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P S E C 0 R 5 . Conceptual Site Model March 24, 2004 Page 17 V (B4-29-S) to 4,800 mg/kg (B-4114-S) Benzene was detected in groundwater at concentrations of 0 057 pg/L in 64-67-W and 1 8 pg/L in 135-85-W These activities are summarized in Stratus's October 27, 2000 Additional Soil and Groundwater Investigation Report Excerpts from the Dolly Madison Bakery reports are presented in Appendix M X 6 7 Shell Branded Service Station 6 7 1 Site Description The site is currently an operating Shell branded service station located on the southeast corner of West Charter Way and Interstate 5 The site consists of a service station building, six dispenser Y islands, USTs, and a car wash In November of 1989, four USTs were excavated and removed Based on a review of available documents during a file review conducted by SECOR, the date Shell initiate retail gasoline operations could not be determined and current USTs design criteria could not be ascertained These activities are summarized in Cambria's July 20, 2000 Site Investigation Report n 672 Remedial Activities In April of 1990 a free product skimming system was installed in monitong well MW-2, reports ri iindicate approximately 180 gallons of free product was removed A SVE system operated at the site ; from September 1993 to November 1996 Between December 1989 and January 1990 five SVE wells (MW-2 through MW-5, and MW-7) were installed along the eastern property boundary, in the vicinity of the former dispenser islands product piping and former USTs SVE wells were screened from approximately 20 feet bgs to 40 feet bgs The SVE system removed approximately 14,980 r pounds of petroleum hydrocarbons in the first year of operation Based on a review of available t documents during a file review conducted by SECOR, the rationale for shutting down the SVE system could not be determined 67.3 Historical Report Summary In January of 1993, Aegis Environmental, Inc converted the SVE system from thermal oxidizer mode to catalytic oxidizer mode The conversion reduced the hydrocarbon emissions from the SVE system by greater than 95% A thermal oxidizer had been operating at the site since September 17, 1992 (Cambria, 2000) These activities are summarized in Aegis's February 1, 1993 Catalyst Installation/Systems Status Soil Vapor Extraction and emission Control System In March of 2000, Cambria advanced four CPT borings (CPT-1 through CPT-4) to define the extent of hydrocarbon impact to soil and groundwater at the site Groundwater was first encountered from 16 5 feet bgs to 17 5 feet bgs Silt was encountered from approximately 70 feet bgs to 77 feet bgs, sand and silty sand was encountered to approximately 85 feet bgs Groundwater flows predominantly to the northeast and east Stratigraphy encountered consisted predominantly of at TPHg was detected in soil at concentrations ranging from 1 28 mg/kg (CPT-1 at 40 5 feet bgs) to 356 mg/kg (CPT-4 at 73 feet bgs) Benzene was detected in soil at concentrations ranging from 0 00564 Smg/kg (CPT-4 at 79 5 feet bgs) to 0 219 mg/kg (CPT-1 at 40 5 feet bgs) MtBE was not detected in f soil above laboratory reporting limits in any of the samples submitted for chemical analysis TPHg 11Chevron1920331REPORTSICSMICSM 92033(REV B)doc Y �w.n