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e• KLEINFELDER ASSESSMENT/REMEDIAL WORK PLAAMENDMENT SAN 1JOAQUIN COUNTY GENERAL HOSPITAL FRENCH CAMIP, CALIFORNIA 1 D 11March 5, 1993 APR 2 3 .. In September and October of 1991, Kleinfelder conducted an investigation of two tank sites (Site T1 and Site 12/T3) at the San Joaquin County General Hospital complex in French Camp, California (Plate 1). A geophysical survey was conducted to evaluate the actual locations of the tanks, and a limited boring program was performed to assess the potential that the tanks may have leaked. The geophysical survey reported that the west (fill and vent) ends of tanks T2 and T3 were partially beneath the wall of a maintenance building. An awning extended from the maintenance building covering access to the south of the tanks. In addition, a utility tunnel was reported adjacent to the tanks on the north side. In order to collect soil samples from beneath both ends of the tanks, soil borings were angle drilled from the east side of the tanks. Soil samples submitted from the T1 tank site did not contain petroleum hydrocarbons, however, soil samples collected from beneath the west end of the T2/T3 tank site were reported to contain petroleum hydrocarbons. The results of the investigation are reported in Kleinfelder's Soil Assessment Report dated December 6, 1991. Based on these results and Kleinfelder's recommendations, San Joaquin County Department of Capital Projects requested further assessment of the 12/T3 tank site. For continuity, the tanks have retained their original designations (T2/T3). SUBSEQUENT ACTIVITIES In January 1993, Kleinfelder drilled a boring adjacent to the west end of the T2/T3 site, and installed three groundwater monitoring wells within 10 feet of the tanks (B-3 and MW -1 through MW -3, Plate 2). The wells were triangulated around the site to allow an assessment of the groundwater gradient. Water samples and depth to water measurements were collected on January 26, 1993. Soil samples were collected at 5 -foot intervals for lithologic description, qualitative screening, and potential analysis. Generally, the soil consisted of sand to a depth of approximately 14 feet. Silt, clay, and/or silty clay -underlaid the sand to a depth of approximately 28 feet. Another sand was encountered from approximately 28 feet to 35 feet. This sand was underlain by a stiff clay to a depth of approximately 40 feet. From 40 feet to the terminus of the monitoring well borings (approximately 50.5 feet) another sand was encountered. Groundwater was first encountered at approximately 40 feet, but rose several feet in each of the borings drilled into groundwater. Based on the change of lithology at first -encountered groundwater and the subsequent rise of the measured water surface, it is possible that groundwater in this area is either confined or semi -confined. Qualitative field screening was conducted with a photoionization detector (PID). PID readings ranged from 0 parts per million by volume (ppmv) to nearly 2,000 ppmv. PID readings greater than 100 ppmv generally coincided with detectable concentrations of hydrocarbons. FWP3-2(1993) Page 1 of 4 24-220152-D00 Copyright 1993 Kleinfelder, Inc. N A