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' 31134 to 36 feet bgs. In boring HP4, soil sampling began at a depth of 19 feet bgs. Soil from 19 to g i 21124 feet bgs consisted of lean clay, which coarsened into silt to a depth of 25 feet bgs. Underlying the silt, a five foot thick bed of well graded sand was present. From the contact at 30 feet bgs to a depth of 31134, soil consisted of lean clay, and silty clay from 31134 to 36 feet bgs the maximum depth explored. The depth to water was approximately 29 feet bgs in borings BPI through HP3 and I ' approximately 30 feet bgs in boring HP4. No petroleum odors or abnormal discolorations were noted in samples collected from any ' borings. FID readings from the samples ranged from non-detect to 2 ppm. Soil boring logs are included in Attachment A. ' 4.2 Laboratory Analysis Soil and groundwater samples were analyzed for TPHg, using EPA method 8015 modified, BTEX I ' and MTBE using EPA method 8020, and gasoline oxygenate additives using EPA method 8260. 4.3 Soil Analytical Results I Soil samples collected to borings HPI through 11P4 were reported to have non-detectable concentrations of all analytes. Analytical data are summarized in Table 3. Laboratory reports ' and chain of custody documentation are included in Attachment B. 4.4 Groundwater Analytical Results 1 MTBE was not detected in water samples from any boring. Borings HP2, HP3 and HP4 had non- detectable concentrations of TPHg and BTEX. However, boring BPI contained TPHg and benzene at concentrations of 180 and 27 parts per billion (ppb), respectively. Analytical data are presented in Table 2. Laboratory reports and chain of custody documentation are included in Attachment B. 5,0 NATURE AND EXTENT OF CONTAMINATION 1 Extensive investigation reveals that contamination at the site consists of highly weathered gasoline, depleted in BTEX, contained within soil immediately beneath the former USTs. The area of ' contamination comprises approximately 700 square feet. The impacted soil lies interval lies beneath 10 feet and above 35 feet. Based on analytical data and field observations, the best estimate of the affected interval is 17.5 to 32.5 feet below grade. The lateral extent of soil contamination is ' depicted on Figure 3. Since the initial sampling event no groundwater impact by TPHg or BTEX has been observed in ' monitoring well MW1, located within the UST pit (the initial samples are believed to have been affected by soil disturbance resulting from well installation). However, MTBE has been present in samples from the well. The groundwater sample collected at a depth of 30 feet from 1HP4 during the ' recent investigation contained no detectable hydrocarbon analytes, including MTBE. This boring was located immediately downgradient of the UST pit. The lack of groundwater impact at this location indicates that the rise of groundwater into the residually contaminated soil has not resulted i � I ' datalgoundzelvalleyvwlsummary.doc 5