> references are implied or should be inferred. The evaluation of the geologic conditions at the site for this <br /> investigation is made from a limited number of data points. Subsurface conditions may vary away from these <br /> data points. <br /> Please contact Mr. Greg A. Gurss, Cardno ERI's project manager for this site, at greq.qurss(,a_)cardno.com or at <br /> (916)692-3100 with any questions regarding this report. <br /> Sincerely, <br /> /QST �-�C�AROD l�Cs' <br /> CrQ 4 �r w, <br /> tp&r4*4/ * No. 7 7 <br /> aA 4IPAG E s �xP <br /> IMAGE 9r ��• <br /> Jennifer L. Lacy David R. Daniels eOF CAL�F� <br /> Senior Staff Scientist P.G. 8737 <br /> for Cardno ERI for Cardno ERI <br /> 707 766 2000 707 766 2000 <br /> Email: Email: david.daniels(a)_cardno.com <br />