ARCHIVED REPORTS_XR0006394 - Laserfiche WebLink

Home Browse Search

S E C 0 R ' Conceptual Site Model Chevron Service Station#9-6171 March 25, 2005 Page 5 Subsurface Investigation — 1987 On January 8, 1987, Groundwater Technology, Inc (GTI) Installed a monitoring well (MW- 1) at the northern end of the tank pit to a depth of 60 feet During drilling activities, the drillers noted slight to moderate gasoline odors Soil samples were collected from the boring at 5 foot intervals, but the only samples sent for analysis were SB-1 C, collected at a depth of 14 ft below ground surface (bgs) and SB-1J collected at a depth of 49 ft bgs This was due to the presence of moderate to slight gasoline odors In the shallow soils and the absence of any gasoline odors in the deeper soils No petroleum hydrocarbons at or above method detection limits were detected in the samples submitted for laboratory analysis by EPA Methods 5020, 8015, and 8020 Groundwater was encountered in the soil boring at approximately 47 feet bgs A groundwater grab sample was collected and analyzed for petroleum hydrocarbons by EPA Method 602 The concentration of total dissolved petroleum hydrocarbons was 990 parts per billion (ppb) The concentrations of benzene, toluene and total xylenes were 32 ppb, 47 ppb and 43 ppb respectively Tables 1 through 4 summarize the historical soil and groundwater data results Soli Vapor Survey Probe— 1988 In 1988, Dames and Moore (DM) installed 8 soil vapor survey probes (VP-1 through VP-8) to a depth of 3 ft bgs No data exists regarding the vapor probe locations No chemical constituents were detected above their method detection limits in soil vapor samples submitted for laboratory analysis Subsurface Investigation Report-- 1990 Between June 24 and August 5, 1990, Sierra Environmental Services (SES) Installed four groundwater monitoring wells (MW-2 through MW-5) on site Soil samples from each boring were analyzed at 5 5 feet, 15 5 feet, and 50 5 feet bgs The soil samples from all four borings were analyzed for TPHg by Environmental Protection Agency (EPA) Method 8015, for benzene, toluene, ethylbenzene, and total xylenes by EPA Method 602, and for ethyl dibromide (EDB) by EPA Method 504 Samples from monitoring well MW-5 were analyzed for the presence of volatile organic compounds (VOCs) by Method 624 No petroleum hydrocarbons were detected In the soil and groundwater samples collected from each well boring The presence of VOCs were limited to 7 ppb of 1,2-dichloroethane (1,2- DCA)detected in the groundwater samples collected from monitoring well MW-5 N IFdesTrojectslChevronIRelaii1"-81711Site conceptual ModeI1FINAL_CSM doc