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i <br /> .` Mr. Brian Cobb <br /> May 31, 1996 <br /> Page 2 <br /> I <br /> Quarterly Monitoring Results <br /> Depth-to-water measurements and calculated groundwater elevations are summarized in Table 1 <br /> Groundwater elevations have increased in all of the monitoring wells relative to last quarter <br /> From the data collected on February 21, 1996, the groundwater flow direction was determined <br /> to be southwest. The hydraulic gradient across the site was approximately 0.004 feet per foot <br /> (calculated between wells MW-8 and MW-5). Groundwater elevations and flow directions for <br /> February 21, 1996 are shown on Figure 1. <br /> TPHg was identified in two of the eight wells sampled (wells MW-3 and MW-8) at <br /> concentrations of 1,200 micrograms per liter (µg/L) and 110 µg/L, respectively Benzene was <br /> detected in two of the eight wells (wells MW-1 and MW-3) at concentrations of 2.8 µg/L and <br /> 460 µg/L, respectively Analytical results of groundwater samples are summarized in Table 1 <br /> and illustrated on Figure 1. The analytical laboratory report for the February 21, 1996 sampling <br /> event is included in Attachment A. <br /> Discussion <br /> The laboratory results of the duplicate sample (MW-51)) collected at well MW-5 identified <br /> .j benzene at a concentration of 2.8 µg/L, although the laboratory results of the original sample <br /> did not identify benzene above the analytical reporting limit of 0.05 µg/L. The difference in the <br /> results between the original and duplicate samples could be due to field an/or laboratory cross- <br /> contamination In addition the laboratory results of the field blank collected at well MW-5 <br /> identified ethylbenzene slightly above the analytical reporting limit. This could also be due to <br /> field and/or laboratory cross-contamination <br /> If you have any questions regarding this quarterly monitoring report, please contact me at <br /> (510) 210-2278 <br /> Sincerely, <br /> BROWNAND WELL / <br /> Todd Miller <br /> California Registered Geologist No 6328 l <br /> TM:lkg <br /> Attachment <br /> cc* Mr. John Reeves, Attorney at Law <br /> Ms. Linda Turkatte, San Joaquin County Public Health Services Department <br />. Mr. Steve Camp, Brown and Root <br /> f <br /> GE UJWj36rQr5U.Y"n1oo966119T 19%VM <br />