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k <br /> �.r <br /> May 13, 1987 <br /> 0513cnic <br /> Page 2 <br /> hacid were <br /> added <br /> as a preservative. Tb <br /> e vials <br /> were then sealed with teflon-1ined lis, checkedfor ubbles, <br /> container <br /> to <br /> labelled, and Placed in an ice-cooled <br /> isrcertifiedtbp <br /> Applied GeaSystems laboratory. <br /> the state of California for the types of analyses run. Copies of <br /> chain of custody and laboratory records of analyses are attached. <br /> We understand that pacific Environmental Group, Inc. (PEG) <br /> installed monitoringc , 74re1They e ncounterednd drilled <br /> evidencesoil <br /> of highnlevels <br /> s on <br /> site on Marc. <br /> of hydrocarbon contamination at a depth of 15 feet, and noted a <br /> strong hydrocarbon odor between 15 feet and total depth in S-1, <br /> which was installed immediately adjacent odor and <br /> lowt the west of the <br /> site tank cavity. Only <br /> of <br /> hydrocarbons were reported in samples collected from the other <br /> three borings. <br /> PEG inferred a ground water gradientandtoward <br /> drainagenorthwest, <br /> patterns. or. the <br /> basis of general surface topography <br /> However, the San Joaquin Local Health District infers that ground <br /> water flow is directed eastward, toward areas of high ground <br /> water usage. Because there is only one observation well present <br /> at the site, it is not possible to measure the ground water flow <br /> direction. <br /> It is our understanding, from information supplied by USA <br /> Petroleunil, that the tanks have passed at least two precision <br /> pressure tests in the last year. It. is possible that the <br /> contamination found in the ground water may be due to off site <br /> problems. An active Chevron service station is located to the <br /> e <br /> northwest of the USA station, an inactive formerstationse <br /> ��asation <br /> is located southwest of the site, <br /> and a demolished directly to the west. However, the reported presence <br /> of hydrocarbon contamination at 15 feet and hydrocarbon odor <br /> between 15 and 55 feet in S-1 implies that the USA tank cavity <br /> epossibly as a result of <br /> may e the source f the contamination, <br /> past releases or overfilling of tanks. round <br /> clayey nature of the <br /> soil underlying the site implies that ground water flow is <br /> limited, and that the contaminants may not have migrated <br /> significant lateral distances. <br /> Applied GeoSystems proposes to provide the data necessary to <br /> better define the source and distribution of contamination on, tandee <br /> evaluate the llsushouldwater <br /> beflow <br /> installed, which;will rallowlevaluation <br /> monitoring wein <br /> _of--t.he ground water flow direction and lateral changes such <br /> _..--_._---- <br /> hydrocarbon concentration.- --The _we3.ls_will.__h� Baca ed sa <br /> contamination originating form other sources can be <br /> . recognized. <br /> .�4p�rr.reg' GeoGy�Pem�� <br />