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' SOIL OCAVATICN AND SUBSURFACE INVESnGATION RESULTS R82MT 32 Tokay Street Lodi Caldornia Based on soil borings at the site, the shallow subsurface consists primarily of sandy and clayey salts to a depth of 30 feet below grade An approximately 3-foot-thick silty sand layer was noted at a depth of approximately 24 feet A discontinuous sand layer was also reported from approximately 14 to 16 feet below grade (Figure 4) Regional surface topography slopes primarily to the west According to the San Joaquin County Flood Control and Water Conservation District's Spring 1990 Groundwater Elevation Map, groundwater is approximately 50 to 60-feet-deep in the area of the site This map also indicates groundwater flows to the north, toward the nearest surface water body, the Mokelumne River The river is located approximately 1 5 miles north of the site 30 RESULTS 3,1 Soil Excavation Trenching, sampling, and excavation of the area indicated on Figures 2 and 3 was conducted on December 14 and 15, 1992 The final excavation depth was approximately 8 to 10 feet The excavation was performed by Manley and Sons Trucking of Sacramento, California, using a 446 Caterpillar backhoe, under the direction of Aegis personnel Approximately 200 cubic yards of soil were removed and stockpiled temporarily on site prior to disposal Soil samples were collected on December 14, 1992, from the excavation bottom and sidewalls, as indicated on Figure 3 3.2 Soil Sampfing Analylical Results Most of the sal samples were analyzed on site by Sparger Technology, Inc (Sparger), of Sacramento, California, a state-certified mobile laboratory Some split samples were also analyzed at Sparger's Sacramento laboratory, at the request of Ms Linda Turkette of the County The samples were analyzed for a) BTEX, by EPA Method 8020, b) TPH, as gasoline, by modified EPA Method 8015, and c) TPH, as diesel and motor oil, by modified EPA Method 8015 The analytical results are summarized in Table 1 and indicated on Figure 5 The laboratory analytical reports and chain-of-custody form are included in Appendix B Figure 5 and Table 1 show only two samples from the excavation contained TPH, as diesel, at concentrations exceeding the County-allowed maximum of 100 ppm SW-W1� (12,000 ppm) and DC-S (510) ppm Sample SW-W1 was collected from a depth of 8 feet The excavation was subsequently deepened in this area to 10 feet, and the nearby sample collected from this depth (EX-W) contained only 24 ppm TPH, as diesel, indicating successful removal of the significantly impacted soil Sample DC-S was a discolored sample collected from a depth of 8 feet near the existing building Further excavation rcould not be accomplished in this area without threatening the structural integrity of the building 92-074A ERR 3