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�;. 15 August 1996 <br /> AGE-NC Project No. 95-01$5 <br />' Page 7 of 8 <br /> 660 ppb, respectively. <br /> BTE&X were detected in samples collected from MW-1 and MW-4 at concentrations as high as 54 <br /> ppb (xylenes, MW-4). MTBE was detected in water samples from each well at concentrations <br />' ranging from 5.2 ppb(MW-4)to 12 ppb(MW-3).Analytical results of monitoring well ground water <br /> samples are summarized in Table 3 -Analytical Results of Ground Water Samples. The laboratory <br /> report (MAI Laboratory I.D. Nos. 66296 to 66299), and chain-of-custody form are included in <br /> Appendix G. <br /> 5.0. CONCLUSIONS AND RECOMMENDATIONS <br />' 5.1. HYDROCARBON-IMPACTED SOIL <br /> Based upon results of the soil samples collected during this assessment, hydrocarbon-impacted soil <br />' within the saturated zone extends north of the Highway 99 frontage road, south to the center of the <br /> site and west to the vicinity of MW-3. Soil within the unsaturated zone, near the southwest portion <br /> of the former UST area, is impacted from depths of 10 to 20 feet bsg. <br /> AGE anticipates that additional investigation north and east of the site will be required to determine <br />' the lateral extent of impacted soil. <br />' 5.2. HYDROCARBON-IMPACTED GROUND WATER <br /> Petroleum hydrocarbons were detected in both grab samples collected in December 1995; the higher <br /> concentration of hydrocarbon-impacted ground water was encountered in the sample collected from <br /> probe boring P4, near the former UST excavation. <br />' TPH and BTE&X were detected in samples collected from three of the four ground water monitoring <br /> wells;MTBE was detected in samples from all four monitoring wells. Well MW-2 appears to be near <br /> the southern edge of the dissolved hydrocarbon plume; however, additional investigation will be <br /> required north and east of the site to determine the down-gradient extent of dissolved hydrocarbons. <br />' - We recommend the installation of three additional wells in the City of Ripon right-of-way. One well _ <br /> should be installed at north of MW-3; a second well should be installed northeast of MW-1 along <br /> Wilma Avenue, and the third well should be installed on the east side of the Highway 99 ramp. <br /> The next quarterly monitoring should be scheduled for September 1996. <br /> i <br />