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December 2, 1998 <br /> Page 5 - <br />' Offsite Sensitive Receptor Survey <br /> PEG reviewed well records available at the California Department oVvater Resources, <br />' Sacramento branch within a '/2-mile radius of th!e.subject site Fifteen sites were <br /> identified within a %2-mile radius containing 25 wells total Two irrigation, hine <br /> municipal, one domestic, one "other", and twelve monitoring wells were identified <br />' Two downgradient wells (Wells 1 and 2) were identified (Figure 1 ) Well 1 is used for <br /> irrigation and Well 2 is a municipal well Well data is presented as Table 1 <br />' Offsite Potential Sources <br /> PEG obtained a VISTA report of facilities containing hazardous materials within a Y2- <br /> mile radius of the subject site The VISTA report identified 24 sites with a %2-mile <br />' radius of the site Two dr/cleaners were identified'directly upgradient 6f the subject <br /> site Two leaking underground storage tank (LUST) sites are located crossgra lent of r <br />' the subrst <br /> site within 0 04 miles In addition, as stated previously, the northeast and <br /> corners of 1 I' Street and Central Avenue were formerly occupied by filling <br /> stations PEG also reviewed historical aerial photographs of the area surrounding the <br />' subject site Results of the aerial photograph review and a subsequent site visit were <br /> consistent with the VISTA report -The VISTA report is presented as Attachment E <br /> Preferential Pathways <br /> PEG obtained outlines of public utilities located in the vicinity of the subject site The <br />' locations of underground gas, electric, water, storm drains, sewer, and phone lines are <br /> shown on Figure 4 <br /> CONCLUSION <br /> Based on the results of the site investigation, low levels of TPH-g, TPH-d, and VOCs in <br /> the groundwater appear to be moving downgradient of the subject site PEG believes <br />' that the VOCs reported in the groundwater may originating from o dry <br /> cleaning establishments located upgradient of the subject site This is supported by the <br />' fact that VOCs were not detected In sblls beneath the former waste oil tank, and their <br /> presence In groundwater in lMgradienfwell U-5 Future groundwater monitoring will <br /> substantiate the validity of an upgradient VOC source Because MtBE has never been <br /> detected at the site, nor would it be expected given the age of the release, Unocal <br /> respectfully requests that MtBE be removed from the quarterly monitonpg proVam <br /> 910017 1A/30LGWRPT doe <br /> t <br />