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City of Everett W-7747 ; <br />30 July 1991 Page 2 - <br />li <br />!.. <br />cobFles (till) exists below the organic soil. The vapor samples were colleded from within <br />this dense gravelly sand with cobbles (till} layer, while the hand augered soii samples " <br />were obtained from the top portion of the till. Therefore, the soil sampies were colleded � <br />from shallower depth than the vapor samples (fable 1). The gravel and cobble cantent � <br />of the till layer prevented deeper penetration of auger holes. Gasoiine-like odor was •= <br />emanating from borings B-1 and B-6. <br />Two soil samples were sent for laboratory chemical analyses for total peVoleum <br />I;ydrocarbons (TPH) by EPA Method 8015 modfied and benzene, tolusne, <br />ethylh�nzene, xylenes (BTE� by EPA Method 8240. Both sal samples exhibited below <br />detection limit concerrtrations of TPIi (fable -1) soil sample B-1 exhibited 0.071 parts per <br />miliion (ppm) concentration of xylene. <br />The vapor samples were analyzed for BTIX by RZh's photovac 10550 portable gas — <br />chromatograph. The highest concentrations of BTEX compounds were detected in soil <br />probe V-4 lucated southeast of the removed UST. The combustible gas concerwati�ons _ <br />of this sampie was measured with a gas-tech model 1238 combustibte gas indicator in % <br />LEL (Lower Explosive Limit). The vapor sample V-4 was measured at 55% LEL The <br />farthest extont of BTIX compounds detected in a soil probe was V-3 located between <br />the house and the garage. <br />Conclusions: <br />The soil gas swvey indicates the presence of benzene, toluene, ethylbenzene snd <br />xylene in the soil;; of the properry located adJacertt to the firestation. The vapor samples <br />were coliected from � � greater depth than the soii samples. The detecdon of <br />contaminants in the soil vapar probe locations probably defines the top of the <br />contaminarit plurne. Thereforo, the concentration of contaminants is F�robably higher at <br />depth. The base of the contaminant plume can be defined by advancing deeper bore <br />holes. These bore holes can be strategically located and constructed in such a way that <br />'rIk'O �� ., <br />