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IN- <br /> a <br /> 1-4 <br /> S <br /> rmm� <br /> PRE-TANK REPLACEMENT Site Assessment Results <br /> 420 HEST KETILERAN LANE,LOOI, CA, <br /> Aegis Project No. 89-013 <br /> Page 8 <br /> 3.3.3 PETROLEUM HYDROCARBONS IN SOIL: WESTERN PUEL ISLAND <br /> Samples B-9/1 and B-10/1 from borings B-9 and &-1o, respectively, were <br /> submitted to state certified laboratory for analysis. Toluene was <br /> detected in sample B--10/1 at 0.007 ppm, petroleum hydrocarbons were <br /> not detected in sample B-9/1. The concentration ::f Total Lead in <br /> sample B-10/1 is presented in Table 2. <br /> 3.4 GEOTECHNICAL ANALYSIS <br /> Several representative soil Samples were submii.ted to a soils <br /> engineering firm for review. A qualitative analysis of slope stability <br /> in the proposed new tank location has been performed by Vector <br /> Engineering, Inc. The results of the analysis are presented in <br /> Appendix D. <br /> 4.0 DISCUSSION OF RESULT'S <br /> The following subsections discuss the results of sampling in the <br /> existing tank. basin and proposed new tank location. <br /> -' 4.1 PETROLEUM HYDROCARBONS IN SOIL: EXISTING TANK BASIN <br /> r 1 <br /> The soil borings drilled near the existing tank basin and associated <br /> plumbing :systzm (B-1 through B--6, figura 2) , were advance several feet <br /> away .from the tank basin. The samples that were obtained are therefore <br /> r representative of native soil conditions—Gasoline odor observations, <br /> f` PID readings and soil sample analytical laboratery results do no <br /> indicate marked impact to the subsurface adjacent:to the existing tank . <br /> basin (Tables 1&2, App B) . There is. some <br /> probability. bhckfillsoils `in <br /> the tank basin may contain petroleum hydrocarbons-. <br /> 4.2 PETROLEUM HYDROCARBONS IN SOIL: PROPOSED NEW TANK LOCATION <br /> Gasoline oder observations and soil sample analytical laboratory <br /> results indicate the presence of petroleum hydrocarbons in the <br /> northwestern corner of the proposed new tc" lk location. Gasoline odors <br /> noted .in boring B-8 terminated between 15 `ft and 20 ft. belota the <br /> ground surface. The source of petroleum hydrocarbons in soil at: the <br /> I new tr:nk`location may have resulted from the .existing vapor lines and <br /> a "thief" port. The location of the existing vapor line within the <br /> ' propose3 new tank location ; g <br /> Ae is :s shown an figure 2 of Aegis work__plan- _- <br /> �- - ( g ,_-Avgust-, -1989) A--thief port consists of a vertical riser pipe <br /> -- ---- - - <br /> F connected in a "T" to a horizontal vapor line graded to drain back ` <br /> into the underground storage tanks. -Air bubbles in- the lines and tank <br /> can result in vapors and liquids being expelled through the vertical <br /> }�.. J riser: pipe: <br />