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u-➢ <br /> PROBLEM ASSESSMENT REPORT <br /> Poore Petroleun, Inc. <br /> 5941 F Street, Ranta, CA <br /> NCA Project No. 10-90.481 <br /> Page 9 <br /> 4.0 DISMARTnV aF' igE8 T8 <br /> 4.1 Extent of Petroleum Co>�stituents in Boil <br /> Law concentrations of BTEX constituents have been detected in soil: <br /> samples from soil borings drilled at the. site. The highest <br /> concentration of a BTEX constituent was detected in the sample <br /> collected from ten feet at Mw--1. Xylenes were detected in this <br /> sample at the relatively low concentrationof 8.5 ppm, BTEX <br /> constituents have not been detected at concentrations exceeding <br /> .015 ppm in any other soil sample from the site. <br /> TPH was not detected in soil samples collected at MW-2, MW-4, and <br /> MW-6. TPH was detected at very low concentrations in soil samples <br /> collected from five feet at Mw-1 (3 PPM) , and ten feet at MW-5. (2.4 <br /> ppm) . TPH has only been detected at a significant concentration <br /> in the ten foot sample collected at MW-1 (450 ppm) . <br /> Based on results of analyses <br /> the of soil samples from soil borings at <br /> site, the distribution of hydroaarbons" in:site soils <br /> �- primarily: / <br /> analytical data tto date does not indicate e area ,in the vthatih�gh concentrations <br /> �v <br /> Of petroleum constituents are widely distributed in native _oils <br /> at the site. <br /> 4.2 Extent of Petroleum Constituents in Ground Water <br /> Results of recent ground-water sampling at the site indicates that <br /> petroleum constituents are present at concentrations exceeding <br /> California mcls at monitoring wells MW-1 and MW 5. <br /> c°nitoruerts have been detected at :low <br /> -concentrations" An ,.all, <br /> monitoring Wells 'at the site with the .exception;of:. welli W=6j. <br /> 1 Benzene concentrations at MW-1 have decreased from 750 parts per <br /> bi?.lion (ppb) (June, 1989 sampling event) to 11 ppb during the <br /> July, 1990 sampling event. There is inadequate data presently.L-✓_� <br /> available to determine if this decrease in benzene concentrations <br /> represents a significant downward trend in benzene concentrations <br /> within the upper-most water-bearingsediments at the site. Figure <br /> 7 presents the interpreted extent of petroleum constituents <br /> - ground water at the site. in <br />