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S E C ® R Conceptual Site Model March 24, 2004 ; Page 12 1 On August 28, 1995, Best Environmental Inc , under a subcontract with SECOR, performed the startup, testing, and sampling for the system The vapors were analyzed for TPHg and BTEX The inlet concentrations for TPHg, benzene, toluene, ethylbenzene, and total xylenes were 1,900 milligrams per cubic meter (Mg/M3), 27 mg/m3, 77 mg/m3, 16 mg/m3, and 58 mg/m3, respectively F These activities are summarized in SECOR September 12, 1996 Soil Vapor Extraction System " Installation and Start-Up Report In October of 1999, Cambria Environmental Technology, Inc (Cambria) documented the removal of three gasoline UST, one diesel UST, fuel dispenser Islands, associated product piping and vent R Imes, and subsequent over-excavation activities During the excavation and removal of UST's, a approximately 860 tons of petroleum hydrocarbons impacted soil was removed from the site Sod a sample concentrations for TPHg ranged from 298 mg/kg In T7-S to 1 30 mg/kg in DSW, total petroleum hydrocarbons as diesel (TPHd) ranged from 8,550 mg/kg in T6-S to 1 44 mg/kg in PLW 1, 1 and MtBE ranged from 1 26 mg/kg in June of 1999 to 0 0158 mg/kg in August of 1999 In DNW Benzene concentrations were detected at 0 0164 mg/kg in PLE1 After excavation and removal of the UST's groundwater monitoring wells were Installed and quarterly groundwater monitoring and Y sampling was Initiated These activities are documented in Cambria's October 22, 1999 h 3 Underground Storage Tank Removal Report " The second quarterly groundwater monitoring report for 2003, completed by Cambria indicated that • groundwater flow direction in the shallow zone was east at a gradient ranging from 0 003 to 0 007 feet per foot (ft/ft) The groundwater flow direction in the deeper zone was southeast at a gradient a ranging from 0 005 to 0 007 ft/ft Quarterly groundwater monitoring has been conducted regularly since February, 1992 These activities are documented in Blain Techs September 4, 2003 Y Groundwater Monitoring Report-Second Quarter 2003 Excerpts from the former Texaco service station reports are presented in Appendix I 6.3 Former Arco Service Station 2168 b 6 3 1 Site Description The site is currently a vacant lot located on the northeast corner of West Charter Way and South Lincoln Street The land surface slopes gently towards the San Joaquin river, which is approximately 1 5 miles west southwest of the site ARCO terminated retail gasoline operations at the site in November 1995 Historically five USTs were located on site consisting of one waste oil UST (reportedly removed in 1986), two 6,000 single-walled steel USTs, one 8,000 gallon single-wailed steel UST, and one 10,000 gallon single-walled fiberglass UST (reportedly removed in February 1996) Based on a SECOR review of UST removal Information from a Delta report, dated November 1 2000 the date ARCO initiated retail gasoline operations could not be determined 632 Remedial Activities A SVE system operated at the site from January 1997 to February 1998 SVE wells were screened , from approximately 5 feet bgs to 40 feet bgs Thirteen SVE wells (VW-1 through VW-13) were installed in the northeast, southeast and southwest corner of the site, in the vicinity of the former dispenser islands product piping and former USTs The SVE system removed approximately 10,000 E 3 11Chevron1920331REPORTSICSMICSM 92033(REV B) doc a