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i <br /> Atlantic Richfield Company 4 <br /> ARCO 5450, 1617 West Fremont Street,Stockton,CA April 10 2002 <br /> . SUMMARY OF FINDINGS <br /> • MtBE by EPA Method 8260B was reported in soil samples from soil <br /> borings SB-1 at concentrations of 0.0079 mg/kg (SB-1 @ 15') and <br /> 0.011 mg/kg (SB-1 @20'); <br /> • TPHg, benzene, and fuel oxygenates (MtBE, TAME, DIPE, EtBE, <br /> TBA, EDB and 1,2-DCA) were reported as nondetect in all soil <br /> samples analyzed; <br /> • MtBE by EPA Method 8260B was reported in groundwater samples <br /> from all three borings at concentrations of 3.7 µg/L (SB-2), 43 µg/l, <br /> (SB-3), and 68 µg/L (SB-1); <br /> • TBA was reported in the groundwater sample from SB-3 at a <br /> concentration of 24 µg/L. Toluene was reported in the groundwater <br /> sample from SB-2 at a concentration of 4.4 µg/L and xylenes (total) <br /> were reported in the groundwater sample from SB-1 at a concentration <br /> of 0.68 µg/L. All other analytes were reported as nondetect in <br /> groundwater samples collected from SB-1 through SB-3; <br /> • Groundwater was encountered at approximately 12 to 13 feet bgs in a <br /> sandy to clayey silt. <br /> i <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Based on the data collected during this assessment, groundwater beneath the site in the <br /> vicinity of the UST's and product lines has been impacted by low-levels of petroleum <br /> hydrocarbons. SECOR recommends that an additional site assessment, including the <br /> installation of groundwater monitoring wells, be conducted to verify that groundwater <br /> has been impacted by petroleum hydrocarbons, and to determine groundwater flow <br /> direction. <br /> LIMITATIONS <br /> This report presents our understanding of existing conditions at the subject site. The <br /> conclusions contained herein are based on the analytical results, and professional <br /> judgment in accordance with current standards of professional practice; no other <br /> warranty is expressed or implied. SECOR assumes no responsibility for exploratory <br /> borings or data reported by other consultants or contractors. <br /> If you have any questions or comments regarding this report, please feel free to call us at <br /> (916) 861-0400. <br /> i <br /> 77BP.43323.00.0230lsite assessment.doc <br />