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�°wi��� :�� aN`i'�� .�k3�-' ^1'ITY5�.,� T•�t� '��ya�-' �1���� �' r� _ �•, `'�':4� •4-Y.m.` "��` ..T- �� - _ <br /> e <br /> E <br /> F <br /> d <br /> _ Quarterly Monitoring, Third Quarter April 30, 1991AGS 3$412-4 <br /> Former Unocal Station 2859, Stockton, California <br /> I 'led in Table 2. Copies of the <br /> The results of these and previuus analyses are summarized P <br /> labo►atory analysis reports are included with this report. <br /> ;results of laboratory analyses indicated that concentrations of 'ITI lg and BTEX in wells <br /> MNV-4 and MW-5 have decreased or remained below detection limits since the last sampling <br /> event. TPHg was detected in the sample from well MW-4 at a concentration of 93 parts per <br /> billion(ppb). The coi:centration of"I'PI-Ig x=as below detection limits in the water sample <br /> collected frons well MW-5. The benzene and toluene ccu:cent ratio ns wore below detection <br /> limits in the sample from veli MW-4; however, concentr'itions of ethyibenzene and total <br /> xylene isomers were detec'ed �,t 0.6 and 0.5 ppb, respective'l- 13TEX concen!rations in the <br /> sample collected from well :14W-5 were below detection. limits for the analytical methods <br /> used. <br /> Conclusions and Rvcornmenbltions <br /> BTEX concentrations ranged from below detection limits to 0.1 ppb above the detection <br /> limit. Based on thz .dissolved hydrocarbon concentrations detected in the water collected <br /> front well MW-2 before the well went dry, we recol emend continuing quarterly monitoring. <br /> We have scheduled the next sampling for the week of February 18, 1991. $_ <br /> _ -......__ - _ -.._..... 3-.. _. _... <br /> E� <br />