ARCHIVED REPORTS XR0007793 - Laserfiche WebLink

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recommendations based on field observations and laboratory analyses Depending upon the length of delay associated with installing wells along the Mormon Slough, RFA may issue an interim report detailing the results of assessment accrued from installation of monitoring well 1 MW-4 only This document is divided into three sections Section 1 is an introduction and describes the content of the document Section 2 describes the Site and the physical setting of the area ' surrounding the Site Section 3 presents the Site Assessment Workplan The Site Assessment Workplan presented herein was prepared by a State of California Registered Geologist 2.0 SITE DESCRIPTION The Site is located in an industrial portion of west Stockton and is situated between the Santa Fe Railroad and the Mormon Slough The land use in the area historically has been industrial and commercial There is an abandoned linen cleaning facility located immediately to the ' east of the Site On August 14, 1986, American Environmental Management Corporation of Rancho ' Cordova, California removed a 1,000- Gallon underground storage tank (identified as TKI-86 on Figure 2) from the Site The tank historically contained only leaded gasoline Analytical results of the soil sample collected from beneath the former tank location indicated the presence of diesel, motor oil, and total lead No apparent source for the diesel was determined AEMC reported encountering rubble fill material during the tank removal AEMC conduced additional excavation in August, 1986 Two soil samples were collected from the west and east side of the excavation Total lead and low levels of aromatic volatile ' organics were detected in both samples, and 940 mg/kg diesel was detected in the east sample On December 11, 1990 Oil Equipment Services of San Andreas, California, removed a 2000- gallon underground storage tank (identified as TKI-90 on Figure 2) from the Site The tank historically contained only unleaded gasoline Soil samples collected from beneath the former tank indicated gasoline concentrations in the soil Tetraethyl lead and ethyl dibromide ' were not detected in the soil samples A report dated January 2, 1991 was prepared by Condor summarizing the work ' 21 PHYSICAL SETTING 2.1.1 Structure and Geology ' The Site is situated in the northwestern portion of the San Joaquin Valley in the southern Great Valley physiographic province The Great Valley is an elongate northwest trending asymmetric structural basin that has a wide eastern flank and a short western flank expressed ' by the upturned edges of the sediments that have accumulated in the basin The basin has a regional southward tilt, which is interrupted by the Stockton fault The Stockton fault is the boundary that separates the Great Valley into a northern portion known as the Sacramento Valley, and a southern portion referred to as the San Joaquin Valley The San Joaquin Valley is bordered on the north by the Stockton fault, on the east by the Sierra Nevada Range, on the south by the Transverse Ranges, and on the west by the Coast Ranges ' 366-002 -2-