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8200 Hwy 99 <br /> Page 2 <br /> • Analytical results of the deepest soil sample collected at 72.2 feet below surface <br /> grade (bsg) was 33 parts part million (ppm) TPH-g, 0.33 ppm, 0.32 ppm, 0.77 ppm, 1 <br /> 1.7 ppm of BTEX, respectively, and 1.4 ppm tert-Butyl Alcohol (TBA). The <br /> vertical extent of the contamination has not been defined. Once the vertical extent <br /> of the contamination has been defined, the horizontal extent of the contamination i <br /> can be defined. <br /> i <br /> • Groundwater is at approximately 62 to 65 feet bsg. Analytical results of the grab <br /> water sample taken at 65 feet bsg were 9600 parts per billion (ppb) of TPH-g, 910 <br /> ppb, 380 ppb, 430 ppb, 830 ppb of BTEX, respectively, and 620 ppb Methyl tert- <br /> Butyl Ether (MTBE). TBA was not detected in the analysis of the grab water <br /> sample, but the detection limit was 200 ppb. The analytical results of the grab <br /> water sample are above the California Drinking Water Standards Primary <br /> Maximum Contaminant Level (MCL) of 1 ppb for Benzene, and Secondary MCL <br /> of 5 ppb for MTBE. Considering the amount of soil above where the grab water <br /> sample was taken, 620 ppb MTBE is particularly high. Due to the mobile nature of <br /> MTBE, the geology below 73 feet bsg must be characterized in order to assess the <br /> .leaching_p.otential of the contaminants. PHS/EHD recommends characterizing the <br /> `geology below 73 feet bsg sing Cone Penetration Technology. Submit a work <br /> plan that will define o vertical and horizontal extent of the contamination and <br /> characterize the geology to PHS/EHD by June 30, 1999. <br /> • Conduct a survey of all wells within a 2000 foot radius of the site. The survey <br /> should include a map showing the location of all wells and any known <br /> construction details of the wells identified. <br /> • As long as investigation and remediation are not hindered, property development <br /> may occur. PHS/EHD should be notified of property transfers so that responsible <br /> party information is updated. <br /> Please note that your new PHS/EHD contact for this site is Jeffrey Wong. Please <br /> contact him at (209) 468-0335 and direct correspondence to him. <br /> i <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> J�ef"f_rey W no g , REHS Margaret Lagorio, REHS <br /> LOP/Site Mitigation Unit IV Supervisor <br /> c: RWQCB, Central Valley Region- Mark List <br /> c: Ground Zero Analysis, Inc. -John Lane <br />