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����'� --- --- ��- �'���� <br /> - ~ <br /> San Joaquin County <br /> Environmental Health Department oIRECTOm <br /> Donna*omn.nsHa <br /> 600 East Main Street <br /> pRmomuxvoomRDmmroRa <br /> Stockton, ��aUifornia 95202-3029 Robert Moo|onon.REHe <br /> Jeff ua,m0000.nsHa.RD[ <br /> aoxevpo/ox ns*a <br /> kKebaite: m/m/w.ejymv.mrg/ehd Linda rv,kouo.nsna <br /> -=l c�V Phone: (209)468-3420 <br /> Fox: (209)464-0138 <br /> May 1O. 2O11 <br /> Messrs. Kirk Larson, PG. and F(obertTrornnner. CHG <br /> State Water Resources Control Board <br /> Division of Financial Assistance <br /> 1001 | Street <br /> Sacramento CA 95814 CUFC|oinn No. 10841 <br /> Subject: 308 E| Dorado Street S. Stockton CA. <br /> March 2011 Five-Year Review Letter Recommendations <br /> San Joaquin County Environmental Health Department (EHO) has received and reviewed the five- <br /> year review letter dated 15 K8oroh 2011 from Kirk Larson of the State Water Quality Control Board <br /> /SVVClCB\ Cleanup Fund (CUF) for the above-referenced site. The CUF recommended that the <br /> EHD consider the site for closure as the CUF concluded that the plume was limited to the source <br /> area and that water quality objectives (WC>{]a) have been achieved in the down-gradient <br /> monitoring vve||o. <br /> The EHO has considered the site for closure; and vvhi|a the plume of impacted groundwater <br /> appears to be delineated, the EHC) still has concerns with this site. The two newly installed down- <br /> gradient vve||s have been monitored only twice — both Urneo total petroleum hydrocarbons <br /> quantified as gasoline (TPHg), di-isopropyl ether ([)IPE) and benzene have been detected at <br /> concentrations that exceed VVQ(]a in K8VV-8 and the last event detected TPHg in MVV-10 at u <br /> concentration in excess of the VVC\C). More time is required to characterize the contaminant <br /> concentrations in these two new down-gradient wells. <br /> Issues requiring further characterization include; <br /> * No contaminant mass estimates have been provided to the EHD to evaluate the potential <br /> for continued plume expansion; <br /> w Neither a human health risk assessment (HHR/\) nor @ vapor intrusion evaluation has been <br /> completed for the site; and <br /> * There has not been a projection of the time required to achieve VVQC)o. <br /> The concentrations of TPHg in monitoring well K8VV-1/\ have been steadily increasing since August <br /> 2004 and were recently at the highest concentration detected to date. Oddly, the TPHg <br /> concentrations appear to be related to the depth to water (DTVV), which is unusual as the well ' <br /> screen is at least 37 feet under water. Monitoring well MW-1 B, screened above MW-1 A, hos only <br /> intermittent detectable concentrations of TPHg and less frequent detections of BTE}{. The <br /> compound 1.2-dioh|mnoethane (1,2-DCA) hos also been detected in monitoring well MW-1A since <br /> 2004. The following graph ahovva the relationships: <br /> 5-`yearReview Letter Response O511.doc <br />