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3 <br /> January 24,2014 <br /> Cardno ERI 2789C.Q134 Former Mobil Service Station 99CAS,Stockton,California <br /> System performance: <br /> . . A 11 <br /> 09/05/13— 12/04/13 2,216.41 '5• 2 <br /> To Date: 11,774.22 <16.019 <br /> GROUNDWATER RESULTS <br /> Groundwater elevations have increased approximately 5 feet since February 2011. During fourth quarter 2013, <br /> the groundwater flow direction in the shallow water-bearing zone was radial outward from well EX1. There were <br /> not enough data points to calculate the groundwater flow direction and gradient in the deep water-bearing zone. <br /> Maximum concentrations were reported in samples collected from wells MW4, EX1, and EX2, located in the <br /> vicinity of the former USTs, with concentrations of TPHg reported up to 110,000 pg/L (EX1) and concentrations <br /> of benzene reported up to 11,000 pg/L (EX2). <br /> CONCLUSIONS <br /> Dissolved-phase concentrations reported in wells MW5 and DW1 were one to three orders of magnitude lower <br /> than concentrations reported during the previous event in August 2013. Maximum concentrations are present in <br /> the vicinity of the former USTs. <br /> The SV E system removed approximately 2,216 pounds of TPHg during approximately 66 days of operation. <br /> RECOMMENDATIONS <br /> Cardno ERI recommends continued operation of the AS/SVE system and continued quarterly groundwater <br /> monitoring and sampling. <br /> LIMITATIONS <br /> For documents cited that were not generated by Cardno ERI, the data taken from those documents is used "as <br /> 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 and the work performed have been undertaken in goad faith, with due diligence and with the <br /> expertise, experience, capability, and specialized knowledge necessary to perform the work in a good and <br /> workmanlike manner and within all accepted standards pertaining to providers of environmental services in <br /> California at the time of investigation. No soil engineering or geotechnical references are implied or should be <br /> inferred. The evaluation of the geologic conditions at the site for this investigation is made from a limited <br /> number of data points. Subsurface conditions may vary away from these data points. <br /> Please contact Mr. Greg A. Gurss, Cardno ERI's project manager for this site, at areg.gurss(aD-cardno.com or at <br /> (916)692-3130 with any questions regarding this report. <br /> Sincerely, ct \CHAT?t) <br /> CL <br /> C'A C EC N � No. 77 �' <br /> Christine M. Capwell David R. DanielsCA1.��G��` <br /> Senior Technical Editor P.G. 8737 �-�.= <br /> for Cardno ERI for Cardno ERI <br /> 707 766 2000 707 766 2000 <br /> Email: christine.capwell(aD-cardno.com Email: david.daniels(cD-cardno.com <br />