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Subsurface Investigation and Page 9 <br /> Remedial Excavation of Hydrocarbon-affected Soil <br /> Proposed Cintra Park Phase II Development, Tract 2705, Tracy, California <br /> August 8, 1997 CTE Job No. 20-0445 <br /> SS#11 @ 11 fbg (1.7 mg/kg). However, sidewall samples collected for field analysis (CGI) near <br /> these locations did not contain hydrocarbons. Additionally, none of the sidewall samples in the <br /> r <br /> northern and eastern portion of the site contained hydrocarbon concentrations. <br /> 4.3 Groundwater Sample Anal <br /> The collected groundwater grab sample contained TPH-G concentrations of 1,400 µg/1. <br /> Additionally, benzene(2.0 µg/1),ethylbenzene(0.68 µg/l),and total xylenes(4.0µg/1)were detected <br /> r in the analyzed sample. MTBE concentrations of 13 µg/1 were also detected. <br /> r^ <br /> 5.0 CONCLUSIONS AND DISCUSSION <br />'— Based on the findings of site characterization investigations to date the following conclusions are <br /> t <br /> offered: <br /> i <br /> • A release of fuel hydrocarbons (gasoline) occurred from the former USTs onsite. This <br /> release apparently penetrated the soil column to a depth of approximately eight to 10 fbg. <br /> 1 ' • The lateral and vertical extent of hydrocarbon-affected soil onsite has generally been assessed <br /> and removed. Hydrocarbon-affected soil remaining onsite appears to be limited in extent. <br /> 1 Although four sidewall and bottom soil samples contained TPH-G concentrations, these <br /> concentrations were 2.0 mg/kg or less. Additionally, field analytical results are interpreted <br /> r- to indicate hydrocarbon-affected soil at each of the detected locations is generally confined <br /> to areas of approximately five horizontally and less than two feet vertically. <br /> • Groundwater, encountered at an approximate depth of eight fbg, has been slightly impacted <br /> F by the petroleum hydrocarbons. However, no free product was,detected at any time in the <br /> excavations. <br /> F <br /> CAPROJECTS120-04451ENRP02.WPD <br /> F <br />